Title Embryonic Development and Pregnancy.pdf ✅

01 NOTES HUMAN REPRODUCTION BIOLOGY POST IMPLANTATION EVENTS, PARTURITION, LACTATION Key Takeaways • Parturition • Lactation • Post implantation events » Gastrulation » Formation of placenta » Gestation » Foetal ejection reflex Prerequisites • Steps involved in the formation of the embryo 01 Transfer of gametes Ovum and sperms are transported to the ampulla region of the fallopian tube 02 Fertilisation Fusion of ovum and sperm to form zygote 03 Development of zygote Zygote undergoes cleavage and gives rise to blastocyst 04 Implantation The blastocyst gets embedded in the endometrium of uterus
02 Transfer of gametes Fertilisation Development of zygote Implantation Ampulla Sperm nucleus Inner cell mass Trophoblast Late Blastocyst Trophoblast Endometrium of uterus Inner cell mass (Embryoblast) Post Implantation Events • The blastocyst formed after mitotic division of the zygote gets implanted into the endometrium of the uterus. • Blastocyst has two types of cell layers: » Outer trophoblast » Inner cell mass or embryoblast • Placenta formation and gastrulation are important processes that follow implantation. Trophoblast Endometrium Placenta Inner cell mass Germinal layers + Gastrulation The process by which the inner cell mass gives rise to a structure with various germinal layers is known as gastrulation. Gastrulation

04 • These germinal layers further give rise to various organs and organ systems. Germinal layers Ectoderm Mesoderm Endoderm Ectoderm (external layer) Mesoderm (middle layer) Skin cells of epidermis Neurons Pigment cells Cardiac muscle cells Skeletal muscle cells Tubule cells of the kidney Red blood cells Smooth muscle cells (in gut) Endoderm (internal layer) Lung cell (alveolar cell) Thyroid cells Digestive cells