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1
Mosby items and derived items © 2007, 2003 by Mosby, Inc.
Chapter 31
Male Reproductive System
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Introduction
Ensures the survival of the speciesfunctions are to produce, transfer, and
introduce mature sperm into the female reproductive tract where fertilization can occur
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Male Reproductive Organs
Essential organs = production of gametes Gonads of the male = testes
Accessory organs that support the reproductive process Accessory organs of reproduction
• Genital ducts convey sperm to outside of body• paired epididymis, paired vas deferens, pair of ejaculatory
ducts, and the urethra Accessory glands produce secretions that nourish, transport,
and mature sperm• pair of seminal vesicles, the prostate, and pair of
bulbourethral glands Supporting structures— scrotum, penis, and pair of
spermatic cords
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Perineum
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
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Testes
Structure and location Located in scrotum 10-15g each Left generally 1 cm lower than right
in scrotal sac Several lobules composed of
seminiferous tubules and interstitial cells (of Leydig), separated by septa
Seminiferous tubules in testis rete testis epididymis vas deferens
If unraveled, seminiferous tubules would be 75 cm long!
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Testes
> 5 layers in seminiferous tubuleSertoli cells-
cells that provide support and protection for developing germ cells
Play a role in release of mature spermatozoa into lumen of tubule
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Spermatogenesis —formation of mature male gametes (spermatozoa) by seminiferous tubules
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Testes
Functions Spermatogenesis— formation of mature male gametes
(spermatozoa) by seminiferous tubules http://highered.mcgraw-hill.com/olc/dl/120112/anim0043.
swf Secretion of hormone
Testosterone:• Promotes male secondary sex characteristics• Promotes anabolism of proteins (muscular and
bone development)• Inhibits female hormones (FSH and LH)
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Testes
Structure of spermatozoa consists of
head (covered by acrosome)• Acrosome contains hydrolytic
enzymesNeckMidpieceTail
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Reproductive (Genital) Ducts
Epididymis Structure and location
Single tightly coiled tube Lies along top and side of each testis About 20 feet long!
Functions Duct for seminal fluid secretes part of seminal fluid Sperm become capable of motility while they are passing
through epididymis
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Reproductive (Genital) Ducts 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 Enlarges and joins duct of seminal vesicle
Function One of excretory ducts for seminal fluid Connects epididymis with ejaculatory duct
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Reproductive (Genital) Ducts
Ejaculatory duct Formed by union of vas
deferens with duct from seminal vesicle
Passes through prostate gland, terminating in urethra
Urethra
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Accessory Reproductive Glands
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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Accessory Reproductive Glands
Prostate gland Structure and location
Doughnut-shaped Encircles urethra just below
bladder Function
adds slightly alkaline, watery, milky-looking secretion to seminal fluid
30% of semen volume Alkalinity neutralizes the acidity of
the urethra and the vagina
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Accessory Reproductive Glands
Bulbourethral gland Structure and location
Small, pea-shaped structures with ducts about 2.5 cm (1 in) 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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Supporting Structures
Scrotum Skin-covered pouch suspended from
perineal region Divided into two compartments Contains testis, epididymis, and lower
part of a spermatic cord muscles elevate the scrotal pouch when
it is cold and lower it when it is hot
lymphangioma
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Supporting Structures Penis
Structure composed of three cylindrical masses of
erectile tissue, one of which contains the urethra
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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Supporting Structures
Spermatic cords (internal) Consists of vas deferens,
blood vessels, lymphatics, and nerves
Passes through inguinal canal
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Composition and Course of Seminal Fluid
Consists of secretions from testes, epididymides, seminal vesicles, prostate, and bulbourethral glands
Each mL contains millions of spermFrom testes epididymis vas
deferens ejaculatory duct urethra
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TYPICAL REFERENCE INTERVALS
COMPONENT CONVENTIONAL UNITS
Liquefaction Within 20 min
Sperm Morphology
>70% normal, mature spermatozoa
Sperm Motility >60%
pH >7.0 (average 7.7)
Sperm Count 60-150 X 106/mL
Volume 1.5-5.0 mL
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Male Fertility
Relates to many factors number of sperm size, shape, and motility
Infertility may be caused by antibodies some men make against their own sperm- “immune infertility”
<25 million sperm/mL of semen = functional sterility Possible Hypothesis:
Semen with enough sperm contains hydrolytic enzymes to breakdown the cells around the ovum
Without this, a single sperm cannot penetrate these layers
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Cycle of Life: Male Reproductive System
Reproductive functions begin at time of puberty Development of organs begins before birth
immature testes descend into scrotum before or shortly after birth
Puberty high levels of hormones stimulate final stages of
development System operates to permit reproduction until advanced old age Late adulthood
gradual decline in hormone production may decrease sexual appetite and fertility