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MaryBiraiDigestiveSystem (General Functions & Structure of Digestive…
MaryBiraiDigestiveSystem
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Stomach
Function: store food, mechanical and chemical digestion
- Parietal cells/glands: secretes hydrochloric acid and intrinsic factor that is used to absorb vitamin B12. Vitamin B12 produces erythrocytes
- Chief cells/gland: secrete acid and pepsinogen. Pepsin is the enzyme used to breakdown protein.
Sphincters:
- Cardiac sphincter prevents reflux of acid into the esophagus
- Pyloric sphincter regulates the amount of chyme moving on into the small intestine
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Peritoneum & Mesenteries
Mesentery: double layered peritoneum that stores fat, provides place for nerves and blood vessels to "hang out", and holds organs in place
- Mesentery proper: within the jejunum & ileum
- Mesocolon: within the transverse and sigmoid colon
- Lesser omentum: from the liver to the lesser curvature of the stomach
- Greater omentum: stores fat. has the ability to wrap around and enclose an infected area or inflamed organ (ex appendix)
Intraperitoneal: surrounded by the peritoneal cavity
- liver, stomach, ileum, jejunum, sigmoid colon and transverse colon
Retroperitoneal: outside the peritoneum against the posterior abdominal wall
- ascending and descending colon, pancreas, rectum, duodenum ( almost all of it)
Small Intestine
Function:
- absorption
- chemical digestion - enzymes
- mechanical digestion - segmentation
Structures:
- Duodenal glands that secrete alkaline mucous to neutralize the acidic stomach
- intestinal glands: secrete a watery intestinal juice
- Peyer patches - collection of lymphocytes
Features:
- Circular folds: that slow down the movement
- Villi: increase surface area
- Microvilli: absorption
- Ileocecal valve prevents content from moving backwards
Large Intestine, Rectum &
Anal Canal
Large Intestine Function
- water and electrolyte (ions) absorption
Rectum Function
- storage. well developed muscle to expel feces
Anal canal Function
- mucous glands - lubrication
- internal sphincter - smooth muscle; involuntary
- external sphincter - skeletal muscle; voluntary
Teniae coli, haustra, and epiploic appendages
- Teniae coli: 3 strips of longitudinal muscle
- Haustra: contract and pull colon into pouches (sacs)
- Epiploic appendages - has fat
Liver Function
- remove toxins from the blood
- process fat and amino acids
- produce blood proteins: albumin, fibrinogen, globulin
- making bile - stores some vitamins
- stores glucose as glycogen
Hepatic Portal System
- Most nutrients absorbed by the intestine pass through the liver which serves as a filter that can remove potentially harmful xenobiotics before they get into the systemic circulation
- Portal circulation is heart -> arteries to digestive system-> capillaries-> hepatic portal vein-> capillaries of liver -> hepatic vein -> inferior vena cava -> heart
Gallbladder function
- store bile and concentrate bile
Pancreatic Acini Function
- exocrine part of gland that produces bicarbonate which is an alkaline substance that neutralizes acid in stomach and secretes 22 + enzymes that enter the duodenum