Large Intestine Function

Question 1

What is the approximate length of the large intestine?

Answer 1

1.5m long

Question 2

What is the function of the mucosa-associated lymphoid tissue?

Answer 2

It provides a role in immunity

Question 3

How many bacteria are found within the large intestine?

Answer 3

over 700

Question 4

What happens to the undigested polysaccharides in the large intestine?

Answer 4

They are metabolised to short chain fatty acids by the bacteria and absorbed by passive diffusion

Question 5

How is the neutrality achieved by the large intestine after the short chain fatty acids are formed?

Answer 5

Bicarbonate is secreted

Question 6

What gas is produced by the bacterial flora of the large colon and why?

Answer 6

They produce flatus, a mixture of nitrogen and carbon dioxide. This is produced due to bacterial fermentation of undigested polysaccharides

Question 7

Which vitamins are produced by the intestinal bacteria?

Answer 7

K and biotin (vitamin B)

Question 8

What type of antibodies are produced by the intestinal bacteria and what are their functions?

Answer 8

They produce cross-reactive antibodies against the normal flora that are also effective against related pathogens, and prevent infection or invasion

Question 9

What are the most prevalent bacteria in the large intestine and what diseases have they been implicated in?

Answer 9

Bacteriodes - colitis and colon cancer

Question 10

What protects the large intestine from attacks of the bacterial flora

Answer 10

A mucous layer

Question 11

What disrupts the microorganism population of the large intestine?

Answer 11

Antibiotics and stress

Question 12

What are the functions of the gut flora?

Answer 12

Ferment unused energy substrates
Training the immune system
Preventing growth of harmful, pathogenic bacteria
Production of vitamins for host
Regulation hormones to direct the host to store fats

Question 13

Which carbohydrates require help from the gut flora for digestion

Answer 13

certain starches
fibre
oligosaccharides
sugars like lactose
sugar alcohols
mucus produced by the git
various proteins

Question 14

What are the products of carbohydrate fermentation?

Answer 14

SCFAs through saccharolytic fermentation

Question 15

Which minerals are absorbed by the large intestine?

Answer 15

Ca, Mg and Fe

Question 16

When does water absorption stop in the large intestine?

Answer 16

It continues until the familiar semi-solid consistency of faeces is achieved

Question 17

What gives the faeces its brown colour?

Answer 17

Stercobilin

Question 18

How is the faeces lubricated?

Answer 18

It is lubricated by the mucous secreted by the goblet cells of the large intestine

Question 19

What is mass movement?

Answer 19

Strong peristaltic waves that occur at long intervals in the transverse colon to move the contents to the descending and sigmoid colons

Question 20

What triggers mass movement?

Answer 20

Arrival of food into the stomach

Question 21

What is defaecation?

Answer 21

A combination of voluntary and involuntary processes that create enough force to remove waste material from the digestive system

Question 22

What does the stretch receptors in the walls of the rectum trigger?

Answer 22

Contraction of rectal muscles
Relaxation of IAS
Contraction of EAs

Question 23

What does the relaxation of IAS cause?

Answer 23

It causes an impulse to be sent to the brain, indicating the urge to defaecate

Question 24

What happens when voluntary signals to defaecate are sent back from the brain?

Answer 24

It causes the anorectal angle to decrease and the EAS to relax

Question 25

What occurs if defaecation is delayed for a prolonged period?

Answer 25

It causes the faecal matter to harden and autolyse, resulting in constipation