The Reproductive Systems

1. The Reproductive Systems The male and female reproductive systems -producegametes, that is, sperm and egg cells, and -ensure the union of gametes in fertilization - in women, the uterus provides the site for the developing embryo/fetus until it is sufficiently developed to survive outside the womb

2. MEIOSIS • The cell division process of meiosis produces the gametes—sperm or egg cells. • In meiosis, one cell with the diploid number of chromosomes (46 for humans) divides twice to form four cells, each with the haploid number of chromosomes. • Haploid means half the usual diploid number, so for humans the haploid number is 23.

3. SPERMATOGENESIS • Spermatogenesis is the process of meiosis as it takes place in the testes,. • Within each testis are seminiferous tubules that contain spermatogonia, which are stem cells that generate sperm. • A spermatogonium divides by mitosis to form two cells, one of which will remain in place as a stem cell, while the other differentiates (specializes) to become a primary permatocyte that will undergo meiosis .

4. Role of Hormones • Follicle-stimulating hormone (FSH) from the anterior pituitary gland initiates sperm production. • Testosterone,secreted by the testes when stimulated by luteinizing hormone (LH) from the anterior pituitary, promotes the maturation of sperm. * Inhibin, also produced by the testes, decreases the secretion of FSH. For each primary spermatocyte, four functional sperm cells are produced.

5. Sperm &Ova production • Sperm production begins at puberty (10 to 14years of age), and millions of sperm are formed each day in the testes. *Although sperm production diminishes with advancing age, there is usually no complete cessation, as there is of egg production in women at menopause

6. OOGENESIS • Oogenesis is the process of meiosis for egg cell formation; • it is regulated by hormones: - FSH initiates the growth of ovarian follicles, each of which contains an oogonium, a stem cell for egg cell production . This hormone also stimulates the follicle cells to secrete estrogen, which promotes the maturation of the ovum.

7. Notice for each primary oocyte that undergoes meiosis, only one functional egg cell is produced. The other three cells produced are called polar bodies. They have no function, • and will simply deteriorate. • A mature ovarian follicle actually contains the secondary oocyte. • The second meiotic division will take place if and when the egg is fertilized

8. Oogenesis • The production of ova begins at puberty (10 to 14years of age) and continues until menopause (45 to 55years of age), when the ovaries atrophy and no longer respond to pituitary hormones. • During this 30- to 40-year span, egg production is cyclical, with a mature ovum being produced approximately every 28 days • Actually, several follicles usually begin to develop during each cycle. • However, the rupturing (ovulation) of the first follicle to mature stops the growth of the others

9. Fertilization • It is union of nuclei of sprm &ovum • The haploid egg and sperm cells produced by • meiosis each have 23 chromosomes. • When fertilizaTion occurs, the nuclei of the egg and sperm merge,and the fertilized egg (zygote) has 46 chromosomes, the diploid number. • Thus, meiosis maintains the diploid number of the human species by reducing the number of chromosomes by half in the formation of gametes

12. MALE REPRODUCTIVE SYSTEM • The male reproductive system consists of • 1- two testes • 2- series of ducts : epididymis, ductus deferens, ejaculatory duct, and urethra . • 3- the reproductive glands: seminal vesicles, prostate gland, and bulbourethral glands.

13. TESTES • The testes are located in the scrotum, a sac of skin between the upper thighs. • The temperature within the scrotum is about 34c, slightly lower than body temperature, which is necessary for the production of viable sperm. • In the male fetus, the testes develop near the kidneys, then descend into the scrotum just before birth. Cryptorchidism is the condition in which the testes fail to descend, and the result is sterility unless the testes are surgically placed in the scrotum.

15. Testis • Each testis is about 1.5 inches long by 1 inch wide (4 cm by 2.5 cm) and is divided internally into lobes • Each lobe contains several seminiferous tubules, in which spermatogenesis takes place. • Among the spermatogonia of the seminiferous tubules are sustentacular (Sertoli) cells, which produce the hormone inhibin when stimulated by testosterone.

16. Testis • Between the loops of the seminiferous tubules are interstitial cells, which produce testosterone when stimulated by luteinizing hormone (LH) from the anterior pituitary gland. • Besides its role in the maturation of sperm, testosterone is also responsible for the male secondary sex characteristics, which begin to develop at puberty .

17. sperm cell • A sperm cell consists of several parts: - The head contains the 23 chromosomes. -On the tip of the head is the acrosome, which is similar to a lysosome and contains enzymes to digest the membrane of an egg cell. - Within the middle piece are mitochondria that produce ATP. -The flagellum provides motility. It is the beating of the flagellum that requires energy from ATP. • Sperm from the seminiferous tubules enter a tubular network called the rete testis, then enter the epididymis, the first of the reproductive ducts.

19. EPIDIDYMIS • The epididymis (plural: epididymides) is a tube about 20 feet (6 m) long that is coiled on the posterior surfaceof each testis. • within the epididymis the sperm complete their maturation, and their flagella become functional. • Smooth muscle in the wall of the epididymis propels the sperm into the ductus deferens.

21. DUCTUS DEFERENS • Also called the vas deferens, • It extends from the epididymis in the scrotum on its own • side into the abdominal cavity through the inguinal canal. • This canal is an opening in the abdominal wall for the spermatic cord, a connective tissue sheath that contains the ductus deferens, testicular blood vessels, and nerves. • Because the inguinal canal is an opening in a muscular wall, it is a natural “weak spot,” and it is the most common site of hernia formation in men

22. Once inside the abdominal cavity, the ductus deferens extends upward over the urinary bladder, then down the posterior side to join the ejaculatory duct on its own side . • The smooth muscle layer of the ductus deferens contracts in waves of peristalsis as part of ejaculation

23. EJACULATORY DUCTS • Each of the two ejaculatory ducts receives sperm from the ductus deferens and the secretion of the seminal vesicle on its own side. • Both ejaculatory ducts empty into the single urethra

24. SEMINAL VESICLES • The paired seminal vesicles are posterior to the urinary bladder . • Their secretion contains fructose to provide an energy source for sperm and is alkaline to enhance sperm motility. *The duct of each seminal vesicle joins the ductus deferens on that side to form the ejaculatory duct.

25. PROSTATE GLAND • A muscular gland just below the urinary bladder, it is 3 cm by 4 cm by 2 cm, about the size of a walnut). • It surrounds the first inch of the urethra as it emerges from the bladder . • The glandular tissue of the prostate secretes an alkaline fluid that helps maintain sperm motility. *The smooth muscle of the prostate gland contracts during ejaculation to contribute to the expulsion of semen from the urethra

26. BULBOURETHRAL GLANDS • Also called Cowper’s glands, about the size of peas and are located below the prostate gland; they empty into the urethra. • Their alkaline secretion coats the interior of the urethra just before ejaculation,which neutralizes any acidic urine that might be present. • the secretions of the male reproductive glands are alkaline. This is important because the cavity of the female vagina has an acidic pH created by the normal flora .

27. URETHRA • The urethra is the last of the ducts through which semen travels, - and its longest portion. • Circumcision is the surgical removal of the foreskin • This is a common procedure performed on male infants,

28. SEMEN • Semen consists of sperm and the secretions of the seminal vesicles, prostate gland, and bulbourethral glands; • its average pH is about 7.4. During ejaculation. • approximately 2 to 4 mL of semen is expelled. • Each milliliter of semen contains about 100 million sperm cells

29. CONTRACEPTION • There are several methods of contraception, or birth control; some are more effective than others. • Sterilization—Sterilization in men involves a relatively simple procedure called a vasectomy. • The ductus (vas) deferens is accessible in the scrotum, in which a small incision is made on either side. The ductus is then sutured and cut. * Although sperm are still produced in the testes, they cannot pass the break in the ductus, and they simply die and are reabsorbed.

30. Sterilization in women • Sterilization in women is usually accomplished by tubal ligation, the suturing and severing of the fallopian tubesby way of a small incision in the abdominal wall. • Ova cannot pass the break in the tube, nor can sperm pass from the uterine side to fertilize an ovum. • When done properly, these forms of surgical sterilization are virtually 100% effective.

31. Oral contraceptives • Birth control pills contain progesterone and estrogen in varying proportions. They prevent ovulation by inhibiting the ecretion of FSH and LH from the anterior pituitary gland. • When taken according to schedule, birth control pills are about 98% effective

32. PROSTATIC HYPERTROPHY • Prostatic hypertrophy is enlargement of the • prostate gland. • Benign prostatic hypertrophy is a common occurrence in men over the age of 60 years. • The enlarged prostate compresses the urethra within it and may make urination difficult or result in urinary retention. • A prostatectomy is the surgical removal of part or all of the prostate. • Newer surgical procedures may preserve sexual function. • Medications are available to shrink enlarged prostate tissue.

33. Cancer of the prostate • is the second most common cancer among men (lung cancer is first). Most cases occur in men over the age of 50 years. • Treatment may include surgery to remove the prostate, radiation therapy, or hormone therapy to reduce the patient’s level of testosterone