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Lecture 28, The Reproductive System

Lecture 28, The Reproductive System. Lecturer: Dr. Barjis Room: P313 Phone: (718) 260-5285 E-Mail: ibarjis@citytech.cuny.edu. Learning Objectives. Specify the components of the reproductive system, and summarize their functions

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Lecture 28, The Reproductive System

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  1. Lecture 28, The Reproductive System Lecturer: Dr. Barjis Room: P313 Phone: (718) 260-5285 E-Mail: ibarjis@citytech.cuny.edu

  2. Learning Objectives • Specify the components of the reproductive system, and summarize their functions • Describe the components of the male and female reproductive systems • Outline the processes of meiosis and gametogenesis in both sexes • Explain the roles played by the male reproductive tract and accessory glands in the functional maturation, nourishment, storage, and transport of spermatozoa

  3. Learning Objectives • Summarize the anatomical, physiological, and hormonal aspects of the male and female reproductive cycles • Discuss the physiology of sexual intercourse

  4. Reproductive System • The only system not essential for life, but ensures continued human existence • Functions of Reproductive system include: • Production of gametes • Storage gametes • Nourishment gametes • Transport gametes • In female additional functions such as provide nutrient and support to the developing embryo, fetus and infant • Fertilization • Fusion of male and female gametes to form a zygote

  5. Reproductive system includes: • Organs of reproductive system include: • 1) Gonads (testes, ovaries) – produce sperm/egg • Testes produce gametes (spermatozoa/ sperm) 1.5 billion each day and secrete sex hormones (testosterone) • Ovaries release one immature gamete (oocyte) per month • 2) Ducts – a passageway that opens to the exterior and transport gamete • Sperm is mixed with secretion of accessory glands along ducts and converted to semen • Oocyte travels along uterine tube to uterus • 3) Accessory glands and organs – these organs secrete fluid e.g. seminal vesicle secrete seminal fluid • 4) External genitalia

  6. Male Reproductive System: Sperm Passageway • Spermatozoa is produced in testes in the seminiferous tubules • Seminiferous tubules are tightly coiled tubes found in lobules of testes • From seminiferous tubules sperms are passed to afferent ductules • Afferent ductules pass the sperm to retestestes • From rete testes spearm leave the testes by efferent tuctules • Efferent tuctules deliver the sperm to the epididymis

  7. The Structure of the Testes

  8. Male Reproductive System: Sperm Passageway • Epididymis pass the sperms to the duct deference • From ductus deferens, sperms are passed to the ejaculatory duct • Ejaculatory duct is connected to the urethra Accessory organs of male reproductive system • Seminal vesicles • Prostate gland • Bulbourethral glands • Scrotal sac encloses testes • Penis

  9. The Male Reproductive System

  10. Sperm production: Spermatogenesis • Sperm production takes place in seminiferous tubules • Seminiferous tubules contain sustencular cells and stem cells called spermatogonia • Stem cells involved in spermatogenesis • Sustencular cells sustain and promote development of sperm • Interstitial cells between seminiferous tubules secrete sex hormones (testosterone)

  11. Sperm production: Spermatogenesis • Spermatogenesis involves three processes • 1) Mitosis • In this process spermatocytes are produced from spermatogonium • 2) Meiosis • In this process spermatocytes go through meiosis I and meiosis II and produce 4 spermatids • 3) Spermiogenesis • In this process spermatids differentiate into spermatozoa

  12. Sperm production: Spermatogenesis Figure 28.7

  13. Sperm production: Spermatogenesis

  14. Sperm production: Spermatogenesis

  15. Sperm production: Spermatogenesis

  16. Sperm production: Spermatogenesis

  17. Sperm production: Spermatogenesis

  18. The testes • Descent of the testes • Movement of testes through inguinal canal into scrotum • Occurs during fetal development • Testes anatomy • Tunica albuginea surrounds testis • Septa extend from tunica albuginea and divides testes into lobules • Within each lobule tightly coiled tubes called seminiferous are located • Sperm production occurs in seminiferous tubules

  19. The Descent of the Testes

  20. Anatomy of spermatozoon • Each spermatozoon is divided into 3 part: • 1) Head that contains: • Nucleus and densely packed chromosomes • 2) Middle piece that contains • Mitochondria that produce the ATP needed to move the tail • 3) Tail • The only cell with flagellum in the human body • It enables the spermatozoa to swim

  21. Spermiogenesis and Spermatozoon Structure

  22. Male reproductive tract: Epididymus • Epididymus is elongated tubule with head, body and tail regions • Functions of epididymus are to: • 1) Monitor and adjust fluid in seminiferous tubules • 2) Store and protect spermatozoa • 3) act as a recycling center for damaged spermatozoa • 4) Facilitates functional maturation of spermatozoa • Although spermatozoa leaving the epididymis are mature, but they remain immobile. • Spermatozoa will become functionally mature when: • 1) mixed with secretions of the seminal vesicles,(become mobile • 2) exposed to conditions in the female reproductive tract(become capable of fertilization)

  23. The Epididymus

  24. Ductus deferens AKA vas deferens • Begins at epididymus • Passes through inguinal canal • Enlarges to form ampulla • Peristaltic contractions propel spermatozoa and fluid along the duct • Functions of Duct Deferens: • Transport spermatozoa, • Store spermatozoa (for several months) • The junction of the ampulla with the duct of the seminal vesicle marks the start of the ejaculatory duct • Ejaculatory duct is a short passageway that penetrates the muscular wall of the prostate gland and empties into the urethra

  25. Urethra • This passageway is used by both urinary and reproductive systems • This passageway begins at the urinary bladder and ends at the tip of the penis • Urethra divides into three regions • Prostatic • Membranous • Penile

  26. Accessory glands • Important glands include the seminal vesicles, the prostate gland, and the bulbourethral glands • Seminal vesicles • Contributes about 60% of the total volume of semen • Secretions of seminal vesicle contain fructose, prostaglandins, fibrinogen • Fructose is metabolized by spermatozoa and used as a source of energy • Prostaglandins stimulates smooth muscle contractions along the reproductive tracts (e.g. vagina), thus it helps spermatozoa to move • Fibrinogen forms a temporary clot within the vagina to prevent damage to the spermatozoa by the acidic environment of vagina. • Spermatozoa become mobile after mixing with seminal vesicles secretion

  27. Accessory glands • Prostate gland • Secretes an alkaline prostatic fluid that accounts for about 20-30 % of semen volume • Contains seminalplasmin (an antibiotic that prevents urinary tract infection) • The alkaline secretion helps to neutralizes acid along the urethra and in the vagina • Bulbourethral glands • Secrete alkaline mucus with lubricating properties

  28. The Ductus Deferens and Accessory Glands

  29. Contents of Semen • Typical ejaculate = 2-5 ml fluid that contain: • 1) Contains between 20 – 100 million spermatozoa per ml • 2) Seminal Fluid about 60% • 3) Prostatic Fluid about 20-30 % • 4) Enzymes such as: • Protease – helps dissolve mucous secretion in the vagina • Seminalplasmin – antibiotic enzyme that kills bacteria • Enzymes that convert fibrinogen to fibrin that will clot the semen • Fibrinolysis – liquefies the clotted semen after the virginal environment is neutralized

  30. External genitalia • Male external genitalia consist of the scrotum and the penis • Skin overlying penis resembles scrotum • Penis • Contains three masses of erectile tissue • 2 corpora cavernosa beneath fascia • 1 corpus spongiosum surrounding urethra • Dilation of erectile tissue produces erection

  31. The Penis

  32. Hormones of male and female reproductive system • At puberty Hypothalamus produces GnRH (Gonadotropin releasing hormone) • GnRH stimulates production of FHS and LH by the pituitary gland • FSH (Follicle stimulating hormone) • In male FSH targets sustentacular cells of testes and stimulates spermatogenesis (production of sperm) • In female FSH stimulates development of follicle (egg) • Developing follicle produces estrogen • LH (leutinizing hormone) • In male LH causes secretion of testosterone and other androgens by the interstitial cells • In female LH stimulates secretion of progesterone by corpus luteum • In female LH surge leads to ovulation

  33. Hormones of male and female reproductive system • Testosterone • 1) stimulating spermatogenesis • 2) affect sexual drive(libido) • 3) stimulate metabolism • 4) stimulate the male secondary sexual characteristics • 5) maintaining accessory glands and organs of male reproductive tract • Progesterone • Stimulateendometrial growth and secretion • Estrogen • 1) stimulating bone and muscle growth • 2) stimulate female secondary sexual characteristics • 3) initiating the repair and growth of the endometrium

  34. Hormonal Feedback and the Regulation of the Male Reproductive Function

  35. The Hormonal Regulation of Ovarian Activity

  36. The Reproductive System of the Female Principle organs of the female reproductive system • Ovaries • Uterine tubes • Uterus • Vagina

  37. The Female Reproductive System

  38. The ovaries • Held in position by ovarian and suspensory ligaments • Blood vessels enter at ovarian hilus • Tunica albuginea covers ovary

  39. The Ovaries and Their Relationships to the Uterine Tube and Uterus

  40. Oogenesis • Oogenesis is the process of ovum production • It occurs monthly in ovarian follicles • Part of ovarian cycle • Follicular phase (preovulatory) • Luteal phase (postovulatory)

  41. The ovarian cycle • Steps in the ovarian cycle • 1) Formation of primary, secondary, and tertiary follicles • 2) Ovulation • 3) Formation and degeneration of the corpus luteum • Corpus luteum begins to degenerate roughly 12 days after ovulation if fertilization does not occur • 4) Degradation of the corpus luteum

  42. The Ovarian Cycle

  43. The Ovarian Cycle

  44. The Uterine tubes • Uterine tubes (Fallopian tubes or oviducts) is divided into: • 1) Infundibulum • End of infundibulum closest to the ovary has numerous fingerlike projections called fimbriae • 2) Ampulla • The middle portion • 3) Isthmus • A short segment connected to the uterine wall • Each uterine tube opens directly into uterine cavity • Fertilization occurs in uterine tube • 12-24 hours after ovulation

  45. The Uterine Tubes

  46. The uterus • The uterus is a muscular organ • Its functions are: • 1) Mechanical protection • 2) Nutritional support • 3) Waste removal for the developing embryo and fetus • Major anatomical landmarks of uterus • Body • Isthmus • Cervix • Cervical os (internal orifice) • Uterine cavity • Cervical canal • Internal os (internal orifice)

  47. The Uterine Wall • Uterine wall consists of 3 layer: • Myometrium – outer muscular layer • Endometrium – a thin, inner, glandular mucosa • Perimetrium – an incomplete serosa continuous with the peritoneum

  48. Uterine cycle • Repeating series of changes in the endometrium • Uterine cycle continues from menarche (the first minstruation) to menopause (the last minstruation) • Uterine cycle is divided into 3 phases: • 1) Menses • Degeneration of the endometrium • Menstruation • 2) Proliferative phase • Restoration of the endometrium • 3) Secretory phase • Endometrial glands enlarge and accelerate their rates of secretion

  49. The Uterine Cycle

  50. The vagina • Vagina is an elastic, muscular tube • Major functions of vagina are: • 1) Passageway for elimination of menstrual fluids • 2) Receives the penis during sexual intercourse • Also hold spermatozoa prior to their passageway into the uterus • 3) Forms the inferior portion of the birth canal

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