Large Intestine

Question 1

What are the 6 main parts of the large intestine called?

Answer 1

Cecum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon
Rectum

Question 2

What kind of enema is used as contrast in imaging of the large intesting

Answer 2

Barium enema

Question 3

What are haustra?

Answer 3

The haustra (singular haustrum) of the colon are the small pouches caused by sacculation, which give the colon its segmented appearance.

Question 4

What kind of valve is the ileoceacal valve?

Answer 4

flutter valve - one way

Question 5

During ileal distension is the ileoceacal valve open or closed?

Answer 5

open

Question 6

During caecal distension is the ileocaecal valve open or closed?

Answer 6

closed

Question 7

What is haustration?

Answer 7

Slow contractions of the circular muscle squeeze contents to and fro, as in segmentation

Question 8

What is a mass movement?

Answer 8

Occasionally (a few times a day), become organised into a peristaltic wave. Haustra briefly disappear as the mass movement sweeps by, then reform.

Question 9

What is the coordination of motility in the large intestine controlled by?

Answer 9

Most control is intrinsic, via the enteric nervous system.

Some parasympathetic control.

Question 10

Motility also affected by enteroendocrine and neurocrine influences, from cells releasing what?

Answer 10

5-HT and Peptide YY

Question 11

What reflexes can trigger mass movements?

Answer 11

Gastrocolic and orthocolic reflexes.

Question 12

What is an ileal brake?

Answer 12

The presence of undigested lipid in distal ileum and proximal colon releases peptide YY, slowing gastric emptying and small bowel peristalsis

Question 13

What is responsible for digestion in the colon?

Answer 13

Bacteria, not enzymes!

Question 14

When bacteria digest fibre, what is produced?

Answer 14

short chain fatty acids such as butyric acid, hydrogen, and methane.

Question 15

When bacteria digest urea and amino acids, what is produced?

Answer 15

ammonia

Question 16

When bacteria digest bilirubin, what is produced?

Answer 16

urobilinogen and stercobilins

Question 17

When bacteria digest cysetine and methionine, what is produced?

Answer 17

hydrogen sulphide

Question 18

How are short chain fatty acids absorbed by colonocytes?

Answer 18

Na+ linked transporter. important source of energy for colonocytes

Question 19

What are ENaC channels?

Answer 19

allow transcellular sodium transport

Question 20

What hormone is salt absorption in the colon stimulated by?

Answer 20

aldosterone

Question 21

Which 2 toxins increase cAMP?

Answer 21

cholera and E.coli

Question 22

What secretagogue does C.Dificile increase?

Answer 22

Ca2+

Question 23

What type of diarrhoea do cholera, E.coli and C.Dificile lead to?

Answer 23

secretory diarrhoea

Question 24

What is the balance of potassium in the colon determined by?

Answer 24

plasma [K+], adosterone and cAMP

Question 25

What type of muscle does the internal anal sphincter have?

Answer 25

smooth muscle

Question 26

What type of muscle does the external anal sphincter have?

Answer 26

skeletal muscle

Question 27

What is the dentate (pectinate) line?

Answer 27

Where the epithelium becomes stratified squamous

Question 28

As faeces enter the rectum, the pressure rises. What does this trigger?

Answer 28

reflex relaxation of the internal anal sphincter, and the urge to defaecate.

Question 29

What is the purpose of sitting or squatting to defecate?

Answer 29

Sitting or squatting increases the rectosigmoid angle, facilitating the passage of faeces.

Question 30

What provides the motive force of defecation?

Answer 30

Rectal peristalsis, sometimes triggering

a colonic mass movement, plus raised intraabdominal pressure (Valsalva manoeuvre)