Large Intestines

Question 1

What cells line the large intestine?

Answer 1

Columnar epithelium

Question 2

Function of the large intestines

Answer 2

• proximally removes water from indigestible gut contents > turns chyme into a semi solid
• distally acts as temporary storage until defaecation
• production of vitamins
• microbiome for commensals bacteria

Question 3

Describe the large intestines in relation to the peritoneum

Answer 3

• ascending + descending colon are retroperitoneal
• transverse colon has its own mesentery > transverse mesocolon
• sigmoid colon has its own mesentery
• upper 1/3 of rectum: intraperitoneal
• middle 1/3 of rectum: recto peritoneal
• lower 1/3 of rectum: no peritoneum

Question 4

Arterial blood supply to the caecum

Answer 4

Ileo-colic artery form SMA

Question 5

Arterial blood supply to the ascending colon

Answer 5

Right colic artery from SMA

Question 6

Arterial blood supply to transverse colon

Answer 6

Middle colic artery from SMA

Question 7

Arterial blood supply to descending colon

Answer 7

Left colic artery

Question 8

Arterial blood supply to upper 1/3 of rectum

Answer 8

Superior rectal artery

Question 9

What makes up the large intestine?

Answer 9

Caecum to anal canal

Question 10

What is the venous drainage of the midgut?

Answer 10

Superior mesenteric vein

Question 11

What is the venous drainage of the hindgut?

Answer 11

Inferior mesenteric vein

Question 12

What is the venous drainage of the rectum?

Answer 12

• upper 1/3 into superior rectal vein
• middle + lower 1/3s into systemic venous system

Question 13

Describe the process of water absorption in the colon

Answer 13

• facilitated by ENaC which are induced by aldosterone
• mainly in proximal colon
• tighter tight junctions > allows for bigger gradient to form + less back diffusion of ions

Question 14

How many parts of the colon are there?
Name them

Answer 14

5 parts
Caecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon

Question 15

What are the paracolic gutters?

Answer 15

The paracolic gutters lie lateral to the ascending + descending colons
Between them and the abdominal wall on either side

Question 16

What is the clinical significance of paracolic gutters?

Answer 16

Allow passage of fluids from different compartments in the abdomen
e.g. ruptured ectopic pregnancy blood can fill up the parabolic gutters

Question 17

Name the structure that connects the transverse colon to the posterior wall of the abdomen

Answer 17

Transverse mesocolon

Question 18

Name the structure between the transverse colon and the stomach

Answer 18

Gastrocolic ligament

Question 19

Why can a patient with a ruptured ectopic pregnancy present with shoulder pain?

Answer 19

• Blood can press against the diaphragm
• diaphragm is innervated by phrenic nerve
• phrenic nerve - C3,4,5
• dermatomes of C3,4,5 are at the shoulder