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Reproductive System.doc

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Western University
Physiology 2130
Sarah Mc Lean

Reproductive System Fetal development - each cell contains 23 pairs of chromosomes - all eggs contain X chromosomes, sperm contains either an X or Y chromosomes - sex of future baby is determined at fertilization - during first 6 weeks of development, male and female embryos contain common gonads o Gonads: eventually will form testes or ovaries  Contains two sets of primitive reproductive tracts  Mesonephric (Wolffian Duct)  Paramesonephric (Mullerian Duct) - in the developing male embryo (6-7 weeks) the presence of Y chromosome causes the indifferent gonads to develop into testes - in the developing female embryo (9 weeks) the XX chromosomes are activated and ovaries develop Male Female - at 7 weeks testicular cells begin - no hormonal control to produce Mullerian inhibiting - no Mullerian inhibiting hormone, the hormone which causes the Mullerian duct develops into the Mullerian duct to regress fallopian tubes, uterus, cervix and part - at 9 weeks, testicular cells begin of the vagina to produce testosterone - no testosterone  Wolffian duct - testosterone stimulates the regresses and female external genitalia Wolffian duct to develop into the develop epididymis, vas deferens, seminal vesicles and urethra Male Reproductive system  Function is to produce testosterone, to produce sperm and to deliver it to the female vagina Female Reproductive system  Function is to produce estrogen and progesterone, also produce eggs and provide optimal conditions for the development of the fetus Male Reproductive System Structure - external genitalia consists of penis and scrotum - penis is made up of urethra, glans penis, and erectile tissue (corpus spongiosum and corpus cavernosum) - scrotum contains the testes where sperm and testosterone are produced - after production, sperm is stored in the epididymis - during ejaculation, sperm travels through the ductus deferens (vas deferens), mixes with fluid from seminal vesicles, passes through prostate, receives more fluid from the bulbourethral gland, enters urethra and passes through penis - testes consist of 1000 coiled seminiferous tubules (each roughly 150 cm long) - after formation in the seminiferous tubule, the sperm move into the epididymis (coiled tube roughly 6 m long) Function Seminifeerous tubules: site of spermatogenesis Sertoli cells: regulate spermatogenesis and maintain the developing sperm cells - produce hormone inhibin - secrete fluid that pushes immature sperm to the epididymis - form the blood-testis barrier (BTB)  isolates developing sperm cells from blood so that immune cells do not attack these genetically different cells Leydig cells: located in interstitial space between the seminiferous tubules  produce testosterone Epididymis: final maturation area and storage site for sperm Vas deferens: carries the sperm from epididymis to ejaculatory duct Seminal vesicles: contribute a large amount of fluid to the semen during ejaculation (rich in fructose and enzymes  help to maintain and nourish sperm) Prostate gland: secretes enzymes and fluid that help neutralize the acid environment of the urethra and vagina Bulbourethral gland: secretes a fluid that helps to neutralize the pH and lubricate the urethra and vagina to create an optimal environment for sperm Urethra: transports sperm during ejaculation and drains bladder during urination Spermatogenesis - Spermatogonia (germ cells)  contain 46 chromosomes and are located at the outer edge of the seminiferous tubules - These cells will divide by mitosis into two cells: Spermatogonia and spermatocyte - Primary spermatocyte divides by meiosis into two secondary spermatocyte and then into four spermatid - Throughout the process, the dividing cells work their way to the center of the tubule - Spermatids develop into sperm cells  released by Sertoli cells into lumen of seminiferous tubules - Process takes 64 days to complete and ends with 4 sperm cells (23 chromosomes) - Sperm cell contains a head (with acrosome and nucleus), a midpiece (mitochondria) and long tail - Complete maturation takes 12 days Control of Testicular Function - functions of testes are controlled by follicle stimulating hormone (FSH) and luteinizing hormone (LH) released by the anterior pituitary gland in response to gonadotropin releasing hormone (GnRH) - FSH acts on Sertoli cells to promote spermatogenesis while also producing inhibin - Inhibin feeds back to the anterior pituitary to decrease the release of LH and FSH - LH stimulates the Leydig cells to produce testosterone - Testosterone will feed back to both the hypothalamus and anterior pituitary to decrease the production and secretion of LH and FSH Testosterone - steroid hormone produced by Leydig cells - reactions that begin with cholesterol Testosterone Levels and Age - vary throughout l
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