Jejunum, Ilium and the Large Intestines

Question 1

Name the abdominal organs of the foregut

Answer 1

Oesophagus to mid-duodenum, liver, gall bladder, spleen and half of the pancrease

Question 2

Name the organs of the mid gut

Answer 2

Mid-duodenum to proximal 2/3rds of transverse colon, and the other half of pancreas

Question 3

What are the organs of the hindgut?

Answer 3

Distal 1/3rd of transverse colon to proximal 1/2 of anal canal

Question 4

Explain how the Jejunum and Ilieum are attached to abdominal wall.

Answer 4

They hang from the posterior wall by mesentery which contains branches of superior mesenteric artery, superior mesenteric vein, lymphatic vessels and nerves.

Question 5

Describe the different characteristics of the jejunum and Ileum

Answer 5

Jejunum - Wide, more plica circulates (small folds that increase surface area), has MALT (mucosa associated lymphoid tissue and no peyer’s patches.

Ilium - Narrow, fewer plica circulates and has MALT and Peyer’s patches (lymph tissue opposite mesentery attachment)

Question 6

What are the functions of the large intestines?

Answer 6

Fluid-electrolyte balance (absorbs fluid and salts) and it dries out the chyme to form faeces

Question 7

Describe some of the characteristic features of the large intestine

Answer 7

• Longitudinal smooth muscle fibres thicken to form three taenia coli which are shorter than large intestine (which compress laterally to give haustra)
• Omental Appendices which are tags of fat (more frequent distally)
• Lacks Peyer’s patches (lymphoid tissue)

Question 8

Describe features of the caecum

Answer 8

Its the first and widest part of the large intestine which is continuous with ascending colon. It is covered by peritoneum but isn’t attached by mesentery. Has appendix attached

Question 9

What is the Ileocaecal valve and explain its function

Answer 9

It consists of 2 horizontal folds of mucous membrane that project around the orifice of the ileum. It limits the reflux of colonic contents into the ileum.

Question 10

Describe features of the vermiform appendix

Answer 10

• It is a diverticulum from the posteromedial aspect of the caecum. Its submucosa is filled with lymphoid tissue.
• It lies posterior to the convergence of 3 taeniae coli but can be in different anatomical positions.

Question 11

Describe the most common area where the appendix lays.

Answer 11

It is found most often at McBurney point, this is 1/3 along the oblique line joining the right ASIS to the umbilicus

Question 12

Describe features of the ascending colon

Answer 12

It lies between the caecum and hepatic flexure and is retroperitoneal. The right paracolic gutter is formed between this and the posterior abdo wall

Question 13

Describe features of the transverse colon and flexures

Answer 13

It is suspended by the transverse mesocolon and is intraperitoneal so can move freely. It is between the hepatic flexure and splenic flexure

Question 14

Describe features of the descending colon

Answer 14

It is retroperitoneal. Attached to sigmoid colon. Left paracolic gutter formed between left side of descending colon and posterior abdo wall.

Question 15

Describe features of the signmoid colon

Answer 15

It is intraperitoneal and is suspended by the sigmoid mesocolon (very long which makes it a risk for volvulus, which is twisting of mesentery) Continuous with the rectum in front of S3

Question 16

Describe features and functions of the rectum

Answer 16

It is retroperitoneal that begins at S3 and ends at the dip of the coccyx. It lacks taenia, haustra or appendices epiplocia and stores faeces.

Question 17

Name the three midline branches of the abdominal aorta

Answer 17

1) Coeliac trunk which supplies the foregut.
2) Superior mesenteric artery (L1) which supplies the midgut organs.
3) Inferior mesenteric artery (L3) which supply the hindgut organs.

Question 18

Name what the lateral branches of the abdominal aorta supply

Answer 18

• Kidneys/adrenal glands,
• Gonads,
• Posterolateral abdominal wall

Question 19

Name the branches of the superior mesenteric artery

Answer 19

• Inferior pancreaticoduodenal artery,
• Middle colic artery (supplies transverse colon)
• Right colic artery (supplies ascending colon),
• ileocolic branches,
• Jejunal and ileal arteries,
• Appendicular (supplies apendix)

Question 20

Describe the differences between the Jejunal and Ileal arteries

Answer 20

Jejunal - One or two arcades with long vasa recta in its mesentery.

Ileal - Many arcades with short vasa recta in its mesentery.

Question 21

Name the branches of the inferior mesenteric artery

Answer 21

• Left colic artery (supplies splenic flexure and descending colon)
• Sigmoid arteries,
• Superior rectal artery

Question 22

Name the arterial anastomoses between the SMA and IMA and its clincal significance

Answer 22

The Marginal Artery of Drummond. It can prevent intestinal ischaemia

Question 23

Describe the blood supply of the rectum and anal canal

Answer 23

• Since the hindgut extends to the proximal half of the anal canal then this is supplied by the superior rectal artery.

The remainder of the anal canal is supplied by the internal iliac artery

Question 24

Describe the lymphatic drainage and movement of fats

Answer 24

Peyer’s patches then to mesenteric nodes then to superior mesenteric nodes then to intestinal trunk, then cisterna chylii. Fats are absorbed lacteals and then trained to lymph vessels to the cisterna chylii

Question 25

Blood from the foregut drains to?

Answer 25

The splenic vein which drains to hepatic portal vein

Question 26

Where does blood from the mid gut drain to?

Answer 26

The superior mesenteric vein which then drains to the hepatic portal vein

Question 27

Where does blood from the hindgut drain too?

Answer 27

The inferior mesenteric vein which then drains to the splenic vein which then drains to the hepatic portal vein

Question 28

Describe the nerve supply of the foregut

Answer 28

• Nerves from coeliac trunk; Sym from greater splanchnic nerve (T5-9) and PSym from vagus. Referred pain is therefore felt by areas supplied by coeliac trunk = epigastric region (T6-9)

Question 29

Describe the nerve supply of the midgut

Answer 29

Superior mesenteric ganglia; Sym from lesser splanchnic (T10-11) and PSym from vagus. Referred pain is therefore felt at the periumbilical region (T10-11)

Question 30

Describe the nerve supply of the hindgut

Answer 30

Inferior mesenteric ganglia; Sym from least splanchnic and lumbar splanchnic nerves (T12-L3) and PSym from S2-S4 and therefore referred pain is referred to the suprapubic region (T12) as visceral sensory afferents run with sympathetics