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Module 14: The Reproductive System Great diagrams, organized by colour, everything you need to know for Module 14

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Physiology 1021
Tom Stavraky

Physiology: Module 14 March 2011 The Reproductive System Each cell in the body contains 23 pairs of chromosomes (this includes a pair of sex chromosomes) Sex chromosomes: large X chromosome & smaller Y chromosome. Eggs: X chromosome Sperm: X or Y chromosome The sex of the baby is determined at the point of fertilization. Female: XX Male: XY Development First 6 weeks: male and female embryos contain common (indifferent) gonads (*these structures will eventually form the testes in the male or the ovaries in the female) Two sets of primitive reproductive tracts: 1. The mesonephric or Wolffian Duct 2. The paramesonephric or Mullerian Duct With the correct cues, these structures will form either the male or female reproductive tracts *Once the testes or ovaries have developed, the reproductive tracts and external genitalia follow. Developing male embryo: at roughly 6 to 7 Developing female embryo: at about 9 weeks weeks the presence of the Y chromosome of development the XX chromosomes are causes the indifferent gonads to develop activated and ovaries develop. into the testes. Female reproductive system: Function of the male reproductive system: -Responsible for producing estrogen (sex steroid) & To produce the sex steroid testosterone progesterone (hormone) & eggs To produce sperm (called spermatogenesis) -To receives the sperm To deliver sperm to the female vagina -To provide optimal conditions for the development of the fetus 7 weeks: testicular cells begin to produce Mullerian inhibiting No Mullerian inhibiting hormone: Mullerian duct hormone (MIH): Mullerian duct regresses develops into the fallopian tubes, uterus, cervix, 9 weeks: testicular cells produce testosterone, stimulating the and part of the vagina. No testosterone: Wolffian Wolffian duct to develop into the epididymis, vas deferens, duct regresses; female external genitalia develop seminal vesicles & urethra *Development of the female reproductive tract and external genitalia requires no hormonal control. Presence of testosterone=development of male external genitalia March Physiology: Module 14 2011 Male Reproductive System External genitalia: Penis: urethra, glans penis, & the erectile tissue corpus spongiosum & corpus cavernosum Scrotum: 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 the seminal vesicles Passes through the prostate Receives fluid from Bulbourethral (Cowper's) gland Enters the urethra Passes out through the penis -After formation in the seminiferous tubule, sperm move to the epididymis which drains into the Glans Penis ductus deferens Epididymis: the final maturation area and storage site for sperm. 1. Penis 2. Scrotum Vas deferens: carries the sperm from the 3. Prostate epididymis to the ejaculatory duct. The 4. Cowpers Gland ejaculatory duct drains into the urethra. 5. Testes 6. Ureter Seminal vesicles: contribute a large amount of 7. Urethra fluid (thats rich in fructose & enzymes; helps 8. Bladder nourish & maintain the sperm) to the semen 9. Rectum during ejaculation. 10. Ejaculatory Duct 11. Vas Deferens Prostate gland : secretes enzymes & fluid that help neutralize the 12. Seminal Vesicles acid environment of the urethra and vagina Bulbourethral gland (Cowper's gland) : secretes a fluid that helps neutralize the pH and lubricate the urethra and vagina to create an optimal environment for the sperm. Urethra: transports the sperm during ejaculation and drains the bladder during urination. Seminiferous tubules: site of spermatogenesis Sertoli cells: - regulate spermatogenesis -maintain the developing sperm cells (called spermatogonia) -produce the hormone inhibin, -secrete fluid that pushes the immature sperm to the epididymis -form the blood-testis barrier (BTB)- isolates the developing sperm cells from the blood so that immune cells do not attack these genetically different cells. If the BTB did not develop properly, immune cells would attack and destroy the developing sperm resulting in sterility. Leydig cells: produce testosterone Seminiferous Tubules : -contain Sertoli cells & developing sperm; outside the seminiferous tubule are the Leydig cells (interstitial cells) -Physiology: Module 14 March 2011 Spermatogenesis MITOTIC DIVISION Primary Spermatocyte FIRST MEOTIC DIVISION Spermatigonium (germ cell) 46 Secondary Spermatocytes -located at the outer edge of the seminiferous tubules SECOND MEOTIC DIVISION Spermatigonium Spermatids (23) Sperm cells (23) Spermatids differentiate into sperm cells Complete maturation of the sperm: 12 days; occurs as sperm are moved to the epididymis by the fluid that is secreted by the Sertoli cells. The functions of the testes are controlled by follicle stimulating hormone (FSH) & luteinizing hormone (LH) and released by the anterior pituitary gland in response to gonadotropin releasing hormone (GnRH) from the hypothalamus. LH stimulates the Leydig cells to produce testoste
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