GAMETOGENESIS - G1.pdf

VAN 212 GAMETOGENESIS CUIZON | LICAYAN | NACIONALES | MANUGAS | OZON | ROFEROS | SENO GAMETOGENESIS OUTLINE LEARNING OUTCOMES - OVERVIEW - Define gametogenesis - GAMETOGENESIS - Illustrate the different types of - SPERMATOGENE...

VAN 212 GAMETOGENESIS CUIZON | LICAYAN | NACIONALES | MANUGAS | OZON | ROFEROS | SENO GAMETOGENESIS OUTLINE LEARNING OUTCOMES - OVERVIEW - Define gametogenesis - GAMETOGENESIS - Illustrate the different types of - SPERMATOGENESIS Gametogenesis - OOGENESIS - Distinguish between - CONCLUSION Spermatogenesis and Oogenesis OVERVIEW KEY TERMS Gametogenesis - the process where sex cells (sperm in males and eggs in females) are made Germ cells – The cells that give rise to gametes (sperm or eggs) through gametogenesis. Spermatocyte: A male germ cell involved in spermatogenesis. Oocyte: A female germ cell involved in oogenesis. KEY TERMS Polar bodies – Small, non-functional cells produced during oogenesis that do not develop into ova. Haploid cells - have one set of chromosomes (n). They contain half the genetics material needed for reproduction. Diploid Cells - have two sets of chromosomes (2n), one set from each parent. They contain the full genetic material. Mitosis - cell division in which the genome is copied and separated into two identical halves. GAMETOGENESIS GAMETOGENESIS ➔ is the process by which gametes are produced through cell division called meiosis. ➔ In males, this process creates sperm cells through a process called spermatogenesis. ➔ In females, it creates egg cells (ova) through a process called oogenesis. GAMETOGENESIS ➔ It occurs by meiotic division of diploid gametocytes into mature gametes which results in to 4 sperm cells and 1 ovum. ➔ In animals, meiosis occurs in specific organs: Males: Testes Females: Ovaries GAMETOGENESIS testis of ram / b Ovaries of Goat, showing graaffian follicles reproductive system of ram/buck (above) and testis of ram / buck (above) and female reproductive track ewe/doe (below) of ewe / doe (below) SPERMATOGENESIS SPERMATOGENESIS - Process by which spermatogonia differentiate into mature spermatozoa - Formation of sperm cells (spermatozoa) Divided into two sections: - Spermatocytogenesis - Spermiogenesis SPERMATOGENESIS: SPERMATOCYTOGENESIS - In this section, spermatogonia divide and grow into spermatocyte - GnRH stimulates the release of luteinizing hormone (LH) and follicle- stimulating hormone (FSH) from the pituitary gland. SPERMATOGENESIS: SPERMIOGENESIS - Morphological transformation of spermatids into spermatozoa. - Where spermatids (which are round, non-motile cells) transform into mature, motile spermatozoa (mature sperm cells).  SPERMATOGENESIS: SPERMIOGENESIS Four basic processes take place: 1. Nuclear condensation 2. Acrosome formation 3. Development of flagellum 4. Cytoplasmic reduction  SPERMATOGENESIS: SPERMIOGENESIS 1. Nuclear Condensation - The nucleus becomes smaller and condenses into a compact pear shape. - Essential for efficient packaging of genetic material. 2. Acrosome Formation - Proacrosomal vesicles from the Golgi form the acrosome cap. - Contains enzymes like acrosin and hyaluronidase to help the sperm penetrate the egg.  SPERMATOGENESIS: SPERMIOGENESIS 3. Flagellum Development - Flagellum (tail) forms from the centriole and provides motility. - The midpiece contains mitochondria for energy. 4. Cytoplasmic Reduction - Excess cytoplasm is removed by Sertoli cells. - Sperm is immotile at this stage and gains motility later in the epididymis. OOGENESIS  OOGENESIS Formation of the ootid/ovum Occurs inside the ovary but last stages occur inside the oviduct (Fallopian tube) A discontinuous process with early stages taking place in the fetus and the rest later in life. Oogenesis is divided into three main phases: Multiplication Phase (occurs during fetal development) Growth Phase This phase begins before birth and continues throughout childhood.  Maturation phase follicle sorrounding the oocyte grows and develops through stages Primary Follicle follicle cells proliferate and become granulosa cells Secondary Follicle fluid-filled spaces develop between the granulosa cells and merge to form central cavity called antrum Tertiary Follicle (Antral Follicle) the primary oocyte completes meiosis I, producing secondary oocyte and first polar body secondary oocyte then enters meiosis II but becomes arrested in metaphase II  Ovulation: the release of secondary oocyte is triggered by a surge of luteinizing hormone luteinizing hormone causes the follicular wall to weaken and rupture, releasing the secondary oocyte into the fallopian tube Luteal phase Corpus Hemorrhagicum The immediate aftermath of ovulation, a blood filled cavity. Corpus Luteum The temporary endocrine gland that produces progesterone and estrogen. Corpus Albicans The scar tissue that remains after the corpus luteum regresses.  Meiosis II : Completion and Fertilization Secondary oocyte remains arrested in metaphase II until fertilization In fertilization, the secondary oocyte completes meiosis II producing mature ovum and secondary polar body Ovum then fuses with sperm, forming zygote  Timing and Egg Production: A Summary Fetal Development Oogonia - a finite number of germ cells formed during fetal development. Childhood Oogonia - Enters meiosis I, becoming primary oocytes - remains in frozen state until puberty  Timing and Egg Production: A Summary The number of primary Oocytes - Decresses from about 2million at birth to around 400,000 by puberty. Follicular Atresia - The degeneration and disappearance of follicles, leading to a gradual decline in the number of primary oocytes.  Timing and Egg Production: A Summary Reproductive years - A group of primordial follicles are selected for maturation. - Most of these follicles undergo atresia and only one or two reach the Graafian stage. - One Graafian follicle responds to LH surge and undergoes ovulation.  Timing and Egg Production: A Summary Menopause - No follicles remain - The number of primary oocytes has dwindled to zero. - The number of oocytes falls below a critical threshold, typically around 1000. CONCLUSION Conclusion SPERMATOGENESIS OOGENESIS LOCATION Testes Ovaries START AGE Puberty (10-14 years) In utero, resumes at puberty FINAL PRODUCTS Four viable sperm One viable egg + three polar bodies PROCESS DURATION Continuous throughout life Monthly cycle during reproductive years MEIOSIS OUTCOME Produces haploid sperm Produces one haploid egg