Large intestines Flashcards
What are the functions of the large intestine?
Water absorption
Production of vitamins
Temporary storage of contents until defecation
What part of the large intestine is responsible for water absortption?
Ascending and proximal transverse colon
How does the large intestine absorb water?
Na+ K+ ATPase on basolateral domain
actively transported 3 sodium ions out of cell into blood, 2 potassium ions from blood into cell
ENaC on apical domain
sodium ions move through it from lumen into enterocyte down its concentration gradient, so by facilitated diffusion
Increased osmolality in direction of sodium ions movement
water moves towards higher osmolality by transcellular route
What stimulates ENaC on the apical domain of enterocytes in the large intestine?
Aldosterone
What type of cell junction is between enterocytes in the large intestine? Why?
Tight
to prevent loss of water from between cells into lumen
Does the small intestine or large intestine absorb more water?
Small intestine
Why is water absorption related to the large intestine instead of the small intestine if the small intestines absorb more water?
Because the large intestines absorb the final bits of water
more difficult to do so
and very important in terms of preventing diarrhoea, dehydration
How does water absorption in the large intestine affect its contents?
Harder, drier
more like faeces
What part of the large intestine is resposible for temporary storage until defecation?
Distal transverse and descending colon
How does the large intestine produce vitamins?
Contains bacteria
which produce vitamins
What is an example of a vitamin produced by bacteria in the large intestine?
Vitamin K
