Thoracic Cavity Development Flashcards
Pleural cavities
space where lungs develop and persist
Pericadial cavity
space where heart develops and persists
Peritoneal cavity
space where abdominal viscera develops and persists
What will the septum transversum become?
central tendon of the thoracic diaphragm
Where does the septum transversum come from?
head fold
When and where does the horseshoe-shaped cavity develop?
during 4th week in the lateral mesoderm
What body cavity does the cranial end become?
pericardial
Where does the heart start out at in development? What must occur?
cranial end, embryo must undergo head fold to bring the pericardium ventrocaudally to take its position anterior to the foregut
What do the mesenteries do during development?
1) convey blood vessels, nerves and lymphatics to organs
2) divides the peritoneal cavity into right and left halves
3) parietal peritoneum (covers body wall)
4) visceral peritoneum (covers organs)
What splits lateral mesoderm into somatic plate and splanchnic plate?
coelomic cavity
Briefly describe the events of lateral folding
1) 2 caudal limbs fold ventrally (big hug)
2) pinches off the yolk sac
3) 2 ends fuse giving rise to peritoneal cavity
4) the gut tube (remnant of yolk sac) is suspended by 2 layers of mesenteries (dorsal and ventral)
What are mesenteries?
double layer of peritoneum that extends from the abdominal wall
Which mesentery is the permanent structure that provides the route for vasculatures, nerves and lymphatics to the developing organs?
dorsal
What happens to the ventral mesentery?
- disappears and becomes continuous with liver and becomes the falciform ligament and lesser omentum
How does the peritoneal cavity form?
lateral folding and fusing of the 2 caudal limbs ventrally
What term is used for intraembryonic coelom after embryonic folding?
pericardioperitoneal canals
Where are the pericardioperitoneal canals?
- lies lateral to foregut (future esophagus)
- dorsal to septum transversum
- each canal forms different partition
Partitions in each pericardioperitoneal canals are formed due to what event?
developing bronchial buds
What are the two partitions the pericardioperitoneal canals will form?
1) cranial ridges - pleuropericardial folds
2) caudal ridges - pleuroperitoneal folds
Which folds are superior to developing lungs?
pleuropericardial folds (cranial ridges) - separate pleural from pericardial cavities
Which folds are inferior to developing lungs
pleuroperitoneal folds (caudal ridges) - separate pleural from peritoneal cavities
Describe the development events that involve cranial ridges
- right and left cranial folds come out from the somatic wall of the thoracic cavity and become ridges
- the ridges merge to form the pleuropericardial membrane that separates the pericardial and pleural cavities
- phrenic nerve gets caught in the folds
Describe the development events that involve caudal ridges
- develops after the cranial ridges
- right and left start on the caudal side and move cranially to form the right and left pleuroperitoneal membranes
- do not fuse together (unlike cranial ridges), but with dorsal mesentery of the esophagus and the septum transversum
- separates pleural cavity and peritoneal cavity
What does the pleuroperitoneal membrane merge with to help form the diaphragm?
septum transversum
Which layer does the phrenic nerve get caught up in and what happens to it?
- pleuropericardial
- becomes part of the fibrous pericardium (somatic mesoderm)
Which pleuroperitoneal fold needs to close last?
left side
What does the diaphragm develop from?
1) septum transversum
2) pleuroperitoneal membranes
3) dorsal mesentery of the esophagus (along with 2 vessels - vena cava and aorta)
4) muscular ingrowth from the lateral body walls
What are the two congenital diaphragmatic hernia?
1) posterolateral defect - pleuroperitoneal of the left side did not fuse with the central tendon of the diagphragm
2) congenital hiatal hernia - can occur with esophagus or stomach (ie stomach may be up in the thorax)
