Gametogenesis and Fertilization Mind Map PDF

Begins during the sixth week of embryonic...

Begins during the sixth week of embryonic development but remains inactive until puberty. At puberty, spermatogenesis is initiated Duration: The complete process of forming sperm cells takes approximately 74 days. The goal of spermatogenesis is to reduce the chromosome **Overview** number (chromatic reduction) through a series of divisions and produce haploid spermatozoa capable of fertilization Chromatic Reduction: Condensation and packaging of genetic material to fit into the sperm head Reductional Division: Refers to meiosis I, where homologous Phases: chromosomes are separated, halving the chromosome number Equational Division: Refers to meiosis II, ensuring each daughter cell gets a single copy of each chromosome **Spermatogenesis** Final stage of spermatogenesis, lasts approximately 24 days. It involves the morphological transformation of spermatids into mature spermatozoa The DNA becomes densely packed for efficient Nucleus condensation. transport The acrosome, a cap-like structure containing Development of the acrosome (acrosome cap). enzymes, forms to help penetrate the egg Formation of flagellum from the axonemal The distal centriole forms the axonemal **Key Changes:** complex. complex, creating the flagellum for mobility **Spermiogenesis** Mitochondria accumulate in the midpiece. Excess cytoplasm is eliminated by Sertoli cells, and Cytoplasmic fragments removed by Sertoli cells. mitochondria gather in the midpiece to power motility **Head**: Nucleus, acrosome. **Neck**: Connection to flagellum. **Sperm Structure:** **Intermediate Piece**: Mitochondria-rich. **Main Piece & Final Piece**: Flagellum. Gametogenesis is essential for reproduction and involves precise cellular and molecular Tunica vaginalis (parietal and visceral layers). Protective layers surrounding the testis processes. **Conclusion** **Layers:** Tunica albuginea. Disruptions can lead to infertility or serve as **Gametogenesis** targets for contraceptive strategies. **Testis Structure** Sites of spermatogenesis. Germ line cells Lobules containing seminiferous tubules. differentiate into sperm, supported by Sertoli cells Seminiferous tubules (germline cells, Sertoli Germline cells and Sertoli cells in seminiferous cells). **Functional Components:** tubules. Testis: Leydig cells. Blood vessels and vas deferens. Pathways for sperm transport to the urethra Tunica albuginea. Support, phagocytosis, and nutrition for sperm cells. Cortex: Contains follicles. Ovary: **Key Structures** Blood-testis barrier (tight junctions). Medulla: Vascularized stroma. **Sertoli Cells**: Secretes androgen-binding protein and Germinal epithelium. transport fluid. Head, neck, intermediate piece, flagellum. Spermatozoa: Phagocytosis of sperm cytoplasm. **Cellular Roles** Zona pellucida, corona radiata. Oocyte: Promote spermatogenesis and secondary Produce testosterone. sexual characteristics. Promotes the function of glands like the Spermatozoa travel from the cervical canal to **Leydig Cells**: prostate and seminal vesicles the fallopian tubes. Influence male behavior. Protecting sperm from the acidic vaginal environment. Gametogenesis and Seminiferous tubules → Straight tubules → Cervical mucus plays a critical role by: Sperm Migration and Capacitation: Rete testis → Efferent ductules → Epididymis Aiding in their migration by providing an alkaline Fertilization Mind **Pathway of Sperm** → Vas deferens → Urethra. medium. Map Biochemical changes in the sperm plasma membrane. **Pre-Fertilization Phenomena** Differentiation begins in the sixth week of Capacitation occurs in the female reproductive embryonic development, and by birth, oocytes tract: are arrested in meiosis I Removal of inhibitory substances, enabling sperm to bind to the zona pellucida. Follicular Atresia: Only 300-400 oocytes mature out of Sperm reach the outer third of the fallopian tube 200,000-400,000 present at birth due to atresia Meeting Point: (ampulla), where fertilization typically occurs. Transformation of a primordial follicle Simple squamous → simple cubic → increase in size Sperm release hyaluronidase enzymes to break down the intercellular into a unilaminar primary follicle Corona Radiata Dissociation: **Oogonia to Oocyte Development** connections in the corona radiata, allowing access to the zona pellucida Transformation of a unilaminar primary follicle Formation of the granulosa layer by Formation of the zona pellucida, a glycoprotein Formation of the thecae by organization of the Sperm binds to ZP3 glycoprotein receptors on into a multilaminar primary follicle proliferation of epithelial cells matrix produced by granulosa cells layer of connective tissue around the follicle the zona pellucida. The acrosomal reaction: Zona Pellucida Penetration: Transformation of a primary into a Formation of the antrum by fusion of the Formation of the Cumulus Oophorus, eccentric Subdivision of the theca into two distinct zones: Acrosome releases hydrolytic enzymes (e.g., secondary follicle intracellular spaces of the granulosa layer zone of the granulosa occupied by the oocyte theca interna and externa acrosin) that digest the zona pellucida, creating a path for sperm entry. Transformation of a secondary The granulosa layer is the same thickness Oocyte surrounded by the corona radiata and Increasing the size of the antrum follicle into a de Graaf follicle throughout the periphery linked to the granulosa by the cumulus oophorus A single spermatozoon penetrates the zona pellucida and fuses with the oocyte plasma membrane **Primary Follicle**: Begins with the growth of Sperm Entry: oocyte and surrounding granulosa cells. Cortical reaction: Exocytosis of cortical granules, altering the zona pellucida to prevent This triggers: **Fusion of Gametes** Antrum forms (fusion of spaces in granulosa polyspermy (entry of additional sperm) layer). The secondary oocyte, upon sperm **Gametogenesis in Females** **Follicular Development** 28 days **Secondary Follicle**: Cumulus oophorus surrounds oocyte. penetration, completes meiosis II. **Fertilization** Completion of Meiosis II in Oocyte: Theca interna and externa differentiate. A mature ovum. Forms: Large antrum, corona radiata surrounding The second polar body (extruded). oocyte. **Tertiary or Graafian Follicle**: The sperm nucleus transforms into the male Ready for ovulation. pronucleus Several follicles undergo this development The oocyte nucleus becomes the female process but only one is dominant and ovulates Formation of Pronuclei: pronucleus The dominant follicle ruptures, releasing the secondary oocyte Both pronuclei migrate toward the cell center surrounded by the corona radiata into the peritoneal cavity Pronuclei membranes disintegrate, allowing After ovulation, the broken follicle collapses Membrane Disappearance: **Ovulation** chromosomal alignment and fills with blood - haemorrhagic body Chromosomes align on the equatorial plane of Karyogamy (Fusion of Pronuclei): Non-pregnancy - the corpus luteum begins a the spindle apparatus. process of degeneration which occurs after Chromosomal Alignment: around 10 days. This process gives rise to a Results in the formation of a zygote with a The granulosa cells increase in size and, together with the cells of fibrous structure knownnas the corpus albicans diploid chromosome set (44 autosomes + 2 sex the internal theca, form a new endocrine gland - corpus luteum - chromosomes). secretes progesterone and oestrogen Pregnancy - the corpus luteum persists for 3 months until the placenta replaces it in its The zygote is the first cell of the new organism, endocrine formation containing a full diploid set of chromosomes. Zygote Formation: **Outcomes** Composed of Male and female genetic contributions (restored diploidy) The sperm’s sex chromosome (X or Y) determines the sex of the zygote. Sex Determination: X-sperm results in a female (XX). Y-sperm results in a male (XY). The zygote begins its first mitotic division (cleavage) to form blastomeres, starting Segmentation Initiation embryonic development