GENERAL EMBRYOLOGY Dr Shivarama Bhat EVENTS DIFFERENTIATION OF

GENERAL EMBRYOLOGY Dr Shivarama Bhat

EVENTS • DIFFERENTIATION OF INTRA EMBRYONIC MESODERM • SOMITE FORMATION • INTRA EMBRYONIC COELOME • SEPTUM TRANSVERSUM • FATE OF SOMITES

GASTRULATION WITH NOTOCHORD

NEURULATION

SUB DIVISIONS OF IEMD • PARAXIAL MESODERM. • INTERMEDIATE MESODERM. • LATERAL PLATE MESODERM.

SUBDIVISIONS OF IEMD

INTRA EMBRYONIC COELOME • SMALL SPACES APPEAR AND COALESCE TO FORM INTRAEMBRYONIC COELOME. • IT IS HORSE SHOE SHAPED. • COMMUNICATES WITH EXTRA EMBRYONIC COELOME ON EITHER SIDE. • BENT PORTION LIES INFRONT OF PROCHORDAL PLATE. • IEC DEVELOPS INTO BODY CAVITIES – PERICARDIAL, PLEURAL AND PERITONEAL CAVITIES.

INTRA EMBRYONIC COELOME

INTRA EMBRYONIC COELOME

LATERAL PLATE MESODERM • 2 PARTS – SOMATOPLEURIC AND SPLANCHNOPLEURIC. • Splanchnopleuric mesoderm – muscles of viscera. • Somatopleuric layer – muscles of body wall, limb muscles.

SEPTUM TRANSVERSUM • DEVELOPS FROM IEMD CRANIAL TO PROCHORDAL PLATE. • IEMD BETWEEN THE CRANIAL TO PROCHORDAL PLATE AND IEC IS CARDIOGENIC AREA.

INTERMEDIATE MESODERM • GIVES RISE TO GENITO URINARY SYSTEM.

PARAXIAL MESODERM • DIFFERENTIATES TO FORM SOMITES. • THESE SOMITES FURTHER DIFFERENTIATES TO GIVE RISE TO SCLEROTOME, MYOTOME AND DERMATOME. • IN TOTAL 44 SOMITES ARE FORMED BY 5 WEEKS, WHICH ARE FORMED IN CAUDOCRANIAL DIRECTION. • 8 CERVICAL, 12 THORACIC, 5 LUMBAR, 5 SACRAL AND 8 -10 COCCYGEAL SOMITES. • CRANIAL TO CERVICAL, OCCIPITAL SOMITES ARE FORMED. • SOMITIOMERES ARE POORLY DIFFERENTIATED SOMITES.

SOMITES

SOMITE FORMATION

DIFFERENTIATION OF SOMITES

DERIVATIVES OF SOMITES • SCLEROTOME FORMS – VERTEBRA AND NEURAL ARCH. • MYOTOME – MUSCLES AROUND VERTEBRA. • DERMATOME – SKIN. • OCCIPITAL SOMITES – MUSCLES OF TONGUE. • SOMITOMERES – EXTRA OCULAR MUSCLES.

QUESTIONS • SOMITES. • INTRA EMBRYONIC COELOME. • ENUMERATE THE DERIVATIVES OF SOMITES. • LATERAL PLATE MESODERM.