Lecture 2: Body Folding and Cavities

Question 1

Where does the intraembryonic coelom (cavity) appear?

Answer 1

Between the lateral plate of the mesoderm

*horse-shoe shaped

Question 2

What does the intraembryonic coelom (cavity) divide?

Answer 2

Divides lateral mesoderm into:

1) Somatic (parietal) layer
2) Splanchnic (visceral) layer

Question 3

What does the somatic (parietal) layer line?

Answer 3

Body wall

Question 4

What does the splanchnic (visceral) layer line?

Answer 4

Body gut

Question 5

Describe the consequences of cranial folding.

Answer 5

Cranial folding happens much faster compared to rest of the embryo, allowing:

1) Moves oropharyngeal membrane (future mouth) to correct position
2) Moves primordial heart and surrounding structures to correct position
3) Endoderm is incorporated into foregut

Question 6

After cranial folding, what happens to the intraembryonic coelom?

Answer 6

Has 3 portions:

• Pericardial cavity (ventral)
• 2 Pericardioperitoneal canals (dorsal) on each side of foregut

Question 7

Describe the consequences of caudal folding.

Answer 7

1) Primitive Streak now caudal to cloacal membrane
2) Moves cloacal membrane (future anus) to correct position
3) Endoderm is incorporated into hindgut

Question 8

What folding is happening in the median plane?

Answer 8

Cranial/Caudal Folding

Question 9

What folding is happening in the horizontal plane?

Answer 9

Lateral Folding

Question 10

Describe the consequences of lateral folding.

Answer 10

Umbilical vesicle is compressed and pinches off.

Eventually the gut tube is enclosed.

Question 11

What is gastroschisis?

Answer 11

Birth defect of the abdominal wall

• Baby’s intestines are found outside of the body right of umbilical cord (not midline)
• Organs are uncovered, which is bad because amniotic fluid is corrosive to the organs

Question 12

What is congenital epigastric hernia?

Answer 12

Birth defect of the abdominal wall

• Midline bugle of abdominal wall
• Bowel is not exposed to amniotic fluid and is covered by skin

Question 13

What is the function of the pericardioperitoneal canals?

Answer 13

Connects pericardial cavity to peritoneal cavity

Question 14

What is the function of dorsal mesentery?

Answer 14

Suspends caudal foregut, midgut, and hindgut in peritoneal cavity

Question 15

What does the septum transversum eventually become?

Answer 15

Central tendon of diaphragm

Question 16

Where is the pericardioperitoneal canals located compared to the septum transversum?

Answer 16

Pericardioperitoneal canals is DORSAL to septum transversum

*and lateral to foregut

Question 17

What is the function of the pleuropericardial folds?

Answer 17

Separates heart from lungs and lungs from each other

Question 18

What is the function of the pleuroperitoneal folds?

Answer 18

Separates abdomen from lungs

Question 19

With what structures do the pleuroperitoneal folds fuse with to close the canal?

Answer 19

Dorsal mesentery of esophagus and septum transversum

Question 20

What are the function of myoblasts migrating into the pleuroperitoneal folds?

Answer 20

Completes closure of pleuroperitoneal folds

Question 21

What embryological structures make up the diaphragm?

Answer 21

1) Septum transversum: central tendon
2) Pleuroperitoneal membranes: primordial diaphragm
3) Dorsal mesentery: median portion of diaphragm
4) Myoblasts: Crura of diaphragm

Question 22

What innervates the diaphragm?

Answer 22

Phrenic Nerve (ventral rami C3-C5)

Question 23

What is a congenital diaphragmatic hernia?

Answer 23

Defect of diaphragm

• Viscera will bulge into pleural cavity
• lung maturation may be delayed
• left side typically impacted