Development of body cavities and diaphragm
Learning Objectives
At the end of lecture students should be able to
1.Recall the intra embryonic mesoderm and its parts
2.Know and understand the division of lateral plate mesoderm into visceral and parietal
layers enclosing intra embryonic caelome or body cavity
3.Know the cephalocaudal and transverse foldings of embryonic disc
4.Know the extent of intra embryonic coelom after folding and its divisions into three
serous cavities
5.Understand and know the derivatives of visceral and parietal layers of mesoderm
6.Know the pericardioperitoneal canals and their final fate
7.Know the development of diaphragm from various tissue
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.
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
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
Development of Diaphragm
1. Septum transversum
2. Pleuroperitoneal membranes
3. Dorsal mesentery of esophagus
4. Muscular in growth from parietal body walls