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Anatomy and
Physiology of the
Male
Topics
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Anatomy
Physiology
Spermatogenesis
Hormonal regulation
Development
Anatomy
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Scrotum
Testes
Penis
Glands
Scrotum
• Maintains 34°C
(93.2°F)
• Dartos muscle –
wrinkles the skin
• Cremaster muscles –
draw scrotum toward
abdomen
Testes
• Coverings
• Tunica vaginalis
• Tunica albuginea
• Lobules
• Seminiferous
tubules
• Tubulus rectus
• Rete testis
• Epididymis
Testes Blood Supply
• Countercurrent
heat exchange
• Testicular artery
• Pampiniform
venous plexus
Testes Blood Supply
• Varicocele
• Varicose vein like condition
• 15-20% of males
• 40% of infertile males
Penis external anatomy
• Foreskin
• 60% in US
are
circumcised
• 15%
worldwide
• Shaft
• Glans penis
Penis internal
anatomy
• Corpus
spongiosum
• Bulb of
penis
• Corpora
cavernosum
• Crura of the
penis
Male Duct
System
• Epididymus
• 20 feet!
• 20 days for
sperm to
mature
• Smooth
muscles
expel sperm
during
ejaculation
• Cells have
Male Duct
System
• Epididymus
• Smooth
muscles
expel sperm
during
ejaculation
• Cells have
microvilli
Male Duct
System
• Ductus (vas)
deferens
• 18”
• Very muscular
• Ampulla
Male Duct
System
• Vasectomy
• Almost 100%
effective
• Reversal about
50% success
rate
Male Duct
System
• Ejaculatory duct
• Urethra
• Conveys both
urine and semen
• Prostatic
• Membranous
• Penile
• Urethral glands
secrete mucus
prior to
ejaculation
• Seminal
vesicles
• Size of little
finger
• Surrounded by
smooth muscle
• Seminal fluid
• Fructose
• Ascorbic acid
• Coagulating
enzyme
• Prostaglandins
• Other factors
that enhance
Glands
• Prostate
• Size of peach pit
• Several ducts into the
prostatic urethra
• Surrounded by
smooth muscle
• Secretions
• Citrate
• Enzymes (fibrinolysin,
hyaluronidase, acid
phosphatase)
• Prostate specific
antigen (PSA)
• activate sperm
Glands
Glands
• Bulbourethral
glands
• Pea sized
• Mucus
• Lubrication
• Neutralizes
acidic urine
prior to
ejaculation
Semen
• 2-5ml
• Composed of
• Sperm (10%)
• Testicular fluid
• Gland secretions
• Functions
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Semen
Transport, activation and protective medium
Nutrients for sperm (fructose)
Neutralizes vaginal tract
Prostaglandins reduce viscosity of mucus at
cervix
Enzymes enhance motility
Antibiotics
Chemicals that suppress the female immune
system
Clotting factors that coagulate semen so it
sticks to vagina
Fibrinolysin then dissolves that mass
Physiology
• Erection
• NO (nitric oxide) released (in penis
tissue)
• Causes arterioles (normally constricted)
to relax/dilate
• Blood flows into the corpora cavernosa
• Compresses veins to prevent flow out
• Corpus spongiosum also expands but
maintains open urethra
• Bulbourethral glands secrete lubricant
Physiology
• Ejaculation
• Spinal reflex
• Bladder sphincter muscle constricts
• Reproductive ducts and glands contract
• Contents enter urethra
• Muscles around the blub of penis –
series of rapid contractions
• Other systemic changes
• Rapid heartbeat
• Elevated blood pressure
• Generalized muscle contraction
Erectile dysfunction
• Deficient NO release
• Viagara, Cialis and Levitra increase effects of
NO
• Possible factors
• Psychological factors
• Alcohol or drugs
• Antihypertensives, Antidepressants
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Diabetes mellitus
Arteriosclerosis
Varicose veins
Nervous system issues
Spermatogenesis
Spermatogenesis
• Meiosis
• Sertoli cells
• Nourish and
“clean”
• Secrete
testicular fluid
• androgens
• Tight junction
• Blood-testis
barrier
• prevents sperm
antigens from
the immune
Spermatogenesis
Spermatogenesis
• Spermatogenic cell
• 64-72 days
Infertility
• 1/7 of Americans; most due to sperm
issues
• Estrogen-like compounds
• Antibiotics (tetracycline)
• Compounds that lead to abnormal sperm
• Radiation, marijuana, lack of selenium,
alcohol
• Lack of a specific Ca++ channel (for
motility)
• Anatomical obstruction
• Hormonal imbalance
Hormonal Regulation
• HypothalamicPituitary-Gonadal
Axis
• Hypothalamus
• Anterior pituitary
• Testes
Hypothalamic-Pituitary-Gonadal Axis
• Hypothalamus
• GnRH –
gonadotropin
releasing hormone
• Stimulates the
anterior pituitary
Hypothalamic-Pituitary-Gonadal Axis
• Anterior Pituitary
• LH – luteinizing
hormone
• Released in response
to GnRH
• Stimulates interstitial
cells (Leydig cells) to
secrete testosterone
Hypothalamic-Pituitary-Gonadal Axis
• Anterior Pituitary
• FSH – follicle
stimulating hormone
• Released in response
to GnRH
• Stimulates Sertoli
cells
• ABP – androgenbinding protein:
Keeps concentration
of testosterone high
Hypothalamic-Pituitary-Gonadal Axis
• Testosterone
• meiosis of
spermatogenic cells
• development and
maintenance of
secondary sex
characteristics
• Libido
• Feed back to
pituitary and
hypothalamus
Hypothalamic-Pituitary-Gonadal Axis
• Inhibin
• Secreted by Sertoli
cells
• produced in
response to sperm
count
• Inhibits release of
GnRH and FSH
Hypothalamic-Pituitary-Gonadal Axis
• Absence of GnRH,
FSH and LH
• Testicular atrophy
• Accessory organs
atrophy
• Testosterone
production declines
(or ceases)
Secondary sex characteristics
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Pubic and axillary hair
Facial and chest hair
Larynx enlarges
Skin thickens and becomes
oilier
Bones grow and increase
density
Skeletal muscle increases
Basal metabolic rate increases
Development of libido
Brain development
Reproductive System Development
5 weeks
•gonadal ridges
•Mullerian ducts – female
•Wolffian duct – male
Germ cells migrate to
gonad
Reproductive System Development
7 weeks – ductus
deferens forms
•Seminiferous tubules
form in gonadal ridges
•Join the Wolffian ducts
•Testes secrete MIF –
Mullerian Inhibitory factor
•Mullerian ducts
degenerate
Reproductive System Development
8 weeks – presence of
testosterone
•Genital tubercle enlarges
• forms penis
•Urethral folds fuse
• Forms spongy urethra
•Labioscrotal swellings fuse
• Form scrotum
Reproductive System Development
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• Gubernaculum (G) (blue) – connects testis to floor of
scrotum
• At 7 months G stops growing and becomes fibrous
• Rapid growth of fetus causes G to pull testis into the
scrotum

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