ANAT Development of the Midgut & Hindgut - Week 3

Question 1

Is the stomach intra, retro or secondarily retro?

Answer 1

Intra.

Question 2

Is the liver intra, retro or secondarily retro?

Answer 2

Intra.

Question 3

Is the spleen intra, retro or secondarily retro?

Answer 3

Intra.

Question 4

Is the aorta intra, retro or secondarily retro?

Answer 4

Retro.

Question 5

Is the IVC intra, retro or secondarily retro?

Answer 5

Retro.

Question 6

Is the kidney intra, retro or secondarily retro?

Answer 6

Retro.

Question 7

Is the pancreas intra, retro or secondarily retro?

Answer 7

Secondary.

Question 8

What structure forms the axis of midgut rotation?

Answer 8

SMA.

Question 9

Explain reason for physiological umbilical hernia at birth.

Answer 9

Growth must occur outside of the abdominal cavity, due to a lack of space within the abdomen. Referred to as a physiological umbilical hernia.
Midgut actually extends into the umbilicus during development – it is thus normal, during development, to have the intestines ‘outside’ the abdominal cavity. However, if the gut tube does not retreat from umbilicus, the infant may be born with their intestines ‘outside’ the abdominal cavity.

Question 10

During cranial-caudal folding which limb grows faster and how does this affect rotation? What structures develop from the caudal limb? The cranial limb?

Answer 10

Due to cranial-caudal development, cranial limb grows faster than caudal limb – driving rotation inferiorly.
So caudal limb actually sits superior to cranial limb in an adult. Caudal limb = transverse colon and cranial limb = small intestines.

Question 11

What are the two ligaments which attach to the cranial & caudal limbs and anchor them?

Answer 11

Ligament of Treitz = Suspensory Ligament of Duodenum – derived from skeletal diaphragm & smooth muscle duodenal fibres (for cranial limb).
Phrenico-colic ligament - suggests attachment of caudal limb to diaphragm and colon (for caudal limb).

Question 12

Final positions of the cranial & caudal limbs during development and structures formed?

Answer 12

Cranial limb falls to the R side forming the small intestine (following on from the duodenum).
Caudal limb falls to the L & remains attached to the posterior abdominal wall – forming L 1/3 of the transverse colon & descending & sigmoid colon.

Question 13

To which structures does the stomach’s greater omentum sticks to in the midgut/hindgut?

Answer 13

Transverse colon.

Question 14

Greater omentum functions

Answer 14

Greater omentum actually has the ability to migrate to wall off an infection in the abdominal area and limit its spread. This can trigger pain signals, due to twisting and pressure applied to arteries, veins & nerves held within the greater omentum & depending on amount of movement required, may become a medical emergency.

Question 15

What does the development of the appendix lead to?

Answer 15

Appendix develops in an inferior direction, actually causing the ascending colon to descend along the right side of the abdomen.

Question 16

Pain radiation from appendicitis & relationship to embryology.

Answer 16

Pain from appendix can be experienced anywhere across either RUQ OR RLQ. This is due to variation in appendix’s anatomical position, indicating of embryological transition from R hypochondriac to R iliac region.

Question 17

Structure which separates the bladder & rectum in normal adults.

Answer 17

Urorectal septum.

Question 18

What occurs if the cloaca is not separated?

Answer 18

Faeces w consistency of bird droppings.

Question 19

What dermal layer (embryologically) lines the gut tube?

Answer 19

Endoderm.

Question 20

How is the pectinate/dentate line formed?

Answer 20

Invagination of the ectoderm.

Question 21

Symptoms of hernia above pectinate line

Answer 21

Feeling of fullness/incomplete emptying.

Question 22

Symptoms of hernia below pectinate line.

Answer 22

Excruciating pain upon each bowel movement.

Question 23

Epithelium above pectinate line

Answer 23

Columnar.

Question 24

Epithelium below pectinate line

Answer 24

Stratified squamous.

Question 25

Arterial supply above pectinate line.

Answer 25

Sup rectal artery.

Question 26

Arterial supply below pectinate line.

Answer 26

Inf rectal artery.

Question 27

Lymphatic drainage above pectinate line

Answer 27

Internal iliac nodes.

Question 28

Lymphatic drainage below pectinate line.

Answer 28

Inguinal nodes.

Question 29

Innervation above pectinate line - visceral/parietal.

Answer 29

Visceral.

Question 30

Innervation below pectinate line - visceral/somatic.

Answer 30

Somatic.