The Digestive System Chapter 15

Section 15.1 Functions: Mechanical and chemical breakdown of food Absorption of nutrients Excretion of wastes *Consists of alimentary canal and accessory organs

Alimentary Canal Pathway by which food enters the body and solid wastes are expelled Includes: Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anus

Wall of the Alimentary Canal

Section 15.2 Layers of the Canal 1.  Mucosa - protects tissues and carries out absorption 2.  Submucosa - glands, blood vessels, nerves 3.  Muscular Layer - smooth muscle tissue, pushes food  (PERISTALSIS) 4.  Serosa (serous layer) - outer covering of the tube, lubricates surfaces (serous fluid)

Mixing Movements Contractions mix food with digestive juices   Peristalsis - pushes food down the tube

Anatomy of the Mouth

Teeth  -responsible for mechanical breakdown of food

Submandibular - below jaw Sublingual - under tongue Salivary Glands Parotid - ear, cheek Submandibular - below jaw Sublingual - under tongue AMYLASE – enzyme in saliva that breaks down starch *Food begins to turn into a BOLUS

Pharynx    nasopharynx oropharynx hypopharynx

Esophagus Long, tube-shaped structure made of smooth muscle that takes food from mouth to the stomach

Stomach Regions Cardiac region Fundus Body (greater and lesser curvature) Pyloric region

Stomach Lining Mucus prevents stomach from digesting itself Gastric glands secrete acids that breakdown food   PEPSIN - most important digestive enzyme for breaking down food Mucus prevents stomach from digesting itself  

STOMACH ULCERS

STOMACH MUSCLES:    Longitudinal Circular Oblique

Food becomes… Chyme – the semifluid mass of partly digested food expelled by the stomach into the duodenum

ACCESSORY ORGANS PANCREAS Secretes: Insulin which breaks down sugars Other pancreatic juices that break down fat

 Liver  Made of 1 large right lobe and 1 smaller left lobe

Major Liver Functions 1. Produces and secretes bile*** 2.  Metabolizes fats, proteins, and carbohydrates 3.  Stores vitamins, glycogen, and minerals 4.  Detoxifies and purifies blood

Gall Bladder -under liver -stores bile & digests fat   Gallstones

Gallstones - made from built up cholesterol or bilirubin *Can be as small as grain of sand or as large as a golf ball

Gallstones within the gall bladder

Approximately 7 meters long (~18-23 ft) 1. Duodenum 2. Jejunum Small Intestine  Approximately 7 meters long (~18-23 ft) Starts at the pyloric sphincter 1.  Duodenum 2.  Jejunum 3.  Ileum   *Mesentery - membrane holds small intestines together, contains blood vessels

Main function of small intestines is ABSORPTION of NUTRIENTS

Intestinal villi - increase surface area to absorb nutrients, connect to vessels

Large Intestine Cecum – entrance from small intestines Appendix Colon (4 parts) Ascending Transverse Descending Sigmoid Rectum Anus

Function of Large Intestine The main job is WATER REABSORPTION... Mass Movements (defecation) - removes undigested food

Colonoscopy is a screening technique to detect cancer.