Embryology Lecture 1 PDF

 Dr. NOHA ISSA Professor of Anatomy and Embryology  Intended learning outcomes (ILOs) At the end of lecture, the student should be able to answer these questions Describe the phases of cell division. Define the gametogene...

 Dr. NOHA ISSA Professor of Anatomy and Embryology  Intended learning outcomes (ILOs) At the end of lecture, the student should be able to answer these questions Describe the phases of cell division. Define the gametogenesis. Compare between the male and female gametes.  The genital system ‫الجهاز التناسلى‬ Is composed of Primary sex organ ‫العضو الجنسي األساسي‬ Secondary sex organs ‫األعضاء الجنسية الثانوية‬ (As ducts & glands ‫) القنوات والغدد‬ External genitalia ‫األعضاء التناسلية الخارجية‬  Male genital system Primary Secondary External sex organ (testis) sex organs genitalia Ducts: Glands : ‫البربخ‬ epidydimis ‫البروستات‬ Prostate ‫األسهر‬ vas deference ‫ الحويصلة‬Seminal vesicle ‫المنوية‬ ‫القناة القاذفة‬ Ejaculatory duct ‫اإلحليل‬ urethra  Female genital system Primary sex Secondary sex External organ (ovary) organs genitalia Ducts Glands Vagina Uterus Fallopian tube ‫المهبل‬ ‫الرحم‬ ‫قناة فالوب‬  Cell division There are two distinct types of cell division: mitosis and meiosis, each one of them is preceded by the interphase )‫(الطور البينى‬. During the interphase, the DNA is replicated )‫(يستنسخ‬converting the single stranded chromosomes into double stranded chromosomes. ‫أثناء الطور البينى‬ 1- Mitosis gives rise 2 daughter cells, each one is genetically identical to the mother cell. It has four phases: prophase, metaphase, anaphase and telophase.  Prophase (Preparation) )‫(الطور التمهيدى‬ Metaphase (Meeting in the middle) )‫(الطور االستوائى‬ Anaphase (Apart) )‫(الطور االنقسامى‬ Telophase (The end) )‫(الطور النهائى‬ Prophase Metaphase Anaphase Telophase  Telophase Anaphase Metaphase Prophase During the interphase 2- Meiosis, gives rise to four daughter cells (haploid gametes, ‫ )األمشاج‬through two divisions (each division has four phases). A. First meiotic division (meiosis I): it is characterized by pairing of the homologous chromosomes Results: 2 daughter cells; each cell contains: 23 d- chromosomes (double-stranded). B. Second meiotic division (meiosis II): it is characterized by 23d-chromosomes (double-stranded) divide at the centromere into 23 s- chromosomes (single-stranded) The end results of meiotic division: 4 daughter cells; each cell contains 23 s- chromosomes (single- stranded).  Pairing of homologous chromosomes in meiosis I ‫اقتران األزواج‬ ‫المتجانسة‬  What is the karyotyping? ‫النمط النووى‬ Female Male Miosis I Miosis II Meiosis Let's get to the serious talk  GAMETOGENESIS ❑ Definition: It is the process of gametes formation through cell division. ❑ Site: In male:  Gametogenesis occurs in the seminiferous tubules of the testis  The process is known as spermatogenesis. In female:  Gametogenesis occurs in the cortex of the ovary.  The process is known as oogenesis. ❑ Aim: 1) Preparation of gametes for fertilization )‫)التخصيب‬. 2) Reduction of number of chromosomes from diploid number (46 chromosomes) into haploid number (23 chromosomes)  Spermatogenesis ❑ Definition: It is the process of transformation of spermatogonia (primitive germ cells) into spermatozoa (mature sperm) ❑ Site: Seminiferous tubules in the testis. ❑ Duration: 2 months (roughly 60 days) ❑ Onset: From puberty (13 –16 Y) till old age. ❑ Stages: 4 stages ( proliferation, growth, maturation and spermiogenesis)  Stages of spermatogenesis 1- Proliferation: (mitosis) increase in number of spermatogonia. 2- Growth: increase in size of spermatogonia to become primary spermatocyte. 3- Maturation: (meiosis) Meiosis I…..1ry spermatocytes(46 d ) gives 2 2ry spermatocytes(23 d) Meiosis II…..2ry spermatocytes(23 d) gives 2 spermatids (23 s) 4- Spermiogenesis: Spermatid…………sperm  Spermiogenesis ❑ Definition: morphological transformation of the spermatids to mature sperms (spermatozoa) ❑ Process: 1)The nucleus: condensed and forms most of head of the sperm. 2)Golgi apparatus: covers the anterior 2/3 of the nucleus to form the head cap or acrosomal cap of the sperm. 3)Centrioles: directed towards the opposite side of the nucleus and elongate gradually to form flagellum that forms the tail of the sperm. 4)Mitochondria (sheath): surround the first part of the tail and it is concerned with energy production for movement. 5) The cytoplasm: most of the cytoplasm of the head is removed by the sertolli cells.  Sperm structure 1- Head 2- Neck 3- Flagellum: midpiece, principle piece and end piece ENDPIECE PPRINCIPLE PRINCIPLE PIECE  Golden knowledge 1- Sperm length is about 60 microns. 2- Spermatogenesis takes roughly 60 days. 3- About 600 millions of sperms are present in each ejaculate)‫(القذف‬ 4- Sperm takes minutes (variable from 6-60 minutes) till reach the site of fertilization. 5- Sperm has the fertilization power for 1-2 days and can live for maximum 5 days in the female genital tract.  Oogenesis ❑ Definition: It is the process of transformation of oogonia (Primitive germ cells) into mature ovum ❑ Site: In the outer cortex of the ovary ❑ Stages: 3 stages (proliferation, growth and maturation)  During intrauterine life (proliferation, growth & 1st meiotic till prophase I)  At puberty (Immediately before 1st ovulation, completion of the 1st meiotic division, the secondary oocyte starts the 2nd meiotic division and arrested in the metaphase II )  Immediately after fertilization ( completion of the 2nd meiotic division to give the mature ovum and the second polar body)  Spermatogenesis Oogenesis Site Onset Stages Result End