The Reproductive System

1. The Reproductive System

2. Male and Female Reproductive Systems • Are functionally different • Female produces 1 gamete per month: • retains and nurtures zygote • Male disseminates large quantities of gametes: • produces 1/2 billion sperm per day

3. Functions • To ensure survival of the species • produce egg and sperm cells • transport & sustain these cells • nurture the developing offspring • produce hormones

4. The Male Reproductive System

5. Pathway of Sperm • Testes or male gonads: • secrete male sex hormones (androgens) • testosterone • produce male gametes (spermatozoa or sperm) • contribute X and Y chromosomes

6. Pathway of Sperm • Epididymis • superior to each testis • tubular (5-6cm) • takes ~2 weeks for sperm to mature/ travel through

7. Pathway of Sperm • Vas deferens: • tubes • transport sperm from testes to the ejaculatory ducts • where a vasectomy occurs

8. Pathway of Sperm • Ejaculatory duct • Urethra • passes urine & semen out • entrance way for STDs

9. Accessory Organs • Secrete fluids into ejaculatory duct & urethra • Seminal vesicles • secrete alkaline fluid containing fructose, vitamin C, and coagulating enzymes • Prostate gland • produces milky white fluid which activates sperm • Bulbourethral gland • thick clear ejaculate fluid which neutralizes traces of acidic urine in the urethra

11. External Genitalia • Scrotum: • surrounds testes • scrotal skin lengthens and shrinks to maintain optimal temperature • Penis: • erectile organ

13. Sperm

15. Spermatogenesis

16. Testosterone • Stimulates spermatogenesis • Affects CNS functions • libido & related behaviors • Stimulates metabolism • blood cell formation, muscle growth

17. Testosterone • Establishes male secondary sex characteristics: • distribution of facial hair • increased muscle mass and body size • characteristic adipose tissue deposits • Maintains accessory glands and organs of male reproductive tract

19. Female Reproductive System

20. Functions • Produces sex hormones and functional gametes • Protects and supports developing embryo • Nourishes newborn infant

21. Female Organs • Ovaries or female gonads: • release 1 immature gamete (oocyte) per month • produces estrogen & progesterone

22. Female Organs • Ovum (egg): • female reproductive cell • contributes X chromosome

23. Female Organs • Fallopian tubes: • carry oocytes to uterus

24. Female Organs • Uterus: • “womb” • encloses and supports developing embryo • lining is shed when no fertilized egg is present • Cervix: • lower end of the uterus

25. Female Organs • Vagina: • connects uterus with exterior • pathway for menstrual flow, birth canal, sperm, & STDs

26. Mammary Glands • Modified sweat glands • Ducts and glands do not complete development unless pregnancy occurs

27. Estrogen • Stimulates bone and muscle growth • Maintains female secondary sex characteristics: • body hair distribution • adipose tissue deposits

28. Estrogen • Affects central nervous system (CNS) activity (especially in the hypothalamus, where estrogens increase the sexual drive) • Maintains functional accessory reproductive glands and organs • Initiates repair and growth of endometrium

29. Oogenesis • Begins before birth • Accelerates during puberty • Ceases at menopause

30. Aging - Females • Menopause • ovulation and menstruation cease • ~ ages 45-55 • levels of estrogen & progesterone decline • reduction in uterus & breast size • reduction in bone deposits (osteoporosis)

31. Aging - Males • Andropause • aka male climacteric • occurs over a gradual period of time • testosterone declines • ~ age 50-60 • sperm production continues

33. Fertilization • May occur when: • sperm are present • a few days after ovulation • Location: • fallopian tube • Process: • head of sperm enters ovum • nuclei fuse • zygote is formed

34. Fertilization • Cleavage: • initial division of the zygote • continues as the zygote moves towards the uterus • the zygote becomes a blastocyte (hollow ball of cells) • Implantation: • ~ 6 days after fertilization • blastocyte burrows into the lining of the uterus

35. Early Zygote Development

36. Pregnancy • 9 month gestation period • Divided into trimesters • 3-month periods • First 8 weeks of pregnancy: • developing human is called an embryo

37. Pregnancy • First Trimester: • supportive membranes • rapid growth • amnion closes & protects the embryo • chorion forms the placenta • structure through which the mother nourishes the embryo

38. Structure of the Placenta

39. Pregnancy • First Trimester: Development of Embryo • 4th week: • major organs are formed • heart begins to beat • 2nd month: • arms and legs take shape • major internal organs are evident

40. Embryo Development

41. Pregnancy • First Trimester: Development of Fetus • from 8th week - delivery • After 1st trimester: • sex can be distinguished • recognizable body features • organ systems have begun to form

42. Pregnancy • Second and Third Trimesters: • fetus grows rapidly • organs become functional • 3rd trimester: • fetus can exist outside the mother’s body • ~9 months: • fetus leaves the mother’s body in a process called labor • usually lasts several hours

43. Events of Human Fetal Development

44. Pregnancy • During childbirth, the fetus exits the mother’s body through the vagina.