GI ANATOMY

Question 0

Why is the way the abdominal organs are contained advantageous in function?

Answer 0

Allows protection of organs whilst still allowing flexibility for respiration, posture and locomotion.

Question 1

How are the abdominal organs contained?

Answer 1

Diaphragm superiority, musculoaponeurotic walls laterally, pelvic muscles inferiorly.
Musculoaponeurotic walls are supported superiorly by the thorax and inferiorly by the pelvic girdle.

Question 2

What is the mechanism of increasing intra-abdominal pressure? What functions does the increase in pressure allow?

Answer 2

Voluntary or reflexive contraction of the muscular roof and floor and musculoaponeurotic walls of the abdomen.
Allows expulsion of air from the thorax and expulsion of liquid (urine/vomit) or solid (faeces, flatus or foetuses) from the abdominopelvic cavity.

Question 3

What type of epithelia makes up the peritoneum?

Answer 3

Both layers of peritoneum consist of a single layer of squamous epithelial cells - mesothelium.

Question 4

From which embryological tissue does parietal peritoneum originate?

Answer 4

Somatic mesoderm.

Question 5

From which embryological tissue does visceral peritoneum originate?

Answer 5

Splanchnic mesoderm.

Question 6

Explain the concept of visceral referred pain.

Answer 6

Nocioceptors (2 primary sensory neurones) from several locations converge on a single ascending tract in the spinal cord. Convergence of visceral afferents with somatic afferents at a secondary sensory neurones. Skin is the usual stimulus rather than the viscera so the pain is felt over the corresponding dermatomes.

Question 7

What is the name given to the doubling up of the visceral peritoneum between the stomach and other organs?

Answer 7

Omenta.

Question 8

What is the name given to the doubling up of the visceral peritoneum between other organs and the posterior abdominal wall?

Answer 8

Mesentery.

Question 9

What is the fate of the dorsal mesogastrium?

Answer 9

Persists in jejeunum and ileum as mesentery
NOT ASCENDING COLON (secondarily retroperitoneal)
Persists in transverse colon as transverse mesocolon
NOT DESCENDING COLON (secondarily retroperitoneal)
Persists in sigmoid colon as sigmoid mesocolon
NOT RECTUM

Question 10

Which viscera are retroperitoneal?

Answer 10

Suprarenal glands
Aorta/ IVC
Duodenum
Pancreas
Ureters
Colon (ascending and descending)
Kidneys
Esophagus
Rectum

Question 11

How superiorly does the abdominal cavity extend?

Answer 11

4th intercostal space.

Question 12

What are the contents of the RUQ?

Answer 12

Superior ascending colon, right transverse colon, right lobe of liver, gall bladder, pylorus, D1-3, head of pancreas, right kidney and supra renal gland, hepatic flexure.

Question 13

What are the contents of the LUQ?

Answer 13

Left lobe of liver, spleen, stomach, jejeunum, proximal ileum, body and tail of pancreas, left kidney and supra renal gland, splenic flexure, left transverse colon, superior descending colon.

Question 14

What are the contents of the RLQ?

Answer 14

Caecum, appendix, ileum, inferior ascending colon, right ovary, right uterine tube, ureter, spermatic cord, urinary bladder.

Question 15

What are the contents of the LLQ?

Answer 15

Sigmoid colon, inferior descending colon, left ovary, uterine tube, ureter, spermatic cord, urinary bladder.

Question 16

What are the layers of the anteriolateral abdominal wall, superficial to deep?

Answer 16

Skin
Camper's fascia
Scarpa's fascia
Superficial investing fascia
External oblique
Intermediate investing fascia
Internal oblique 
Deep investing fascia
Transversus abdominis
Tranversalis fascia
Extraperitoneal fat
Parietal peritoneum

Question 17

What are the borders of Hasselbach’s triangle?

Answer 17

Floor - inguinal ligament
Roof - inferior epigastric vessels
Medially - rectus abdominis

Question 18

What are the borders of the inguinal canal?

Answer 18

Anterior - external oblique
Roof - internal oblique, transversus abdominis
Posterior - transversalis fascia
Floor - inguinal and lacunar ligament

Question 19

How is the likelihood of herniation decreased by the arrangement of the inguinal canal?

Answer 19

Deep and superficial rings don’t overlap - lie obliquely.

When intra abdominal pressure is increased, the posterior wall is forced against the anterior wall to close the canal.

Question 20

Into which compartments does the transverse mesocolon divide the abdominal cavity? How are these compartments further divided?

Answer 20

Supracolic

Infracolic - root of mesentery of small intestine divides this into left and right

Question 21

What are the paracolic gutters?

Answer 21

Free communication between supracolic and infracolic regions, grooves between ascending or descending colon and posterior abdominal wall.