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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)
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Location of Testes
Located in scrotum, one testis in each of two scrotal compartments
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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
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Testes function
- Spermatogenesis —formation of mature male gametes (spermatozoa) by seminiferous tubules
- –Secretion of hormone (testosterone) by interstitial cells
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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
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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
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Epdidymis Functions
- •Duct for seminal fluid
- •Also secretes part of seminal fluid
- •Sperm become capable of motility while they are passing through epididymis
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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
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Vas deferens- Function
- •One of excretory ducts for seminal fluid
- •Connects epididymis with ejaculatory duct
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Ejaculatory duct
- –Formed by union of vas deferens with duct from seminal vesicle
- –Passes through prostate gland, terminating in urethra
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Urethra
- (three parts)
- Prostatic urethra, membranous urethra, & penile urethra
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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)
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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)
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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)
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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
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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
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Spermatic cords (internal)
- Fibrous cylinders located in inguinal canals
- –Enclose vas deferens (ductus deferens), blood vessels, lymphatics, and nerves.
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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
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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%
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Male fertility
- related to # of sperm; size, shape and motility
- Fertile sperm have uniform size and shape and highly motile
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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
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Erection
is a parasympathetic reflex initiated mainly by certain tactile, visual, and mental stimuli
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Emission
is the reflex movement of sperm cells and secretions from the genital ducts and accessory glands into the prostatic urethra
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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
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