develops. Symptoms usually clear up
in a few days; antihistamine drugsmay
hasten recovery. In severe cases, a
corticosteroid drugmay be prescribed.
sexAnother term for gender and a com-
monly used term for sexual intercourse.
sex changeRadical 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 chromosomesA pair of chromo-
somesthat 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 chromosomescalled autosomes. In
women, there are 2 similar sex chromo-
somes calledX chromosomes. Men have
1 X and 1 Y chromosome. The geneson
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 determinationThe 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 toform. In the absence of these hormones,
a female reproductive tract develops. At
puberty, another surge of hormones pro-
ducessecondary sexual characteristics.
Chromosomal abnormalities or hor-
monal defects can lead to ambiguous
sex (see genitalia, ambiguous), although
true hermaphroditismis rare.
sex hormonesHormones 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 inheritanceThe passing
on to the next generation of a trait or
disorder determined by thesex chromo-
somes, or by the genescarried 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 recessivegenes on the
X chromosome (see genetic disorders).
sex therapyCounselling 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 techniqueor 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 abuseThe 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-
tivelife. 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.SEX SEXUAL CHARACTERISTICSS
SEX CHROMOSOMES
X chromosome Y chromosome