Gametogenesis-1 Dr.Ayesha (2023-24) PDF

Course Biology II General Embryology GAMETOGENESIS-1 Dr. Ayesha Fatima CMMS - AGU Dr. Ayesha F  Human Development ‫ﻗﺻﺔ ﺧﻠﻖ اﻹﻧﺳﺎن‬ ٍ ‫ﺳ َﻼﻟَ ٍﺔ ِ ّﻣن...

Course Biology II General Embryology GAMETOGENESIS-1 Dr. Ayesha Fatima CMMS - AGU Dr. Ayesha F  Human Development ‫ﻗﺻﺔ ﺧﻠﻖ اﻹﻧﺳﺎن‬ ٍ ‫ﺳ َﻼﻟَ ٍﺔ ِ ّﻣن ِط‬ )12( ‫ﯾن‬ ُ ‫ﺎن ِﻣن‬ َ ‫ﺳ‬ ِ ْ ‫َوﻟَﻘَ ْد َﺧﻠَ ْﻘﻧَﺎ‬ َ ‫اﻹﻧ‬ And indeed, We created humankind1 from an extract of clay, ْ ُ‫ﺛ ُ ﱠم َﺟﻌَ ْﻠﻧَﺎهُ ﻧ‬ ٍ ‫طﻔَﺔً ِﻓﻲ ﻗَ َر ٍار ﱠﻣ ِﻛ‬ )13( ‫ﯾن‬ then placed each ˹human˺ as a sperm-drop1 in a secure place(uterus), ‫ﺎم‬ َ ‫ظ‬َ ‫ﺳ ْوﻧَﺎ ْاﻟ ِﻌ‬ َ ‫ﺿﻐَﺔَ ِﻋ‬ َ ‫ظﺎ ًﻣﺎ ﻓَ َﻛ‬ ْ ‫ﺿﻐَﺔً ﻓَ َﺧﻠَ ْﻘﻧَﺎ ْاﻟ ُﻣ‬ْ ‫ﻋﻠَﻘَﺔً ﻓَ َﺧﻠَ ْﻘﻧَﺎ ْاﻟﻌَﻠَﻘَﺔَ ُﻣ‬ َ َ‫طﻔَﺔ‬ ْ ‫ﺛ ُ ﱠم َﺧﻠَ ْﻘﻧَﺎ اﻟﻧﱡ‬ )14( ‫ﯾن‬ َ ‫ﺳ ُن ْاﻟﺧَﺎ ِﻟ ِﻘ‬ َ ‫ﺎر َك ﱠ ُ أ َ ْﺣ‬ َ َ‫ﻟَ ْﺣ ًﻣﺎ ﺛ ُ ﱠم أَﻧﺷَﺄْﻧَﺎهُ ﺧ َْﻠﻘًﺎ آﺧ ََر ۚ ﻓَﺗَﺑ‬ ]‫[اﻟﻣؤﻣﻧون‬ then We developed the drop into a clinging clot ˹of blood˺, then developed the clot into a lump ˹of flesh˺, then developed the lump into bones, then clothed the bones with flesh, then We brought it into being as a new creation.1 So Blessed is Allah, the Best of Creators. Dr. Ayesha F Dr. Ayesha F What is Embryology? It is the branch of biology that studies the development of the human being in utero (Intrauterine development or Prenatal Development). The normal gestational period /intrauterine period of human beings is 280 days /40 weeks. ‫اﻟﻐرس‬ ‫ﺑوﯾﺿﺔ‬ )13( ‫ﯾن‬ ْ ُ‫ﺛ ُ ﱠم َﺟ َﻌ ْﻠﻧَﺎهُ ﻧ‬ ٍ ‫طﻔَﺔً ﻓِﻲ ﻗَ َر ٍار ﱠﻣ ِﻛ‬ SPERM ‫ﺣﯾوان ﻣﻧوى‬ a. Pre-embryonic period 1st & 2nd Weeks b. Embryonic period 3rd to 8th Weeks c. Fetal period 3rd to 9th Months Dr. Ayesha F Anatomy of Male and Female Genital Systems Dr. Ayesha F  MALE GENITAL SYSTEM The primary sex organ: is the testis. It is the site of production of hormones and sperms. Seminal vesicle Vas deferens Testes lie in the scrotum outside the body as the formation of the sperms needs temperature lower than body temperature. Ejaculatory duct Penis. Semen: Fluid produced and secreted by the male reproductive organs. Composed of sperms and secretions from the glands. Prostate Urethra. Bulbourethral gland Male external genital organ is called Penis Epididymis Testis Scrotum Dr. Ayesha F  FEMALE GENITAL SYSTEM External : 1.The primary sex organ: is the Ovary. It produces ovum. 3.External genital organ of male-Penis female-vulva females is called Vulva. 2. The genital (ductal) tract: includes the It includes the distal part of Vagina. uterine(fallopian) tubes, uterus, cervix and the vagina. Fallopian tube Ovary Uterus Cervix Rectum Urinary Bladder Anal Canal Vulva Vagina Sagittal Section Coronal section Dr. Ayesha F  BEGINNING OF HUMAN DEVELOPMENT ▪ Gametes: The cells that carry out the function of reproduction(Sperm & Ovum) ▪ FERTILIZATION: The process of fusion of the Day 9 male gamete(Sperm,n) with the female gamete(ovum, n) to form Perimetrium the zygote(2n) sperm + ovum = zygote Dr. Ayesha F  ‫ﺑﺳم ﷲ اﻟرﺣﻣن اﻟرﺣﯾم‬ {46} ‫{ ِﻣﻦ ﻧﱡ ْﻄﻔَ ٍﺔ إِذَا ﺗ ُ ْﻤﻨَﻰ‬45} ‫اﻟﺰ ْو َﺟ ْﯿ ِﻦ اﻟﺬﱠﻛ ََﺮ َو ْاﻷُﻧﺜَﻰ‬ ‫ﻖ ﱠ‬ َ َ‫َوأَﻧﱠﮫُ َﺧﻠ‬ ‫ﺳﻮرة اﻟﻨﺠﻢ‬ And He created the pairs—males and females from a sperm-drop when it is emitted َ ُ‫ﺎن ِﻣﻦ ﻧﱡ ْﻄﻔَ ٍﺔ أ َ ْﻣﺸَﺎجٍ ﻧﱠ ْﺒﺘ َ ِﻠﯿ ِﮫ ﻓَ َﺠﻌَ ْﻠﻨَﺎه‬ ‫ﺳ ِﻤﯿﻌﺎ‬ َ ‫ﺴ‬ ِ ْ ‫إِﻧﱠﺎ َﺧﻠَ ْﻘﻨَﺎ‬ َ ‫اﻹﻧ‬ {2} ً ‫ﺑَ ِﺼﯿﺮا‬ ‫ﺳﻮرة اﻹﻧﺴﺎن‬ For indeed, We alone created humans from a drop of mixed fluids(zygote), in order to test them, so We made them hear and see. Dr. Ayesha F GAMETOGENESIS Dr. Ayesha F  Gametogenesis(Gamete formation) Definition: It is the process of conversion of diploid primordial germ cells(Spermatogonia & oogonia,46 chromosomes) into haploid from mother father , to gametes(Sperm and ovum,23 chromosomes) in the gonads. individual Germ cells Gametes (ovum, sperm) 46 chromosomes 23 chromosomes Diploid number (2n) Haploid number(n) It is divided into:- 1. Spermatogenesis: formation of mature sperm. 2. Oogenesis: formation of ovum. Dr. Ayesha F  GAMETOGENESIS Meiosis: a cell division to reduce Cytodifferentiation: to change the the number of chromosomes in size and shape of germ cells the cell from diploid( 2n) to before fertilization. {cytoplasm}. haploid(n). {nucleus}. Source of primordial germ cells (PGCs): ▪ PGCs migrate from the wall of the yolk sac to reach the developing gonads in the genital ridge (future testis or ovary) to become spermatogonia in males or oogonia in females (at the 5th week). NB: PGCs are formed in the epiblast during the 2nd week and then are moved to the yolk sac. Dr. Ayesha F  (Diploid,2n) - Chromosomes are found carrying your DNA in the nucleus of the cells. DNA looks like a spiral staircase (double helix). - Each cell has 46 chromosomes. Dr. Ayesha F  (Haploid,n) Dr. Ayesha F Dr. Ayesha F  Meiosis I (reduction division) Melos is : diploid to haploid mitosis : replication 1- Immediately before meiosis, germ cells (2n chromosomes and 2n DNA) replicate their number 2n DNA replicate= 4n DNA of DNA in the chromosomes (2n chromosomes and 4n DNA or chromatids) 2- Crossing over occurs: this generates new individual genetically different from his parents. 3- The new pair of chromosomes then separate and divide ie. haploid number of chromosomes (n chromosomes) but a diploid number of DNA (2n DNA) (n chromosomes) 4- The new daughter cells are 2n DNA not identical genetically: to their parent cells nor to each other. Dr. Ayesha F  In Meiosis II (mitosis like) n DNA 5- In each cell, the two sister chromatids of each chromosome then separate (without DNA replication) and are distributed into two daughter cells called gametes each contains 23 single chromosomes ie. the haploid number (n chromosomes) with a haploid number of DNA (n DNA). Dr. Ayesha F Chiasmata Dr. Ayesha F  Summary of Meiosis I and II. n chromosomes(23) 2n chromosomes(46) 2n Chromatids/DNA (46) 4n Chromatids/DNA(92) n chromosomes(23) n chromosomes(23) 2n Chromatids/DNA (46) n Chromatids/DNA (23) Dr. Ayesha F Dr. Ayesha F MITOSIS 2n Parent cell (Diploid, 2n) MEIOSIS (Haploid, n) 4 different daughter cells, Haploid, n Parent cell (Diploid, 2n) Crossover (Haploid, n) Gametes Dr. Ayesha F REFERENCES Dr. Ayesha F