Large Intestine Flashcards
What are the main regions of the large intestine?
Cecum, colon (ascending, transverse, descending, sigmoid), rectum, and anal canal.
What are the major functions of the large intestine?
- Absorption of water/ions
- Fermentation
What is secreted in the large intestine and why?
Glands in mucosa secrete mucous for protection/lubrication - HCO3- to neutralise VFAs.
What are the 2 major cell types in the large intestine and their functions?
- Colonocytes - absorptive function
- Goblet cells - secrete mucous/HCO3-
What role do microbes play in the large intestine?
Fermentation of structural carbohydrate (fibre) –> VFAs (used as an energy source)
What are three VFAs and their functions?
- Acetate - used in liver, oxidised in most other cells to generate ATP, major source of acetyl CoA for lipid synthesis
- Propionate - substrate for gluconeogenesis
- Butyrate - energy production, cellular homeostasis
What is the primary mechanism of VFA absorption?
Passive diffusion, especially in their non-ionized form.
Which transporter facilitates the uptake of ionized VFAs?
Monocarboxylate transporters (MCTs), particularly MCT1.
What are haustral contractions, and what is their function?
Slow segmental movements that mix contents and aid in water absorption.
What are mass movements in the large intestine?
Strong, coordinated contractions that move feces over long distances, often triggered by eating.
What triggers the defecation reflex?
Stretching of the rectal walls.
What is the difference between the internal and external anal sphincters?
The internal sphincter relaxes involuntarily, while the external sphincter requires voluntary control (except in horses and ruminants).
