Development in humans begins as a fertilized egg undergoes cell division and differentiation through defined stages. The embryonic period involves cleavage of the zygote, formation of the blastula and gastrula stages. Gastrulation restructures the embryo's morphology through cell migration, producing the three germ layers - ectoderm, endoderm and mesoderm. Organogenesis follows, as the germ layers differentiate into specific tissues and organs through both cell movements and differentiation. Growth continues post-embryonically until maturity is reached.

1. DEVELOPMENT
IN HUMANS

2. DEVELOPMENTAL BIOLOGY:-
• It is the field of biology that deals with study of
development of an organism from its earlier
beginning to its maturity.
• Dynamic process.
• Two ways: 1)sexually and 2)asexually.
• Two distinct phases : 1)Embryonic period and
2) Post embryonic period.
• Embryology :Development in embryonic period.

3. GAMATOGENESIS:-

4. FERTILIZATION:-
1. Sperm contacts the egg
2. Sperm or its nucleus enters the egg
3. Egg becomes activated and developmental
changes begin
4. Sperm and egg nuclei fuse

5. CLEVAGE:-
• ZYGOTE
• MORULA
• BLASTULA
• GASTRULA

6. GASTRULATION:-
• A phase early in the development of most animal embryos,
during which the morphology of the embryo is dramatically
restructured by cell migration.
• These cellular movements are called morphogenetic movements.
• Two types: 1) Epiboly and 2) Emboly
• Emboly –
• Invagination is the local inward movement of cells from a cavity.
• Involution is similar, but more dramatic. It is an inward expansion
of epithelial cells around an edge such as the blastpore.
• Ingression is the movement of individual cells from an epithelium
into an embryonic cavity.

7. • The three layers produced by gastrulation are
called embryonic germ layers
• The ectoderm
• Forms the outer layer of the gastrula
• The endoderm
• Lines the embryonic digestive tract
• The mesoderm
• Partly fills the space between the endoderm
and ectoderm

8. ORGANOGENESIS:-
• Differentiation of primary germ layers into tissues
and organs.
• Organogenesis is the period of animal
development during which the embryo is
becoming a fully functional organism capable of
independent survival .
• It is the process by which specific organs and
structures are formed, and involves both cell
movements and cell differentiation.

9. Major derivatives of the embryonic germ layers

10. GROWTH:-