Growth
stage of cell growth
Morphogenesis
development of shape and size that is controlled by gene expression
Differentiation
cells turn on specific genes to form organs and tissues with specialized function
What week does folding occur?
Four
Median/Longitudinal Head Folding
- the brain moves posterior–> cranially, and this causes the heart and the septum transversum to move anterior
- endoderm will become foregut of the GI
- ST develops central tendon of the diaphragm
- after folding, the intra coelom lies anterior to the heart and superior to the ST, and can communicate with the extra coelom
Median/Longitudinal Tail Folding
- as the embryo grows, caudal eminence projects over the cloacal membrane
- endodermal layer becomes the hind gut of the GI
- SC overgrows the tail, and pushes the cloaca and connecting stalk on the anterior side
- lastly, the allantois is partially incorporated into the embryo
Horizontal Folding
- endoderm becomes mid gut of GI
- anterior fusion f the lateral folds helps reduce distance between intra/extra coelom to aid in communication, but this stops once the somatic layer fuses (pinches off)
The intra and extra coelom communication helps to give rise to….
body cavities
Mesenteries
suspend the organs
Somatic mesoderm lines _____. Splanich mesoderm lines ____.
- Posterior body wall
2. Endoderm
Ectopia Cordis
- issue with horizontal folding (somatic layers pinch off with heart outside) where the heart gets trapped outside of the body
- the sternum is bifed, there is no pericardium, susceptible to disease, can be surgically corrected
Pericardial cavity
- heart (folds so that the ST is caudal to it)
- the two pericardial coelom come together to form the cavity, and the two endocardial primordial fuse to form one heart tube
Pericardioperitoneal canals
partitions form in each canal:
1. Separate pericardial cavity from the pleural cavities (heart from lungs)
2. Separate pleural cavities from peritoneal cavity
(lungs from abdomen)
*the portion of the embryonic celom that joins the pericardial cavity to the peritoneal cavity, developing into the pleural cavities.
Pleural cavities
lungs
Peritoneal cavity
abdomen
The heart tube is lined by ___ pleura. The pericardial cavity is lined by ___ pleura.
- Visceral
2. Parietal
What separates the pericardial and pleural cavities?
pleuropericardial folds/membrane (somatic layer of LP)
Between which two membranes do lungs develop?
pleuropericardial membrane and pleuroperitoneal membrane
The ST fuses with the pleuroperitoneal membrane to form the ____.
Diaphragm
Somatopleure
somatic mesoderm overlying embryonic ectoderm form body wall
Splanchnopleure
splanchnic mesoderm & underlying embryonic endoderm form embryonic gut
