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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