Physiology Of Colon And Anus

Question 1

How long is colon

Answer 1

1.5m long

Question 2

What are the muscular bands of colon colon

Answer 2

Taenia Coli

Question 3

Namer 3 parts of colon

Answer 3

1. → caecum (starts at junction of small intestine - lleocaecal valve) forms pouch to which appendix attaches
2. → colon (ascending transverse and descending portion)
3. → rectum ( as anal canal opening a anus)

Question 4

Name the anal sphincter and which control they are under

Answer 4

• Internal anal sphincter= smooth muscle: involuntary control
• External anal sphincter= skeletal muscle: voluntary control

Question 5

How does bacteria in Colon influence metabolism?

Answer 5

They digest non-digestable carbohydrates (fermentation)
They produce short chain fatty acids
Which is used as energy by colon cells
Or absorbed into blood to increase lipogenesis

Question 6

Bacteria and gut morphology

Answer 6

• Increase mucus, reduce cell permeability, increase vascular flow, increase tissue repair,
• promote barrier integrity (most likely due to formation of short chain fatty acids)

Question 7

Bacteria and immune system

Answer 7

Influence maturation and development of lymphoid tissue;
Increases IgA,
Influence composition of t-cells in Latina propria

Question 8

Bacteria and nervous system

Answer 8

Influence synaptic connectivity

Question 9

Bacteria and bone homeostasis

Answer 9

Increases uptake of calcium in gut

Question 10

Difference in mixing movements between colon and small intestines

Answer 10

Usually more sluggish → peristaltic propulsive movements

Question 11

Summarise peristalsis in colon

Answer 11

→ less frequent only 2 times per day typically after a meal installed in stomach or duodenum
→ waves produce mass movement in which largo segment of colon constricts vigorously forcing contents towards rectum
→abnormal irritation of mucosa also triggers colon movements

Question 12

Name the four factors in contractile activity of colon

Answer 12

1. Intrinsic smooth muscle properties
2. Intrinsic nerves
3. Extrinsic nerves
4. Circulating or locally released chemicals.

Question 13

How long does it tater for a meal to reach caecum

Answer 13

4 hours (on average undigested remnants of a meal reach hepatic flexure in 6 hours,splenic flexurer in 9 hours and pelvic colon in 12 )
25% of residues of 9 meal may be in rectum after 72 hours and remain up to 9 week

Question 14

How does defaercation initialer

Answer 14

Distention of rectum initiates signals that spread over myenteric plexus to cause peristaltic waves in descending colon, sigmoid and rectum
When peristaltic wave nears anus - internal sphincter relaxes

Question 15

What is involved in defection reflex

Answer 15

Involves sacral spinal cord and can occur independently of higher nervous control
Impulses elicited in rectum are transmitted to spinal cord and then back to colon and rectum via parasympathetic fibres - Nervi erigentes

Question 16

What is contained in faeces

Answer 16

• Inorganic material
• Bile pigments
• indigested plant fibres
• bacteria= few in ejejenum and even fewer in ileum, many in colon
• water

Question 17

What is constipation

Answer 17

Bowel movement less than 3 times per week = if Faeces in colon for too long = will become dry as water is absorbed

Question 18

What are the causes of constipation

Answer 18

• Prolonged inhibition of defection reflex
• lack of tone in smooth muscle fibres of colon and spasms of muscle layer of larger intestine
• slight anorexia and mild abdominal discomfort may result.

Question 19

What it are the consequences of diarrhoea

Answer 19

• Dehydration - hypovolaemia and shock with cardiovascular collapse

Question 20

What is appendix

Answer 20

Extension of bowel

Question 21

What are the inner appendix layers

Answer 21

Submucosa, muscularis, and serosa layer