Lab 8 Digestive System Announcements l Exams l
Lab 8: Digestive System
Announcements l Exams l Lab notes will be on reserve in library and on the web
Goals of the Digestive System 1. Extract nutrients from food 2. Transform nutrients into useful forms Ex- oreo= glucose 3. Absorb nutrients and distribute them where they are needed
Functions of the Digestive System l Ingestion: intake of nutrients l Digestion: breakdown of large particles into smaller ones l Absorption: uptake of nutrient molecules l Defecation: elimination of undigested residues
Actions of the Digestive System 1. Motility - 2. Secretion - 3. Breaks up food Moves food through the GI tract (Peristalsis) Mixes with digestive enzymes Release of enzymes and hormones for chemical digestion and regulation Membrane Transport - Absorption of nutrients from the tissues by the blood and lymph for transport
Stages of Digestion l Mechanical: physical breakdown of food l Chemical: digestive enzymes hydrolyze food particles to break larger molecules into smaller ones l Some nutrients are absorbed with out digestion – Vitamins, minerals, cholesterol, water
Anatomy of the Digestive System l l l l Oral Cavity Pharynx Esophagus Stomach Pyloric Sphincter Small Intestine Large Intestine
Accessory Organs Teeth l Tongue l Salivary Glands l Liver l Gall Bladder l Pancreas l
l Functions: – A. Oral Cavity Ingestion: cheeks lips and tongue mobilize food – B. Digestion: Mechanical – Mastication l Chemical – 3 salivary glands – Digests some starches and fat l
Pharynx Motility: pharyngeal constrictors force food down during swallowing
Esophagus l Straight muscular tube about 1 foot long l Motility: muscular contraction moves food towards stomach l www. mywebmd. ca. com
Heartburn and the Esophagus Heartburn, “ acid reflux”, is caused by acid and food going from the stomach into the esophagus The diaphragm normally prevents acid reflux, in conjunction with the lower esophageal sphincter. When this fails, the burning sensation felt is known as “heartburn” May be linked to a rare type of cancer, adenocarcinoma
Stomach l Muscular sac on the left side of the peritoneal cavity l Functions: – Food storage – Mechanical digestion – Chemical digestion
Rugae in the Stomach l Rugae- folds in the stomach lining that allow it to expand with more food l How do we vomit? l http: //arbl. cvmbs. colostate. edu/hbooks/pathphys/digestion
Pyloric Sphincter l Ring of smooth muscle l Regulates the passage of material from the stomach into the duodenum http: //arbl. cvmbs. colostate. edu/hbooks/pathphys/digestion
Digestion in the Stomach l Mechanical Digestion: – Muscular contraction l Chemical Digestion: – Secretes digestive enzymes and HCl
Small Intestine l http: //www. afns. ualberta. ca/bbo/1/ANATOMY/SI 1. asp l 2 meters long, 1 inch in diameter, 5 -6 meters in cadaver l Functions: – Chemical Digestion – Nutrient Absorption – Motility
Anatomy of the Small Intestine l Duodenum (25 cm): 1. Receives stomach contents, pancreatic juice and bile 2. Neutralizes stomach acid and pepsin 3. Pancreatic enzymes and bile take over chemical digestion l Fig 25. 22
Anatomy of the Small Intestine l Jejunum (2. 5 m) l Ileum (3. 6 m) – Reabsorbs bile acids
Functions of the Small Intestine l Motility: smooth muscle contract l Digestion: chemical enzymes received from the pancreas, liver and gall bladder l Nutrient reabsorption: microvilli increase surface area Microvilli
Dynamic Human: Microvilli
Large Intestine l Functions – Motility – Reabsorbtion of Water and Electrolytes l Symbiotic bacteria – Synthesis Vitamins B & K
Anatomy of the Large Intestine Transverse Colon: right to left Ascending Colon: up the right side Descending Colon: down the left side Cecum: sac on lower right side Sigmoid Colon: S-shaped
Anatomy of the Large Intestine Rectum: straight down l Anal Canal: out the body l Appendix: hangs off cecum l – Important in Immunity
Enzymes Involved in Chemical Digestion l Saliva: – Amylase: breaks down starch – Lipase: breaks down fats when it enters the stomach l Low p. H of the stomach activates the enzyme
Enzymes Involved in Chemical Digestion • Stomach: • Digestive chemicals • • • HCL: activates enzymes, breaks up foods Pepsin: digests proteins Renin: digests milk
Pepsin Formation • Interactions between Cells • • • Chief Cells make pepsinogen Parietal Cells make HCl Pepsinogen is cleaved by HCl into Pepsin
Dynamic Human: Pepsin Formation
Enzymes Involved in Chemical Digestion • Small Intestine • Two sources of enzymes • Liver and Gall bladder • Pancreas
Enzymes Involved in Chemical Digestion in the Small Intestine • Liver secretes bile that is active in the small intestine • Bile: aids in fat digestion and absorption • Activates pancreatic enzymes • Synthesized from cholesterol • Bacteria in the small intestine use bilirubin to make your feces brown • Gall bladder stores and concentrates bile
Gall Stones l What is a gall stone? l How do they treat gall stones? l How is the gall bladder removed?
Enzymes Involved in Chemical Digestion in the Small Intestine l Pancreas: secretes pancreatic juice 1. Amylase: breaks down starch 2. Lipase: breaks down fats 3. Ribonuclease (RNAase): breaks down RNA 4. Deoxyribonuclease (DNAase): breaks down DNA 5. Zymogens: inactive enzymes that activate in the small intestine
Mechanism of Absorption l Membrane Transport: – Nutrients pass through membrane surface – The greater the membrane surface area, the greater the amount of nutrients that can be transported l Surface Area – Rugae – Microvilli
Final Destinations of Digestion Products l Starches l Fats bloodstream lymph vessels (lacteals) l Proteins bloodstream
Dynamic Human: Visualization
Cat Dissection l Be able to locate and identify l Also know accessory organs – Esophagus – Tongue – Stomach – Teeth – Small Intestine – Gall Bladder – Large Intestine – Liver Ascending colon l Transverse colon l Descending colon l
Conclusion l Review today’s material – Dynamic Human Overview l Know cat anatomy l Lab Practical II returned – well done! l Next week – Endocrine!!!
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