Chapter 16 The Digestive System

Chapter 16 The Digestive System
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Topics (1 of 2) Introduction An Overview of the Digestive Tract
The Oral Cavity The Pharynx The Esophagus The Stomach The Small Intestine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Topics (2 of 2) The Pancreas The Liver The Gall bladder
The Large Intestine Digestion and Absorption Aging and the Digestive System Integration with Other Systems Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Introduction Provides the fuel to keep all cells functioning
Provides the building blocks for cell growth and repair Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Introduction Components Digestive tract Accessory organs Muscular tube
Salivary glands Gallbladder Liver Pancreas Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Introduction Functions involve 6 related processes Ingestion
Mechanical processing Digestion Secretion Absorption Excretion Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Introduction Ingestion Mechanical processing
Food enters digestive tract through the mouth Mechanical processing Physical manipulation of solid foods Tongue and teeth Swirling and mixing motions of the digestive tract Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Introduction Digestion Secretion
Chemical breakdown of food for absorption Secretion Release of water, acids, enzymes, and buffers Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Introduction Absorption Excretion
Movement of substances across digestive epithelium into interstitial fluid of digestive tract Excretion Removal of waste products from body fluids through defecation Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Introduction Defensive roles of the digestive tract
Protects surrounding tissues against corrosive effects of digestive acids and enzymes Protects against bacteria using nonspecific defenses Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

An Overview of the Digestive Tract

Begins at the oral cavity Continues through the pharynx, esophagus, stomach, and small and large intestines Ends at the rectum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Histological organization 4 major layers Mucosa Submucosa Muscularis externa Serosa Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The mucosa Inner lining of the digestive tract Consists of Mucosal epithelium Moistened by glandular secretions Lamina propria Underlying layer of loose connective tissue Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The mucosa Formed into folds Folds increase surface area for absorption Folds permit expansion after a large meal Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The mucosa Features in the small intestine Form fingerlike projections Called villi Further increase the area for absorption Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The mucosa Stratified squamous epithelium Allows for most severe mechanical stresses Found in the oral cavity, pharynx, esophagus, and anus Simple columnar epithelium Lines the rest of the digestive tract Contains various types of secretory cells Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The mucosa Muscularis mucosae Narrow band of smooth muscle and elastic fibers Located in most regions of the digestive tract Move the mucosal folds and villi Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The submucosa Second layer of loose connective tissue Immediately deep to the muscularis mucosae Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The submucosa Contains Large blood vessels Lymphatic vessels Network of nerve fibers Sensory neurons Parasympathetic motor neurons Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The submucosa Submucosal plexus Neural tissue Controls and coordinates contractions of the smooth muscle layers Regulates secretion of digestive glands Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The muscularis externa Band of smooth muscle cells Inner circular layer Outer longitudinal layer Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The muscularis externa Muscle contractions Autonomic reflexes Agitate materials Propel material along the digestive tract Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The muscularis externa Myenteric plexus Nerve network Located between the smooth muscle layers Controls autonomic reflexes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The muscularis externa Autonomic control Parasympathetic stimulation Increases muscle tone and activity Sympathetic stimulation Promotes muscle inhibition and relaxation Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The serosa Serous membrane Covers the muscularis externa within the peritoneal cavity Visceral peritoneum is continuous with the parietal peritoneum Parietal peritoneum lines the inner surface of the body wall Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The serosa Mesenteries Suspend portions of the digestive tract within the peritoneal cavity Stabilize the positions of attached organs Prevent entanglement of the intestines Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The serosa Mesenteries Double sheets of serous membrane Composed of the visceral and parietal peritoneum Loose connective tissue between epithelial surfaces Pathway for blood vessels, nerves, and lymphatic vessels Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Adventitia Dense network of collagen fibers Surrounds are the muscularis mucosae in the absence of serosa Firmly attaches components of the digestive system to adjacent structures Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The movement of digestive materials Pacesetter cells Found in the smooth muscle of the digestive tract Trigger waves of contraction Results in rhythmic cycles of activity Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The movement of digestive materials Coordinated contractions important for 2 processes Peristalsis The movement of material along the tract Segmentation The mechanical mixing of material Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Peristalsis Waves of muscular contractions of the muscularis externa Propels food through the digestive tract Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Peristalsis Circular muscles contract behind contents Longitudinal muscles contract Contraction shortens adjacent segments of the tract Wave of contraction of the circular muscles Forces material in the desired direction Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Segmentation Movements that churn and fragment digestive materials Results in a thorough mixing of contents with intestinal secretions Does not propel material in any direction Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity The first part of the digestive tract to receive food
Lined by a mucous membrane of stratified squamous epithelium Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Senses and analyzes materials before swallowing
Mechanically processes material with the tongue and teeth Lubricates material with mucous and salivary secretions Begins digestion of carbohydrates and lipids with enzymes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Also referred to as the buccal cavity
Cheeks form the lateral walls Anteriorly Continuous with the lips or labia Vestibule Space between the cheeks or lips and teeth Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Gums or gingivae
Pink ridges that surround the base of the teeth Cover tooth-bearing surfaces of the upper and lower jaws Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Hard and soft palates Form the roof of the oral cavity

The Oral Cavity Tongue Dominates the floor of the oral cavity
Free anterior portion connected to underlying epithelium Thin fold of mucous membrane Called the lingual frenulum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Division between the oral cavity and oropharynx
Base of the tongue Uvula Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity The tongue Manipulates materials inside the mouth
Brings food into the oral cavity Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity The tongue Primary functions
Mechanical processing through compression, abrasion, and distortion Manipulating to assist in chewing Preparing materials for swallowing Performing sensory analysis by touch, temperature, and taste receptors Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity The tongue Lies mostly within the oral cavity
Base extends into the oropharynx Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity The tongue Lingual tonsils
Prominent lateral swellings at the base of the tongue Lymphoid nodules that help resist infection Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Salivary glands 3 pairs Secrete into the oral cavity
Parotid salivary glands Sublingual salivary glands Submandibular salivary glands Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parotid salivary glands Lie under the skin
Located in the lateral and posterior surfaces of the mandible Parotid duct Empties into the vestibule at the level of the second molar Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Sublingual salivary glands
Located beneath the mucus membrane On the floor of the mouth Sublingual ducts Numerous ducts Open along either side of the lingual frenulum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Submandibular salivary glands
Located in the floor of the mouth Along the inner surfaces of the mandible Ducts Open into the mouth behind the teeth On either side of the lingual frenulum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Salivary glands Produce 1–1.5 liters of saliva per day
99.4% water Also contains mucins, ions, buffers, waste products, metabolites, and enzymes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Salivary glands Mucins Absorb water Form mucus

The Oral Cavity Salivary glands Saliva
Produced in large quantities at mealtimes Lubricates the mouth Dissolves chemicals that stimulate the taste buds Reduces friction with food, enabling swallowing Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Salivary glands Saliva
Flushes and cleans oral surfaces Contains IgA antibodies and lysozymes Control oral bacteria Leads to recurring infections Causes progressive erosion of the teeth and gums Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Salivary secretions
Different kinds produced by different glands Parotid glands Secretion rich in salivary amylase Breaks down starches into smaller molecules Allows absorption in the digestive tract Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Salivary secretions
Submandibular and sublingual gland secretions Contain fewer enzymes Contain more buffers and mucus Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Salivary secretions During meals Submandibular glands
Produce 70% of secretions pH rises from acidic to basic Secretions controlled by autonomic nervous system Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Teeth Perform chewing or mastication
Breaks down tough connective tissues in meat Breaks down plant fibers in vegetables Helps saturate materials with salivary secretions Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parts of the tooth Neck
Marks the boundary between the root and the crown Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parts of the tooth Enamel Covers the crown
Contains a crystalline form of calcium phosphate Hardest biologically manufactured substance Requires adequate amounts of calcium, phosphates, and vitamin D3 during childhood Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parts of the tooth Dentin
Mineralized matrix similar to that of bone Does not contain cells Makes up the bulk of each tooth Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parts of the tooth Pulp cavity
Contains cytoplasmic processes cells Extend into the dentin Receives blood vessels and nerves through the root canal Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parts of the tooth Root Base of the tooth
Sits within a bony socket Called an alveolus Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parts of the tooth Periodontal ligament
Collagen fibers Extends from the dentin of the root to surrounding bone Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parts of the tooth Cementum
Layer that covers the dentin of the root Provides protection and firmly anchors the periodontal ligament Similar in structure to bone Softer Does not undergo remodeling Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Parts of the tooth Penetration of the gum surface
Epithelial cells form tight attachments to the tooth Prevent bacterial access to the cementum or the root Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity 4 types of teeth Incisors Cuspids or canines
Bicuspids or premolars Molars Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Functions of teeth Incisors Blade-shaped teeth
Found at the front of the mouth Used for clipping or cutting Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Functions of teeth Cuspids Conical
Sharp ridgeline and a pointed tip Used for tearing or slashing Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Functions of teeth Bicuspids and molars
Flattened crowns with prominent ridges Used for crushing, mashing, and grinding Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Dental succession 2 sets form during development
Deciduous teeth First to appear Also referred to as primary teeth, milk teeth, or baby teeth Full set is 20 Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Dental succession Secondary dentition
Also referred to as permanent dentition Permits processing of a wider variety of foods Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Dental succession
Periodontal ligaments and roots of deciduous teeth erode Deciduous teeth fall out or are pushed aside Secondary teeth erupt Full set of 32 teeth 3 new teeth appear on each side of the upper and lower jaws Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Oral Cavity Dental succession Wisdom teeth Third molars
Become impacted if eruption is not permitted May form abscess Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pharynx Common passageway
Allows for passage of solid food, liquids, and air 3 major subdivisions Regions composed of stratified squamous epithelium Lamina propria Contains mucous glands and tonsils Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pharynx Pharyngeal muscles Initiate swallowing process
Cooperate with muscles of the oral cavity and esophagus Force food into the esophagus Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Muscular tube 25 cm long 2 cm in diameter
Conveys solid food and liquids to the stomach Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Begins at the pharynx Runs posterior to the trachea
Passes through the mediastinum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Enters the peritoneal cavity Empties into the stomach
Through the esophageal hiatus Opening in the diaphragm Empties into the stomach Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Lined with stratified squamous epithelium
Resists abrasion Resists hot or cold temperatures Resists chemical attack Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Epithelial surface lubricated by mucous gland secretions
Prevent materials from sticking to the esophagus during swallowing Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Muscularis externa Upper third contains skeletal muscle
Middle third contains skeletal and smooth muscle Lower third contains smooth muscle Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Esophageal sphincter Circular muscle
Located in the superior and inferior ends Inferior sphincter normally in active contraction Prevents backflow of material from the stomach Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Swallowing Deglutition Complex process
Can be initiated voluntarily Proceeds automatically Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Swallowing Before swallowing
Food must have the proper consistency and texture Tongue compacts debris into a small mass Referred to as a bolus Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Process of swallowing Oral phase Pharyngeal phase
Esophageal phase Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Oral phase of swallowing
Begins with the compression of the bolus against the hard palate Tongue retracts Bolus forced into the pharynx Elevates the soft palate to prevent entrance into the nasopharynx Only phase that can be consciously controlled Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Pharyngeal phase of swallowing
Bolus contacts sensory receptors Located around the pharynx and pharyngeal wall Initiates the involuntary swallowing reflex Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Swallowing reflex Larynx elevates
Epiglottis folds to protect the glottis Directs food past the closed glottis Pharyngeal muscles contract Bolus forced through the esophageal entrance Guarded by the upper esophageal sphincter Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Esophageal phase of swallowing
Begins when the bolus enters the esophagus Peristaltic contractions push the bolus toward the stomach Bolus triggers the opening of the lower esophageal sphincter Bolus enters the stomach Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Esophagus Swallowing Typically takes about 9 seconds
Fluids move faster Do not require peristaltic contractions Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Located in the left upper quadrant of the abdominopelvic cavity Receives food from the esophagus Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach 4 primary functions Temporary storage of ingested food
Mechanical breakdown of ingested food Breakdown of chemical bonds in foods Through actions of acids and enzymes Production of intrinsic factor Necessary for the absorption of B12 Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Chyme Mixture of ingested material and secretions from stomach glands Viscous Highly acidic Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Muscular, J-shaped organ 4 main regions Cardia Fundus Body
Pylorus Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Cardia Smallest part of the stomach
Connects with the esophagus Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Fundus Superior bulge of the stomach
Extends above the cardia Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Body Large area
Located between the fundus and the curve of the J Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Pylorus Distal part of the J
Connects the stomach with the small intestine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Pyloric sphincter
Regulates flow of chyme between the stomach and small intestine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Rugae Prominent ridges and folds of mucosa
Visible when the stomach is empty Stomach resembles a muscular tube with a narrow lumen Flatten out as the stomach expands Stomach can hold 1–1.5 liters of material when fully expanded Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Muscularis externa 3 layers
Extra layer adds strength and assists in movement necessary to form chyme Longitudinal layer Circular layer Inner oblique layer Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Visceral peritoneum
Covers the outer surface of the stomach Is continuous with a pair of mesenteries Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Mesenteries Greater omentum Lesser omentum
Extends below the greater curvature Forms an enormous pouch Hangs over and protects the abdominal viscera Lesser omentum Extends from the lesser curvature to the liver Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach The gastric wall Lined by simple columnar epithelium
Dominated by mucous cells Produces an alkaline mucus Protects cells from acids, enzymes, and abrasive materials Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach The gastric wall Gastric pits Shallow depressions
Open onto the gastric surface Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach The gastric wall
Mucous cells located at the base, or neck, or the gastric pits Actively divide Replace superficial cells of the mucous epithelium Cells are shed into the chyme Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach The gastric wall Fundus
Gastric pits communicate with gastric glands Glands extend deep into lamina propria Glands secrete 1.5 liters of gastric juice per day Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach The gastric wall Gastric juice
Components produced by parietal cells and chief cells Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach The gastric wall Pylorus
Gastric glands also contain endocrine cells These walls regulate gastric activity Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Parietal cells Secrete intrinsic factor
Facilitates absorption of B12 across intestinal lining Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Parietal cells Secrete hydrochloric acid
Lowers the pH of gastric juice pH of 1.5–2 Kills microorganisms Breaks down plant cell walls Breaks down connective tissues in meat Activates enzyme secretions of chief cells Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Chief cells Secrete pepsinogen into the stomach lining
Protein that converts to pepsin on contact with hydrochloric acid A proteolytic enzyme Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Chief cells In newborns Produce renin
Coagulates milk Slows passage through the stomach Allows more time for digestion Produce gastric lipase Initiates the digestion of milk fats Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach The regulation of gastric activity
Central nervous system controls acid and enzyme production Regulated by Reflexes within the walls of the digestive tract Hormones of the digestive tract Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach The regulation of gastric activity 3 overlapping phases
Named according to the location of the control center Cephalic phase Gastric phase Intestinal phase Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Cephalic phase of gastric regulation
Initiated by the smell, sight, taste, or thought of food Directed by the CNS Prepares the stomach to receive food Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Cephalic phase of gastric regulation
Parasympathetic fibers innervate mucous cells, parietal cells, chief cells, and endocrine cells Fibers found in the submucosal plexus Controlled by the vagus nerves Phase last only a few minutes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Gastric phase of gastric regulation
Begins with the arrival of food in the stomach Stimulates Stretch receptors in the stomach wall Chemoreceptors in the mucosa Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Receptor stimulation triggers local reflexes Reflexes controlled by submucosal and myenteric plexuses Myenteric plexus stimulates mixing waves in stomach wall Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Gastric phase of gastric regulation Submucosal plexus
Stimulates parietal cells and chief cells Stimulates endocrine cells Release gastrin into circulatory system Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Gastric phase of gastric regulation Gastrin
Stimulates parietal and chief cells Accelerates secretory activities Effect on parietal cells most pronounced Drops the pH of gastric juice Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Phase continues for several hours Gastrin stimulates stomach contractions Swirl and churn gastric contents Mix materials to form chyme Contractions move chyme through the stomach Pylorus contracts, pushing chyme through pyloric sphincter Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Intestinal phase of gastric regulation
Begins when chyme starts to enter the small intestine Regulatory controls are primarily inhibitory Control the rate of gastric emptying Ensure efficiency of small intestine Secretory, digestive, and absorptive functions Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Intestinal phase of gastric regulation Movement of chyme
Reduces stimulation of stretch receptors in the stomach Increases stimulation of stretch receptors in the small intestine Produces enterogastric reflex Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Enterogastric reflex Inhibits neural stimulation Reduces gastrin production Reduces gastric motility Reduces further movement of chyme Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Chyme enters small intestine Stimulates the release of intestinal hormones Secretin Cholecystokinin (CCK) Gastric inhibitory peptide (GIP) Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Stimulation of inhibitory reflexes that depress gastric activity Occurs when the proximal portion of the small intestine Becomes too full Becomes too acidic Is excessively irritated by chyme Is filled with partially digested proteins, carbohydrates, or fats Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Rate of chyme movement Highest with a distended stomach and little protein Alcohol and caffeine stimulate gastric secretion and motility Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Digestion in the stomach
Pepsin performs the preliminary digestion of proteins Salivary amylase continues carbohydrate digestion Remains active until pH falls below 4.5 Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Stomach Digestion in the stomach Pepsin
Becomes more active as contents become fluid and pH drops to 2.0 Begins protein disassembly Not completed in the stomach Breaks complex proteins into small peptide and polypeptide chains Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Nutrients not absorbed in stomach Epithelial cells covered by alkaline mucus Not directly exposed to chyme Epithelial cells lack specialized transport mechanisms Gastric lining is impermeable to water Digestion is incomplete when chyme exits the stomach Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Responsible for 90% of nutrient absorption
Approximately 20 feet long Diameter of 4 cm at the stomach Reduces to 2.5 cm at the large intestine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Contains 3 segments Duodenum Jejunum Ileum

The Small Intestine Duodenum 25 cm long Closest segment to the stomach
Curves in a C-shape Encloses the pancreas Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Duodenum Receives chyme from the stomach
Receives digestive secretions from the pancreas and liver Lies outside the peritoneal cavity Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Jejunum Connects to the duodenum at a sharp bend
8 feet long Supported by a sheet of mesentery Responsible for the bulk of chemical digestion and nutrient absorption Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Ileum Averages 12 feet in length
Ends at the ileocecal valve Sphincter Controls material flow from the ileum to the cecum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Fills much of the peritoneal cavity
Stabilized by mesentery attached to dorsal body wall Connective tissue in mesentery contains blood vessels, lymphatic vessels, and nerves Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine The intestinal wall Plicae
Also referred to as plicae circulares Series of transverse folds in the intestinal wall Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine The intestinal wall Villi
Fingerlike projections on the intestinal lining Covered by simple columnar epithelium with microvilli Resemble the bristles on a brush Referred to as a brush border Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine The intestinal wall
Epithelium contains several plicae Each plica contains many villi Each villus covered by epithelium blanketed in microvilli Absorptive area roughly 2,200 ft² Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine The intestinal wall Villus
Contains a capillary network Transports respiratory gases Transports absorbed nutrients to hepatic portal circulation Contains nerve endings Contains a lymphatic capillary Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine The intestinal wall Lymphatic capillary
Called a lacteal Transports materials that cannot enter blood capillaries Example: protein-lipid packages of absorbed fatty acids Called a chylomicron Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine The intestinal wall Intestinal glands
Entrances located at the base of the villi Contain stem cells that divide continuously Replenish intestinal epithelium Contain endocrine cells that produce intestinal hormones Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine The intestinal wall Duodenum
Contains duodenal glands Submucosal glands Secrete alkaline mucus Buffers the acids in chyme Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal movements
Chyme enters the small intestine Segmentation contractions mix chyme, mucous secretions, and enzymes Weak peristaltic contractions slowly move material Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal movements Peristaltic contractions
Allow increased time for digestion and absorption Local reflexes not under CNS control Limited to a few centimeters from the stimulus site Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Stomach distention initiates the gastroenteric reflex Accelerates glandular secretion and peristalsis Increased peristalsis moves material through the small intestine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Food entering the stomach triggers gastrin release Gastrin responsible for the gastroileal reflex Relaxes the ileocecal valve Allows food to enter the large intestine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal secretions Intestinal juice
Arrives through osmosis Secreted by intestinal glands Stimulated by touch and stretch receptors in the intestinal walls Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal secretions Intestinal juice
Moistens intestinal contents Helps buffer acids Keeps digestive enzymes and products of digestion in solution Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal secretions
Regulated by hormonal and CNS controls Focused in the duodenum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Functions of intestinal secretions
Acid content of chyme must be neutralized Appropriate enzymes must be added Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal secretions Duodenal glands
Protect the duodenal epithelium from gastric acids and enzymes Increase secretions stimulated by Local reflexes Parasympathetic stimulation through the vagus nerve Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal secretions Parasympathetic stimulation
Duodenal glands begin secreting during cephalic stage of gastric secretion Before chyme reaches the pyloric sphincter Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal secretions Sympathetic stimulation
Inhibits the activation of the duodenal glands Duodenal lining unprepared for the acid chyme Stress may result in duodenal ulcers Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal hormones
Various peptide hormones produced by duodenal endocrine cells Coordinate the stomach, duodenum, pancreas, and liver Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal hormones Gastrin Secretin
Cholecystokinin (CCK) Gastric inhibitory peptide (GIP) Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal hormones Gastrin
Secreted by duodenal cells In response to large quantities of incompletely digested proteins Increases stomach motility Stimulates production of acids and enzymes Also secreted in the distal portion of the stomach Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal hormones Secretin
Released as pH of the duodenum falls Occurs when acidic chyme arrives from the stomach Increases the secretion of bile and buffers From the liver and pancreas High concentration reduces gastric motility and secretion Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal hormones Cholecystokinin (CCK)
Secreted when chyme arrives in the duodenum Especially with the presence of lipids and partially digested proteins Also targets the pancreas and gall bladder High concentration reduces gastric motility and secretion Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Intestinal hormones Cholecystokinin Pancreas
Accelerates the production and secretion of all types of digestive enzymes Gallbladder Causes the ejection of bile into the duodenum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Gastric inhibitory peptide (GIP) Released by the presence of fats and carbohydrates in the small intestine Inhibits gastric activity Causes insulin release from the pancreatic islets Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Digestion in the small intestine
Location of most of the important components of digestion Final products of digestion are absorbed Simple sugars, fatty acids, and amino acids Most of the water content is absorbed Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Small Intestine Digestion in the small intestine
Enzymes and buffers for digestion Only a few produced in the small intestine Most are contributed by the liver and pancreas Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas Lies behind the stomach
Extends from the duodenum toward the spleen Roughly 6 inches long Located retroperitoneal Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas Surface Pinkish-gray organ Lumpy texture
Tissue is soft and easily torn Only anterior surface covered by peritoneum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas Histological organization Pancreatic islets
Endocrine cells Secrete insulin and glucagon 1% of the cellular population of the pancreas Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas Histological organization
Exocrine cells and ducts make up most of the pancreas Produce pancreatic juice Mixture of digestive enzymes and buffers Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas Histological organization Exocrine ducts
Branch throughout the pancreas End at the pancreatic acini Saclike pouches Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas Histological organization Acinar cells
Located in the pancreatic acini Secrete enzymes and buffers Mix with enzymes and buffers produced by epithelial cells in the ducts Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas Histological organization Pancreatic duct
Collects secretions from all ducts in the pancreas Carries secretions to the duodenum Penetrates duodenal wall with the common bile duct Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas Histological organization Pancreatic enzymes
Responsible for most of the digestion in the small intestine Classified according to intended targets Carbohydrases digest sugars and starches Lipases break down lipids Nucleases break down nucleic acids Proteases break proteins apart Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Pancreas The control of pancreatic secretion
1000 ml of pancreatic juice produced daily Secretion controlled mainly by duodenal hormones Secretin released in duodenum Triggers pancreas to secrete watery, alkaline fluid pH between 7.5–8.8 Contains buffers, primarily sodium bicarbonate Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Largest visceral organ Firm, reddish-brown
Roughly 2.5% of total body weight Lies in the right hypochondriac and epigastric regions Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Anatomy of the liver Wrapped in a tough fibrous capsule
Covered by a layer of visceral peritoneum Divided into 4 unequal lobes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Anatomy of the liver Left and right lobes Caudate lobe
Larger Caudate lobe Quadrate lobe Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Anatomy of the liver Falciform ligament
Tough connective tissue fold Marks the division between the left and right lobes Thickened posterior margin Referred to as the round ligament Fibrous remnant of the umbilical vein Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Anatomy of the liver Gallbladder
Located in a recess under the right lobe Muscular sac Stores and concentrates bile Excretes bile into the small intestine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver
Lobes divided by connective tissue Tissue forms 100,000 liver lobules Basic functional unit of the liver Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver Liver lobules
Contain hepatocytes Liver cells Arranged into irregular plates Resemble the spokes of a wheel Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver Plates
Only 1 cell thick Covered with microvilli where exposed Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver Sinusoids
Specialized and highly permeable capillaries Form passageways between adjacent plates Empty into the central vein Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver Kupffer cells
Phagocytic cells Located in the sinusoidal lining Part of the monocyte-macrophage system Engulf pathogens, cell debris, and damaged blood cells Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver Blood flow
Enters sinusoids From branches of the hepatic portal vein and hepatic artery Forms the hepatic triad Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Hepatic triad Portal area Includes a small branch of the bile duct, the hepatic portal vein, and the hepatic artery Located at the 6 corners of each lobule Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Blood continues through the sinusoids Hepatocytes absorb solutes from the plasma Secrete plasma proteins Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Blood leaves the sinusoids Enters the central vein of the lobule Central veins of each lobule merge Form the hepatic veins Empty into the inferior vena cava Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver Hepatocytes
Secrete bile Released into bile canaliculi Network of narrow channels Located between adjacent liver cells Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver Bile canaliculi
Extend outward from the central vein Carry bile to increasingly larger bile ducts Bile eventually leaves through the common hepatic duct Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Histological organization of the liver Common hepatic duct
Flows into the common bile duct Empties into the duodenum Flows into the cystic duct Leads to the gallbladder Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Liver functions 3 general roles Metabolic regulation
Hematological regulation Bile production Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Metabolic regulation
Primary organ that regulates the composition of circulating blood Exposed to all blood that leaves absorptive areas of the digestive tract Before blood reaches general circulation Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Metabolic regulation Hepatocytes
Extract absorbed nutrients or toxins from the blood Monitor and adjust circulating levels of organic nutrients Remove and store excess Correct deficiencies Mobilize reserves or synthesize compounds Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Hematological regulation Largest blood reservoir in the body
Receives 25% of cardiac output Kupffer cells remove aged or damaged red blood cells Also remove debris and pathogens Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Hematological regulation Kupffer cells
Antigen-presenting cells Can stimulate an immune response Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver Hematological regulation Hepatocytes
Synthesize plasma proteins Determine the osmotic concentration of blood Transport nutrients Make up the clotting and complement systems Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver The production and role of bile Synthesized in the liver
Excreted into the lumen of the duodenum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver The production and role of bile Consists of Water Ions
Bilirubin Cholesterol Bile salts Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver The production and role of bile Bile salts
Assortment of lipids Synthesized from cholesterol Required for the normal digestion and absorption of fats Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver The production and role of bile
Dietary lipids are not water soluble Mechanical processing in the stomach produces large droplets Pancreatic lipase only interacts with the surface Not lipid soluble Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver The production and role of bile Lipids
The larger the droplet, the more lipids present Remain isolated and protected from digestive enzymes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Liver The production and role of bile Bile salts
Break lipid droplets apart Process called emulsification Creates tiny droplets Increases surface area for enzyme attack Superficial coating of bile salts Facilitates interaction with enzymes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Gallbladder Hollow, muscular, pear-shaped organ
Stores and concentrates bile prior to excretion Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Gallbladder Cystic duct Extends from the gallbladder
Joins with the common hepatic duct Forms the common bile duct Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Gallbladder Common bile duct Joins the pancreatic duct
Enters the duodenum at the duodenal papilla Entrance surrounded by the hepatopancreatic sphincter Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Gallbladder Bile storage Bile secreted continuously
Approximately 1 liter per day Released into duodenum only when stimulated by CCK Hepatopancreatic sphincter remains closed without CCK CCK forces bile to enter the cystic duct CCK stored in the gallbladder Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Gallbladder Bile release Chyme enters duodenum CCK released
Secretion increases with the fat content of chyme Hepatopancreatic sphincter relaxes Wall of gallbladder stimulated to contract Bile released Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Gallbladder Bile modification
Gallbladder holds 40–70 ml of bile when full Composition of bile changes while inside the gallbladder Water absorbed Increased concentration of bile salts and other components Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Gallbladder Gallstones Precipitation of bile salts
Results when bile salts become too concentrated Cause a variety of clinical problems Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Horseshoe-shaped Begins at the end of the ileum
Ends at the anus Lies below the stomach and liver Frames the small intestine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Main functions
Reabsorption of water and compaction of intestinal contents into feces Absorption of important vitamins freed by bacterial action Storage of fecal material prior to defecation Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Also referred to as the large bowel
Approximately 5 feet long Width of 3 inches Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine 3 divisions Cecum Colon Rectum Pouchlike
Largest portion Rectum Final 6 inches End of the digestive tract Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The cecum Expanded pouch
Receives material from the ileum Entrance guarded by the ileocecal valve Begins compaction Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The cecum Appendix
Also referred to as the vermiform appendix Slender and hollow Attaches to the posterior medial side of the cecum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The cecum Appendix Approximately 3.5 inches long
Shape is variable Lymphoid nodules dominate the walls Functions primarily as a lymphatic organ Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The colon
Larger diameter and thinner wall than the small intestine Haustra External pouches Permit distention and elongation Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The colon Taeniae coli
3 longitudinal bands of smooth muscle Run along the outer surface of the colon Just beneath the serosa Muscle tone creates the haustra Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The colon Divided into 4 segments Ascending colon
Transverse colon Descending colon Sigmoid colon Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Ascending colon Begins at the ileocecal valve
Ascends along the right side of the peritoneal cavity Reaches the inferior margin of the liver Turns horizontally Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Transverse colon
Continues toward the left side of the body Passes below the stomach Follows the curve of the body wall Turns inferiorly near the spleen Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Descending colon
Continues along the left side of the body Curves to form the sigmoid Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Sigmoid colon S-shaped section
Empties into the rectum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The rectum Forms the end of the digestive tract
Expanded organ for the temporary storage of feces Last portion called the anal canal Contains longitudinal folds Called anal columns Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The rectum Anal columns
Distal margins joined by transverse folds Transverse folds mark the boundary between columnar epithelium of the rectum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The rectum Epidermis becomes keratinized
Occurs close to the anus Identical to the epidermis on the skin surface Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine The functions of the large intestine Absorption
Preparation of the fecal material for elimination Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Absorption in the large intestine
Reabsorption of water 1500 ml of material enter daily 200 ml of feces ejected Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Composition of feces 75% water 5% bacteria Remaining contents Indigestible materials Inorganic materials Remains of epithelial cells Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Other absorbed substances Bile salts and vitamins Organic waste compounds Example: bilirubin Toxins generated by bacterial actions Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Bile salts
Most bile salts that remain in the cecum are reabsorbed Transported to the liver for secretion in bile Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Vitamins Organic molecules
Related to lipids and carbohydrates Essential for many metabolic reactions Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Vitamins
Enzymes require binding of an additional molecule before binding to substrates Referred to as a cofactor Coenzymes Nonprotein molecules that function as cofactors Many vitamins are coenzymes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Vitamins Bacteria in colon generate 3 vitamins
Vitamin K Biotin Vitamin B3 Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Vitamins Vitamin K Fat-soluble Needed in the liver
Allows the synthesis of 4 clotting factors Includes prothrombin Half of daily requirement produced by intestinal bacteria Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Vitamins Biotin Water-soluble
Important in glucose metabolism Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Vitamins Vitamin B3 Pantothenic acid Water-soluble
Required to manufacture steroid hormones and some neurotransmitters Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Organic wastes
Bacteria convert bilirubin into other products Some absorbed in bloodstream Excreted in the urine Produce the yellow color Others remain in the colon Further modified after exposure to oxygen Produce pigments that give feces its color Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Toxins
Bacterial action breaks down peptides, generating Ammonia Nitrogen-containing compounds Hydrogen sulfide Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Toxins
Hydrogen sulfide and nitrogen-containing compounds Responsible for odor in feces Ammonia and other toxins Absorbed into hepatic portal system Removed by the liver for excretion in urine Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Indigestible carbohydrates Not altered by intestinal enzymes Arrive in the colon intact Provide nutrient source for resident bacteria Metabolic activities responsible for intestinal gas Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Movements of the large intestine
Caused by the gastroileal and gastroenteric reflexes Movement through the cecum to the transverse colon Very slow Takes hours to allow for reabsorption of water Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Movements of the large intestine
From the transverse colon through the rest of the large intestine Mass movements Powerful peristaltic contractions Occur a few times per day Stimulated by distention of the stomach and duodenum Force material into the rectum for defecation Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Defecation Rectum remains empty
Powerful peristalsis forces material out of the sigmoid colon Rectal wall becomes distended Defecation reflex triggered Involves 2 positive feedback loops Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Defecation Shorter positive feedback loop
Stretch receptors in rectal wall activated Receptors stimulate series of increased local peristaltic contractions Confined to the sigmoid colon and rectum Contractions move feces toward the anus Increase the distention of the rectum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Defecation Longer positive feedback loop
Stretch receptors in rectal wall activated Stimulate parasympathetic motor neurons Located in the sacral spinal cord Stimulate increased mass movements in descending and sigmoid colons Push feces toward the rectum Further increases distention Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Defecation Passage of feces through the anal canal
Requires relaxation of the internal anal sphincter External anal sphincter automatically closes Must be opened through voluntary control Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Defecation Voluntary control If not received
Peristaltic contractions cease Additional rectal expansion triggers the defecation reflex again Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Defecation Other consciously directed activities
Tensing of the abdominal muscles Exhaling while closing the glottis Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The Large Intestine Defecation
Responses of consciously directed activities Elevates intra-abdominal pressure Helps force material out of the rectum Forces blood into veins in the anal canal Causes them to stretch Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Digestion and Absorption

Components broken down differently Large organic molecules Broken down before absorption Water, electrolytes, and vitamins Absorbed before processing May require special transport mechanisms Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The processing and absorption of nutrients Digestive system breaks down physical structure Disassembles component molecules into smaller fragments Produces small organic molecules Can be released into the bloodstream Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The processing and absorption of nutrients Small organic molecules Absorbed by cells Used to generate ATP; synthesize carbohydrates, proteins, and lipids Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The processing and absorption of nutrients Foods Complex chains of simpler molecules Carbohydrates composed of simple sugars Proteins composed of amino acids Lipids are fatty acids Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The processing and absorption of nutrients Hydrolysis Component molecule bonds broken by digestive enzymes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The processing and absorption of nutrients Digestive enzymes have specific targets Carbohydrases break up sugars Lipases separate fatty acids from glycerides Proteases break amino acid bonds Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Carbohydrate digestion and absorption Begins in the mouth Salivary amylase Breaks down complex carbohydrates Produces a mixture of disaccharides and trisaccharides Continues to digest starches and glycogen Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Carbohydrate digestion and absorption Pancreatic amylase Breaks down remaining complex carbohydrates Occurs in the duodenum Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Carbohydrate digestion and absorption Disaccharides and trisaccharides Fragmented by brush border enzymes Found on the surfaces of intestinal microvilli Produce simple sugars Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Carbohydrate digestion and absorption Monosaccharides Absorbed by intestinal epithelium Require carrier-mediated transport mechanisms Facilitated diffusion or cotransport For example, glucose uptake requires cotransport with sodium ions Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Carbohydrate digestion and absorption Simple sugars in intestinal cells Diffuse through the cytoplasm Cross the basement membrane through facilitated diffusion Enter interstitial fluid Delivered to the hepatic portal vein and liver Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Lipid digestion and absorption Triglycerides 3 fatty acids connected to a glycerol molecule Unaffected by conditions in the stomach Form large lipid droplets Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Lipid digestion and absorption Bile salts in duodenum Emulsify large lipid drops into tiny droplets Can be attacked by pancreatic lipase Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Lipid digestion and absorption Pancreatic lipase Enzyme that breaks triglycerides apart Creates a mixture of fatty acids and monoglycerides Mix with bile salts Form micelles Lipid-bile salt complex Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Lipid digestion and absorption Micelles Contact the intestinal epithelium Triglyceride products diffuse across the cell membrane Enter the cytoplasm Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Lipid digestion and absorption Intestinal cells Use the fatty acids and monoglycerides Manufacture new triglycerides Coated with proteins Creates a soluble complex Referred to as a chylomicron Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Lipid digestion and absorption Chylomicrons (1 of 2) Secreted by exocytosis into interstitial fluids Pass through large gaps between adjacent endothelial cells Enter intestinal lacteals Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Lipid digestion and absorption Chylomicrons (2 of 2) Proceed along lymphatic vessels Travel through the thoracic duct Enter the bloodstream at the left subclavian vein Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Protein digestion and absorption Complex structure Digestion complex and time-consuming Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Protein digestion and absorption Structure of food disrupted Proteolytic enzymes attack individual protein molecules Involves mechanical processing through mastication Chemical processing with hydrochloric acid Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Protein digestion and absorption Acidic contents of the stomach Provides the proper environment for pepsin Proteolytic enzyme Secreted by chief cells of the stomach Reduce large proteins into polypeptide segments Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Protein digestion and absorption Pancreatic proteolytic enzymes Begin when chyme enters the duodenum Trypsin, chymotrypsin, and carboxypeptidase Break peptide bonds in different amino acids Complete disassembly of polypeptide fragments Create short peptide chains and amino acids Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Protein digestion and absorption Peptidases Enzymes on the surface of the intestinal microvilli Complete the breakdown of peptide chains into amino acids Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Protein digestion and absorption Amino acids absorbed into intestinal epithelial cells Requires facilitated diffusion and cotransport Carrier proteins release absorbed amino acids into interstitial fluid Most diffuse into intestinal capillaries Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Water and electrolyte absorption Water conservation Roughly 9000 ml of water enter the digestive tract daily 150 ml lost through fecal wastes Occurs passively, following osmotic gradients Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Water and electrolyte absorption Dissolved nutrients and ions Continually absorbed by intestinal epithelial cells Gradually lower solute concentration of intestinal contents Forces water to move into surrounding tissues Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Water and electrolyte absorption Calcium absorption Occurs under hormonal control Requires the presence of parathyroid hormone and calcitrol Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The absorption of vitamins Essential organic compounds Required in very small quantities 2 major groups Fat-soluble vitamins Water-soluble vitamins Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

4 fat-soluble vitamins A, D, E, and K Enter the duodenum in fat droplets Mixed with dietary lipids Remain associated with lipids with micelle formation Absorbed from micelles with the products of lipid digestion Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

9 water-soluble vitamins B vitamins common in milk and meats B12 not easily absorbed by digestive epithelium Must bind with intrinsic factor first Vitamin C found in citrus Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Aging and the Digestive System

Digestion and absorption remain essentially normal Changes in the digestive system parallel changes in other systems Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The division rate of epithelial stem cells declines Digestive epithelium becomes more susceptible to damage Abrasion, acids, or enzymes Peptic ulcers more likely Stratified epithelium becomes thinner and more fragile Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Smooth muscle tone decreases General motility decreases Peristaltic contractions are weaker Slows intestinal movement and promotes constipation Sagging and inflammation of the haustra Weakened muscular sphincters lead to reflux Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

The effects of cumulative damage become apparent Gradual loss of teeth Dental caries or cavities Gingivitis or inflammation of the gums Chronic exposure to toxins and chemicals Leads to liver diseases Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Cancer rates increase Most common in organs with stem cell division to maintain epithelium Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Changes in other systems have direct or indirect effects on the digestive system Reduction in bone mass and calcium content in the skeleton Leads to erosion of the tooth sockets Decline in smell and taste sensitivity Leads to dietary changes Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Integration with Other Systems

Summary Identify the organs of the digestive system and describe their functions Describe the histology of the digestive system components Describe the process of digestion and how the parts of the digestive tract interact Describe the functions of the accessory organs of digestion Understand how materials are digested and absorbed Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc. Upper Saddle River, NJ

Chapter 16 The Digestive System

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Chapter 16 The Digestive System

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