Small intestine
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small intestine
Primary role is absorption of nutrients Performs mechanical digestion (peristalsis) and chemical digestion (enzymes) All digestion is completed herehow are nutrients passed to the circulatory system in the small intestine
how are nutrients passed to the circulatory system in the small intestine
walls have folds covered with villi to greatly increase surface area for absorption.
structure of villi
Small, finger-like projections in the small intestine. Each villus has a capillary beside it
function of the villi
Increase surface area for more efficient absorption Nutrients diffuse into capillaries Nutrients travel through the bloodstream to the rest of the body
main parts of small intestine
Duodenum → Jejunum → Ilium
duodenum
digestion occurs located directly after the stomach V-shaped receives secretions from the pancreas and gallbladder
Jejunum
absorption occurs contains more folds than the duodenum breaks down the remaining proteins and carbohydrates
Ilium
absorption occurs contains fewer and smaller villi than either the duodenum and jejunum pushes the remaining undigested materials into the large intestine
main functions of the large intestine
• absorbs water from alimentary canal (recovers it) • formation & storage of feeces
Feces
Waste product of digestion, composed of 75% water and 25% solid toxic to the body
What do anaerobic bacteria in the colon do
break down undigested matter and produce essential vitamins
Where are vitamins produced by bacteria absorbed
absorbed into the bloodstream through the large intestine
what is billiruben
A by-product of hemoglobin breakdown, secreted into bile by the liver makes poop brown
Colon
collective term for most of lange intestine
3 sections of the colon
Ascending Colon → Transverse Colon → Descending Colon
ascending colon
physically runs upwards towards the stomach
transverse colon
runs horizontally across the body
Descending Colon
last part of the colon runs down towards the anus
Appendix
helps fight infections attached to the large intestine, but food materials do not physically enter here may need to be removed if it becomes infected
Rectum
stores feeces until they are eliminated last 20 cm of the large intestine opens at the anus, which is where feces leave the body
Defecation (pooping or bowel movement)
removal of feces from body feces forces into rectum by parastasis the walls of the rectum stretch this starts nerve impulses when feeces leave, rectal muscles contract and the anal sphincters relax