GI Anatomy

Question 1

What are aponeuroses?

Answer 1

Sheets of tendon (take place of a tendon in flat muscles, forms the abdominal wall)

Question 2

Which muscles form the abdominal wall and what is their direction?

Answer 2

Rectus abdominis

Vertical

Question 3

Name the 3 layers of muscle that lie lateral to the rectus sheath, and give the direction of fibres.

Answer 3

External oblique (diagonally down and in)
Internal oblique (diagonally up and in
Transversus abdominis (transversely)

Question 4

From which muscle’s aponeuroses is the inguinal ligament formed?

Answer 4

External oblique
(Aponeuroses are sheets of tendon)

Question 5

Name the 9 anatomical regions of the abdomen.

Answer 5

Central (top to bottom): epigastric, umbilical, hypogastric/suprapubic
Lateral (top to bottom): hypochondrial, lumbar, iliac

Question 6

What is McBurney’s point?

Answer 6

Usual site of the base of the appendix

Question 7

What are the contents of the rectus sheath?

Answer 7

Rectus abdominis and pyramidalis muscles.

It is formed by the aponeuroses of the internal & external obliques, and the transversus abdominis muscles.

Question 8

Which embryological structure forms the ligamentum teres?

Answer 8

Umbilical vein
(Ligamentum teres = round ligament of the liver)

Question 9

Which artery supplies the foregut?

Answer 9

Coeliac trunk

Question 10

What is the foregut?

Answer 10

Mouth –> duodenum

Question 11

Which nerves supply the foregut?

Answer 11

Greater Splanchnic Nerve (T5-T9, sympathetic) and vagal trunks (CN 10, para-sympathetic)

Question 12

What are the four main areas of the stomach?

Answer 12

Cardia (level T11)
Fundus (often gas-filled)
Body
Pylorus

Question 13

Describe the anatomy and function of the greater omentum.

Answer 13

Hangs from the greater curvature of the stomach, folds back on itself and attaches to the transverse colon.
Contains many lymph nodes and may adhere to inflamed areas.
Therefore minimises spread of intraperitoneal infections.

Question 14

What is the venous drainage of the stomach?

Answer 14

Right and left gastric veins drain into the hepatic portal vein

Question 15

Anatomically, what are the 3 parts of the small intestine?

Answer 15

Duodenum, jejunum, ileum

Question 16

What are the four parts of the duodenum?

Answer 16

Superior, descending, inferior, ascending

• form ‘C’ shape which wraps around the head of the pancreas
• 25cm long

Question 17

Where do duodenal ulcers most commonly occur and what are the most common causes?

Answer 17

Superior duodenum

Helicobacter pylori infection and long-term NSAIDs

Question 18

What is the arterial supply of the duodenum?

Answer 18

Gastroduodenal artery (branch of coeliac trunk)
Inferior pancreaticoduodenal artery (branch of superior mesenteric)
 - the change of blood supply marks the change from the embryological foregut to the midgut

Question 19

What is the arterial supply of the jejunum and ileus?

Answer 19

Superior mesenteric artery (arises from aorta at L1)

Question 20

How are the vasa recta formed?

Answer 20

Superior mesenteric artery splits into approx. 20 branches.
Branches anastomose to form loops called arcades.
From the arcades long and straight arteries arise called vasa recta.

Question 21

What are the four anatomical parts of the large intestine?

Answer 21

Ascending, transverse, descending, sigmoid (40cm)

- total length = 150cm

Question 22

Describe the anatomy of the hepatic and splenic flexures.

Answer 22

Hepatic flexure = where the ascending colon turns 90 degrees to move horizontally and start the transverse colon (occurs when large bowel meets right lobe of liver)
Splenic flexure = where transverse colon turns 90 degrees to move inferiorly and start the descending colon (occurs when large bowel meets the spleen)

Question 23

Embryologically divide up the colon.

Answer 23

Ascending colon and proximal 2/3 of transverse colon are derived from the midgut.
Distal 1/3 of the transverse colon, descending and sigmoid are derived from the hindgut.

Question 24

Of the foregut, midgut and hindgut, which does the superior mesenteric artery generally supply?

Answer 24

Midgut-derived structures

Question 25

Of the foregut, midgut and hindgut, which does the inferior mesenteric artery generally supply?

Answer 25

Hindgut-derived structures

Question 26

Which nerve plexus supplies sympathetic, parasympathetic and sensory innervation to midgut-derived structures? (ascending colon and proximal 2/3 of transverse colon)

Answer 26

Superior mesenteric plexus

Question 27

Which nerve plexus supplies sympathetic, parasympathetic and sensory innervation to hindgut-derived structures? (distal 1/3 of the transverse colon, descending and sigmoid)

Answer 27

Inferior mesenteric plexus

• parasympathetic = pelvic splanchnic nerves
• sympathetic = lumbar splanchnic nerves

Question 28

The superior aspect of the anal canal has the same epithelial lining as the rectum, what is this?

Answer 28

Columnar epithelium

Question 29

Which line separates the anal canal into upper and lower parts?

Answer 29

Dendate/pectinate line

Question 30

What is the gut above the dendate line embryologically derived from?

Answer 30

Embryological hindgut

Question 31

What is the gut below the dendate line embryologically derived from?

Answer 31

Ectoderm of the proctodeum

Question 32

What epithelium lines the anal canal below the pectinate line?

Answer 32

Non-keratinised stratified squamous epithelium

Question 33

What is the arterial supply of the anal canal above the dendate line?

Answer 33

Superior rectal artery (branch of inferior mesenteric)

Question 34

What is the arterial supply of the anal canal below the dendate line?

Answer 34

Inferior rectal artery (branch of internal pudendal artery)