392 CHAPTER 10
The Physical Side of Human Sexuality
Before discussing gender and gender identity, it may help to understand the physical struc-
tures of the human sexual system and the function of those structures. These structures differ
for females and males and develop at different times in an individual’s life. As you read this
next section, keep in mind that physical sex characteristics are not the same as the experi-
ence of gender, the psychological aspects of identifying oneself as male or female. One’s sex is
about biology, but gender is a social expectation for behavior, an expectation that varies from
culture to culture and that changes as societal views of acceptable and desirable behavior
related to being perceived as male or female change.The Primary and Secondary Sex Characteristics
- 1 Distinguish between primary and secondary sex characteristics.
The sexual organs include structures that are present at birth (called primary sex
characteristics) and those that develop during puberty, the period of physiologi-
cal change that takes place in the sexual organs and reproductive system during late
middle childhood and adolescence (called secondary sex characteristics). to
Learning Objective 8. 9.
THE PRIMARY SEX CHARACTERISTICS Primary sex characteristics are directly
involved in human reproduction. While not fully developed until puberty, these phys-
ical characteristics are present in the infant at birth. In the female, these characteristics
include the vagina (the tube leading from the outside of the body to the opening of
the womb), uterus (the womb), and ovaries (the female sex glands). In males, the pri-
mary sex characteristics include the penis (the organ through which males urinate and
which delivers the male sex cells or sperm), the testes or testicles (the male sex glands),
the scrotum (an external pouch that holds the testes), and the prostate gland (a gland
that secretes most of the fluid that carries the sperm). (See Figure 10.1.)
THE SECONDARY SEX CHARACTERISTICS Secondary sex characteristics develop
during puberty and are only indirectly involved in human reproduction. These char-
acteristics serve to distinguish the male from the female and may act as attractants to
members of the opposite sex, ensuring that sexual activity and reproduction will occur.
They are also, in many cases, a physical necessity for reproduction.
FEMALE SECONDARY SEX CHARACTERISTICS In females, secondary sex characteristics include
a growth spurt that begins at about ages 10 to 12 and finishes about 1 year following the first
menstrual cycle, in which the blood and tissue lining of the uterus exit the body through the
vagina if there is no pregnancy to support. This first cycle is known as menarche and occurs at
an average age of about 12 in more developed countries such as the United States.
The earlier onset of menarche in more developed countries is associated with the
availability of better health care and nutrition, and, along with an increase in height and
weight compared to previous generations, is an example of a secular trend, a change or series
of changes that takes place over a long period of time (Bellis et al., 2006; Roche, 1979). But
better physical health is not the only factor in the decrease in age of menarche. Stress, in the
form of marital strife, absentee fathers, and increasing rates of divorce also plays a part in
speeding up the changes of puberty (Gluckman & Hansom, 2006; Parent et al., 2003). Some
of the consequences of an earlier menarche (and an earlier production of sperm in boys, as
well) include the possibility of pregnancy in children at a far younger age than previously
thought possible (Wellings et al., 2001). Pregnancy in adolescence is not only hard on the
young mothers physically but has negative social impact—poverty, child abuse and neglect,
and a failure to continue in school, to name a few (Kirchengast, 2009).
Other changes include enlarged breasts about 2 years after the growth spurt,
wider hips to allow the passage of the fetus through the pelvic bones, pubic hair, and
primary sex characteristics
sexual organs present at birth
and directly involved in human
reproduction.
secondary sex characteristics
sexual organs and traits that develop
at puberty and are indirectly involved
in human reproduction.
vagina
the tube that leads from the outside
of a femaleos Dody to the oRening
of the womD.
uterus
the womD in which the DaDy grows
during pregnancy.
penis
the organ through which males
urinate and which delivers the male
sex cells or sperm.
scrotum
external sac that holds the testes.
prostate gland
gland that secretes most of the fluid
holding the male sex cells or sperm.
menarche
the first menstrual cycle, the monthly
shedding of the blood and tissue
that line the uterus in preparation
for Rregnancy when conceRtion does
not occur.