1 Male Reproductive System

2 Male Reproductive Organs n scrotum and testes n ducts n accessory sex glands n penis

3 Male Reproductive Organs penis testicle within scrotum epididymis ductus deferens seminal vesicle prostate gland

4 Scrotum (cont.) n pendulous sac of loose skin and fascia n supports testes n divided internally by medial septum, supporting each testis n left testes is usually suspended lower than the right so they are not compressed against each other

5 Scrotum (cont.) n location (outside the body) and muscle fibers regulate temperature of the testes n production and survival of sperm require temperature about 3 o lower than normal body temperature n contains Dartos muscle - contains smooth muscle fibers - causes wrinkling of scrotum

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7 Cremaster Muscle n continuation of internal oblique muscle n stimulation by touch or cold results in contraction of muscle pulling testicles closer to the body n presence of cremasteric reflex indicates integrity of the first lumbar nerve segment n absence of reflex indicates damage

8 Testes n primary sex organs; male gonads n paired oval glands n two inches long, one inch in diameter n develop high in posterior fetal abdominal wall n descend into scrotum during seventh month of fetal development n suspended in scrotum by spermatic cord

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10 Testes (cont.) n Produce: - sperm - testosterone n divided into compartments (about 250) called lobules formed by inward extensions of tunica albuginea - contain several highly coiled tubules called seminiferous tubules spermatozoa are formed in walls of tubules

11 Covering of Testes n tunica vaginalis - pouch-like sac of peritoneum - formed during descent of the testes n tunica albuginea - internal to tunica vaginalis - dense, white, fibrous tissue

12 Cryptorchidism n occurs when testes fail to descend into scrotum n results in sterility because of higher temperature in pelvic cavity - higher temperature destroys cells involved in development of sperm cells n Treatment: - human growth hormone - surgery

13 Seminiferous Tubules n Consists of: - spermatogenic cells - sustenacular cells - blood-testis barrier - basement membrane

14 Spermatogenic Cells n line walls of seminiferous tubules n towards lumen of tubules cells are progressively more mature n Cells in various stages of development: - spermatogonia - primary spermatocytes - secondary spermatocytes - spermatids

15 Spermatogonia n most immature cells n lie next to basement membrane n have 46 chromosomes (diploid) Primary Spermatocytes n produce four spermatids n have 46 chromosomes (diploid)

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17 Secondary Spermatocytes n cells formed by first nuclear division (reduction division) n each cell has 23 chromosomes (haploid) Spermatids n cells formed by second nuclear division (equatorial division) - mitotic n each cell has 23 chromosomes (haploid)

18 Sustentacular Cells n extend from outer basement membrane to the lumen n support and nourish developing cells n immature cells are embedded in luminal membranes n secrete inhibin - protein hormone - directly affects anterior pituitary by inhibiting FSH secretion

19 Follicle-Stimulating Hormone n FSH encourages spermatogenesis and stimulates sustentacular cells n once adequate spermatogenesis level is achieved, inhibin is secreted - inhibits FSH secretion and decreases spermatogenesis n if spermatogenesis occurs too slowly, lack of inhibin permits FSH secretion - increases rate of spermatogenesis

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21 Blood-Testis Barrier developing sperm have surface antigens recognized as foreign by immune system n prevents an immune response against sperm n isolates cells from blood Basement Membrane n surrounds each seminiferous tubule

22 Mature Sperm n travel through seminiferous tubules to straight tubules through rete testis and from testes into epididymis

23 Epididymis n half-moon-shaped organ encircling posterior of each testis n site of sperm maturation n contains highly coiled tube called the ductus epididymis used for storage of spermatozoa n continuous with ductus deferens n during ejaculation, muscle contractions move sperm and seminal fluid into ductus deferens

24 Ductus Deferens n also called vas deferens or seminal duct n 18 inch long tube n carries spermatozoa from epididymis of each testis to an ejaculatory duct n ascends along posterior border of epididymis

25 Ductus Deferens (cont.) n enters pelvic cavity through inguinal canal n loops over side and down posterior surface of urinary bladder n terminal end is called ampulla n stores sperm and moves sperm from epididymis to urethra n seminal vesicle joins at distal end of ampulla

26 Vasectomy n method of sterilization n portion of each ductus deferens is removed n sperm production continues but cannot be expelled from body

27 Ejaculatory Duct n distal end of ampulla n one inch long n formed from union of duct from seminal vesicle and ductus deferens n passes into prostate gland n joins prostatic urethra n eject sperm into prostatatic urethra just prior to ejaculation

28 Urethra n tube n extends from urinary bladder to tip of penis n about 8 inches long n Three parts: - prostatic urethra - membranous urethra - spongy urethra

29 Prostatic Urethra n passes through prostate gland Membranous Urethra n passes through urogenital diaphragm Spongy Urethra n passes through corpus spongiosum of penis

30 Male Reproductive Glands n seminal vesicles n prostate gland n bulbourethral glands

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32 Seminal Vesicles n paired, convoluted, pouch-like structures n posterior to and at base of urinary bladder n secrete an alkaline, viscous fluid - contains fructose, prostaglandins, and fibrinogen - helps to neutralize acid of female tract - provides nourishment for sperm - 60% of the volume of semen

33 Fructose n used for ATP production Prostaglandins n contribute to sperm motility and viability n may also stimulate muscular contraction within female reproductive tract Fibrinogen n aids in semen coagulation

34 Prostate Gland n single, donut-shaped, walnut size n inferior to urinary bladder n surrounds superior portion of urethra n secretes milky, slightly acidic fluid - contains citric acid, acid phosphate, clotting emzymes, and fibrinolysin - aids in sperm motility and viability - 25% of the volume of semen

35 Bulbourethral Gland n also known as Cowper’s glands n paired, size of peas n lie beneath prostate gland on either side of membranous urethra n ducts open into spongy urethra n secrete alkaline, mucus-containing fluid - neutralizes acid ; lubricates end of penis - 10% of the volume of semen

36 Penis n cylindrical organ n transports urine and semen through urethra to the outside of body n Consists of: - body - glans penis - root

37 Body of the Penis n composed of three cylindrical masses of spongy erectile tissue n enclosed in fascia and skin permeated by blood sinuses n sexual stimulation causes dilation of arteries supplying penis n blood accumulates in erectile tissue, and penis swells and elongates, producing an erection

38 Erectile Tissue n corpora cavernosa penis - two dorsolateral masses n corpus spongiosum penis - smaller midventral mass - contains spongy urethra

39 Glans Penis n distal end of corpus spongiosum n slightly enlarged n forms tip of penis n Anatomy: - corona - external urethral orifice - prepuce or foreskin

40 Corona n margin of glans penis External Urethral Orifice n slitlike opening of urethra Prepuce or Foreskin n covers the glans penis n often removed in circumcision

41 Circumcision n removal of part or all of the prepuce n many physicians believe it decreases risk of urinary tract infections, possible protection from penile cancer, and lowers risk of sexually transmitted diseases

42 Root of Penis n attached portion n Consists of: - bulb of penis expanded portion of the base of the corpus spongiosum penis - crura separated and tapered portions of the corpora cavernosa penis

43 Semen n Mixture of: - sperm n secretions of the seminal vesicles, prostate gland, and bulbourethral glands

44 Characteristics of Semen n volume ml per ejaculation n color - milky appearance because of prostate secretion n sperm count million sperm per ml

45 Characteristics of Semen (cont.) n motility of sperm - at least 60% active, good forward motility in order to be viable n pH is slightly alkaline ( ) n specific gravity - denser than water (1.0280) n morphology - at least 80% normally shaped in order to be viable

46 Characteristics of Semen (cont.) n antibiotics - seminalplasmin - has ability to destroy certain bacteria n nutrients - fructose - provides energy source necessary for sperm motility n buffers - phosphate and bicarbonate - maintain relatively constant pH of semen

47 Characteristics of Semen (cont.) n enzymes - hyaluronidase, proteinases - digest material covering ovum n clotting enzymes - coagulate semen n fibrinolysin - liquifies coagulated semen

48 Hormonal Control of Male Reproductive System n Controlled by: - GnRH (gonadotropin releasing hormone) - FSH (follicle-stimulating hormone) - LH (luteinizing hormone) - inhibin - testosterone

49 Gonadotropin Releasing Hormone n secreted by hypothalamus n carried by anterior pituitary gland - stimulates the release of gonadotropins, follicle-stimulating hormone, and luteinizing hormone

50 Follicle-Stimulating Hormone n stimulates sustentacular cells in seminiferous tubules - secrete chemicals that stimulate spermatogenesis - secrete inhibin which has a negative feedback effect on anterior pituitary gland, inhibiting secretion of FSH

51 Luteinizing Hormone n stimulates interstitial endocrinocytes located in spaces within seminiferous tubules n stimulates testosterone secretion

52 Androgens n male sex hormones n testosterone is principal androgen - synthesized from cholesterol in the testes - in some target cells testosterone is not active and must be reduced and converted into dihydrotestosterone (DHT)

53 Androgen Functions n male pattern of development before birth n sexual characteristics n sexual functions n metabolism

54 Male Pattern of Development Before Birth n development of reproductive system ducts n descent of testes n development of external genitals (by DHT) n converts some androgens into estrogens which aid in brain development

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57 Sexual Characteristics n development and enlargement of male sex organs n development of male secondary sex characteristics

58 Male Secondary Sex Characteristics n muscular and skeletal growth n wide shoulders, narrow hips n pubic, axillary, facial, and chest hair growth n thickening of skin n increased sebaceous gland secretion n enlargement of larynx and deepening of voice

59 Sexual Functions n male sexual behavior n spermatogenesis n sex drive

60 Metabolism n androgens are anabolic hormones which stimulate protein synthesis - leading to heavier muscle and bone mass in males n cause cessation of bone growth by stimulating closure of epiphyseal plate n increase rate of metabolism and production of red blood cells