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Physiology 1021
Angela Nissen

Reproductive Physiology Male Reproductive System: Function: to produce hormones and sperm - not essential in maintaining homeostasis, but crucial for procreation - the reproductive organ is not a homeostatic organ and we can therefore live without them Where is the site of hormone and sperm production? - the testis, which are located inside the scrotum (the balls) - to produce healthy sperm the testis need to be 2 degrees below normal body temperature - they are located outside the body and the cremaster muscles can elevate the position of the testis to regulate temperature Structure of the Testis: Epididymis: mature, store and transports sperm to the vas deferens Vas Deferens: transports sperm from the epididymis for ejaculation Seminiferous Tubule: location of meiosis and gamete creation (spermatozoa) – sperm and sex hormone production (testosterone) - surrounded by Leydig cells that produce androgens Components of the Seminiferous Tubule: Spermatagonia/spermatocytes: developing sperm cells (germ cell) Leydig Cell: lays outside of the seminiferous tubule (adjacent), produces testosterone in the presence of LH which goes into the blood stream to affect and release androogens Sertoli Cell: testosterone diffuses from the Leydig cells to support and regulate spermatogenesis (nourishes developing sperm cells) - activated by FSH - found inside seminiferous tubule * spermatogenesis (mitosis and meiosis of cells) is initiated at puberty because by then sufficient testosterone has been produced to enable spermatogenesis Describe Spermatogenesis: Mitosis of Spermatagonia: 1. The spermatogonium is a stem cell found in the outer wall of the seminiferous tubules within the testes. They are in contact with the epithelial basal lamina. 2. Each spermatogonium has two sets of chromosomes (one maternal, one paternal) and is said to be diploid (2n). Thus, each spermatogonium has 23 pairs of homologous chromosomes 3. A spermatogonium undergo mitosis, which results in 2 new cells-type A and type B. o Type A cells remain at the basement membrane and maintain the germ line o Type B cells move toward the lumen and become primary spermatocytes - Thus, we say mitosis of spermatogonia  spermatocytes Meiosis of Spermatocytes: A primary spermatocyte undergo meiosis I, forming two secondary spermatocytes. 1. Secondary spermatocytes undergo meiosis II and their daughter cells are called spermatids. 2. Spermatids are small round cells seen close to the lumen of the tubule. • Spermatids only have 23 chromosomes and are said to be haploid (n) • Gamete formation is by meiosis, in which the number of chromosomes is halved (from 2n to n). - Thus, we say meiosis of spermatocytes  spermatids. - spermatagonia populate the seminiferous tubules prior to birth Spermiogenesis: when the spermatids lose their cytoplasm and become mature sperm What type of chemical signaling occurs by testosterone on Sertoli cells and other target cells? - paracrine signalling occurs, releases a signal to respond to another signal (cell-cell communication) What class of hormone is testosterone and what are the properties of testosterone ? HORMONE: a steroid hormone from the androgen family SOLUBILITY: TRANSPORTATION: PRECURSOR: RECEPTOR LOCATION: How is testosterone regulated in the body? ADD DIAGRAM 1. The hypothalamus releases gonadotropin-releasing hormone (GnRH) 2. GnRH stimulates the anterior pituitary to secrete FSH and LH 3. FSH causes sustentacular (Sertoli) cells to release androgen-binding protein (ABP) 4. LH stimulates interstitial (Leydig) cells to release testosterone 5. ABP binding of testosterone enhances spermatogenesis What are the other functions of testosterone in the male? - synthesized from cholesterol - negative feedback (shuts off its own production) - supports spermatogenesis - causes secondary sex characteristics (results of puberty)- deeper voice, chest hair etc. - causes libido - produces anabolic reactions (muscle mass increase) The male reproductive system and the functions of each organ: What are the other secretions found in semen and what is the origin of secretion? 1. Seminal Vesicles: 60% of volume of semen - glucose, clotting protein (alkaline) - where sperm and seminal fluid mix 2. Prostate Gland: 30% of volume of semen - citric acid, enzymes (slightly acidic) - helps activate sperm 3. Boulbourethral Gland: minor contribution (10%) - mainly mucus (alkaline)- pre cum * as men age prostate problems and erectile dysfunction is common What are common conditions of the reproductive system? Diagnosis/Treatment? Erectile dysfunction: lack of blood flow to make hard enough - treatment is medication Female Reproductive System: - production of sex hormones occurs in the ovaries, which are located in the pelvis, and are suspended on each side of the uterus - reproductive cells are known as oocytes and the production of these is oogenesis - oogenesis starts with oogenia which are produced prior to birth, about 5-10 million in each ovary and about 1 million of these progress to the primary oocyte stage around birth, a few will progress to secondary which will last until there all gone (menopause) The Ovaries: - Are the primary female reproductive organs - Produce female gametes (ova) - Secrete female sex hormones (estrogen and progesterone) - Have ovarian follicles embedded in the ovary cortex; each follicle consists of an immature egg called an oocyte Compare Spermatogenesis with Oogenesis: Spermatogenesis Vs Oogenesis . After the 2 meiotic divisions in a single Vs After the 2 meitoic divisions in a single spermatogonium, you get 4 spermatids (1:4) . oogonium, you get 1 ovum (secondary oocyte) and 3 polar bodies (1:1)- so we don’t produce a litter All different stages of development in sperm Vs Only one stage of development at a time (every 90 days, so not all sperm are at the . same stage) Supporting cells, Setoli and Leydig, never Vs Supportive cells change so can’t change and can reproduce forever . reproduce after certain age (menopause) Reproductive stage starts at puberty Vs Born with oogenia, does not start at . puberty, secondary oocytes are produced at puberty (which get fertilized) FACT: The male makes millions of tiny sperm while the female invests all her energy in one egg, and even goes to the point of conserving that energy further by not completing meiosis unless there is fertilization What distinguishes a primary follicle from a secondary follicle? Primary Follicle Secondary Follicle - at puberty and each month after, 20 - 20 primary become 5 secondary follicles premordial follicles become primary follicles - surrounded by theca cells (new development - surrounded by zona pellucida cells) - contain granulose cells (layers) - androgens move from theca into granulosa cells which use aromatase to turn androgen into estrogen Describe the Process of Oogenesis: - production of female sex cells by meiosis During fetal period • Oogonia (2n ovarian stem cells) multiply by mitosis and store nutrients • Primordial follicles appear as oogonia are transformed into primary oocytes • Primary oocytes begin meiosis but stall in prophase I During childhood the ovaries are inactive from puberty • Each month one activated primary oocyte completes meiosis one to produce two haploid cells  The first polar body  The secondary oocyte • The secondary oocyte arrests in metaphase II and is ovulated • If penetrated by sperm the second oocyte completes meiosis II, yielding:  One large ovum (the functional gamete)  A tiny second polar body Follicular Development (Ovarian Cycle) 1. Follicular Phase • Period of follicle growth (days 1–14) • The primordial follicle, surrounded by granulose cells (flat) and directed by the oocyte, becomes a primary follicle • The primary follicle, surrounded by zona pellusida, becomes a secondary foll
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