Paraxial mesoderm contributes to development of ?
Ans. is 'c' i.e., Skeletal muscles The intraembryonic mesoderm located on each side of notochord proliferate and is arranged in three columns : (i) paraxial mesoderm (immediately lateral to notochord); (ii) intermediate mesoderm (just lateral to paraxial mesoderm); and (iii) lateral plate mesoderm (more laterally placed mesoderm). Small spaces appear in lateral plate mesoderm which later fuse to form intraembryonic coelom. This space divides the lateral plate mesoderm into : (i) an outer parietal layer (somatopleuric mesoderm) continous with mesoderm covering the amnion, and (ii) an inner visceral layer (splanchnopleuric mesoderm) continous with mesoderm covering the yolk sac. During 2nd month the intraembryonic coelom is divided into three cavities : (i) pericardial cavity (ii) pleural cavity, and (iii) peritoneal cavity. Somatopleuric mesoderm forms the parietal layer of these cavities (i.e., parietal pericardium, perietal layer of pleura and parietal peritoneum) and splanchnopleuric mesoderm forms the visceral layer of these cavities. Paraxial mesoderm differentiates into somites. By the end of 20th day, the first pair of somites have formed in neck region. After this, about 3 pairs of somites are formed per day and by the end of 5th week about 42-44 somite pairs are formed (4-occipital, 8-cervical, 12-thoracic, 5-lumbar, 5-sacral and 8-10 cooccygeal). Somites are fuher differentiated into :? Dermatomyotome :- Give rise to skeletal muscles and dermis. Sclerotomes :- Give rise to veebral column. Sclerotomes which surround notochord stas projecting posteriorly (dorsally) to surround neural tube and forms. Ventral sclerotomes :- Give rise to veebral body and annulus fibrosus. Lateral sclerotomes :- Give rise to veebral arch (pedicle and lamina). Dorsal sclerotomes :- Give rise to spinous process. The notochord forms the nucleus pulsosus.
Parietal peritoneum
Visceral peritoneum
Skeletal muscles
Peritoneal cavity