Brief overview of the male sexual act..

1. Physiology of the Male Sexual
Act
Leul Biruk
MD 014/15
Myungsung Medical college

2. Introduction
 The Human Sexual Response is classified into four phases
1.Excitement
2.Plateu
3.Orgasim
4. Resolution
3/17/2017
2
coitus and CAD

3. Introduction
1.Excitement
 An increase in muscle tone (myotonia) of
certain muscle groups.
 An increase in breathing rate , heart rate and
blood pressure .
 Flushed skin (vasocongestion )
 Erection of the man's penis, scrotal sac
thickens, elevates
3/17/2017
3
coitus and CAD

4. Introduction
2. Plateau
 Increased sexual pleasure with increased
stimulation, and further increased muscle
tension.
 Breathing rate continues at an elevated level.
 Copious perspiration
 Increased myotonia
 Both males and females continue
vasocongestion to max
 Cowper’s glands secrete fluid through tip of
penis: may contain live sperm!
 scrotum even higher and testicles bigger
3/17/2017coitus and CAD
4

6. Introduction
3. Orgasm
 The shortest phase of the sexual
response cycle, typically lasting only
several seconds.
 Heart rate and blood pressure increases
maximally.
 contraction of seminal vesicles,
vas and prostate
 contraction of urethra and penis:
ejaculation
3/17/2017
6
coitus and CAD

8. Introduction
4 . Resolution
 Begins immediately after orgasm.
 Allows the muscle to relax.
 The body returns to its original, non excited
state.
 Blood pressure and heart rate drop.
3/17/2017
8
coitus and CAD

9. Nervous control of the male sexual cycle
 Sensory input from the genital tract is carried by the
pudendal nerve to the S2–S4 segment of the spinal
cord.
 The somatic motor fibers -S2–S4 and supply the
pelvic floor muscles and the external anal sphincter.

10.  Descending parasympathetic innervation exits the
spinal cord at the S2–S4 level and reaches the penis.
 It is responsible for the corporeal vasodilatation and
corporeal smooth muscle relaxation, and hence the
penile transformation from the flaccid to the erect
state.

11.  The sympathetic innervation exits the spinal cord at
T11–L2 level and reaches the penis.
 It is responsible for the emission and ejaculation
through coordinated contractions of the vas
deferens, ampulla, seminal vesicles, prostate, and the
bladder neck.

13. Stimulation
 Mechanisms of stimulation
psychic stimulation from the brain
actual sexual stimulation from the sex organs
usually it is a combination of both.

14.  Glans Penis - most important source of sensory nerve
signals for initiating the male sexual act
 Areas adjacent to the penis - stimulation of the anal
epithelium, the scrotum
 Psychic Element of Male Sexual Stimulation:
 Thinking sexual thoughts dreaming that the act of
intercourse is being performed can initiate the male
act, culminating in ejaculation.
Eg. nocturnal emissions during the teens.

16.  Increased inflow and blocked outflow
 impulses in afferents from the genitalia and
descending tracts that mediate erection in response
to erotic psychological stimuli. (integrating centers in
LS)
 The efferent parasympathetic fibers are in the pelvic
splanchnic nerves (nervi erigentes).
 The fibers presumably release acetylcholine and
the vasodilator vasoactive intestinal
polypeptide (VIP)

17.  Nonadrenergic noncholinergic fibers are also present
in the nervi erigentes, and these contain large
amounts of nitric oxide synthase (NOS), the
enzyme that catalyzes
 NO activates soluble guanylyl cyclase, resulting in
increased production of cGMP
 PDE V
 Normally, erection is terminated by sympathetic
vasoconstrictor impulses to the penile arterioles

20. EJACULATION
 Sympathetic nervous system.
 Spinal cord reflex arc.
 Afferent pathways are mostly fibers from touch receptors in
the glans penis that reach the spinal cord through the
internal pudendal nerves.
 Considerable voluntary inhibitory control over this phase of
the sexual response.
 Two sequential processes.
 A) Emission - deposition of seminal fluid into the posterior
urethra. Simultaneous contractions of the ampulla of the vas
deferens, the seminal vesicles, and the smooth muscles of the
prostate
 B)True ejaculation -expulsion of the seminal fluid from
the posterior urethra through the penile meatus.

24.  Sympathetic innervation (the cord at T-12 to L-2) to
the genital organs through the hypogastric and pelvic
sympathetic nerve plexuses to initiate emission.
 contractions of the prostate gland followed by
contraction of the seminal vesicles expel prostatic
and seminal fluid – urethra
 Male Orgasm=The entire period of
emission and ejaculation

25. Disorders with Ejaculation
 Premature Ejaculation
 a male sexual dysfunction characterized by ejaculation which
always or nearly always occurs prior to or within about one
minute of vaginal penetration; and, inability to delay
ejaculation on all or nearly all vaginal penetrations
 Retrograde Ejaculation
 Sympathetic efferent fibers (T10-L3)
 During the expulsive phase, it is necessary that the bladder neck
(internal urethral sphincter) be closed to prevent the reflux of semen
into the bladder as the urethral pressure increases.
 Anejaculation
 inability to ejaculate semen despite stimulation of the penis by
intercourse or masturbation.

26. References
 Eric P. Widmaier, Hershel Raff, Kevin T. Strong
Vanders Human Physiology The Mechanisms of
Body Function 2008
 Medical Physiology - Prins. for Clin. Med. 4th ed. - R.
Rhoades, D. Bell (Lippincott, 2013)BBS
 Katzungs Basic & Clinical Pharmacology -13th 2015

27. THANK YOU
Leul Biruk
MD 014/15