This document provides information about human sexual intercourse from a physiological perspective. It discusses the anatomy and biological process of sexual intercourse, including common positions. It also covers fertilization and conception, noting that intercourse can result in pregnancy unless contraceptive measures are used. Finally, it mentions some common problems that can occur with intercourse and emphasizes the importance of consent.

1. Physiology of
Human Sexual Intercourse

2. 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". Many higher
vertebrates animals (reptiles, birds. dogfish) reproduce
internally, but their fertilization is in the cloacae. Other
animals, such as catfish and most amphibians reproduce
sexually but rely on external fertilization/ rather than
copulation.

3. 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 and natural lubrication of the vagina.
The erect penis is inserted into the vagina
and one or both of the partners move back
and forth to stimulate themselves and each
other usually to the point of ejaculation and
orgasm.

4. Sexual Intercourse Positions
-Sexual intercourse may be performed in a wide list of
sex positions, the most common ones being:
·The woman lying on her back, the man on top and facing
her ("missionary position")
·The woman on hands and knees, the man kneeling
behind her ("doggy style" or in Latin ''coitus more
ferarum''/"sex in the manner of beasts")
·The man on his back or sitting, the woman kneeling or
squatting on top (slang "cowgirl sex position") if the
woman faces the man or "reverse cowgirl sex position”(if
the woman faces away from him)
·Both partners lying on their sides, the man entering from
the front ("side-by-side position")
·Both partners lying on their sides, the man entering from
behind ("spoons sex position/ spooning")

5. Sexual intercourse:
Biology of conception
-Coitus is the basic reproductive method of ''Homo sapiens'' 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. 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. 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.

6. 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. 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. 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.

7. Problems of intercourse
-Many males suffer from erectile dysfunction, or
impotence, at least occasionally. Some men also have
dysfunction with orgasm in intercourse, called
anorgasmia. Anorgasmia is much more common in
women, however, and usually needs attention from both
partners over a long time span to solve. Many women,
especially younger women and women with relatively
little sexual experience, experience difficulty achieving
orgasm or may be unable to achieve orgasm. Vaginismus
is involuntary tensing of the pelvic floor musculature,
making coitus distressing or impossible. Dyspareunia is
painful or uncomfortable intercourse; it can be due to a
variety of reasons.

8. Sexually transmitted diseases (STD)
-Sexual intercourse, like other sexual activities that
involve the possibility of transfer of body fluids, is also a
means of propagating sexually transmitted diseases.
Health care professionals suggest that condoms should be
used to lessen the risk of contracting STDs, but they
should by no means be considered an absolute safeguard.
The best suggestion is to avoid sexual intercourse with
anyone known to have a sexually transmissible disease,
and, indeed, with anyone whose disease-negative status is
in doubt.

9. Sexual intercourse:Morality and legality
-Various laws, moral rules and taboos surround sexual
intercourse. Unlike some other sexual activities, sexual
intercourse itself has rarely been made taboo on religious
grounds or by government authorities. It is believed that all
of the cultures that prohibited sexual intercourse entirely
no longer exist, save the Shakers, a sect of Christianity,
which has very few adherents. Within some ideologies,
coitus has been considered the only "acceptable" sexual
activity. Relatively strict designations of "appropriate" and
"inappropriate" sexual intercourse have been almost
universal in human societies.

10. These have included prohibitions against specific list of
sex positions, against intercourse among partners who are
not married (this is called fornication) or are married, but
not to each other (called adultery), against sexual
intercourse with a close relative (called incest), and
against intercourse during a woman’s menstrual period.
Most countries have age of consent laws specifying the
minimum legal age for engaging in sexual intercourse.
Sexual intercourse with a person against their will, or
without their informed consent informed legal consent, is
called rape and is considered a serious criminal law crime
in most cultures.

11. Birth Control

12. What is birth control?
-Birth control, also called contraception, is any
method used to prevent pregnancy. It allows
you to choose whether or when to have a child.
Most women can become pregnant from the
age when they start their menstrual periods
until their late 40s or early 50s. During the
many years before menopause, using birth
control is key to avoiding an unplanned
pregnancy.

13. Which birth control method
should I use?
-There are many different kinds
of birth control. Each has its
own pros and cons. Learning
about all the methods will help
you find the one that is right for
you.

14. Available methods include:
-Hormonal methods such as the birth control pill ("the
Pill"), shot, skin patch, and vaginal ring. The
intrauterine device (IUD) contains a hormone. Hormone
birth control works very well. It prevents pregnancy by
stopping monthly egg production. It can also relieve
heavy periods and cramping.
• -Intrauterine devices (IUDs). An IUD is placed in the
uterus through the vagina and cervix. The IUD
interferes with a sperm as it tries to reach and fertilize
an egg. It can also stop a fertilized egg from implanting
and growing into an embryo. IUDs work very well for 5
to 10 years at a time, and are far safer than they were
decades ago. The hormonal IUD can also help with
heavy periods and cramping.

16. • -Barrier methods, such as condoms, diaphragms, cervical
caps, Lea's Shield, sponges, and spermicides. In general,
barrier methods are less effective than IUDs or hormonal
methods. To make a barrier work as well as possible, you use it
with a spermicide. This kills any sperm that get past the barrier,
before they can travel through the cervix. Unless you know that
your sexual partner does not have any sexually transmitted
diseases (STDs), use a condom every time you have sex.
• -Fertility awareness (natural family planning), such as the calendar
method. Natural family planning can work well if you and your partner are
very careful. However, do not use fertility awareness if you need highly
dependable pregnancy prevention. First, you pinpoint your fertile times of the
month. (This means charting your body's "fertile" signs and your basal body
temperature daily for at least 2 months.) On fertile days, you must not have
sex or you must use a birth control method. If you are a sexually active teen
or are not able to predict when you are fertile, you cannot count on fertility
awareness to prevent pregnancy.

17. •-Permanent birth control, such as
vasectomy or tubal ligation surgery, gives
you permanent protection against
pregnancy. (On rare occasion, vasectomy
or tubal ligation does fail to prevent
pregnancy.) However, it is only a good
option if you are absolutely sure that you
will never want to conceive a pregnancy.

18. Lifestyle
When choosing a method, first consider how well it works
and whether it fits your lifestyle. For example, if you are a
single woman who has no plans to raise a child on your
own, you will want to use a highly effective birth control
method.
Future fertility
When deciding about birth control, think about how soon, if
ever, you would like to start a family. Although you can
become pregnant after stopping any birth control method
(or forgetting a few days of pills), some women take
several months to become pregnant after using Depo-
Provera shots or high-dose birth control pills.

19. Do health factors limit
some birth control
options?
-Some birth control methods may not
be right for you if you have certain
health problems or other risk factors.
To make sure a method is safe for
you, tell your health professional
about whether you smoke or have
any health problems

20. •High blood pressure.
•Blood clots (deep vein thrombosis) in your
personal or family history.
•Migraine headaches.
•Heart disease.
•High triglyceride levels.
•Diabetes with complications.
•Sexually transmitted disease (STD)
infection.
•A history of breast cancer.

21. Which methods cost the least and
are easiest to get?
Barrier methods that you can buy at a drugstore
are the easiest form of birth control to get. Either
partner can buy them without a prescription.
These methods include:
•Condoms and spermicides.
•Sponges, which have spermicide in them. The
sponge is tucked up against the cervix. (The
popular Today sponge is expected to again be
available in the United States by end of summer
2005.)

22. Long-lasting birth control measures, such
as the intrauterine device (IUD), are more
costly when you first pay for them.
However, these methods work for months
to years, making them low-cost over time.
These longer-lasting methods include:
•IUDs.
•Hormonal methods such as the shot or ring.
•Sterilization surgery (tubal ligation for a woman
or vasectomy for a man.)