SEX
SEXUAL CHARACTERISTICS
develops. Symptoms usually clear up
in a few days;
antihistamine drugs
may
hasten recovery.
In
severe cases, a
corticosteroid drug
may be prescribed.
sex Another term for gender and a com-
monly used term for
sexual intercourse
.
sex change Radical surgical procedures,
usually combined with hormone therapy,
that alter a person's anatomical gender.
Sex-change operations are performed on
transsexuals (see
transsexualism
) and
on infants whose external sex organs
are neither completely male nor female
(see
genitalia, ambiguous).
sex chromosomes A pair of
chromo-
somes
that determines an individual's
sex. All human cells (except egg or
sperm cells) contain a pair of sex chro-
mosomes, together with
22
other pairs
of chromosomes called autosomes. In
women, there are
2
similar sex chromo-
somes called
X chromosomes
. Men have
1 X and 1
Y chromosome.
The
genes
on
the Y chromosome are concerned solely
with
sex determination
; their presence
ensures a male, their absence a female.
The X chromosome carries genes vital
to general development and functioning.
SEX CHROMOSOMES
X chromosome
Y chromosome
sex determination The factors that
determine biological sex. The underlying
determinants are the
sex chromosomes
which cause the differential development
of the gonads in the embryo. In males,
the testes then produce hormones that
cause the male reproductive organs to
form. In the absence of these hormones,
a female reproductive tract develops. At
puberty,
another surge of hormones pro-
duces secondary
sexua characteristics.
Chromosoma abnormalities
or hor-
monal defects can lead to ambiguous
sex (see
genitalia, ambiguous
), although
true
hermaphroditism
is rare.
sex hormones Hormones that control
the development of primary and secon-
dary
sexual
characteristics
and that
regulate sex-related functions, such as
the menstrual cycle. There are 3 main
types:
androgen hormones
,
oestrogen
hormones
, and
progesterone hormone
.
sex-linked inheritance The passing
on to the next generation of a trait or
disorder determined by the
sex chromo-
somes,
or by the
genes
carried on them.
Disorders caused by an abnormal num-
ber of sex chromosomes include
Turner's
syndrome
and
Klinefelter's syndrome.
Most other sex-linked traits or disorders
are caused by
recessive
genes on the
X chromosome (see
genetic disorders
).
sex therapy Counselling for and treat-
ment of sexual difficulties not due to a
physical cause. It may involve changing
the attitude of the partners towards sex,
increasing their understanding of sexual
needs, and teaching techniques, such as
the
sensate-focus technique
or
pelvic floor
exercises,
for specific problems. Sex ther-
apy is particularly successful in treating
vaginismus,
premature ejaculation (see
ejaculation, disorders
of), lack of orgasm
(see
orgasm, lack
of), and
impotence.
sexual abuse The subjection of a per-
son to sexual activity that has caused or
is likely to cause physical or psychologi-
cal harm. (See also
child abuse; rape.)
sexual
characteristics,
secondary
Physical features appearing at
puberty
that indicate the onset of adult reproduc-
tive life. In girls, breast enlargement is
the first sign. Shortly afterwards, pubic
and underarm hair appears, and body fat
increases around the hips, stomach, and
thighs to produce the female body shape.
In boys, the first sign is enlargement of
the testes, followed by thinning of the
scrotal skin and enlargement of the
penis. Pubic, facial, axillary, and other
body hair appears, the voice deepens,
and muscle bulk and bone size increase.
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