Sex is not just going backs and force, we need to understand its physiology and neural concepts, here is a detailed presentation about the physiology of sexual human response and the intercourse, in addition to the benefits and some clinical aspects

1. ‫الرحيم‬ ‫الرحمن‬ ‫الرحمن‬ ‫هللا‬ ‫بسم‬
University of Gezira-faculty of medicine
Physiology department
Batch 8
Sexual intercourse
Presented by Dr ; Mogahed.I.H.Hussein

3. Physiology of
Human Sexual Intercourse

4. Sexual intercourse
The act of inserting the erect penis of the male into
the vagina of the female for reproduction/ and also
for sexual enjoyment.
The terms "sexual intercourse" and "coitus" are used
in reference to people.
The term for the higher vertebrates and some other
animals is "copulation".

5. The Act of Sexual Intercourse
Sexual intercourse is usually preceded by foreplay
which leads to sexual arousal of the partners,
resulting in erection of the penis in male and natural
lubrication of the vagina in the female.

6. Biology of conception
Coitus is the basic reproductive method of humans
as of all mammals.
During ejaculation, which normally accompanies the
male orgasm, a series of muscular contractions
delivers semen containing male gametes known as
sperm cells or spermatozoa into the vault of the
vagina.

7. Biology of conception
The subsequent route of the sperm from the vault
of the vagina, is through the cervix and into the
uterus, and thence into the fallopian tubes.

8. Biology of conception
When a fertile ovum from the female is present in the
fallopian tubes, the male gamete joins with the ovum
resulting in fertilization and the formation of a new
embryo.
When a fertilized ovum reaches the uterus, it becomes
implanted in the lining of the uterus and pregnancy
begins.

9. Biology of conception
Sexual intercourse should always be considered
likely to result in pregnancy unless adequate
contraceptive (birth control) measures are in force.
Even then, pregnancy should be considered a
possible outcome of the activity since no birth
control measure is 100% effective.

10. Biology of conception
Coitus interruptus, or "withdrawal" of the penis from
the vagina just before the man’s orgasm, cannot be
considered an effective method of contraception
and is not recommended.
Sexual abstinence -abstinence from heterosexual
sexual intercourse is the only 100% effective way to
avoid pregnancy.

11. Biology of conception
Outercourse, in which there is sexual activity without
insertion, can be performed without resulting in
pregnancy provided that semen does not come in
contact with the vulva.

12. External Genitalia
Mole Crura of penis are continuous with the corpora
cavernosa of the penis.
Bulb of penis is continuous with corpus spongiosus
of the penis (contains urethra).
Corpora cavernosa and corpus spongiosus form the
shaft of the penis.

19. The neurobiology of sexual responses
In males and females it relies on multiple systems,
including:
 Neuroendocrine.
Limbic.
Autonomic.
Somatic.

20. Sexual responses
At the level of the spinal cord, somatic and visceral
afferents and efferents come together to form reflex
arcs, which lead to sexual responses (Next Figure).
In males, these include erection, emission and
ejaculation, and components of orgasm.

21. Sexual responses
In females, these include vaginal lubrication,
engorgement of erectile tissue, and components of
orgasm.
Sexual response is dependent on both the somatic
and the visceral nervous systems.
The pudendal nerve (S2–S4) carries the somatic
innervation to the perineum, including the genitalia.

22. Sexual responses
Sensory information from the erogenous areas of
the perineum is carried by the pudendal nerve, as is
voluntary motor information to the pelvic floor
muscles.
Their rhythmic contraction is part of orgasm in both
males and females.

23. Sexual responses
The visceral nervous system innervates the blood
vessels and glands and is responsible for erection
and vaginal lubrication as well as emission and
ejaculation in males and components of orgasm in
both sexes.

24. Sexual responses
1. Engorgement: Penile erection is controlled by one of
two mechanisms.
A- A psychogenic or mental erection is mediated by
sympathetic fibers (T12–L1). These fibers are usually
directly inhibited by higher centers, but arousal can
release this inhibition and lead to activation of these
fibers, which in turn leads to erection.

25. Sexual responses
B- The second mechanism for erection is dependent
on sensory input through the pudendal nerve (S2–S4)
to parasympathetic fibers (S2–S4).
This can lead to a reflex erection independent from
descending influences.

26. Sexual responses
Parasympathetic fibers can also be activated via
descending influences from cortical areas, which
have been activated through other erotic sensory
influences.
In females, vaginal lubrication and engorgement of
erectile tissue is also mediated by PAN

28. Erection
• Erection is caused by dilation of the blood vessels (a
parasympathetic response) in the erectile tissue of the penis
(the corpora- and ischiocavernous sinuses).
• This dilation increases the inflow of blood so much that
the penile veins get compressed between the engorged
cavernous spaces and the Buck's and dartos fasciae.
• Nitric oxide (NO), working through cGMP, mediates the
vasodilation.

31. With sexual stimulation, increased blood flow to the
clitoral cavernosal and labial arteries resulting in
increased clitoral intracavernous pressure, tumescence,
and protrusion of the glans clitoris, and eversion and
engorgement of the labia minora.
Studies show that, unlike the penis, the clitoris and
vestibular bulbs lack a subalbugineal layer between the
erectile tissue and the tunica albuginea layer.

32. In the male, subalbugineal layer possesses a rich
venous plexus that, during sexual excitement,
expands against the tunica albuginea, reducing
venous outflow and making the penis rigid. The
absence of this venous plexus in the clitoris and
vestibular bulbs is the reason why clitoris achieves
tumescence, but not rigidity during sexual arousal.

33. Emission
• Sympathetic nervous system stimulation (lumbar
splanchnic nerves) mediates movement of mature
spermatozoa from the epididymis and vas deferens into the
ejaculatory duct.
• Accessory glands, such as the bulbourethral (Cowper)
glands, prostate, and seminal vesicles, secrete fluids that aid
in sperm survival and fertility.

34. • Simultaneously with emission, there is also a sympathetic
adrenergic mediated contraction of the internal sphincter of
the bladder, which prevents retrograde ejaculation of
semen into the bladder. Destruction of this sphincter by
prostatectomy often results in retrograde ejaculation.
• Emission normally precedes ejaculation but also continues
during ejaculation.

35. Pathway of sperm during ejaculation— SEVEN
UP:
Seminiferous tubules
Epididymis
Vas deferens
Ejaculatory ducts (Nothing)
Urethra
Penis

39. 2-Ejaculation
• Ejaculation is caused by the rhythmic contraction of the
bulbospongiosus and the ischiocavernous muscles, which
surround the base of the penis.
• Contraction of these striated muscles that are innervated
by somatic motor nerves causes the semen to exit rapidly in
the direction of least resistance, i.e., outwardly through the
urethra.
• Peristaltic waves in the vas deferens aid in a more
complete ejection of semen.

42. The physiology of the sexual response
William H. Masters
and Virginia E.
Johnson (1915 - 2001,
and 1925 - )
Two basic physiological responses:
• Vasocongestion (penile and clitoral erection, breasts)
• Myotonia (flexion and contraction of muscles)
four-phase model
• Excitement
• Plateau
• Orgasm
• Resolution

44. Excitement
in women
– Vaginal lubrication:
– Inner 2/3 of vagina expands
– Labia majora flatten and move
apart
– Labia minora and clitoris enlarge
– Contraction of small muscle
fibers in nipples
in men
– Penis become engorged
– Erection of penis (variable)
– Scrotal skin tightens

47. Plateau
•women
–Prominent vasocongestion
in outer 2/3 of vagina
cause tissue to swell
–Clitoris pulled back
against pubic bone
• Men
–Full erection of penis
–Muscular tension
–Cowper’s glands secrete
the pre-ejaculatory fluid
–Testes are pulled up
closely against the body

49. Orgasm
• Women
– Contractions at 0.8
second intervals
– Contractions of vagina,
uterus and anal
sphincter
• Men
– Rhythmic contractions
of genital ducts,
muscles at the base of
the penis, and penis
– Followed by ejaculation
of semen

54. Sexual Response Cycle

56. Frequency of Female Orgasm
(Western populations)
25
35
26
10
5
0
5
10
15
20
25
30
35
%FrequencyofOrgasm
Always
Frequently
Sometimes
Rarely
Never

58. Problems with Masters & Johnson
Theoretical Model
• Model does not allow for individual variation, and suggests
that most people proceed smoothly through discrete stages.
• Model focuses on orgasm as the climax of a sexual encounter;
may deemphasize other forms of sexual pleasure, and
pressure couples to meet this sexual “goal”.
• Model is physiological, and does not include cognitive or
emotional aspects of sexuality.
– Implication may be that sexual function (and dysfunctions)
are mainly physiological, rather than psychological or
relational

60. Summary

63. Libido
Libido is a comprehensive and yet elusive word that
indicates basic human mental states--and their
biological counterparts--involved in the beginning of
sexual behavior.
It has three main roots: biological, motivational-
affective and cognitive.
Other names: Desire or sexual drive

64. Libido
Sexual drive is produced through
psychoneuroendocrine mechanisms.
The limbic system and the preoptic area of the
anterior-medial hypothalamus are believed to play a
role in sexual drive.

65. Libido
A person may have a desire for sex, but not have the
opportunity to act on that desire, or may on
personal, moral or religious reasons refrain from
acting on the urge.
Psychologically, a person's urge can
be repressed or sublimated.
On the other hand, a person can engage in sexual
activity without an actual desire for it.

66. Libido
 Sex drive is influenced by biological, psychological and
social factors.
Biologically, the sex hormones and associated
neurotransmitters that act upon the nucleus
accumbens (primarily testosterone and dopamine,
respectively) regulate libido in humans.
Social factors, such as work and family, and internal
psychological factors, like personality and stress, can
affect libido.

67. Libido
Sex drive can also be affected by medical conditions,
medications, lifestyle and relationship issues, and age
(e.g., puberty).
Loss of desire has been proven to be a significant
consequence of diabetes, multiple sclerosis and
polycystic ovary syndrome and can occur as a side-
effect of statins and 5α-reductase inhibitors.

68. How sexual intercourse affect various
body function

69. 1. Relieves stress.
When you have sexual intercourse, your body
dopamine, endorphines, and other feel good
hormones. This makes sex an awesome stress reliever.
2. Exercise.
Sexual intercourse is about as good as other types of
exercise. Sex for just 15 minutes three times a week is
the same as jogging for about an hour.

70. 3. Lowers high blood pressure.
Sexual intercourse lowers high blood pressure and
reduces diastolic blood pressure. If you're looking for
something a little less romantic, hugs do the same
thing.
4. It boosts your immune system.
Immunoglobin A is an antibody that fights off
and it's increased when your frequency of sex

71. 5. You'll look younger.
Having sexual intercourse three times a week may
you look up to ten times
6. Your heart will be stronger.
This ties in with exercise. If you exercise more, your
heart will be stronger. All that sexual intercourse is a
big boost to your cardiovascular system.

72. 7. Pain relief.
Dr. George E. Elrich is an arthritis specialist from
Philadelphia. He conducted a study on the link
arthritis and sexual intercourse and found that those
who had sex more often experienced less pain.

73. 8. Lowered risk of cancer.
Routine ejaculation in men reduces the chance of
getting prostate cancer, and an Australian study found
that men who ejaculated 21 times a month were less
likely to develop the cancer.

74. 9. Regular periods.
Sexual intercourse helps regulate hormones in women
that makes the menstrual cycle a bit more routine.
Stress is one of the biggest reasons women miss
periods too. Stress relief will help make the period
more routine too.

75. 10. You'll live longer.
Summing it all up, less stress, a stronger heart,
increased circulation of oxygen and happiness are all
factors that help you live longer! And who doesn't
to live a little bit longer?

76. Sexual pneumoperitoneum
Is not a bizarre sex accident but a rare and serious patho-
mechanism.
Vaginal gas insufflation can lead to dangerous and fatal
gas embolism, especially during pregnancy.
In cases of atypical non-surgical pneumoperitoneum in
sexually active women, a sensitive sexual medical history
can reveal the cause for non-surgical
pneumoperitoneum.

77. Comprehensive, expensive, painful, invasive and
unnecessary diagnostics and procedures can be
avoided.
For this reason, more attention should be given to
sexual history, especially as a diagnostic tool in
unclear cases of pneumoperitoneum.

81. Sexual intercourse and thromboembolic
disorders
 Sexual intercourse may trigger the acute onset of coronary
heart disease, sudden death and haemorrhagic stoke.
 Little scientific evidence exists on the role of sexual
intercourse as a risk factor for coronary heart disease and
stroke.
 Frequent sexual intercourse is associated with lower risk of
fatal coronary heart disease, but this attenuates with duration
of follow up.
 Frequency of sexual intercourse is not strongly associated
with risk of ischaemic stroke.

82. Sexual intercourse and pregnancy
 Sexual intercourse is generally considered safe in pregnancy.
 Abstinence should be recommended only for women who are
at risk for preterm labour, or antepartum hemorrhage because
of placenta previa.
 There is little evidence to show that sex at term may help
induce labour, but this practice is considered safe in women
with low-risk pregnancies.
 The resumption of intercourse postpartum should be dictated
by a woman’s level of comfort.