1. Biology – Premed Windsor University School of Medicine and Health Sciences Human Reproduction

2. Pre Med – Biology Chapter 18 Human Reproduction There is more to lectures than the power point slides! Engage your mind

3. REPRODUCTIVE SYSTEM The reproductive system of the human male is designed to produce sperm and deliver them, in semen, to the female of the species during sexual intercourse. The function of the female reproductive system is to mature and make available an egg by ovulation

4. Definitions Gonad - Reproductive organ that produce gametes –E.g. Testis in males, Ovary in females Gametes - Sexual reproductive cell –E.g. Sperm in males, Egg in females –Contain only one set of chromosome called “haploid” (one set of 23 chromosomes)

5.  Reproductive Anatomy of the Human Male.  The scrotum and the penis are the external components of the reproductive system.  The internal reproductive organs consist of gonads, accessory sex glands, and ducts. Human reproduction involves intricate anatomy and complex behavior

6. Male Reproductive System

8.  External structure of the penis:  The shaft of the penis is covered by relatively thick skin.  The sensitive glans penis is covered by thinner skin.  The glans is covered by the prepuce (foreskin) which may be removed by circumcision.  There is verifiable health benefit to circumcision.

9.  The penis is composed of three layers of spongy erectile tissue.  During sexual arousal the erectile tissue fills with blood from arteries.  The resultant increased pressure seals off the veins that drain the penis.  The engorgement of the penis with blood causes an erection.  An erection is essential to the insertion of the penis into the vagina.  The penis of some mammals possesses a baculum, a bone that helps stiffen the penis.

11.  Impotence (Failed erection) can result from the consumption of alcohol and other drugs, and emotional, nervous system, or circulatory problems.  Treatment includes drugs and penile implant devices.  Viagra ®

12. Testes

13.  Testes are the male gonads.  Consists of many highly coiled Seminiferous Tubules surrounded by layers of connective tissue.  Sperm produced in seminiferous tubules.

14. Testis also have interstital cells in between the seminiferous tubules  Leydig cells (interstitial cells), scattered between seminiferous tubules produce androgens (ex. Testosterone)  Stimulated by Leutinizing Hormone (LH)  Sertoli Cells found within the seminiferous tubules  Surround and nurture the spermatids  Stimulated by Follicle Stimulating Hormone (FSH)

15.  Testes are located in the scrotum, outside the body cavity.  This keeps testicular temperature cooler than the body cavity.  The testes develop in the body cavity and descend into the scrotum just before birth.  From the seminiferous tubules sperm pass to the coiled tubules of the Epididymis.  It takes about 20 days for sperm to pass through the tubules of the epididymis.  In the epididymis sperm become motile and gain the ability to fertilize.

16. Epididymis Coiled duct located outside on the surface of testis Site for maturation of the sperm Sperm initiates its propelling motion

17. Ductus ( Vas) Deferens From epididymis, sperm moves into vas deferens where it is stored In vas deferens, sperm travel up and around both sides of the bladder, entering the ejaculatory duct Ejaculatory ducts merge into a urethra carrying out urine Vasectomy - Surgical blockage of vas deferens, permanent form of birth control

18. Semen  Seminal fluid is thick, yellowish, and alkaline.  It contains mucus, fructose, a coagulating enzyme, ascorbic acid, and prostaglandins. Accessory glands:  seminal vesicle  prostate gland  bulbourethral gland

19. Seminal vesicle: A pair of glands that secrete a liquid component of semen into the vas deferens. Secretion is alkaline, which neutralizes the acidic condition of the female genital tract. Seminal fluid contains fructose (nourishment) Each seminal vesicle contributes seminal fluid via ducts into the vas deferens Seminal Vesicle

20. Prostate gland: Location- surrounds and opens into the urethra where it leaves the bladder. Secretion- slightly alkaline fluid that activates the sperm and prevents them from sticking together Provides Buffers that adjust the pH of semen  Prostate problems are common in males over 40.  Prostate cancer is one of the most common cancers in men.

21. Prostate

22. Bulbourethral gland (Cowper’s gland): Location- paired glands that lie beneath the prostate Secretion- a thick, clear alkaline mucous that drains into the membranous urethra. Function- It acts to wash residual urine out of the urethra when ejaculating semen-- raises pH; neutralizes acidity of urine. Bulbourethral gland

23.  Ejaculation propels sperm from the epididymis to the vas deferens.  The vas deferens run from the scrotum and behind the urinary bladder.  Here each vas deferens joins with a duct from the seminal vesicle to form an ejaculatory duct.  The ejaculatory ducts open into the urethra.  The urethra drains both the excretory and reproductive systems. Ejaculation

24.  A male usually ejaculates about 2 – 5 mL of semen; each milliliter containing about 50 – 130 million sperm. –Bulbourethral fluid also carries some sperm released before ejaculation. This is one of the reasons why the withdrawal method of birth control has a high failure rate. Ejaculate

25. SPERMATOGENESIS

30. SPERM Head The head contains the 23 chromosomes (genetic material) capable of merging with an egg to produce a new individual. Acrosome The acrosome resembles a toque which covers the upper portion of the head of the sperm. The covering contains enzymes that help the sperm penetrate the egg.

31. Midpiece The midpiece connects the head of the sperm to the tail. It contains many mitochondria that produce ATP. This ATP is used to move the microtubules in the tail and create propulsion for the sperm Once in the female system, sperm will "swim" for up to 2 days looking for an egg. Tail The tail of a sperm is really a flagellum with the common 9+2 arrangement of microtubules. The microtubules within the tail move past each other and move the tail in a whip-like motion. ATP provided by the midpiece is required for this movement.

33. spermatogonium 1º spermatocyte 2º spermatocyte spermatids Sertoli cell spermatozoa Seminiferous Tubules

34. Sperm Maturation & Development (maturation: 62-72 days)

35. Hormones Involved in Spermatogenesis Gonadotropin Releasing Hormone (GnRH) Follicle Stimulating Hormone (FSH) Interstitial Cell Stimulating Hormone (ICSH), also called LH Testosterone Inhibin

37. HypothalamusHypothalamus Anterior Pituitary GnRH FSHICSH/LH Hormonal Control of Spermatogenesis

38. Interstitial Cells ICSH/LH Testosterone Hormonal Control of Spermatogenesis

39. Sertoli Cells Testosterone Spermatogenesis FSH Inhibin Hormonal Control of Spermatogenesis

40. Feedback Inhibition Inhibin Acts on anterior pituitary Inhibits FSH production Testosterone Acts on hypothalamus Inhibits GnRH production Hormonal Control of Spermatogenesis

41. Some Other Effects of Testosterone muscle and bone growthmuscle and bone growth facial and pubic hair growthfacial and pubic hair growth thickening of vocal cordsthickening of vocal cords growth of pharyngeal cartilagegrowth of pharyngeal cartilage hair follicle effectshair follicle effects stimulates sebaceous glandsstimulates sebaceous glands

42. Female Reproductive System

43. Reproductive Anatomy of the Human Female  External reproductive structures:  labia  clitoris  vaginal opening  Internal reproductive structures:  ovaries  fallopian tube (uterine tube)  cervix  uterus  vagina  fimbrae

46. Biology 100 Human Biology cervix vagina fimbriae uterine tube ovary uterus bladder urethra clitoris l. minora l. majora vaginal orifice Female Reproductive System

47. Biology 100 Human Biology uterine tube ovary egg uterus cervix vagina endometrium myometrium perimetrium

48. Oogenesis in the Ovary

49. Oogenesis Ovary- contains 400,000 oocytes; release about 500 in a lifetime Ovary- under influence of FSH. The follicles mature every 28 days Primary follicle produces estrogens And primary oocyte completes its 1 st division produces 2ndary oocyte and polar body

50. Oogenesis Aprox 1/2 way through the 28 day cycle the follicle reaches the mature Vesticular or Graffian follicle stage. Estrogen levels rise and release LH and FSH and triggers ovulation. The 2ndary oocyte travels down the uterine tube to the uterus. If fertilized by sperm, it will produce a zygote

52. Oogenesis

53. Ovum

54. Hormones Involved in the Female Reproductive Cycle Gonadotropin Releasing Hormone (GnRH)Gonadotropin Releasing Hormone (GnRH) Follicle Stimulating Hormone (FSH)Follicle Stimulating Hormone (FSH) Luteinizing Hormone (LH)Luteinizing Hormone (LH) EstrogenEstrogen ProgesteroneProgesterone

55. HypothalamusHypothalamus Anterior Pituitary GnRH FSHLH Female Hormonal Cycle

56. Follicle Cells LH Estrogen FSH Female Hormonal Cycle

62. The Uterine Cycle The Uterine Cycle

63. Ovarian Cycle

66. Hormone Fluctuation

67. Some Other Effects of Estrogen breast development external genitalia growth stimulates bone growth increases HDL and lowers LDL

68. Menopause: cessation of ovarian and menstrual cycles.  Usually occurs between ages 46 and 54.  Due to ovaries decreased responsiveness to gonadotropins. Menopause affects:  changes in sexual desire  triggers mood swings  causes debilitating hot flashes  may lead to bone and heart problems  short-term memory loss  insomnia

69.  Mammary glands.  Are present in both males and females.  Are not a component of the reproductive system.  Contain epithelial tissue that secrete milk.  Milk drains into a series of ducts opening at the nipple.

70. Female Reproductive System Produce hormones (estrogen and progesterone) for secondary sexual characteristics. Produce one large oocyte at regular intervals and release it in such a way that it enters the oviduct (“Fallopian tube”,“uterine tube”). Receive semen from the male and transport it into the oviduct. Produce hormones (estrogen and progesterone) which prepare the uterus for pregnancy each cycle by thickening its inner lining; Getting rid of this thickened lining each cycle if pregnancy does not occur. Protect and nourish the embryo and fetus during pregnancy, then expel it through the vagina Produce milk to nourish the newborn

72. Ovary: Located within pelvis, 2 to 5 cm (1 to 2 inches) lateral to the uterus Approximately 3cm x 2cm x 1cm Central region, or “medulla”, consists of connective tissue with many blood vessels. Outer region, or “ ”, has all of the oocytes. One or two of these oocytes may be developing before ovulation; undeveloped ones are stored here. Also contains the remnant from the previous cycle’s ovulation, called a “ “, which secretes progesterone to keep uterus ready for implantation of the embryo

73. Maturation of an oocyte is called oogenesis, which leads to ovulation During oogenesis, the oocyte is surrounded by follicular cells granulosa cells in one or more layers, forming a.

74. The developing oocyte and its follicle: Four stages before ovulation

75. 2. : Develop only after puberty; 3 to 4 enter this stage each cycle No change in primary oocyte Follicle has begun development – cells are larger

76. The developing oocyte and its follicle: Four stages before ovulation : 3. : 1 or 2 primary follicles progress to this stage each cycle Primary oocyte larger, finishes first division of meiosis to become a secondary oocyte, also forming a polar body. Follicle grows larger as follicular cells divide to form many layers; spaces begin to develop in center of follicle

77. The developing oocyte and its follicle: Four stages before ovulation. 4.. Most follicles which made it to “secondary” will reach this stage Follicle is very large; Many layers of cells surrounding fluid-filled center called antrum Secondary oocyte covered with thick, clear membrane called zona pellucida; pushed to one side in follicle and surrounded by mass of follicular cells called cumulus oophorus

78. Big Question: How is this process of oogenesis regulated? Oogenesis, as well as ovulation and many other things, is regulated by the pituitary gland, which lies just below the brain

79. Oogenesis and growth of the follicle in the ovary are initiated and stimulated by from the pitutitary During this oogenesis under the stimulation of FSH, follicular cells surrounding the oocyte secrete the hormone, which stimulates the inner lining of the uterus to thicken and begin secreting mucus, getting ready for pregnancy This estrogen from the follicular cells also inhibits the pituitary gland from secreting any more FSH. Thus, no more follicles will be stimulated to develop until it stops.

80. Rupture of the follicle is ovulation. The secondary oocyte, surrounded by the zona pellucida and cumulus oophorus, is released from the surface of the ovary, where it can be captured by the open end of the oviduct. The cumulus oophorus now called the corona radiata.

81. Luteinizing hormone also causes the follicular cells of the now empty follicle to develop into a. This structure secretes the hormone Ovulation is triggered when the pituitary gland secretes a different hormone, called.

82. Before ovulation: FSH stimulates cells of follicle to secrete, which stimulates the lining of the uterus to develop. After ovulation: LH stimulates cells of the corpus luteum to secrete, which maintains the uterine lining in this “ready for pregnancy” condition If fertilization and pregnancy occur, the placenta of the embryo secretes a hormone called, which stimulates the corpus luteum to keep secreting progesterone, which in turn keeps the lining of the uterus thick and full of blood vessels. If fertilization and pregnancy do not occur, after a few days the corpus luteum deteriorates and stops producing progesterone. Without its stimulus, the uterus can not maintain its thick lining, so this falls off and is shed as menstruation.

84. When the oocyte is released from the surface of the ovary during ovulation, it is picked up by the oviduct, or Fallopian Tube, a hollow muscular tube which leads from near the uterus to the ovaries.

85. Oviduct: Lateral End: Wide opening, or, surrounds the surface of the ovary. The edge is surrounded by finger-like. Middle Part: Wide Medial End: Narrow leads into uterus. Cavity of oviduct is continuous with cavity of uterus

86. By mechanisms not completely understood: The oviduct moves the oocyte toward the uterus The oviduct moves sperm away from the uterus Fertilization occurs in ampulla of oviduct, forming the zygote, which goes through repeated mitotic cell divisions to eventually form the embryo. Oviduct moves this growing mass of pre-embryo cells toward uterus: takes 3 or 4 days. Secretions from oviduct are necessary to keep sperm, oocyte, and embryo alive.

87. Uterus: Anterior to rectum; Posterior & superior to bladder Narrowed inferiorly to form cervix, which projects into vagina

88. Uterus: Outer layer = : Thick layer of muscle Inner layer = : Lots of glands & blood vessels Two layers of endometrium: : Closer to myometrium; Remains after menstruation; Regrows functional layer : Closer to cavity; Thickens every cycle; Embryo implants here during pregnancy; Dies and falls off during menstruation Inferior end narrows to form, which projects down into vagina

89. Mass of Uterus: Immediately before menstruation: 100 – 150 grams Immediately after end of menstruation: 50 – 100 grams End of pregnancy: 1,000 – 1,500 grams At end of pregnancy: Uterus extends from vagina inferiorly to bottom of sternum superiorly Lies anterior to all other abdominal organs except bladder

90. Vagina: Thin-walled, tubular Inferior to uterus; Anterior to rectum Posterior to bladder & urethra Receives penis and semen during sexual intercourse Passage for delivery of fetus or menstrual flow

91. External Genitalia: The vagina opens between the into a space called the Outside of those are the At the anterior junction of the outer labia is the Note that

92. The head, or glans, of the clitoris which is visible externally is only a small part of this organ. Two shafts of erectile tissue extend backwards along the pelvic floor on either side of the urethra and vagina.

93. Uterus Vagina Clitoris Oviduct Labium majora Ovary Lateral to uterus Bladder Rectum Pubic Bone Urethra Labium minora x

94. PLACENTA

95. Following fertilization of the egg by a sperm cell, the zygote travels down the oviduct towards the uterus. At this stage in the uterine cycle, the endometrium or uterine lining is well developed and ready to receive the zygote When the zygote reaches the uterus a few days after fertilization, it settles into the endometrium. This process is called implantation The embryonic and maternal tissues are both involved in formation of the placenta The placenta allows the exchange of materials (nutrients and wastes) to take place between the blood vessels of the mother and the fetus.

96. When the placenta begins development, it releases human chorionic gonadotropin (HCG) which stimulates the corpus luteum in the ovary to continue production of estrogen and progesterone High levels of estrogen and progesterone prevent menstruation, maintain the endometrium, and inhibit FSH and LH production by the anterior pituitary so the ovarian cycle does not begin again during early pregnancy

97. The placenta is fully formed by the end of ten weeks. At this point, the placenta is producing estrogen and progesterone The production of these hormones now maintains the uterine lining and prevents the maturation of a new egg and ovulation by feedback inhibition. The corpus luteum is no longer needed.