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Digestive System (Peritioneum & Mesenteries (Mesocolon - connected to…
Digestive System
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Major Functions of the Digestive System:
- Breakdown of food into small pieces to be absorbed by Circulatory System
- Eliminate what cannot be broken down
Mechanical & Chemical Digestion:
- Mechanical Digestion: cut food up small, use teeth, stomach churns food, small intestine does segmentation (mixing together food)
- Chemical Digestion: adds chemicals (enzymes)
mouth - adds saliva, stomach - adds chemicals, small intestine - adds more chemicals from pancreas
Functions of the Stomach
- Store food
- Mechanical digestion (churning)>chyme
- Chemical Digestion
Gastric Glands
- Parietal Cells: Hydrochloric acid and intrinsic factor needed to absorb vitamin B12, which produces B12
- Chief cells: secretes pepsinogen + acid = pepsin (enzyme to breakdown proteins)
Cardiac & Pyloric Sphincter
- Cardiac Sphincter: prevents reflex of acid into esophagus
- Pyloric Sphincter: regulating amount of chyme moving onto the small intestine
Functions of Small Intestine
- Mechanical Digestion>segmentation
- Chemical Digestion>enzymes
- Absorption
Features of the Small Intestine
- Circular Folds: slow the passage of the partly digested food along the intestines, and increase surface area for absorption
- Villi: finger-like projections that increase surface area and contain specialized cells to transport substances into the bloodstream
- Microvilli: hairs that guide in the absorption of nutrients
Functions of Small Intestine Structures
- Duodenal glands AKA Brunner glands: secreting alkalin mucus (to neutralize acid from stomach and protect)
- Intestinal glands AKA crypts of Lieberkuhn: secreting watery intestinal juice
- Lymphatic Nodule AKA Peyer patches: collections of lymphocytes
Ileocecal Valve
- Prevent movement from going backwards
- Keeps waste in the large intestine
Functions of the Large Intestine, Rectum, Anal Canal
- Large Intestine: water and electrolytes (ions: K+, Na+, Ca2+, CL) absorption
- Rectum: storage of feces, well developed muscles to expel
- Anal Canal: last inch or so, mucus glands>lubrication, internal/external sphincters
Functions of Teniae Coli, Haustra, Epiploic Appendages
- Teniae Coli: 3 strips of muscle, contract and pull large intestines into pouches
- Haustra: sacs or pouches within the large intestine
- Epiploic Appendages: fatty globs along teniae coli, visceral peritoneum
Intraperitoneal vs Retroperitoneal
- Intraperitoneal: within the peritoneal cavity, ex. liver, stomach, transverse colon, jejunum, ileum, sigmoid colon
- Retroperitoneal: behind peritoneal cavity, ex. duodenum, pancreas, ascending/descending colon, rectum
GI Tract & Accessory Digestive Organs
- GI Tract: tube that goes from mouth to anus
- Accessory Digestive Organs: organs that add to the tube, salivary glands, liver, gallbladder, pancreas
- Liver: makes bile, filters toxins out of blood, stores glucose as glycogen, stores some vitamins, processes fats, amino acids, makes blood proteins
- Gallbladder: stores bile + concentrated bile = emulsify fat
- Pancreatic Acini: produce and secrets 22+ enzymes>enter duodenum
Duct cell = produce bicarbonate - to neutralize stomach acid with alkaline substance