Large Intestine Structure and Function Flashcards
Parts of the colon?
Caecum Ascending Transverse Desending Sigmoid
What is the role of the colon in nutrient absorption?
No important role
Explain the muscular layer of the colon.
Has a complete circular layer
But incomplete longitudinal layer - 3 bands run entire length of colon
What are the 3 bands of longitudinal muscle called?
Teniae coli
What are haustra?
When teniae coli contract longitudinally it creates the pouches/pouched appearance of the colon
What epithelium sits on the mucosa?
Simple columnar
What lubricates the colon?
Large straight crypt cells lined with a large number of goblet cells
Describe the rectum, its mucosa and muscularis externa.
A straight muscular tube located between the anal canal and sigmoid colon
Mucosal epithelium is simple columnar
Muscularis externa is thicker compared to other regions
What is the epithelium like in the anal canal?
Simple columnar to stratified squamous as you move down canal
What is the muscularis externa like in the anal canal?
Thicker than rectum and forms the internal anal sphinter
What is the external anal sphincter made from?
Skeletal muscle
What does bacterial fermentation of undigested carbs produce?
Vit. K
Short chain fatty acids
Gas/flatulence
What is vit. K used for and why is it important bacteria make it?
Clotting
Cannot get it from diet
What else do bacterial flora protect against?
Pathogenic bacteria in the colon
How is the anus kept closed?
Internal sphincter - smooth muscle under ANS control
External - skeletal muscle = voluntary control
How does defcation start?
Mass movement from colon to rectum causes rectal wall to distend
Distention triggers mechanoreceptors that initiate defecation reflex
What is the defecation reflex?
Contraction of rectum
Relaxing of internal anal sphincter
Contraction of external anal sphincter
Increase if peristalsis in colon
Does constipation cause absorption of toxins from faecal matter?
No
Symptoms of constipation due to distension of rectum?
Heachaches
Nausea
Loss of appetite
Abdo distension
List some enterogenic bacteria.
E.coli
V. cholerae
What do enterogenic bacteria do to the colon?
Release enterotoxins which increases chloride secretion from the crypt cells = increased water secretion
Increased water harms the absorptive ability of villi and creates diarrhea
Treatment for diarrhea?
Na/glucose solutions in ORS
These drive water reabsorption and cause rehydration