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
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