Quiz 2 - Thoracic Embryology

Question 1

Intraembryonic coelem (body cavity) needs to be divided into ___ cavities

Answer 1

4 (3 in the thorax - the pericardial cavity and two pleural cavities for the lungs; 1 abdominal peritoneal cavity)

Question 2

septum transversum

Answer 2

• a thickened sheet of somatic mesoderm that initially lies at the CRANIAL margin of the trilaminar germ disc
• eventually becomes the central tendon of the diaphram

Question 3

during longitudinal folding, where does the septum transversum move?

Answer 3

-moves between the developing heart/primitive body cavity and the yolk sac

Question 4

when longitudinal folding is complete, what has the septum transversum accomplished?

Answer 4

-it has divided the intraembryonic coelem into a more cranial pericardial cavity, and a more caudal peritoneal cavity

Question 5

what allows communication between the pericardial and peritoneal cavities?

Answer 5

-the pericardioperitoneal canals on either side of the foregut

Question 6

what do the pericardioperitoneal canals become?

Answer 6

-the pleural cavities, when the lungs grow into them

Question 7

pleuropericardial membranes

Answer 7

• extensions of the parietal layer of the lateral plate mesoderm
• grow into the cavity from the ventral and lateral body wall (along coronal plane)
• contain the common cardinal veins and the PHRENIC nerves

Question 8

what separates the pleural cavities from the pericardial cavity?

Answer 8

-the pleuropericardial membranes fuse with each other and with the root of the lung

Question 9

eventually, the pleuropericardial membranes become what?

Answer 9

-the fibrous pericardium

Question 10

what 5 embryonic structures form the diaphragm and how?

Answer 10

1. septum transversum: gives rise to central tendon of diaphragm
2. pleuroperitoneal membranes: fuse with the septum transversum and dorsal mesentary of esophagus, separating the thoracic and abdominal cavities
3. dorsal mesentary of esophagus: gives rise to the crura of diaphragm
4. body wall: muscular ingrowth from body wall forms periphery of diaphragm
5. cervical somites (C3-C5): give rise to most of the diaphragmatic musculature

Question 11

after longitudinal folding, where does the septum transversum temporarily lie?

Answer 11

-the cervical region, where HYPAXIAL myoblasts from the C3-C5 somites migrate into it

Question 12

main innervation of the diaphragm

Answer 12

-the phrenic nerve (C3-C5; runs ANTERIOR to root of lung)

Question 13

costal rim innervation and why is it not the phrenic nerve

Answer 13

• lower intercostal nerves

- this is because the lateral edges of the diaphragm develop from the body wall

Question 14

congenital diaphragmatic hernia (CDH)

Answer 14

• failure of the pericardioperitoneal canals to close

- inferiorly allows abdominal viscera to herniate into the chest

Question 15

eventration of diaphragm

Answer 15

• congenital
• failure of the muscular body wall to extend to the pleuroperitoneal membrane on the affected side
• fibroelastic tissue replaces the missing muscular tissue, but this isn’t strong enough to prevent the underlying viscera from pushing the hemidiaphragm into the thoracic cavity

Question 16

respiratory diverticulum (4th week of development)

Answer 16

• the respiratory diverticulum pouches out from the ventral wall of the foregut (endoderm; esophagus).
• this will eventually form the epithelial lining of the respiratory airway passages

Question 17

as it grows, to where does the diverticulum expand?

Answer 17

-it expands into the visceral layer of the lateral plate mesoderm that surrounds the gut tube

Question 18

what will the visceral layer of the lateral plate mesoderm surrounding the gut tube form?

Answer 18

• smooth muscle
• blood vessels
• connective tissues
• cartilages of trachea, bronchi, lungs
• visceral pleura

Question 19

parietal layer of lateral plate mesoderm becomes what?

Answer 19

• parietal pleura
• fibrous pericardium
• septum transversum

Question 20

tracheoesophageal ridge

Answer 20

-separates the respiratory diverticulum from the foregut/esophagus

Question 21

tracheoesophageal fistula (TEF)

Answer 21

• abnormal connection of the esophagus and trachea
• results from the incomplete formation of the tracheoesophageal ridge
• 1 in 3500 births
• many cases of TEF also involve esophageal atresia

Question 22

esophageal atresia

Answer 22

-failure of the esophagus to develop as a continuous passage (ends in a blind pouch)

Question 23

vesicles in lateral plate mesoderm –> ?

Answer 23

intraembryonic coelem (body cavity)

Question 24

intraembryonic coelem –> ?

Answer 24

pericardial cavity, pericardioperitoneal canals

Question 25

pleuropericardial membranes –> ?

Answer 25

fibrous pericardium –> separate pericardial and pleural cavities

Question 26

septum transversum + pleuroperitoneal membranes –> ?

Answer 26

separate thoracic and abdominal caities

Question 27

septum transversum –> ?

Answer 27

central tendon of diaphragm

Question 28

foregut –> ?

Answer 28

respiratory diverticulum –> lung buds –> parenchyma of lungs

*foregut also becomes epithelium of larynx, trachea, bronchi, lungs

Question 29

visceral layer of lateral plate mesoderm –> ?

Answer 29

stroma of lugs + visceral layer of pleura; also smooth muscle, blood vessels, CT of trachea, bronchi, lungs

Question 30

parietal layer of lateral plate mesoderm –> ?

Answer 30

parietal layer of pleura; fibrous pericardium; septum transversum

Question 31

paraxial mesoderm has what role in thoracic development?

Answer 31

–> somites –> myotome –> forms skeletal muscle of anterolateral trunk and diaphragm