Thoracic Cavity Development Flashcards
What is the intraembryonic coelom?
The primordium of embryonic body cavities
Where does the horseshoe shaped cavity develop from?
The lateral mesoderm
What does the cranial end of the intraembryonic coelom form?
Future pericardial cavity
What way does the cranial ends of the intraembryonic coelom fold?
Head fold, brings the pericardium and heart VENTROCAUDALLY, to get heart to its position ANTERIOR to the forgut
What do the caudal limbs of the intraembryonic coelom form?
- Future pleural and peritoneal cavities
- results in a gut tube suspended b/w 2 layers of mesentary
When do the caudal limbs lose connection with the extraembryonic coelom? Why?
- 10th week of development
- developing intestines return to the body cavity
In what direction do the caudal limbs fold?
- folds in the horizontal plane
- brings two caudal limbs VENTRALLY, and fuses to form the peritoneal cavity
What is mesentary?
Double layer of peritoneum that extends from abdominal wall
Dorsal mesentary
permanent structure, persists in entire body
Ventral mesentary
anything attached to the liver, remains attached to the caudal part of the foregut
What is the function of the mesentary?
Divides the cavity into right and left halves; conveys blood vessels, nerves, and lymphatics to organs
What is the pericardioperitoneal canal?
Term for intraembryonic coelem after embryonic folding
Where is the pericardioperitonal canal located?
- lateral to foregut
- dorsal to the septum transversum
What does the septum transversum develop into?
The central tendon of the thoracic diaphragm
What causes partitions to form in each pericardioperitoneal canal? What are these partitions/
- Developing bronchial buds
Partitions = cranial ridges (pleuropericardial folds); caudal ridges (pleuroperitoneal folds)
What do the pleuropericardial membranes contain?
- common cardinal veins
- phrenic nerve
What is the function of the common cardinal veins?
drains the primordial venous system into the sinus venosus of the primordial heart
Pleural cavities expand ventrally around the heart and splits the mesenchyme into what?
Thoracic wall and fibrous pericardium (contains the phrenic nerve)
How and when is the primordial mediastinum formed?
- The pleurocardial membranes fuse with the ventral mesenchyme
- Occurs by the 7th week
What happens in the 6th week of development to the pleuroperitoneal membranes?
The membranes extend VENTROMEDIALLY and fuse with the dorsal mesentary of the esophagus and septum transversum
(pleural and parietal cavities are separated)
What assists the closure of the pleuroperitoneal membranes?
the migration of myoblasts into the pleuroperitoneal membrane
What does the diaphragm develop from? (4)
- septum transversum
- pleuroperitoneal membranes
- dorsal mesentary of esophagus
- muscular ingrowth from lateral body walls
Diaphragm innervation
- myoblasts migrate into pleuroperitoneal membrances from 2-5 cervical myotomes and carry their nerves
- nerves pierce pleuropericardial membranes
Where is the phrenic nerve located?
On the fibrous pericardium
