Development Of The Foregut

Question 1

Where does the foregut start and end?

Answer 1

Distal oesophagus
To
Halfway along the duodenum (1st and 2nd parts of the duodenum are foregut)

Question 2

Where does the midgut start and end?

Answer 2

Halfway along the duodenum (just distal to the entrance of the bile duct – 3rd and 4th parts of duodenum are midgut)
To
Junction of the proximal 2/3 of the transverse colon with the proximal 1/3 (first 2/3 of the transverse colon are midgut)

Question 3

Where does the hindgut start and end?

Answer 3

Distal 1/3 of the transverse colon
To
Upper anal canal

Question 4

What is the arterial supply of the foregut?

Answer 4

Coeliac trunk

Question 5

What is the sympathetic and parasympathetic innervation for the foregut?

Answer 5

S: Greater splanchnic n. (T5 – T9)
P: Vagus

Question 6

Where is visceral pain of the foregut felt?

Answer 6

Epigastric region

Question 7

What is the arterial supply of the midgut?

Answer 7

Superior mesenteric artery

Question 8

What is the sympathetic and parasympathetic innervation for the midgut?

Answer 8

S: Lesser splanchnic n. (T10-11)
P: Vagus

Question 9

Where is visceral pain of the midgut felt?

Answer 9

Umbilical region

Question 10

What is the arterial supply of the hindgut?

Answer 10

Inferior mesenteric artery

Question 11

What is the sympathetic and parasympathetic innervation for the hindgut?

Answer 11

S: Least splanchnic n. (T12 +/- L1) and lumbar splanchnic nerves
P: Pelvic splanchnics

Question 12

Where is visceral pain of the hindgut felt?

Answer 12

Suprapubic region

Question 13

What does the bilaminar disc develop from?

Answer 13

Develops from the inner cell mass

Question 14

What happens in gastrulation?

Answer 14

Primitive streak forms on the epiblast

Epiblast cells migrate to the primitive streak and invaginate through it

Some cells displace the hypoblast and form the endoderm

Some cells create a new layer between the epiblast and endoderm = mesoderm

Epiblast = ectoderm

Question 15

What does the ectoderm layer give rise to?

Answer 15

CNS and PNS
Skin, hair and nails
Pituitary gland, sweat glands, tooth enamel

Question 16

What does the mesoderm layer give rise to?

Answer 16

Muscle, cartilage and bone
Urogenital system, spleen and adrenal cortex
Connective tissue of the gut wall, pancreas and liver
Visceral peritoneum

Question 17

What does the endoderm layer give rise to?

Answer 17

Epithelium of the GI tract, respiratory tract
Hepatocytes (cells of the liver)
Endocrine and exocrine cells of the pancreas

Question 18

What does inner cell mass develop into?

Answer 18

Human beings

Question 19

What does outer cell mass develop into?

Answer 19

Placenta

Question 20

What can failure of closure of the ventral body wall in the thoracic region lead to?

Answer 20

Ectopia cordis

Question 21

What can failure of closure of the ventral body wall in the abdomen lead to?

Answer 21

Gastroschisis

Question 22

What can failure of closure of the ventral body wall in the pelvic region lead to?

Answer 22

Bladder exstrophy

Question 23

What does the foregut develop into?

Answer 23

Oesophagus
Stomach
First half of the duodenum (1st and 2nd parts)

Question 24

What are the derivatives of the foregut?

Answer 24

Liver
Pancreas

Question 25

What are the mesenteries of the foregut?

Answer 25

Dorsal mesentery
Ventral mesentery

Question 26

What is the ventral mesentery?

Answer 26

Arises from the septum transversum

The liver grows into it, and splits it into the lesser omentum and the falciform ligament

Question 27

What is the lesser omentum?

Answer 27

Connects the liver to the stomach and duodenum

Question 28

What is the falciform ligament?

Answer 28

Connects the liver to the anterior abdominal wall

Question 29

What type of muscle does the upper 2/3 of the oesophagus contain?

Answer 29

Striated muscle

Question 30

What type of muscle does the lower 1/3 of the oesophagus contain?

Answer 30

Smooth muscle

Question 31

What is the upper part of the oesophagus innervated by?

Answer 31

Vagus nerve

Question 32

What is the lower part of the oesophagus innervated by?

Answer 32

Splanchnic nerves

Question 33

What happens to the stomach during embryonic development?

Answer 33

This section of the gut tube starts to dilate in week 4

Changes shape due to different rates of growth of different parts

Changes position – rotates 900 clockwise around its long axis: brings the left side to lie anteriorly and the right side to lie posteriorly

Brings duodenum to the right

Question 34

What happens to the liver during embryonic development (Day 25-32)?

Answer 34

Liver bud is an outgrowth from the distal foregut (endoderm epithelium) - appears in week 3

Cells proliferate - grow into the septum transversum

Connection between the liver bud and foregut (duodenum) narrows > bile duct

Question 35

What happens to the liver during embryonic development (Day 36+)?

Answer 35

Small outgrowth from the bile duct > gallbladder

As the liver grows, the remaining mesoderm either side becomes membranous > falciform ligament and lesser omentum

Question 36

What happens to the pancreas during development?

Answer 36

Dorsal and ventral buds arise from the duodenum

Dorsal bud develops in the dorsal mesentery

Rotation of the stomach swings the ventral bud posteriorly

Dorsal and ventral buds fuse

Question 37

What are the final positions of the foregut viscera?

Answer 37

Rotation of the stomach brings its left side to lie anteriorly and swings the duodenum to the right

The dorsal mesentery along the greater curvature bulges down and grows – the greater omentum.
This becomes fixed to the mesentery of the transverse colon (and posterior wall).

Rotation alters the position of the mesenteries, omenta and peritoneal ligaments

Some organs are brought into contact with the posterior abdominal wall (e.g., the pancreas and duodenum) and become retroperitoneal

A small space behind the stomach – the lesser sac – is formed