The Small and Large Intestine

Question 1

The first part of the small bowel is the duodenum which is mostly retroperitoneal. is it fixed or mobile?

Answer 1

position is fixed and constant

Question 2

The first part of the duodenum immediately beyond the pyloric sphincter is prone to peptic ulceration, why is this dangerous

Answer 2

the posterior wall lies directly in contact with a medium sized artery, the gastroduodenal artery.

Question 3

how is the rest of the small intestine, the jejunum and ileum attached to the posterior of the abdomen, is it mobile or fixed

Answer 3

by a mesentery and is relatively mobile

Question 4

What does the fact that the jejunum and ileum are mobile mean

Answer 4

This means that this part of the bowel is often involved in hernias and can become twisted (volvulus).

Question 5

The small bowel is the organ of nutrient absorption and needs a high surface area;
what are the four things that help achieve this

Answer 5

it is long,
the mucosa has multiple mucosal folds (plicae circulares), there are villi on the mucosal folds
and microvilli on each individual epithelial cell.

Question 6

The ileum is marked by

Answer 6

by the appearance of large submucosal lymph nodules known as Peyer’s patches.

Question 7

The artery to the mid-gut is the

Answer 7

superior mesenteric artery, it is a branch off the front of the aorta just below the coelic trunk and supplies from the 3rd part of the duodenum to two thirds of the way along the transverse colon.

Question 8

Where does the superior mesenteric artery come from and what does it supply

Answer 8

it is a branch off the front of the aorta just below the coelic trunk and supplies from the 3rd part of the duodenum to two thirds of the way along the transverse colon.

Question 9

what is Meckel’s diverticulum

Answer 9

Occasionally the ileum bears a blind-ended diverticulum about 1 meter from its termination (Meckel’s diverticulum) this is an embryonic remnant of the attachment of the mid gut loop to the yolk sac.

Question 10

To the right of the main superior mesenteric artery are branches to the colon;

Answer 10

the ileo-colic, right colic and middle colic branches

Question 11

Note that the arteries (of jejunum and ileum) have accompanying veins, trace these upwards to where they pass over the third part of the duodenum, here they pass through

Answer 11

the pancreas, join the splenic vein to form the portal vein, and pass onto the liver.

Question 12

what is the duodeno-jejunal flexure

Answer 12

the border between the duodenum and the jejunum,

Only after the duodenojejunal flexure does the small intestine become mobile.

Question 13

The large intestine starts at the

Answer 13

ileo-caecal valve in the right iliac fossa.

Question 14

the large intestine alternates between a retroperitoneal and a mesenteric disposition; the ascending and descending colon are normally

Answer 14

retroperitoneal

Question 15

the transverse and sigmoid colon lie within

Answer 15

a mesentery

Question 16

The outer longitudinal muscle layer forms three bands,

Answer 16

the taenia coli,

Between the longitudinal taenia coli the circular inner layer bulges repeatedly between them to form characteristic ‘haustrations’.
Away from the mesentry there are two rows of ear-like pads of fat; known as appendices epiploicia, these mark where the blood vessels penetrate the muscles of the bowel wall to supply the mucosa and sub mucosa.

Question 17

the taenia coli arrangement

Answer 17

start at the base of the appendix and broaden out and fuse to form a continuous layer at the recto sigmoid junction.

Question 18

what are appendices epiploicia and what do they mark

Answer 18

Away from the mesentry there are two rows of ear-like pads of fat; known as appendices epiploicia, these mark where the blood vessels penetrate the muscles of the bowel wall to supply the mucosa and sub mucosa.

Question 19

McBurney’s point

Answer 19

The appendix arises from the base of the caecum at a fairly fixed position, whose surface marking is referred to as McBurney’s point but its distal end may lie in a variety of positions within the abdomen or pelvis giving rise to a range of symptoms when it becomes inflamed and involves adjacent structures during appendicitis.

Question 20

The hind gut extends from

Answer 20

the distal third of the transverse colon to one third of the way down the anal canal

Question 21

What is the hindgut supplied by and where does thus arise

Answer 21

supplied by the inferior mesenteric artery which arises from the lower aorta just above the bifurcation

Question 22

The branches of the inferior mesenteric artery anastomose with each other and with a branch of the middle colic artery to form a vessel which runs along the wall of the colon

Answer 22

the marginal artery of Drummond.

Question 23

the superior rectal artery enters the pelvic cavity posterior to the rectum and lies where

Answer 23

in the mesorectum beween the rectum and the sacrum.Within the mesorectum it divides into three branches.

Question 24

Carcinoma of the colon and rectum are common in the western world. They spread directly via

Answer 24

the blood stream, through the portal circulation, to the liver but also through the lymph vessels to regional lymph nodes.

Question 25

Which vein drains blood from the colon and where does it flow to?

Answer 25

Inferior mesenteric vein drains into the splenic vein.

Question 26

Where does lymph from the small bowel drain?

Answer 26

Into the cisterna chyli and to the thoracic duct

Question 27

Which foodstuffs are absorbed through the lymphatic system?

Answer 27

Lipids

Question 28

What 4 anatomical features ensure the small bowel has a high surface area for absorption of nutrients?

Answer 28

Length, mucosal folds (plicae circularis), villi, micro-villi.

Question 29

Where is the junction between the mid gut and the hind gut?

Answer 29

2/3 of the way along the transverse colon.

Question 30

How do you distinguish a loop of large intestine from that of small intestine?

Answer 30

Large intestine has appendices epiploicae and tenea coli. The small bowel is centrally located and the colon round the sides.

Question 31

Which part of the bowel is supplied by sacral nerves 2, 3 and 4?

Answer 31

The hind gut.