Psychology2016

394 CHAPTER 10

At about 5 weeks of pregnancy, two organs called the gonads form in the embryo. Two sets

of ducts (tubes) also develop next to the gonads, the Wolffian ducts (which can become

the male sex organs) and the Müllerian ducts (which can become the female sex organs).

At this point, the gonads are undifferentiated—neither fully male nor fully female—and

the embryo could potentially become either male or female. The deciding factor is con-

trolled by the chromosomes: If the chromosomes of the 23rd pair contain a Y chromosome,

a gene on that Y chromosome causes the gonads to release testosterone, a male hormone or

androgen. (Female hormones are called estrogens.) Testosterone causes the Wolffian ducts

to develop into the male sex organs, while the Müllerian ducts deteriorate. If the 23rd pair

of chromosomes contains two female or X chromosomes, the Y gene is absent so no tes-

tosterone is released, and the gonads will develop into the estrogen-secreting ovaries. The

Müllerian ducts become the female sex organs while the Wo lff i a n d u c t s d e t e r i o r a t e.

On rare occasions, an infant is born with sexual organs that are ambiguous—not

clearly male or female. People with this condition are referred to as intersex, meaning

“between the sexes,” and represent about 1.7 percent of the population (Blackless et al.,

2000; Dreger, 1998, 1999). It is very rare to find a person who truly has both ovary and

testicle material in their body. More commonly, the development of the external geni-

tals is affected by either chromosomes or the presence of hormones associated with the

development of another sex at a critical time in the development of the fetus in the womb

(Hutcheson & Snyder, 2004). A few of the possible hormonal abnormalities include andro-

gen insensitivity (where someone who is genetically male is resistant to the male hormone

androgen), congenital adrenal hyperplasia (several genetic conditions leading to limited

production of hormones by the adrenal glands), and dihydrotestosterone deficiency, lead-

ing to a lack of a particular male hormone (Wiesemann et al., 2010; Wisniewski et al., 2000;

Wolfe-Christensen et al., 2012). In these cases, a female clitoris might look more like a

penis, or a penis might be so small as to resemble a clitoris. Many physicians, psycholo-

gists, and other experts now consider gender reassignment surgery performed on infants

with intersex traits to be unnecessary (Wiesemann et al., 2010). Gender identity is not a

biological concept, remember, and current thinking is in favor of allowing an intersex

individual to make the decision about surgery once the person has determined a concept

of gender. Surgery of this sort can lead to negative consequences for the ability to function

sexually in later life (Creighton et al., 2001; Crouch et al., 2004; Kraus, 2015).

estrogens
female hormones.

androgens
male hormones.

intersex
modern term for a hermaphrodite,
a Rerson who Rossesses amDiguous
sexual organs, making it difficult to
determine actual sex from a visual
inspection at birth.

female: vagina, uterus, and ovaries

male: penis, testicles, scrotum, and prostate gland

The Physical Side of Human Sexuality

physical sex characteristics are not the same as gender, the psychological aspects of identifying as a male or female

embryonic undifferentiated gonads develop

into male or female sex organs as the result

of chromosomes and hormones

chromosomes and variable hormones

can result in ambiguous sex organs/

intersex individuals

primary sexual characteristics:

present at birth, directly involved

in reproduction

female: breast enlargement, widening of hips,

pubic hair, fat deposits on buttocks and thighs

male: deepening of voice, facial and chest hair,

pubic hair, coarser skin texture, increase in height

secondary sexual characteristics:

develop during puberty (indirectly

involved in reproduction)

Concept Map L.O. 10.1, 10.2

Interactive

Reset