Embryology 1

Question 1

When does embryonic folding take place

Answer 1

Week 4

Question 2

Consequences of lateral folding

Answer 2

Creates ventral body wall

Primitive gut tube becomes tubular

Question 3

Consequences of craniocaudal folding

Answer 3

Creates cranial and caudal pockets from yolk sac endoderm

Question 4

Divisions of the primitive gut tube

Answer 4

Foregut
Midgut
Hindgut

Question 5

When does the primitive gut tube begin to develop

Answer 5

Week 3 when it pinches off from the yolk sac cavity

Question 6

Where does the primitive gut tube run from and to

Answer 6

From the stomatodeum to the proctodeum

Question 7

What is the opening of the primitive gut tube called and where is it

Answer 7

Vitelline duct at the umbilicus

Question 8

What are the origins of the internal and external lining of the primitive gut tube

Answer 8

Internal lining - endoderm

External lining - splanchnic mesoderm

Question 9

What is the intraembryonic coelom/ coelomic cavity

Answer 9

Cavity created between the somatic and splanchnic mesoderm layers which the primitive gut tube is suspended in

Question 10

Adult derivatives of foregut

Answer 10

Oesophagus 
Stomach
Pancreas
Liver 
Gall bladder 
Duodenum proximal to entrance of bile duct

Question 11

Adult derivatives of midgut

Answer 11

Duodenum distal to entrance of bile duct 
Jejunum
Ileum
Caecum
Ascending colon
Proximal 2/3 transverse colon

Question 12

Adult derivatives of hindgut

Answer 12

Distal 1/3 transverse colon
Descending colon
Sigmoid colon
Rectum
Upper anal canal 
Internal lining of bladder and urethra

Question 13

Blood supply of foregut

Answer 13

Celiac trunk

Question 14

Blood supply and innervation of midgut

Answer 14

Superior mesenteric artery and vein

Parasympathetic - vagus nerve
Sympathetic - superior mesenteric ganglion and plexus

Question 15

Blood supply and innervation of hindgut

Answer 15

Inferior mesenteric artery and vein

Parasympathetic - pelvic nerve (S2-4)
Sympathetic - inferior mesenteric ganglion and plexus

Question 16

Adult derivative of somatic mesoderm surrounding the gut

Answer 16

Muscles and fascia of abdominal wall

Question 17

Adult derivative of splanchnic mesoderm surrounding the gut

Answer 17

Smooth muscle of gut wall

Question 18

How does the linea alba form

Answer 18

Progression of lateral folding leads to the 2 sides of the developing anterolateral abdominal wall to meet in the midline

Question 19

What is the inguinal canal and what does it allow in males

Answer 19

Oblique through the layers of the abdominal wall

In males, it allows passage of developing testes into the scrotum

Question 20

What is an inguinal hernia

Answer 20

Abdominal contents push against the inguinal canal and herniate through as it is a potential site of weakness

Question 21

What is an umbilical hernia

Answer 21

Congenital malformation

Abdominal contents push against the umbilicus and herniate through as it is a potential site of weakness

Question 22

How is the intraembryonic coelom divided and by what

Answer 22

Diaphragm divides the intraembryonic coelom into the:
Abdominal cavity
Thoracic cavity

Question 23

What connects the primitive gut tube to the abdominal wall

Answer 23

Dorsal mesentery - foregut, midgut and hindgut to the roof of the abdominal cavity
Ventral mesentery - foregut to the floor of the abdominal cavity

Question 24

What do the dorsal and ventral mesenteries in the foregut region divide the peritoneal cavity into

Answer 24

Greater peritoneal sac (left)

Lesser peritoneal sac (right)

Question 25

What is an omentum

Answer 25

A double layered extension/fold of peritoneum that passes from the stomach and proximal duodenum to adjacent abdominal organs

Question 26

What is the greater omentum

Answer 26

4 layered peritoneal fold that descends from the greater curve of the stomach, folds back, and attaches to the anterior transverse colon and its mesentery (Formed from dorsal mesentery of stomach)

Question 27

What is the lesser omentum

Answer 27

Double layered peritoneal fold that connects the lesser curvature of the stomach and proximal duodenum to the liver It's made up of the hepatogastric and hepatoduodenal ligaments (Formed from ventral mesentery of stomach)

Question 28

How do the omenta form

Answer 28

Rotation of the stomach

Question 29

How is the greater curvature of the stomach created

Answer 29

Dorsal border of stomach grows faster than the ventral border

Question 30

What axes does the primitive stomach rotate about

Answer 30

Longitudinal | Anteroposterior

Question 31

Consequences of stomach rotation

Answer 31

Original left side becomes anterior (greater sac) Original right side becomes posterior (lesser sac) Vagus nerve lies anterior/posterior instead of left/right Shifts cardia and pylorus from the midline Creates the greater omentum

Question 32

What is meant by a peritoneal reflection

Answer 32

A change in direction/reflections of peritoneum - mesentery to visceral peritoneum (and vice versa) - mesentery to parietal peritoneum (and vice versa)

Question 33

What determines the mobility of abdominal contents

Answer 33

Whether it has a mesentery or not

Question 34

Define retroperitoneal organs and give some examples

Answer 34

Were never in the peritoneal cavity and therefore don't have a mesentery E.g kidneys, aorta, oesophagus

Question 35

Define secondary retroperitoneal organs and give some examples

Answer 35

Began development invested by peritoneum and had a mesentery but with progressive growth the mesentery is lost by fusion at the posterior abdominal wall E.g ascending colon, descending colon, duodenum

Question 36

Why is the duodenum secondary retroperitoneal

Answer 36

Rotation of the stomach pushes the duodenum against the posterior abdominal wall because the liver is so large

Question 37

How is fusion fascia created

Answer 37

Peritoneum of the posterior abdominal wall is squished together with the duodenum and its mesentery and grows over it, creating fusion fascia

Question 38

How can the duodenum be made mobile

Answer 38

Removal of fusion fascia (avascular so no damage)

Question 39

What happens to the duodenum during weeks 5-6

Answer 39

Lumen is obliterated due to rapid growth of its lining | It's recanalised by the end of the embryonic period (before week 9)

Question 40

When and where is the respiratory diverticulum created

Answer 40

Week 4 | In the ventral wall of the foregut at the junction with the pharyngeal gut

Question 41

What does the respiratory diverticulum become and how

Answer 41

Ventrally - respiratory primordium Dorsally - oesophagus Divided by the tracheoesophageal septum

Question 42

Incidence of abnormal positioning of the tracheoesophageal septum

Answer 42

Up to 1 per 3000 live births

Question 43

Which foregut derived glands are formed in the ventral mesentery

Answer 43

Liver Biliary system Ucinate process and inferior head of pancreas

Question 44

Which foregut derived glands are formed in the dorsal mesentery

Answer 44

Superior head, neck, body and tail of pancreas

Question 45

What does the liver develop from

Answer 45

Hepatic bud