1. Digestive System Anatomy
Digestive tract – (mouth to anus)
Alimentary tract or canal
GI tract (stomach and intestines)
Accessory organs
Primarily glands
Regions
Mouth or oral cavity
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus

2. Oral Cavity 2 Mouth or oral cavity
Vestibule: Space between lips or cheeks and alveolar processes
Oral cavity proper
Tongue: Involved in speech, taste, mastication, swallowing
Frenula – hold lip to alveolar process
Lips (labia)
Palate: Oral cavity roof
hard and soft
Fauces - throat opening into the pharynx
Palatine tonsils 3 6 4 7 5 1 2

3. Teeth Two sets Types Primary, deciduous, milk: Childhood
Permanent or secondary: Adult (32)
Types
Incisors, canine, premolar and molars

4. Teeth

5. Salivary Glands Produce saliva Prevents bacterial infection
Lubrication
Contains salivary amylase
Breaks down starch
Mucous
Secreted by the submandibular and sublingual glands
lubricate
Three pairs
Parotid: Largest, located ant. to ear.
Submandibular: below mandible
Sublingual: Smallest, below the tongue.

6. Deglutition (Swallowing)
Three phases
Voluntary
Bolus of food moved by tongue from oral cavity to pharynx
Pharyngeal
Reflex: Upper esophageal sphincter relaxes, elevated soft palate, which closes nasopharynx and oropharynx. Pharynx elevates and opens the esophagus, food pushed into esophagus
Esophageal
Reflex: Epiglottis is tipped posteriorly, larynx elevated to prevent food from passing into larynx

7. Pharynx and Esophagus Pharynx Nasopharynx Oropharynx: Transmits food
Laryngopharynx: Transmits food
Extends from oropharynx to esophagus and post. to the larynx.
Esophagus
Transports food from pharynx to stomach
Passes through esophageal hiatus (opening) of diaphragm and ends at stomach
Sphincters
Upper
Lower
Regulate movement of material into and out of the esophagus

8. Stomach

9. Peritoneum and Mesenteries
Visceral: Covers organs
Parietal: Covers interior surface of body wall
Retroperitoneal: Behind peritoneum as kidneys, pancreas, duodenum (no mesenteries)
Mesenteries
Hold organs in place
Routes which vessels and nerves pass from body wall to organs. 1 2
Greater omentum – extends from greater curvature and transverse colon
Lesser omentum – connects the lesser curvature of the stomach and the
proximal end of the duodenum of the liver and diaphragm

10. Digestive Tract Histology
(Assist in local nervous control)
Digestive tube consists of four major layers or tunics from the esophagus to the anus.
Three glands are associated with the tract.
Unicellular mucous (mucosa)
Multicellular (mucosa and submuxossa)
Multicellular accessory glands (Outside the digestive tract) 4 1 2 3

11. Stomach Anatomy Openings Regions
Gastroesophageal or cardiac: to fundus
Pyloric: to duodenum
Regions
Cardiac
Fundus
Body
Pyloric 3 1 4 2 8 7 6 5 10 9
Located in the left superior abdomen

12. Stomach Histology Layers Serosa or visceral peritoneum: Outermost
Muscularis: Three layers
Outer longitudinal
Middle circular
Inner oblique
Submucosa
Mucosa
3 sub layers 1 3 1 2 3 2

13. Stomach Histology Rugae: Folds in stomach when empty
Gastric pits: Openings for gastric glands
Mucosa cells
Endocrine – regulatory hormones
Chief - pepsinogen
Parietal - hydorchloric acid & intrinsic factor
Mucous neck - mucus

14. Mucosa cells
Chief
pepsinogen contacts hydrocloric acid and is converted to pepsin which assists in the break down of some proteins.
Parietal
hydorchloric acid – main function is to kill bacteria
intrinsic factor – glycoprotein that binds with vit. B-12 to make it more easily absorbed in the illium
Mucous neck
mucus - lubricates and protects the epithelial cells from the damaging effects of acids, chyme and pepsin
Enteroendocrine cells – see chart on next slide

16. Movements in Stomach
Ingested food and stomach secretion mixed together

17. Small Intestine Site of greatest amount of digestion and absorption
Divisions
Duodenum
Jejunum
Ileum: Peyer’s patches or lymph nodules in mucosa and submucosa where some absorption of nutrients take place
Illeocecal sphincter – junction between the ileum and the large intestine

18. Duodenum Anatomy and Histology3 2 1
Modifications
The mucosa and submucosa form a series of folds (Circular folds or plicae)
At the top of each fold are located villi which are covered in microvilli
Lacteal – capillary network

19. Epithelial cells are produced in the mucosa within the intestinal gland or crypts of lieberkuhn.
Duodenal glands or Brunner’s glands open to the base of the intestinal glands and secrete mucus
Intestinal glands, duodenal glands, and goblet cells all secrete mucus which protects against the irritating effects of acids, chyme, and enzymes entering the duodenum from the pancreas

20. Small Intestine Secretions
Mucus
Protects against digestive enzymes and stomach acids
Digestive enzymes
Disaccharidases: Break down disaccharides to monosaccharides
Peptidases: Hydrolyze peptide bonds
Nucleases: Break down nucleic acids
Duodenal glands (brunners’ glands)
Stimulated by vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa

21. Pancreas Anatomy Secretions Endocrine
Pancreatic islets produce insulin and glucagon
Control blood levels of nutrients such as glucose, amino acids
Exocrine
Acini produce digestive enzymes
Regions: Head, body, tail
Secretions
Pancreatic juice (exocrine) produced in the pancreas and delivered through the pancreatic duct to the small intestine.
Trypsin
Chymotrypsin
Carboxypeptidase
Pancreatic amylase
Pancreatic lipases
Enzymes that reduce DNA and ribonucleic acid

22. Functions of the Liver Bile production Storage
Salts emulsify fats, contain pigments as bilirubin (results from break down of hemoglobin)
No digestive enzymes but plays an important role in digestion by neutralizing stomach acid making it suitable for pancreatic enzymes
Storage
Glycogen, fat, vitamins (A, B12, D, E, 7 K), copper and iron
Nutrient interconversion
Detoxification
Hepatocytes remove ammonia and convert to urea
Phagocytosis
Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria
Synthesis
Albumins, fibrinogen, globulins, heparin, clotting factors

24. Digestion, Absorption, Transport
Breakdown of food molecules for absorption into circulation
Mechanical: Breaks large food particles to small
Chemical: Breaking of covalent bonds by digestive enzymes
Absorption and transport
Molecules are moved out of digestive tract and into circulation for distribution throughout body

25. Functions Ingestion: Introduction of food into stomach
Mastication: Chewing
Propulsion
Deglutition: Swallowing
Peristalsis: Moves material through digestive tract
1. Wave of circular smooth muscle relaxation moves ahead of the bolus allowing the digestive tract to expand
2. A wave of contraction of the circular smooth muscle behind the bolus propels it through the tract

26. Reflexes in Colon and Rectum

27. Digestive System Regulation
Nervous regulation
Involves enteric nervous system
Types of neurons: sensory, motor, interneurons
Coordinates peristalsis and regulates local reflexes
Chemical regulation
Production of hormones
Gastrin, secretin
Production of paracrine chemicals
Histamine
Help local reflexes in ENS control digestive environments as pH levels

28. Blood and Bile Flow

29. Carbohydrates
Consist of starches, glycogen, sucrose, lactose, glucose, fructose
Polysaccharides broken down to monosaccharides
Monosaccharides taken up by active transport or facilitated diffusion and carried to liver
Glucose is transported to cells requiring energy
Insulin influences rate of transport

30. Lipids
Include triglycerides, phospholipids, steroids, fat-soluble vitamins
Emulsification breaks down large lipid droplets to small

31. Lipoproteins Types Chylomicrons VLDL LDL HDL Enter lymph
Transports cholesterol to cells
HDL
Transports cholesterol from cells to liver

32. Proteins Pepsin breaks proteins into smaller polypeptide chains
Proteolytic enzymes produce small peptide chains
Dipeptides, tripeptides, amino acids

33. Water and Ions Water Ions
Can move in either direction across wall of small intestine depending on osmotic gradients
Ions
Sodium, potassium, calcium, magnesium, phosphate are actively transported