Gametogenesis Notes PDF

GAMETOGENESIS MED 1023 GENERAL ANATOMY SARA B IDRIS, M.B.B.S., M.Sc. (Human Anatomy) 19 November 2024 Learning Outcome Differentiate mitosis and meiosis. Describe the process of oogenesis and spermatogenesis. Associate the chromosomal abnormalities with their respective clinical condi...

GAMETOGENESIS MED 1023 GENERAL ANATOMY SARA B IDRIS, M.B.B.S., M.Sc. (Human Anatomy) 19 November 2024 Learning Outcome Differentiate mitosis and meiosis. Describe the process of oogenesis and spermatogenesis. Associate the chromosomal abnormalities with their respective clinical conditions. Gametogenesis THE CHROMOSOME THEORY OF INHERITANCE Humans ~ 23000 genes on 46 chromosomes Cdiploid number) v 23 homologous pairs L S 22 pairs matching chromosomes 1 pair sex chromosomes # & [ ] auto somes X Y XY of of ↑ sperm oocyte 23 chromosomes 23 chromosomes Chaploid) Chaploid) - Clinical Correlates Chromosomal Abnormalities Numerical Structural Chromosomal Abnormalities Numerical Abnormalities Down’s Syndrome Extra copy of chromosome 21 Due to non-disjunction primarily in oocyte formation Risk increases with increased maternal age Chromosomal Abnormalities Numerical Abnormalities Edward’s Syndrome - Trisomy 18 Extra copy of chromosome 18 Chromosomal Abnormalities Numerical Abnormalities Patau Syndrome - Trisomy 13 Extra copy of chromosome 13 Chromosomal Abnormalities Numerical Abnormalities Klinefelter Syndrome Extra copy of sex chromosome XXY Boy born with extra X chromosome Chromosomal Abnormalities Numerical Abnormalities Triple X Syndrome Extra copy of sex chromosome XXX Taller than average Increased risk of learning disabilities and delayed development of speech and language skills Chromosomal Abnormalities Numerical Abnormalities Turner Syndrome Monosomy 45 XO Karyotype Chromosomal Abnormalities Structural Abnormalities Due to breakage of chromosomes and deletion of the broken piece Cri-du-chat (5p-) Syndrome Deletion in short arm 5 Cat-like cry, microcephaly Developmental deficiencies Congenital heart disease Chromosomal Abnormalities Structural Abnormalities Angelman Syndrome microdeletion in maternal chromosome Prader-Willi Syndrome Mcirodeletion in paternal chromosome Oogenesis Intrauterine 5th month Wh of germ cells W2 > - max no ~ 7 million 7th month j differentiate all PRIMORDIAL FOLLICLE W5 > - Y I mitosis ↓ more I 7 oocyte arrested& Prophasea W4-wE differentiate Primary mitosis XXX mitosis q ↓ ! Y mitosis Birth 600 - 800K EXTRAUTERINE Puberty - 40K ↑ FSH 15-20 follides PRIMORDIAL FOLLICLE > - Primary oocyte (diplotene stage) 2 - 1 9 cuboidal stratified 2. Follicular cells I 3. CT ovary - · L · L crescent ↑ LH zp - shaped to oculation anthom 37 his prior cumulus antrum enlarges~ 25 mm oophones w These externa-marges theca orarion CT (fibrous) externa theca interna-steroid secretion theca (secretory) m Blood supply · ↑ Interna -completes meiosis stops@ metaphase s - II  PGCs oo gonia 8 cell epiblast inner mass 000 ⑧ mitosis 0 00 00 00 ⑧00 00 ⑧D - ⑧ > 000 10000000 ⑧ ⑧ 000000 000 00 0 more orgonia PRIMARY FOLLICLE V r Primary oocyte ↑ FSH r PRIMORDIAL FOLLICLE priberty - follicular cells V ovarian CT OmI M / / · o race & ~ - MATURE SECONDARY - oo =. - 00 90 = 8 =0008 80088 8 000808 - 8 : 8 %: - - : - Spermatogenesis Intrauterine internal Wh W2 developing gonads > male genitalia testes I solid sex cords j PGCs W5 differentiate Sustentacular cells (sertoli) Y cells - supporting epit of I from lining - test is mitosis ↓ more I W4-wE mitosis XXX ↓ more Extrauterine spermogenesis Spermatogonia permatid spermatozoa Puberty Testosterone Sertoli cells Promote spermatogenesis ↑ LH Leydig cells > > Primordial Germ Cells cumen > Semineferous ⑧ acquire tubules mitosis L - ⑧ L ↓ V - & ↑ L L ~ = u # E # = & enters meiosis * · => T - rest prophase - 22 days PRIMARY SPERMATOCYTE SPERMIOGENESIS spermatid > spermatozod (morphological changes meiosis I : ↓ au 1 formation of ACROSOME nuclear surface ↑ - covers half of - for penetration of 20 oocyte + layers enzyme 2. CONDENSATION of nucleus. 5 Formation of NECK MIDDLE FECE 74 days TAIL of 4. SHEDDING cytoplasm S spermogenesis spermatogonia -edermatid spermatozoa  PGC PGC ↓ mitosis mitosis ~ orgonia A spermatogonia Type (dark) L ↓ mitosis A spermatogonia mitosis Type orgonia (pale) mitosis V VV Type B spermatogonia primary oocyte ↓ mitosis mclosi I Primary spermatocytes V ↓ meiosis secondary oocyte secondary spematocytes 11 meiosis # ↓ meiosis V spermatids definitive oocyte spermio genesis ~ spermatozoa Clinical Correlates Teratomas Arise from pluripotent stem cells that can differentiate into derivatives of all 3 germ layers Contain variety of tissues (bone, hair, muscle, gut epithelia, etc) Due to abnormal migratory PGCs or tumour of epiblastic cells