8.6 Flashcards
What is the primary function of the large intestine?
Store faeces before defecation
Three layers of longitudinal smooth muscle run along the large intestine, and their short length gives rise to the characteristic haustra. What are these smooth muscle bands called?
Teniae coli
What are haustral contractions?
- Slow, non-propulsive contractions that shuffle chyme back and forth in the large intestine, enabling salt and water to be absorbed
What regulates haustral contractions
Locally-mediated reflexes (change the likelihood of AP being generated from slow wave potential)
What controls mass movements?
Neural and hormonal stimuli, predominantly in response to a meal
What is the defecation reflex?
The process by which defecation occurs involuntarily. As our central nervous system develops, we gain the ability to consciously control the external anal sphincter, thus giving us control over when we defecate.
What is absorbed in the large intestine?
Salt and water, vitamin K, electrolytes
What does large intestine epithelium secrete? Why?
- Secretes protective alkaline mucus
- This is to neutralize acids from bacterial fermentation and lubricate the passage of faeces
How are salt and water absorbed by the large intestine?
- Sodium actively absorbed
- Chloride follows electrical gradient
- Water follows osmotic gradient
What are some roles of colon microbiota?
- Synthesise vitamin K
- Promote mineral absorption
What does fermentation by colon microbiota produce?
- Gases
- Heat
- SCFAs (which can be used by colonocytes for energy)
- Glucose
How doe colon microbiota enables us to digest substances we otherwise couldn’t?
They produce enzymes that break down nutrients that our host enzymes cannot
Metabolism
the chemical reactions in living organisms that maintain life.
Intermediary/fuel metabolism
reactions involving
the degradation, synthesis and transformation of the energy
rich organic molecules – protein, carbohydrate and fats.
Name and describe the four fates of absorbed fuel units
- Metabolic pool (available for use)
- Stored (muscle, triglycerides, glycogen)
- Used
- Lost
