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DEVELOPMENT OF BODY CAVITIES
SEGMENTATION
At the end of third week, the intra embryonic mesoderm on each side
of the mid line differentiates into
Paraxial portion
Intermediate portion
Lateral plate.
When the clefts appear in the Lateral plate mesoderm, the plates
are divided into two layers,
Somatic/ parietal layer
Splanchnic / visceral layer.
The space bordered by these layers forms the intra embryonic / body cavity. At first the left and right sides of intra
embryonic cavity are in open connection with the extra embryonic cavity / chorionic cavity, but when the body of
embryo folds cephalocaudally and laterally, this connection is lost (after 10TH week). In this manner, a large intra
embryonic cavity extending from the thoracic to the pelvic region is formed
Division of intraembryonic body cavity
The intra embryonic cavity initially is horse shoe-shaped and gives rise
to three well defined body cavities during fourth week
1. Pericardial cavity
2. Two pericardioperitoneal canals (future pleural cavities)
3. Peritoneal cavity
During head folding, the heart and pericardial cavity move ventro cuadally,
anterior to the fore gut; the pericardioperitoneal canals pass dorsolateral to the
foregut and dorsal to the septum transversum
( a thick plate of mesoderm that occupies the space between the thoracic cavity and yolk stalk.)
A pair of folds / membranes in lateral wall of each pericardioperitoneal
canal develops (pleuropericardial and pleuroperitoneal membranes)
separating the canals from pericardial and peritoneal cavities
respectively. The canals enlarge due to growth of lung buds and
are converted into pleural cavities.
Differentiation of Intra embryonic Mesoderm,
Lateral Foldings and
Intraembryonic Coelome (Body Cavity) during
weeks 3 and 4 as seen in transverse sections
Craniocaudal Foldings and its effects
on endoderm-lined cavity (gut)
and cardiogenic area during week 3 and 4
as seen in mid sagital sections
With the continued growth of the lungs the
pleural cavities are pushed forward in the body-wall
toward the ventral median line, thus separating the
pericardium from the lateral thoracic walls
Development of Diaphragm
1. Septum transversum
2. Pleuroperitoneal membranes
3. Dorsal mesentery of oesophagus
4. Muscular ingrowth from parietal body walls
The thoracic aspect of the diaphragm of a newly born child in which the communication between the peritoneum and
pleura has not been closed on the left side; the position of the opening is marked on the right side by the spinocostal
hiatus