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PHS 204- REPRODUCTIVE PHYSIOLOGY
NAME >
Kalu anita
MATRIC NO >
13/MHS01/063
DEPARTMENT>
MEDICINE &
SURGERY
Assignment given by>
Akintayo
Mr. Christopher
Submission date>
11/6/2015, via
ABUAD LMS platform.
Question>
Discuss on the Physiologies of Coitus and Erection.
THE PHYSIOLOGY OF COITUS AND ERECTION
THE PHYSIOLOGY OF COITUS
INTRODUCTION
DEFINITION
Coitus is the sexual union between the male and female genitals. It is usually
accompanied by rhythmic movements and orgasms.
During coitus, the male genitalia (penis) enters the vagina of the female and
begins the process of rhythmic movements, in order to stimulate the female
and to cause proper sexual arousal in the female; while in the process, the
male equally becomes increasingly aroused till the release of semen by the
penis deep inside the vagina via ejaculation. This point coincides with sexual
climax. The semen of the male contains the male gamete- spermatozoa, which
then swims along the female reproductive tract to fertilize the female ovum at
the fallopian tube.
In both male and female, the following four phases occur
during coitus:
I.
II.
III.
IV.
Excitement/Arousal phase.
Plateau phase.
Orgasm.
Resolution.
EXCITEMENT/AROUSAL PHASE
i.
In Male
During excitement in males, the following 3 phases occur in succession:
 Erection of the penis:
o This is caused by parasympathetic nerve impulses through the
pelvic nerves to the penis, where the neurotransmitters:
Acetylcholine, Nitric oxideand Vasoactive IntestinalPolypeptide
(VIP)are released. This causes blood vessel dilation and
enlargement of the penis.
 Thickening of the scrotal sac.
 Rising of the testes
ii.
In Females
The sequential order of the processes involved in the arousal phase of
Coitus in females is:




The nipples become erect.
The breasts swell.
The release of vaginal fluid.
Erection of the clitoris: This too, is by the parasympathetic nerves from
the sacral plexus to the external genitalia; the arteries of the erectile
tissue are dilated, due to the release of Acetylcholine, Nitric Oxide, or
VIP at the nerve endings.
These processes allow for the straightening of the Introitus around the
penis during coitus.
PLATEAU PHASE
i.
In Males
During the Plateau phase in males, the following occur:
 Appearance of sex flushes
 Swelling of the Glans Penis.
 Swelling of the testes.
ii.
In Females
The Plateau phase of coitus in females is characterized by the following:
o
o
o
o
Sex flushes (as in males).
Withdrawal of the clitoris.
Enlargement of the Labia Majora.
Rising of the Uterus.
ORGASM
This phase is also called Climax. It is the ultimate stage of Coitus. The
objective of this phase in both sexes is to provide maximum sexual
satisfaction and to terminate sexual arousal. However, this phase differs
in its physiological processes in both males and females.
i.
InMales
Here, this phase is coincident with the function of semen. This is mediated by
the SuperiorHypogastric Plexuses, and it is by sympathetic stimulation. In
paraplegics, ejaculation can be induced by a pacemaker, which acts to
stimulate the Superior Hypogastric Plexuses.
ii.
In Females
The muscle of sexual climax in females is called the Bulbospongiosus. It is
capable of rhythmic contractions and it too is controlled by the Superior
Hypogastric plexus. Although this muscle is skeletal, its nerve supply is
Autonomic.
Female climaxes are associated with Clonic-tonic Contractions, which are
certain forms of spasmodic contractions. The motor function of sexual climax
in which the Bulbospongiosus goes into rhythmic contractions, is due to the
Inferior Hypogastric Plexus.
The following events occur during female climaxes:
 Rhythmic vaginal contractions.
 Rhythmic Bulbospongiosus contractions.
 Contraction of the uterus.
 Spastic contraction of the pelvic floor musculature.
 Heavy breathing.
RESOLUTION PHASE
This is the phase of coitus that occurs after sexual climax has been
attained. Generally, this phase functions to return the male and female
genitalia to the normal physiological states. The events of this phase
differ for both sexes.
i.
In Males
Resolution phase is characterized by:
 Loss of erection
 Blood flow to the penis is returned to the normal. There is a loss of the
erectile position of the penis and eventual relaxation of the penis.
 Restoration of prepuce. This is however common to uncircumcised
males.
ii.
In Females
The resolution phase in females is accompanied by:
 Return of the nipples to normal. I.e., the nipples begin to lose their
erectile position.
 The clitoris becomes erect again.
 Perspiration.
THE PHYSIOLOGY OF ERECTION
INTRODUCTION
DEFINITION
Erection is a state marked by a firm, turgid and erect position of the
previously-flaccid genitialia (such as the penis), which contains cavernous
tissue, as a result of dilation of such tissue with blood.
It is associated with sexual arousal, emanating from sexually-related psychic
and/or physical stimuli. Erection is a hydraulic event, regulated by hormones
and nerves, which allow increased blood flow into and storage of blood within
the erectile bodies, leading to an increase in pressure and the development of
rigidity (hardness).
Penile erection is triggered by either one of the following two
main mechanisms:
I.
II.
By direct stimulation of the genitalia.
By stimulations coming from the brain (fantasy, smell, etc.)
Following stimulations, the following events occur:
 Chemicals are released in the brain, which cause signals to pass down
the spinal cord and outward through special nerves called Nervi
erigentes into the penis.
 The release of Nitric oxide by the Nervi erigentes, which causes
thesmooth muscles to in the penis to relax and then blood rushes into
the erectile bodies to cause erection.
o By this way, the erection mechanism can be likened to a firm tire;
a firm tire is dependent upon a hose that delivers a continuous
supply of adequate amounts of air in a speedy fashion and a valve
mechanism that holds the air in place. In the penis, the hose is
represented by the erection arteries which rapidly carry blood into
the erectile bodies. The valve mechanism, while complicated in its
structure, ensures that blood is trapped inside the erectile bodies
until ejaculation occurs or till sexual stimulus has passed.
 However, there are certain conditions that can inhibit the erection
mechanisms. Some of such include:
 Anxiety or fear, which prevent brain signals from reaching the level
required to induce erection
 Medical conditions such as diabetes,heart and vascular diseases,
neurological disorders, hormonal imbalances, chronic diseases such as
kidney or liver failure; alcoholism and drug abuse, which can block the
erection arteries or cause scarring of the spongy erection tissues and
prevent proper blood flow or trapping of blood and therefore, limit
erection.
APPLIED PHYSIOLOGY
1. ERECTILE DYSFUNCTION
This is a persistent failure to generate sufficient penile body pressure to
achieve vaginal penetration and the inability to maintain this degree of penile
rigidity until ejaculation. Penile diseases such as congenital malformation,
peyronie’s disease, priapism, phimosis and rarely cold abscess may interfere
with erectile function.
There are two classification that have been proposed for erectile
dysfunction; viz
 Psychogenic erectile dysfunction
 Neurogenic erectile dysfunction
PSYCHOGENIC ERECTILE DYSFUNCTION
This is the most common type. It is caused as a result of inhibitory messages
from the spinal erection center sent by the brain as an exaggeration of the
normal suprasacral inhibition or excessive sympathetic outflow which may
increase penile smooth muscle tone to prevent the relaxation necessary for
erection.
NEUROGENIC ERECTILE DYSFUNCTION
An erection is a neurovascular event, any disease or dysfunction affecting the
brain, spinal cord, cavernous and pudendal nerves can induce dysfunction of
penile erection.
2. EJACULATION DISORDERS
There exists a spectrum of disorders of ejaculation ranging from mild
premature to severely retarded or absent ejaculation. Premature ejaculation is
the most common male sexual dysfunction. Psychogenic post ejaculatory pain
syndrome (PEPs) is a rare sexual disorder of male dyspareunia that is described
as a persistent and recurrent pain in the genital organs during ejaculation or
immediately afterward. It may result from epididymal congestion after
vasectomy or from duct obstruction or infection, testicular torsion, mass lesion
or prostatitis.
 REFERENCES
 http://www.webmd.com/sexual-conditions/mens-sexual-problems
 https://www.cornellurology.com/clinical-conditons/erectiledysfunction/causes-of-erectile-dysfunction/
 https://www.cornellurology.com/clinical-conditions/erectiledysfunction/how-erections-work/