Embryology Introduction Gametogenesis INTRODUCTION Embryology Study of prenatal

Embryology Introduction & Gametogenesis

INTRODUCTION Embryology : Study of prenatal stages of development from the fertilization of the ovum to the birth of the new individual. üDescriptive Embryology üComparative Embryology üExperimental Embryology

Uses Helps us understand human anatomy better Helps us understand why some children are born with organs that are abnormal May help us prevent or treat such abnormalities

Introduction First 9 months of every individual spent within the womb During this period we develop from 1 cell to organism with billions of cells 2 stagesü Embryo- first 2 months ü Fetus- 3 rd month to birth

Subdivisions General embryology Systemic embryology

Haeckel's Dictum "ontogeny recapitulates phylogeny”

Descriptive terms of Position, Direction and Planes

MITOSIS

meiosis

CHROMOSOME NUMBER IN SOMATIC CELLS • MAN WOMAN • 44 XY 44 XX • 46 46

Chromosome number • Males 44+ x y females 44+xx • If gametes have the same no. ? • 44 xy+ 44 xx = 88 xxxy ?

GAMETES • OVUM • 22 X 44 XX FEMALE SPERM 22 X • OVUM • 22 X 44 XY MALE SPERM 22 Y

EMBRYO • Male gamete+ female gamete= embryo • Sperm + ovum = zygote (embryo)

Gonads & Gametes • Male gonad- Testis • Male gamete. Spermatozoa

Gonads & Gametes • Female gonad- Ovary • Female gamete. Ovum

Gametogenesis • Process of formation and development of specialized generative cells, called gametes or germ cells. • During this process chromosome number is halved • Diploid haploid • and cell shape is altered

GAMETOGENESIS Oogenesis Spermatogenesis PRIMORDIAL GERM CELLS

OOGENESIS

MATURATION OF OVUM Primary Ovarian Follicle Antral Follicle Graffian follicle

SECONDARY OOCYTE AT OVULATION

SPERMATOGENESIS

SEMINIFEROUS TUBULE SHOWING ARRANGEMENT OF SPERMATOCYTES

SPERMIOGENESIS

Structure of a sperm

COMPARISON

COMPARISON OOGENISIS Maturation starts as early in the 7 th month of IUL 1 st & 2 nd meiotic division are not continuous. Nuclear division is equal but the cytoplasmic division is unequal. Only one ovum formed Life span- 24 to 48 hours. Size of matured Ovum 135 microns. SPERMATOGENESIS Maturation starts during puberty, the germ cells are kept dormant. 1 st & 2 nd meiotic division are continuous without arrest. Nuclear division and the cytoplasmic division is equal. 4 spermatids formed Life span- 48 to 72 hours. Length of matured sperm 45 microns.

ABNORMAL GAMETES Abnormal oocytes Abnormal sperms