Where does the embryonic body cavity created?
The embryonic body cavity is created within the space between the parietal mesoderm and visceral mesoderm (divisions of lateral plate mesoderm).
How is the anterolateral body wall closed?
How is the gut tube formed?
The anterolateral body wall is closed by the midline fusion of the ectoderm and parietal mesoderm.
The gut is formed by the midline fusion of the endoderm and visceral mesoderm, which is then surrounded by the parietal mesoderm-lined body cavity.
What is mesothelium?
Mesothelium consists of simple squamous cells forming srous membranes lining internal body cavities. It is formed by mesenchymal cell differentiation from both layers of mesoderm.
What is included in the endoderm-lined gut tube and where can the primitive heart tube be found?
The endoderm-lined gut tube includes the foregut, hindgut, and interconnecting midgut (not labeled).
The primitive heart tube can be found in the pericardial cavity, adjacent to the foregut.
What structure suspends the gut tube from the posterior body wall into the body cavity, and what forms this structure?
The dorsal mesentery suspends the gut tube from the posterior body wall into the body cavity and it is formed by the continuity of the parietal mesoderm with the visceral mesoderm.
What is the septum transversum and what is it made of?
What organ begins as a bud that invaginates into this structure?
The septum transversum is a wedge of visceral mesoderm that separates the distal foregut, midgut, and hindgut from the pericardial cavity. It also horizontally separates the pericardial cavity from the primitive abdominal cavity.
The liver buds from the septum transversum.
How does the lung bud arise?
The lung bud arises by invaginations of the distal foregut endoderm.
What are the consequences of obliterating the yolk sac?
The closure of the gut tube is initially incomplete where the vitelline duct connects the midgut to the yolk sac. Also, the vitelline duct and opbliterated yolk sac become incorporated into the connecting stalk and undergo degeneration.
What is the role of the pericardioperitoneal canals and where are they located?
The pericardioperitoneal canals are located on each side of the foregut and they maintain continuity between the pericardial and peritoneal cavities as growth of the liver progresses into the septum transversum.
What structures project into the pericardial cavity during the growth of the lung bud?
What do these projections become and what do they do?
Pleuropericardial folds project as small ridges into the pericardial cavity during growth of the lung buds.
They eventually thin and transform into pleuropericardial membranes which eventually fuse vertically and separate the central pericardial cavity from the bilateral pleural cavity.
What is the parietal pleura formed from and what does it do?
What is the visceral pleura formed from and what does it do?
The parietal pluera is formed from the parietal mesoderm and it lines the pleural cavities.
The visceral pleura is formed from the visceral mesoderm and it covers the lungs.
What structure becomes the central tendon of the diaphragm?
Where does the muscular part of the diaphragm grow into and which somites do these myoblasts come from?
The septum transversum becomes the central tendon of the diaphragm.
Myoblasts from somites C3-C5 form the muscular part of the diaphragm which surround the central tendon and grows into the pleuroperitoneal membranes.
What nerves grows into the pleuropericardial folds and septum transversum during formation of the diaphragm?
From what spinal cord segments does this nerve arise from?
The phrenic nerves arises from spinal cord segments C3-C5 and grows into the pleruopericardial folds and septum transversum during formation of the diaphragm.
What nerves innervate the diaphragm? Explain why.
The phrenic nerves innervate most of the diaphragm and the lower thoracic spinal nerves innervate the peripheral diaphragm, since the most peripheral part of the muscular diaphragm is formed by myoblasts from the parietal mesoderm of the thoracic wall.
Why can a congenital diaphragmatic hernia be fatal?
A congenital diaphragmatic hernia is caused by failure of one or both of the pleuroperitoneal membranes to close the pericardioperitoneal canals. This allows the peritoneal and pleural cavities to be continuous with each other, thus allowing abdominal visceral (intestine, stomach, spleen, etc) to enter the thoracic cavity, push the lungs anteriorly, and compress the lungs. Also, sometimes a small part of the muscular fibers of the diaphragm fails to develop as a result of this.