The Digestive System and Body Metabolism

1) A healthy digestive system is essential for good health I. Digestive Anatomy 1) A healthy digestive system is essential for good health 2) The organs are divided into 2 groups Alimentary canal & Accessory glands 3) Alimentary canal (GI tract) Path of food: mouth  pharynx  esophagus  stomach  small intestine  large intestine

Organs of the Digestive System Figure 14.1

4) Mouth (Oral cavity): a) Formed by the cheeks, lips and palate b) Uvula: c) Frenulum: d) Tonsils:

5) Pharynx: a) Throat: b) Peristalsis: alternating contractions of muscle propelling the food through the digestive system 6) Esophagus:

b) Layers of the digestive system (esophagus to LI) 1. Mucosa: mucous membrane f orming the lining 2. Submucosa: soft connective tissue contains blood vessels, nerve, lymph nodes 3. Muscularis: smooth muscle layer 4. Serosa: outer layer tissue (peritoneum)

Layers of Alimentary Canal Organs Figure 14.3

7) Stomach: a) C or J shaped organ on the left side of abdomen b) Cardiac (cardioesophageal) sphincter: muscle valve at the top of the stomach c) Pyloric sphincter: muscle valve regulating food entering the small intestine

d) Rugae: e) Functions mainly as a storage site, while physically breaking down food f) Cells of the stomach 1. Chief cells: produce pepsinogen 2. Parietal cells: produce hydrochloric acid 3. Mucous cells: produce mucus

Stomach Anatomy Figure 14.4a

g) Chyme: 8) Small intestine: a) Longest section (21 ft) of the GI tract does most of the digestion and absorption b) Three sections: duodenum, jejunum, ileum c) Ileocecal valve: valve between the small and large intestine

d) Three structures increasing absorptive surface 1. Microvilli: tiny projections of the plasma membrane 2. Villi: fingerlike projections of the mucosa 3. Circular folds (plicae circulares): deep folds in the mucosa and submucosa

Villi of the Small Intestine Figure 14.7a

9) Large intestine a) Large in diameter, but only 6 feet b) Major function is dry out food residue and eliminates waste as feces c) Parts: 1. Appendix: no known function 2. Colon: 3. Rectum: stores feces 4. Anal canal

Large Intestine Figure 14.8

a) Saliva: mixture of mucous and serous fluids II. Accessory Organs: Salivary glands: a) Saliva: mixture of mucous and serous fluids b) Functions to moisten and bind food c) Bolus: chewed food leaving the mouth d) Salivary amylase: begins starch digestion e) Lysozyme and antibodies inhibit bacteria

2) Teeth: a) Deciduous (first set) and permanent b) Wisdom tooth: third molar (sometimes do not rupture or form at all) c) 32 normally develop (4 half jaws of 8 teeth) Incisor 2 cut Canine 1 tear Premolars 2 grind Molars 3 grind d) Enamel: hardest substance in the body

Teeth Figure 14.9

3) Pancreas a) Soft, pink gland from the spleen to the duodenum b) Endocrine function: produces glucagons and insulin c) Exocrine function: produces digestive enzymes

Figure 14.6

4) Liver: a) Largest gland in the body, located in the right side of the abdomen b) Produces bile c) Bile: d) Gallbladder:

c) Mechanical digestion: d) Chemical digestion: e) Absorption: III. Physiology 1) Functional terms: a) Ingestion: b) Propulsion: c) Mechanical digestion: d) Chemical digestion: e) Absorption: f) Defecation:

2) Mouth: physical and chemical breakdown (starch) of food, no absorption (some medications) 3) Stomach: a) Physical breakdown b) Chemical: HCl & Pepsinogen: starts protein breakdown c) Absorbs sugars and some medications

d) Food stays in stomach 4-6 hours 4) Small intestine a) Finishes chemical digestion and absorption of all food materials b) Digestive enzymes from the pancreas and bile enters here c) Bicarbonate ions from the pancreas neutralizes the acid chyme d) Food is in the SI for 3-6 hours

b) Absorbs water and vitamins produced by bacteria 5) Large intestine: a) No digestion b) Absorbs water and vitamins produced by bacteria c) Remains for 12-24 hours 6) Digestion summary