Large Intestine Structure and Function

Question 1

Parts of the colon?

Answer 1

Caecum
Ascending
Transverse
Desending
Sigmoid

Question 2

What is the role of the colon in nutrient absorption?

Answer 2

No important role

Question 3

Explain the muscular layer of the colon.

Answer 3

Has a complete circular layer

But incomplete longitudinal layer - 3 bands run entire length of colon

Question 4

What are the 3 bands of longitudinal muscle called?

Answer 4

Teniae coli

Question 5

What are haustra?

Answer 5

When teniae coli contract longitudinally it creates the pouches/pouched appearance of the colon

Question 6

What epithelium sits on the mucosa?

Answer 6

Simple columnar

Question 7

What lubricates the colon?

Answer 7

Large straight crypt cells lined with a large number of goblet cells

Question 8

Describe the rectum, its mucosa and muscularis externa.

Answer 8

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

Question 9

What is the epithelium like in the anal canal?

Answer 9

Simple columnar to stratified squamous as you move down canal

Question 10

What is the muscularis externa like in the anal canal?

Answer 10

Thicker than rectum and forms the internal anal sphinter

Question 11

What is the external anal sphincter made from?

Answer 11

Skeletal muscle

Question 12

What does bacterial fermentation of undigested carbs produce?

Answer 12

Vit. K
Short chain fatty acids
Gas/flatulence

Question 13

What is vit. K used for and why is it important bacteria make it?

Answer 13

Clotting

Cannot get it from diet

Question 14

What else do bacterial flora protect against?

Answer 14

Pathogenic bacteria in the colon

Question 15

How is the anus kept closed?

Answer 15

Internal sphincter - smooth muscle under ANS control

External - skeletal muscle = voluntary control

Question 16

How does defcation start?

Answer 16

Mass movement from colon to rectum causes rectal wall to distend

Distention triggers mechanoreceptors that initiate defecation reflex

Question 17

What is the defecation reflex?

Answer 17

Contraction of rectum
Relaxing of internal anal sphincter
Contraction of external anal sphincter
Increase if peristalsis in colon

Question 18

Does constipation cause absorption of toxins from faecal matter?

Answer 18

No

Question 19

Symptoms of constipation due to distension of rectum?

Answer 19

Heachaches
Nausea
Loss of appetite
Abdo distension

Question 20

List some enterogenic bacteria.

Answer 20

E.coli

V. cholerae

Question 21

What do enterogenic bacteria do to the colon?

Answer 21

Release enterotoxins which increases chloride secretion from the crypt cells = increased water secretion

Increased water harms the absorptive ability of villi and creates diarrhea

Question 22

Treatment for diarrhea?

Answer 22

Na/glucose solutions in ORS

These drive water reabsorption and cause rehydration