Anatomy + physiology of the GI tract Flashcards
Colon functions
finish absorption of nutrients and water
synthesis certain vitamins
form and eliminate faeces
Is obstruction of the small or large bowel more common?
small
diameter smaller
What is the caecum?
sac-like structure suspended inferior to the ileocaecal valve
receives contents of ileum
Where does the appendix attach?
caecum
What are the taeniae coli?
three bands of smooth muscle that make up the longitudinal muscle layer of the muscularis of the large intestine, except at its terminal end
What are haustra?
tonic contractions of taeniae coli bunch up the colon into a succession of pouches called haustra
responsible for wrinkles appearance of colon
What are epiploic appendages?
small fat-filled sacs of visceral peritoneum attached to taeniae coli
purpose unknown
Rectal valves function
help separate faeces and gas to prevent simultaneous passage
Describe the muscle and control of the internal and external anal sphincters
internal anal sphincter:
- made of smooth muscle
- contractions are involuntary
external anal sphincter:
- made of skeletal muscle
- under voluntary control
both usually closed apart from when defecating
Cell type of anal canal
stratified squamous epithelium
accommodates high level of abrasion as faeces passes through
Colon cell type (apart from rectum)
simple columnar epithelium made mostly of enterocytes and goblet cells
Function of mucus secreted by goblet cells
eases movement of faeces
protects intestine from the effects of the acids and gases produced by enteric bacteria
Enterocytes functions
absorb water and salts as well as vitamins produced by intestinal bacteria
How are most bacteria that enter the alimentary canal killed?
lysozyme
defensins
HCl
protein-digesting enzymes
How does fibre affect the bowel?
softens stool
increases power of colonic contractions
