Development of midgut and hindgut

Question 1

What does the midgut develop into?

Answer 1

Duodenum, distal to bile duct
Ileum
Jejunum
Caecum, appendix
Ascending colon
Transverse colon, proximal 2/3

Question 2

What is the blood supply of the midgut?

Answer 2

Superior mesenteric artery

Question 3

How does the midgut develop?

Answer 3

Elongates a lot

Forms a loop

Herniates into umbilical cord

Rotates

Enters abdominal cavity again

Caecal bud descends

Question 4

Why does the midgut form a loop?

Answer 4

Because as it elongates, it runs out of space

Question 5

What is the structure of the midgut loop?

Answer 5

Cranial end and caudal end

Superior mesenteric artery at its axis

Question 6

What is the name of the midgut loop?

Answer 6

Primary intestinal loop

Question 7

Why does the midgut herniate?

Answer 7

Because as it elongates and forms a loop

it runs out of space

Question 8

How does the midgut loop rotate?

Answer 8

270degrees anti-clockwise

Question 9

What is the arrangement of the midgut loop after rotation?

Answer 9

Cranial end is to the left

Caudal end is to the right

Question 10

What is the effect of the rotation of the midgut loop?

Answer 10

Means that cranial end of midgut loop returns to abdominal cavity first
moving to left side

And that caudal end lies anterior over cranial end

Question 11

Where is the caecal bud initially located?

Answer 11

To the right

at the level of the duodenum

Question 12

Where does the caecum descend to?

Answer 12

To the level of the inferior ileum

Question 13

What is recanalisation?

Answer 13

Cell death in walls of primitive gut tube to increase the lumen of the primitive gut tube

Question 14

Why does the lumen of the primitive gut tube need to be increased by recanalisation?

Answer 14

Because cell growth in walls of primitive gut tube
can be so rapid
that the lumen becomes narrow, closed up

Question 15

What structures commonly require recanalisation?

Answer 15

Oesophagus

Bile duct

Duodenum, ileum, jejunum

Question 16

What does the hindgut develop into?

Answer 16

Transverse colon, distal 1/3
Descending colon
Sidmoid colon
Rectum
Anal canal, superior part
Epithelium of urinary bladder

Question 17

What is the blood supply of the hindgut?

Answer 17

Inferior mesenteric artery

Question 18

Where does the inferior mesenteric artery arise from?

Answer 18

Abdominal aorta

Question 19

What forms the superior part of the anal canal?

Answer 19

Hindgut

Question 20

What forms the inferior part of the anal canal?

Answer 20

Proctodeum

Question 21

What is the proctodeum?

Answer 21

Depression in the ectoderm that lines the cloaca

Question 22

What is the cloacal membrane made up of?

Answer 22

Endoderm lining primitive gut tube

Ectoderm lining proctodeum

Question 23

What is the line that marks the division of the superior and inferior parts of the anal canal?

Answer 23

Pectinate line

Question 24

What is the difference between the epithelial lining of the superior and inferior parts of the anal canal?

Answer 24

Superior part is lined by simple columnar epithelium

Inferior part is lined by stratified squamous epithelium

Question 25

What is the difference between the blood supply of the superior and inferior parts of the anal canal?

Answer 25

Superior part is supplied by inferior mesenteric artery

Inferior part is supplied by pedundal artery

Question 26

What is the difference between the innervation of the superior and inferior parts of the anal canal?

Answer 26

Superior part of anal canal is innervated by sympathetic least splanchnic nerve, parasympathetic pelvic splanchnic nerves

Inferior part of anal canal is innervated by pudendal nerve

Question 27

What is the difference between the sensory functions of the superior and inferior parts of the anal canal?

Answer 27

Superior part of anal canal can only detect stretch

Inferior part of anal canal can detect temperature, pressure, pain

Question 28

What are the openings of the primitive gut tube?

Answer 28

Foregut and hindgut have no openings

Midgut has an opening to the yolk sac at the umbilicus

Question 29

How is the midgut related to the yolk sac?

Answer 29

Midgut is connected to yolk sac

Question 30

What connects the midgut to the yolk sac?

Answer 30

Vitelline duct