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Reproductive System .docx

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Western University
Physiology 2130
Paul Gillespie

Reproductive System Describe the fetal development of the male and female reproductive systems • Function of male and female reproductive systems: o Pass on the genes of the individuals o Maintain the species • Fetal Development o Cells contain 23 pairs of chromosomes o Sex chromosomes: X and Y o All eggs contain X and sperms can contain either X or Y o Sex is determined at fertilization o XX-girl; XY-boy • 6 Weeks o Male and female embryos contain common gonads o Gonads turn into testes or the ovaries o Primitive reproductive tracts  Wolffian Duct (mesonephric)  Mullerian Duct (paramesonephric) • 6-7 Weeks o Male  Y chromosome causes the testes to develop  Testicular cells produce Mullerian inhibiting hormone (MIH) causing Mullerian duct to regress • 9 Weeks o Female  XX chromosomes causes ovaries to develop  Requires no hormonal control (No MIH)  Mullerian duct develops into: • The fallopian tubes • Uterus • Cervix • Part of the vagina  No testosterone causes Wolffian duct to regress and female external genitalia to develop o Male  Testicular cells produce testosterone in males  Surge of testosterone stimulates Wolffian duct to develop into: • Epididymis • Vas deferens • Seminal vesicles • Urethra  Presence of testosterone causes external genitalia to develop Reproductive System List the functions of each of the male reproductive organs • Function of male reproductive system: o Produce the sex steroid testosterone, to produce sperm and deliver it to the female vagina • External genitalia consists o Penis  Urethra  Glans penis  Erectile tissue corpus spongiosum and corpus cavernosum o Scrotum  Testes • Sperm and testosterone are produced • Consists of 1000 coiled seminiferous tubules • Seminiferous tubules o Site of spermatogenesis o Contains Sertoli cells  Regulates and maintains spermatogenesis  Begins at puberty  Maintain developing sperm (spermatogonia)  Produce hormone inhibin  Secrete fluid that pushes the immature sperm to the epididymis  Form the blood-testis barrier (BTB) • Isolates the developing sperm cells form the blood so immune cells from blood do not attack genetically different cells • Without it, immune cells would destroy developing sperm resulting in sterility o Leydig cells  Interstitial space between the seminiferous tubule (outside)  Produce testosterone • After formation of tubules, sperm moves into epididymis  Epididymis • Final maturation area and storage site for sperm • Another coiled tube • Drains into ductus deferens during ejaculation Reproductive System • Internal genitalia o Vas (or ductus) deferens  Carries sperm from the epididymis to the ejaculatory duct  Ejaculatory duct drains into the urethra o Seminal vesicles  Contribute large amount of fluid to the semen during ejaculation  Fluid is rich in fructose and enzymes  Fluid helps to maintain and nourish the sperm o Prostate gland  Secretes enzymes and fluid that help to neutralize the acid environment of the urethra and vagina o Bulbourethral gland (Cowper’s gland)  Secretes fluid that helps • Neutralize the pH • Lubricate the urethra and vagina to create an optimal environment for the sperm o Urethra  Transports the sperm during ejaculation and drains the bladder during urination • During ejaculation  Sperm travels through the ductus deferens (vas deferens)  Mixes with fluid from the seminal vesicles  Passes through the prostate  Receives more fluid from the bulbourethral (Cowper’s) gland  Enters Urethra  Passes through the penis Define spermatogenesis and describe the sequence of events involved in the entire process • Spermatogonia o Cells form which sperm cells arise o Divide by mitosis • Spermatogenesis o Production of sperm o Takes place in the seminiferous tubles o One daughter cell remains a spermatogonium and other becomes a primary spermatocyte o Primary spermatocyte divides by meiosis to form secondary spermatocytes o Both secondary spermatocytes divide again to form spermatids o The four spermatids differentiate into sperm cells • Sperm cell Reproductive System o Head contains  Acrosome and nucleus o Midpiece with mitochondria o Long tail or flagellum  Propel the sperm once it fully matures o 12 days for complete maturation o Maturation occurs while moved to the epididymis by the fluid that is secreted by the Sertoli cells Explain the control and regulation of the male reproductive system, including spermatogenesis and testosterone production • Testes controlled by the: o Follicle stimulating hormone (FSH) o Luteinizing hormone (LH, sometimes called interstitial cell stimulating hormone or ICSH)  FSH and LH are released by the anterior pituitary gland  Response to gonadotropin releasing hormone (GnRH) from the hypothalamus  FSH acts on the 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 the male sex hormone testosterone  Testosterone (essential for spermatogenesis) feedbacks to both the hypothalamus and the anterior pituitary to decrease the production and secretion of LH and FSH • Testosterone o Steroid hormone o Produced by Leydig cells in the testes o Occurs within Sertoli cells (Checkpoint after 14.14) – might be false • Testosterone production involves a serious of complex reactions o Begins with cholesterol and the formation of several intermediated ending in the production of testosterone  Progesterone • Female hormone (presence in males) • Is an intermediate leading to testosterone production • Testosterone Levels andAge o Levels vary throughout life o Rise in testosterone levels during fetal development Reproductive System  Necessary for the development of the male reproductive tract and external genitalia in the fetus o After birth, another brief increase (function is unknown) o Levels of testosterone remain low until puberty o Puberty  Marks transition from non-reproductive state to reproductive state  Occurs from 9-14  Levels of GnRH begin to increase  Increase in LH and FSH, causes testosterone levels to rise • Causes the final maturation of the male reproductive system to the point where mature sperm is produced • Sexual maturity and peak testosterone levels are reached around age 16-18 o Andropause  40 years of age • Slow decrease in levels of testosterone  50 years of age • Sperm production begins to decrease  Leydig cells no longer fully respond to LH  Accompanied with • Decreased sexual desire • Erectile ability • Fatigue • Depression • Decreased lean body mass • Increased obesity • Decreased bone density List the functions of testosterone 1. Development of male reproductive tract and external genitalia in the embryo 2. Growth and development of all male reproductive organs at puberty 3. The development of the male secondary sex characteristics at puberty a. Muscle growth b. Hair growth on face and around genitalia c. Deep voice 4. Sex drive at puberty 5. Spermatogenesis 6. Bone and skeletal muscle growth 7. Increased aggressiveness List the functions of the female reproductive system, showing all the structures List the functions of each of the female productive organs • Function of female reproductive system: Reproductive System o Responsible for producing sex steroid estrogen and the hormone progesterone o Produces eggs o Receives the sperm o Provides optimal conditions for the development of the fetus • External genitalia (vulva) o Clitoris  Small mound of erectile tissue  Derived from same embryonic tissue as the penis o Labium majus (labia majora)  Surrounds the labia minus (labia minora) • Encloses the vaginal orifice (opening to the vagina)  Both majus and minus are folds of skin deriv
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