Male Reproductive System
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Male Reproductive Organs
scrotum and testes
 ducts
 accessory sex glands
 penis

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Male Reproductive Organs
prostate
gland
seminal vesicle
penis
epididymis
ductus deferens
testicle within scrotum
3
Scrotum
(cont.)
pendulous sac of loose skin and fascia
 supports testes
 divided internally by medial septum,
supporting each testis
 left testes is usually suspended lower
than the right so they are not
compressed against each other

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Scrotum
(cont.)
location (outside the body) and muscle
fibers regulate temperature of the testes
 production and survival of sperm require
temperature about 3o lower than normal
body temperature
 contains Dartos muscle
- contains smooth muscle fibers
- causes wrinkling of scrotum

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Cremaster Muscle
continuation of internal oblique muscle
 stimulation by touch or cold results in
contraction of muscle pulling testicles
closer to the body
 presence of cremasteric reflex indicates
integrity of the first lumbar nerve
segment
 absence of reflex indicates damage

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Testes
primary sex organs; male gonads
 paired oval glands
 two inches long, one inch in diameter
 develop high in posterior fetal abdominal
wall
 descend into scrotum during seventh
month of fetal development
 suspended in scrotum by spermatic cord

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Testes
(cont.)
Produce:
- sperm
- testosterone
 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

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Covering of Testes
tunica vaginalis
- pouch-like sac of peritoneum
- formed during descent of the testes
 tunica albuginea
- internal to tunica vaginalis
- dense, white, fibrous tissue

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Cryptorchidism
occurs when testes fail to descend into scrotum
 results in sterility because of higher
temperature in pelvic cavity
- higher temperature destroys cells involved
in development of sperm cells
 Treatment:
- human growth hormone
- surgery

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Seminiferous Tubules

Consists of:
- spermatogenic cells
- sustenacular cells
- blood-testis barrier
- basement membrane
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Spermatogenic Cells
line walls of seminiferous tubules
 towards lumen of tubules cells are
progressively more mature
 Cells in various stages of development:
- spermatogonia
- primary spermatocytes
- secondary spermatocytes
- spermatids

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Spermatogonia
most immature cells
 lie next to basement membrane
 have 46 chromosomes (diploid)

Primary Spermatocytes
produce four spermatids
 have 46 chromosomes (diploid)

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Secondary Spermatocytes
cells formed by first nuclear division
(reduction division)
 each cell has 23 chromosomes (haploid)

Spermatids
cells formed by second nuclear division
(equatorial division) - mitotic
 each cell has 23 chromosomes (haploid)

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Sustentacular Cells
extend from outer basement membrane
to the lumen
 support and nourish developing cells
 immature cells are embedded in luminal
membranes
 secrete inhibin
- protein hormone
- directly affects anterior pituitary by
inhibiting FSH secretion

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Follicle-Stimulating Hormone
FSH encourages spermatogenesis and
stimulates sustentacular cells
 once adequate spermatogenesis level is
achieved, inhibin is secreted
- inhibits FSH secretion and decreases
spermatogenesis
 if spermatogenesis occurs too slowly,
lack of inhibin permits FSH secretion
- increases rate of spermatogenesis

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Blood-Testis Barrier
developing sperm have surface antigens
recognized as foreign by immune system
 prevents an immune response against
sperm
 isolates cells from blood
Basement Membrane

surrounds each seminiferous tubule
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Mature Sperm

travel through seminiferous tubules to
straight tubules through rete testis and
from testes into epididymis
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Epididymis
half-moon-shaped organ encircling posterior of
each testis
 site of sperm maturation
 contains highly coiled tube called the ductus
epididymis used for storage of spermatozoa
 continuous with ductus deferens
 during ejaculation, muscle contractions move
sperm and seminal fluid into ductus deferens

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Ductus Deferens
also called vas deferens or seminal duct
 18 inch long tube
 carries spermatozoa from epididymis of
each testis to an ejaculatory duct
 ascends along posterior border of
epididymis

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Ductus Deferens
(cont.)
 enters pelvic cavity through inguinal canal
 loops over side and down posterior surface
of urinary bladder
 terminal end is called ampulla
 stores sperm and moves sperm from
epididymis to urethra
 seminal vesicle joins at distal end of
ampulla
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Vasectomy
method of sterilization
 portion of each ductus deferens is
removed
 sperm production continues but cannot
be expelled from body

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Ejaculatory Duct
distal end of ampulla
 one inch long
 formed from union of duct from seminal
vesicle and ductus deferens
 passes into prostate gland
 joins prostatic urethra
 eject sperm into prostatatic urethra just
prior to ejaculation

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Urethra
tube
 extends from urinary bladder to tip of
penis
 about 8 inches long
 Three parts:
- prostatic urethra
- membranous urethra
- spongy urethra

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Prostatic Urethra

passes through prostate gland
Membranous Urethra

passes through urogenital diaphragm
Spongy Urethra

passes through corpus spongiosum of
penis
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Male Reproductive Glands
seminal vesicles
 prostate gland
 bulbourethral glands

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Seminal Vesicles
paired, convoluted, pouch-like structures
 posterior to and at base of urinary bladder
 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

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Fructose

used for ATP production
Prostaglandins
contribute to sperm motility and viability
 may also stimulate muscular contraction
within female reproductive tract

Fibrinogen

aids in semen coagulation
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Prostate Gland
single, donut-shaped, walnut size
 inferior to urinary bladder
 surrounds superior portion of urethra
 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

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Bulbourethral Gland
also known as Cowper’s glands
 paired, size of peas
 lie beneath prostate gland on either side of
membranous urethra
 ducts open into spongy urethra
 secrete alkaline, mucus-containing fluid
- neutralizes acid ; lubricates end of penis
- 10% of the volume of semen

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Penis
cylindrical organ
 transports urine and semen through
urethra to the outside of body
 Consists of:
- body
- glans penis
- root

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Body of the Penis
composed of three cylindrical masses of
spongy erectile tissue
 enclosed in fascia and skin permeated by
blood sinuses
 sexual stimulation causes dilation of
arteries supplying penis
 blood accumulates in erectile tissue, and
penis swells and elongates, producing an
erection

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Erectile Tissue
corpora cavernosa penis
- two dorsolateral masses
 corpus spongiosum penis
- smaller midventral mass
- contains spongy urethra

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Glans Penis
distal end of corpus spongiosum
 slightly enlarged
 forms tip of penis
 Anatomy:
- corona
- external urethral orifice
- prepuce or foreskin

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Corona

margin of glans penis
External Urethral Orifice

slitlike opening of urethra
Prepuce or Foreskin
covers the glans penis
 often removed in circumcision

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Circumcision
removal of part or all of the prepuce
 many physicians believe it decreases risk of
urinary tract infections, possible protection
from penile cancer, and lowers risk of
sexually transmitted diseases

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Root of Penis
attached portion
 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

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Semen
Mixture of:
- sperm
 secretions of the seminal vesicles,
prostate gland, and bulbourethral
glands

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Characteristics of Semen
volume
- 2.3 - 2.5 ml per ejaculation
 color
- milky appearance because of prostate
secretion
 sperm count
- 50 - 150 million sperm per ml

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Characteristics of Semen (cont.)
motility of sperm
- at least 60% active, good forward motility in
order to be viable
 pH is slightly alkaline (7.20 - 7.60)
 specific gravity - denser than water (1.0280)
 morphology
- at least 80% normally shaped in order to be
viable

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Characteristics of Semen (cont.)
antibiotics - seminalplasmin
- has ability to destroy certain bacteria
 nutrients - fructose
- provides energy source necessary for
sperm motility
 buffers - phosphate and bicarbonate
- maintain relatively constant pH of
semen

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Characteristics of Semen (cont.)
enzymes - hyaluronidase, proteinases
- digest material covering ovum
 clotting enzymes
- coagulate semen
 fibrinolysin
- liquifies coagulated semen

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Hormonal Control of Male
Reproductive System

Controlled by:
- GnRH (gonadotropin releasing hormone)
- FSH (follicle-stimulating hormone)
- LH (luteinizing hormone)
- inhibin
- testosterone
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Gonadotropin Releasing Hormone
secreted by hypothalamus
 carried by anterior pituitary gland
- stimulates the release of gonadotropins,
follicle-stimulating hormone, and luteinizing
hormone

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Follicle-Stimulating Hormone

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
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Luteinizing Hormone
stimulates interstitial endocrinocytes
located in spaces within seminiferous
tubules
 stimulates testosterone secretion

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Androgens
male sex hormones
 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)

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Androgen Functions
male pattern of development before
birth
 sexual characteristics
 sexual functions
 metabolism

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Male Pattern of Development
Before Birth
development of reproductive system ducts
 descent of testes
 development of external genitals (by DHT)
 converts some androgens into estrogens
which aid in brain development

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Sexual Characteristics
development and enlargement of male
sex organs
 development of male secondary sex
characteristics

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Male Secondary Sex
Characteristics
muscular and skeletal growth
 wide shoulders, narrow hips
 pubic, axillary, facial, and chest hair
growth
 thickening of skin
 increased sebaceous gland secretion
 enlargement of larynx and deepening of
voice

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Sexual Functions
male sexual behavior
 spermatogenesis
 sex drive

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Metabolism
androgens are anabolic hormones
which stimulate protein synthesis
- leading to heavier muscle and bone
mass in males
 cause cessation of bone growth by
stimulating closure of epiphyseal plate
 increase rate of metabolism and
production of red blood cells

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