Gametogenesis: Spermatogenesis Lecture Notes PDF

Gametogenesisi: Spermatogenesis University Of Fallujah College Of Medicine Lecture : (1) Stage : 2nd stage Lecturer : M.Sc. Thair M. Farhan Department: Anatomy Date: 16/9/2024 Objectives Define medical Embryology. Production of gamete...

Gametogenesisi: Spermatogenesis University Of Fallujah College Of Medicine Lecture : (1) Stage : 2nd stage Lecturer : M.Sc. Thair M. Farhan Department: Anatomy Date: 16/9/2024 Objectives Define medical Embryology. Production of gametes. Spermatogonia definition Spermatogenesis Spermiogenesis Definition Is study the developmental process of the fertilized ovum that represents increasingly complex phenomena with contained field includes investigation of molecular, cellular, and structured factors contributing to formation of an organism. Karl Ernst von Baer is the father of Embryology. Terms Embryogenesis (organogenesis): the first 8 weeks of human development. Fetal period: the period after 8 weeks until birth. Teratology : the study of birth defects and compared to organisms with normal developmental patterns. Genomes : codes that contain all the information required to make individual.  Mitosis Miosis Cells divide to 2 daughter cells Cells divide to generate Male & Chromosomes coil, contract & Female gametes. condense in prophase. Required two stage division Miosis I Chromosomes line up in the equatorial &II. plane in Metaphase Miosis I: duplicate into sister Chromosomes attached to microtubules extended from chromosome (homologous centromere to centriole (spindle fiber). chromosome), synapsis, crossover Chromosomes divided by migration of Miosis II : each germ cell contains a chromatids in Anaphase haploid number of chromosome. Chromosomes uncoiled, lengthen and nuclear envelope reform and Cytoplasm divides in Telophase Gametogenesis Gametogenesis is define as conversion of Germ cells into Male and Female gametes. Gametogenesis include: Oogenesis Spermatogenesis  Gametes are derived from primordial germ cells (PGCs) that are formed in the epiblast during the second week, move through the primitive streak during gastrulation, and migrate to the wall of the yolk sac. During the fourth week, these cells begin to migrate from the yolk sac toward the developing gonads. At the end of 5th week PGCs differentiate to Oogonia and Spermatogonia.  Gametogenesis is defined as Conversion of Germ Cells into Male and Female Gametes Gametogenesis include: Oogenesis Spermatogenesis Gametogenesis include: A- Oogenesis B- Spermatogenesis Spermatogenesis is the sequence of events by which spermatogonia are transformed into mature sperms; this maturation process begins at puberty.  At birth, germ cells in the male infant can be recognized in the sex cords of the testis as large, pale cells surrounded by supporting cells, which are derived from the surface epithelium of the testis in the same manner as follicular cells known as Sertoli cells. Sex cord Seminiferous Tubules  Shortly before puberty, the sex cords acquire a lumen and become the Seminiferous Tubules. At about the same time, PGCs give rise to spermatogonia stem cells. At regular intervals, cells emerge from this stem cell population to form type A spermatogonia. Spermatogonia type A (44+X+Y) by mitotic division give type A and type B (44+X+Y).  Their production marks the initiation of spermatogenesis. Type A cells undergo a limited number of mitotic divisions to form clones of cells. The last cell division produces type B spermatogonia , which then divide to form primary spermatocytes (44+X+Y). Each primary spermatocyte subsequently undergoes a reduction division(the first meiotic division)to form two 23 double structure chromosome secondary spermatocytes (22+X) , (22+Y), which are approximately half the size of primary spermatocytes.  Subsequently, the secondary spermatocytes undergo a second meiotic division to form four haploid spermatids(23 single structured chromosome), which are approximately half the size of secondary spermatocytes. The spermatids are gradually transformed into four mature sperms by a process known as Spermiogenesis.  Spermiogenesis steps Is the process by which spermatid convert to sperm, through transporting Golgi apparatus to acrosome cap, sit the mitochondria in the middle peace and nucleus in the head. 1-formation of the acrosome, which covers half of the nuclear surface and contains enzymes to assist in penetration of the ovum and its surrounding layers during fertilization 2- condensation of the nucleus 3- formation of neck, middle piece, and tail 4- shedding of most of the cytoplasm as residual bodies that are phagocytized by Sertoli cells.  The time required for a spermatogonium to become a mature spermatozoon is approximately 74 days. When spermiogenesis is complete, the sperms enter the lumina of the seminiferous tubules. Sperms are transported passively from seminiferous tubules to the epididymis, where they are stored and become functionally mature. The length of mature sperm around 60 microns. maturation of sperms in epididymis undergoes through change the glycoprotein of BM of the head then integrated with prostate secretion.  Sperms are free-swimming, actively motile cells consisting of: The head of the sperm: forms most of the bulk of the sperm with length 4 µm and contains the nucleus. The anterior two thirds of the head are covered by the acrosome, a cap-like saccular organelle containing several enzymes. When released, the enzymes facilitate sperm penetration of the zona pellucida during fertilization. The neck of the sperm is the junction between the head and tail. The tail of the sperm provides the motility of the sperm that assists its transport to the site of fertilization. The tail consists of three segments: middle piece, principal piece, and end piece. The middle piece contains mitochondria, which provide adenosine triphosphate, necessary to support the energy required for motility. Sperm disorders defects in quality or quantity of sperm produced and defects in sperm emission. Diagnosis is by semen analysis and genetic testing. An inadequate quantity of sperm normal range 15-200 ml (Oligozoospermia)(azoospermia). Defects in sperm quality, such as abnormal motility or structure. Semen volume. Morphology: large sperm head, small sperm head, double-headed sperm, crooked sperm tail, short sperm tail, elongated sperm tail, double sperm tail Vitality: 54%,4% Motility: 30% Thank you