Session 2: Embryology

Question 1

What is formed as the embryo folds?

Answer 1

Intrembryonic coelom

Question 2

What is the intramembryonic coelom divided into?

Answer 2

Abdominal and thoracic cavities from one large cavity

Question 3

What is special about the lining of the intrambryonic coelom?

Answer 3

It is lined by one membrane which specialise as the cavities specialises

• Pericardium
• Pleural membrane

Question 4

What surround the new primitive gut?

Answer 4

Splanchnic Mesoderm

Question 5

What is mesentary formed from?

Answer 5

Condensation of splanchnic mesoderm

Question 6

What suspends the entire gut tube from the dorsal body wall?

Answer 6

Dorsal Mesentary

Question 7

What is the only region covered by the ventral mesentary?

Answer 7

Foregut

Question 8

What do the dorsal and central mesentaries divide into in the region of the foregut?

Answer 8

Left and right sacs

Question 9

What does the left sac contribute into?

Answer 9

Greater sac

Question 10

What does the right sac becomes?

Answer 10

Lesser sac

Question 11

What is greater omentum formed from?

Answer 11

Dorsal mesentary

Question 12

What is the lesser omentum formed from?

Answer 12

Ventral mesentary

Question 13

What is peritoneal reflection?

Answer 13

Change of direction

• from parietal peritoneum to mesentery.
• From mesentery to visceral peritoneum

Question 14

What structures that are not suspended within the abdominal cavity called?

Answer 14

Retroperiotneal

-They were never in the peritoneal cavity and never had a mesentary

Question 15

What is described as secondarily retroperitoneal?

Answer 15

• Began development investe by the peritoneum
• Had mesentery but with successive growth and development of the GI tract, the mesentary is lost through fusion at posterior abdominal wall. (fusion fascia)

Question 16

Where does the foregut extend from and to?

Answer 16

Lung bud to the liver bud

Question 17

What form in the ventral wall of the foregut in the 4th at the junction with the pharyngeal gut?

Answer 17

Respiratory diverticulum

Question 18

Where does the liver and biliary system develop?

Answer 18

Ventral mesentary

Question 19

Where does the pancreas develop?

Answer 19

Components develop in both Ventral and dorsal

• Uncinate process and inferior head = ventral
• Superior head, neck, body and tail = dorsal

Question 20

What is the shape of the duodenum determined by?

Answer 20

Roatation of the stomach

Question 21

Why does the duodenum become secondary retroperitoneal?

Answer 21

Rotation of the stomach pushes duodenum to right then against the posterior abdominal wall

Question 22

How does the primitive gut becomes tubular?

Answer 22

The bro folds laterally to create the ventral wall body

Question 23

What is the effect of the embryo folding craniocaudally?

Answer 23

-Creates cranial and caudal pockets from yolk sac endoderm

Question 24

What is the gut tube?

Answer 24

• Endoderm lines tube
• Runs the length of the body
• Blind pouches at the head and tail ends
• Opening at the umbilicus
• Splanchnic mesoderm covering

Question 25

What the embryonic division of the gut?

Answer 25

- Foregut - Hindgut - Midgut

Question 26

What begins as blind diverticula?

Answer 26

Foregut and hindgut

Question 27

What embryonic division the gut is continuous with he yolk sac?

Answer 27

The midgut has an opening at first

Question 28

What does the foregut go on to form?

Answer 28

- Oesophagus - Stomach - Pancreas, Liver, and Gall bladder - Duodenum (proximal to entrance of bile duct)

Question 29

What does the midgut go on to form?

Answer 29

- Duodenum - Jejunum - Ileim - Cecum - Ascending Colon - Proximal 2/3 transverse colon

Question 30

What does the hindgut go on to form?

Answer 30

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

Question 31

What are the implications of the embryological origin on the blood supply?

Answer 31

Arterial supply reflects the embryonic development as each embryonic segment receives blood supply from distinct branch of the abdominal aorta

Question 32

What do structures near the junction of the foregut and midgut have?

Answer 32

They have mixed blood supply

Question 33

What is a mesentery?

Answer 33

Double layer of peritoneum suspending the gut tube from abdominal wall

Question 34

Why do we need mesenteries?

Answer 34

- Allows a conduit for blood and nerve supply | - Allows motility where needed

Question 35

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

Answer 35

Left and right sacs in the region of the foregut only

Question 36

What is the first structure seen when the abdominal cavity is opened anteriorly?

Answer 36

Greater omentum

Question 37

What does the free edge of the lesser omentum conduct?

Answer 37

Portal triad

Question 38

What are 2 secondary retroperitoneal structures of the foregut?

Answer 38

- Duodenum | - Pancreas