chapter 31.txt

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chapter 31.txt
2012-11-12 12:17:42
Male Reproduction

Male Reproduction
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  1. Perineum
    in males, roughly diamond-shaped area between thighs; extends anteriorly from symphysis pubis to coccyx posteriorly; lateral boundary is the ischial tuberosity on either side; divided into the urogenital triangle and the anal triangle (Figure 31-1, B)
  2. Location of Testes
    Located in scrotum, one testis in each of two scrotal compartments
  3. Structure
    • Several lobules composed of seminiferous tubules and interstitial cells (of Leydig), separated by septa, encased in white fibrous capsule called the tunica albuginea (Figure 31-2)
    • –Seminiferous tubules in testis open into a plexus called rete testis, which is drained by a series of efferent ductules that emerge from top of organ and enter head of epididymis
  4. Testes function
    • Spermatogenesis —formation of mature male gametes (spermatozoa) by seminiferous tubules
    • –Secretion of hormone (testosterone) by interstitial cells
  5. Structure of spermatozoa
    consists of a head (covered by acrosome), neck, midpiece, and tail; tail is divided into a principal piece and a short end-piece
  6. Epdidymis- Structure and location
    • •Single tightly coiled tube enclosed in fibrous casing (Figure 31-8)
    • •Lies along top and side of each testis
    • •Anatomical divisions include head, body, and tail
  7. Epdidymis Functions
    • •Duct for seminal fluid
    • •Also secretes part of seminal fluid
    • •Sperm become capable of motility while they are passing through epididymis
  8. Vas deferens (ductus deferens)-Structure and Location
    • Tube; extension of epididymis
    • •Extends through inguinal canal, into abdominal cavity, and over top and down posterior surface of bladder
    • •Enlarged terminal portion called ampulla—joins duct of seminal vesicle
  9. Vas deferens- Function
    • •One of excretory ducts for seminal fluid
    • •Connects epididymis with ejaculatory duct
  10. Ejaculatory duct
    • –Formed by union of vas deferens with duct from seminal vesicle
    • –Passes through prostate gland, terminating in urethra
  11. Urethra
    • (three parts)
    • Prostatic urethra, membranous urethra, & penile urethra
  12. Seminal vesicles- Structure and location —convoluted pouches about 5 to 7 cm long on posterior surface of bladder
    –Function —secrete the viscous, nutrient-rich part of seminal fluid (60% of semen volume)
  13. Prostate gland- Structure and location
    • •Doughnut-shaped
    • •Encircles urethra just below bladder
    • –Function —adds slightly acidic, watery, milky-looking secretion to seminal fluid (30% of semen volume)
  14. Bulbourethral gland
    • Structure and location
    • •Small, pea-shaped structures with ducts about 2.5 cm (1 inch) long leading into urethra
    • •Lie below prostate gland
    • –Function —secrete alkaline fluid that is part of semen (5% of semen volume)
  15. Scrotum
    • Skin-covered pouch suspended from perineal region
    • –Divided into two compartments
    • –Contains testis, epididymis, and lower part of a spermatic cord
    • –Dartos and cremaster muscles elevate the scrotal pouch
  16. Penis
    • –Structure —composed of three cylindrical masses, one of which contains urethra and is called corpus spongiosum. The other upper two cylinders are called corpora cavernosa and they contain erectile tissue.
    • –Functions —penis contains the urethra, the terminal duct for both urinary and reproductive tracts; during sexual arousal, penis becomes erect, serving as a penetrating copulatory organ during sexual intercourse
  17. Spermatic cords (internal)
    • Fibrous cylinders located in inguinal canals
    • –Enclose vas deferens (ductus deferens), blood vessels, lymphatics, and nerves.
  18. Compositon and Course of Seminal Fluid
    • Consists of secretions from testes, epididymis, seminal vesicles, prostate, and bulbourethral glands
    • •Each milliliter contains millions of sperm
    • •Passes from testes through epididymis, vas deferens, ejaculatory duct, and urethra
    • Slide
  19. Seminal Fluid secretions Percentages
    • Testes and epididymis – secretions constitute less than 5% of the seminal fluid volume
    • •Seminal vesicles – contributes about 60%
    • •Prostate gland – about 30%
    • •Bulbourethral glands – about 5%
  20. Male fertility
    • related to # of sperm; size, shape and motility
    • Fertile sperm have uniform size and shape and highly motile
  21. Causes of infertility in Males
    • •If sperm count falls below 25 million/ml of semen, functional sterility results.
    • •Infertility may be caused by antibodies some men make against their own sperm = immune infertility
  22. Erection
    is a parasympathetic reflex initiated mainly by certain tactile, visual, and mental stimuli
  23. Emission
    is the reflex movement of sperm cells and secretions from the genital ducts and accessory glands into the prostatic urethra
  24. Ejaculation
    a sympathetic reflex response; increased HR, increased BP, hyperventilation, dilated cutaneous blood vessels, and intense sexual excitement characterize the male orgasm or sexual climax