DIGESTIVE SYSTEM ALIMENTARY CANAL / GI TRACT & ACCESSORY ORGANS. Mar 16 10:34 PM

Transcription

1 DIGESTIVE SYSTEM ALIMENTARY CANAL / GI TRACT & ACCESSORY ORGANS Mar 16 10:34 PM 1

2 I. Digestive System Functions > Ingestion the taking in of food > Propulsion movement caused by force > Digestion breakdown of foodstuff Mechanical Chemical > Absorption > Defecation intake of nutrients from food elimination of indigestible waste 2

3 II. Organs of the Alimentary Canal (GI tract) Oral Cavity: Mechanical & Chemical Digestion > Tongue mixes food with saliva & initiates swallowing contains taste buds/taste receptors > Salivary Glands saliva is mixture of mucus & serous fluids contains salivary amylase (chemical digestion) moistens food and helps create a bolus helps dissolve food so can taste it > Teeth mastication/chew food (mechanical breakdown) > Epiglottis blocks opening to trachea to allow food to enter into esophagus instead of air passageway > Hard & Soft Palate separates oral cavity & nasal cavity when you swallow soft palate rises to close nasal passage Pharynx: this is subdivided into three parts: > nasopharynx respiratory passageway > oropharynx most posterior part of oral cavity > laryngopharynx most superior part of esophagus Mar 21 8:05 AM 3

4 Mar 16 8:07 AM 4

5 II. Organs of the Alimentary Canal (GI tract) cont'd Esophagus: muscular tube for transport (peristalsis) Stomach: Mechanical & Chemical digestion - produces chyme > Regions: Cardia Fundus Body Pylorus > Rugae folds in the walls of the stomach > Mucosa line with simple columnar epithelium with millions of gastric pits creating gastric juice mucous cells produce alkaline mucus to protect walls gastric pits (with glands) «chief cells produce pepsinogens «parietal cells produce HCl «mucous neck cells produce acidic mucus (not sure of purpose) > Sphincter muscles on both ends of the stomach regulate entry and exit of food stuffs Cardiac Sphincter Pyloric Sphincter > Stomach does aid in small amount of fat soluble substances (aspirin, alcohol) Mar 18 10:31 AM 5

6 Mar 16 10:33 PM II. Organs of the Alimentary Canal (GI tract) cont'd Mese nter y Small Intestine: > Functions: Chemical digestion Absorption of nutrients > Regions: Duodenum Jejunum Ileum > What enters the duodenum? Pancreatic juices (enzyme rich & bicarbonate rich) Bile (from liver & gall bladder) > Brush Border Enzymes Produced by small intestine Completes chemical digestion of carbs, proteins, & nucleic acids > Structural modifications: increases surface area Plicae circulares: deep folds of mucosa «force chyme to spiral through lumen...slowing movement & allows more time for nutrient absorption Villi: finger like projections of mucosa «blood capillary network & lymphatic capillary (lacteal) Microvilli: tiny projections of plasma membrane of mucosa cells 6

7 Mar 19 9:51 PM Mar 19 9:53 PM 7

8 II. Organs of the Alimentary Canal (GI tract) cont'd Large Intestine: > Functions: Water absorption Elimination of indigestible material > Regions: Cecum (appendix) «Ileocecal Valve Colon «Ascending «Transverse «Descending «Sigmoid Rectum Anal canal «Internal Involuntary Sphincter «External Voluntary Sphincter > Defacation Reflex Mar 19 9:58 PM 8

9 III. Layers of the Alimentary Canal (GI tract) From the esophagus large intestine the wall of the GI tract is composed of the following tissues: > Mucosa innermost layer epithelial tissue lined with goblet cells that produce mucus > Submucosa connective tissue containing... blood vessels, nerves, & lymphatic tissue > Muscularis externa layers of smooth muscle > Serosa outermost layer peritoneum & mesentery IV. Accessory Digestive Organs Pancreas flat gland that extends from the spleen to the duodenum > Produces pancreatic juice Emptied in duodenum (vagus nerve & hormones: secretin, CCK) Alkaline solution Consists of enzymes that aid in chemical digestion of all categories of food: «Proteases Proteins -> smaller peptides «Pancreatic Amylase Complex Sugars -> Dissacharides «Lipases Fats -> Glycerol & Fatty Acids «Nucleases Cleaves nucleic acids (DNA/RNA) 9

10 Mar 23 7:35 PM IV. Accessory Digestive Organs cont'd Liver large organ with 4 lobes / located just under diaphragm > Produces bile a yellow green substance containing bile salts, bile pigments, cholesterol, phospholipids, & electrolytes > Bile salts help break large fat globules into smaller ones helps increase surface area so lipases can break fat down at faster rate Emulsification > Exits the liver via hepatic duct 10

11 IV. Accessory Digestive Organs cont'd Gallbladder small sac like organ embedded on underside of liver > Bile leaving liver backs up into gallbladder via cystic duct > Bile is concentrated in gallbladder Secreted into duodenum via common bile duct (when fatty foods are present) Salivary glands Parotid, Sublingual, Submandibular > Contains mucus which helps moisten food > Contains salivary amylase which starts starch digestion > Contains lysozyme and antibodies (protective function) > Dissolves food chemicals (can taste food) Teeth mechanical breakdown by mastication V. Metabolism: all chemical reactions that help maintain life A. Anabolism reaction building molecules B. Catabolism reaction that breaks down molecules > digestion = catabolic process > enzymatic breakdown of food via hydrolysis 1. Carbohydrate metabolism: Metabolism by body cells 2. Fat Metabolism: 3. Protein Metabolism: 11

12 CHEMICAL DIGESTION & ABSORPTION Carbohydrates Oral Cavity Starch Salivary Amylase Proteins Stomach Lumen of Small Intestine Pancreatic Amylase disaccharides Proteins Pepsin large polypeptides Pancreatic Proteases small peptides Nucleic Acids DNA/RNA Pancreatic Nucleases Fats/lipids Triglycerides/Fats Pancreatic Lipases glycerol & fatty acids Epithelium of Small Intestine brush border enzymes brush border enzymes brush border enzymes monosaccharides amino acids nucleotides *All (except some lipids) absorbed in blood...to liver...to rest of body *Some lipid breakdown products absorbed in blood, some in lymph...all end up in liver...then to rest of body Apr 8 2:48 PM 12