At the time of ejaculation, the contents of the
seminal vesicles are emptied into the ejaculatory ducts.
This action greatly increases the volume of fluid that is
discharged by the vas deferens.
The urethra is an important organ of both the
urinary and reproductive systems. The role of the
urethra, in the reproductive system, is to transport
sperm through the penis to outside the body. See The
Urinary System section for information on the
structure of the urethra.
The prostate gland, made of smooth muscle and
glandular tissue, surrounds the first part of the urethra.
It resembles a chestnut in shape and size, and secretes
an alkaline fluid to keep the sperm mobile, protecting it
from the acid secretions of the female vagina. This
substance is discharged into the urethra as part of the
ejaculate, or semen, during the sexual act.
Bulbourethral glands, also known as Cowper's
glands, are two pea-sized bodies located below the
prostate gland and lateral to the membranous urethra.
These glands are enclosed by fibers of the external
urethral sphincter. They release a mucous-like fluid in
response to sexual stimulation and provide lubrication
to the end of the penis in preparation for sexual
Semen is composed of sperm and secretions from
the seminal vesicles, prostate, and bulbourethral
glands. It is discharged as the ejaculate during sexual
intercourse. There are millions of sperm cells in the
semen of each ejaculation, but only one is needed to
fertilize the ovum. It is generally considered that
fertilization of the ovum occurs while it is still in the
fallopian tubes. Therefore, it is apparent that sperm
cells can move actively in the seminal fluid deposited
in the vagina and through the layers of the secretion
lining the uterus and fallopian tubes.
EXTERNAL ACCESSORY ORGANS
The external accessory organs of the male
reproductive system include the scrotum and penis
The scrotum is a cutaneous pouch containing the
testes and part of the spermatic cord. Immediately
beneath the skin is a thin layer of muscular fibers (the
cremaster), which is controlled by temperature and
contracts or relaxes to lower or raise the testes in
relation to the body. This muscular activity of the
scrotum is necessary to regulate the temperature of the
testes, which is important in the maturation of sperm
The penis is a cylindrical organ that conveys urine
and semen through the urethra to the outside. The penis
is composed of three columns of spongy cavernous
tissue, bound together by connective tissue and loosely
covered by a layer of skin. Two of the columns, the
corpora cavernosa, lie superiorly side by side; the
third column, the corpus spongiosum, lies below the
other two columns. The urethra is located in the corpus
spongiosum. The dilated distal end of the corpus
spongiosum is known as the glans penis (fig. 1-60).
The urethra terminates at the glans penis.
The cavernous tissue becomes greatly distended
with blood during sexual excitement, causing an
erection of the penis. The loose skin of the penis folds
back on itself at the distal end (forming the prepuce, or
foreskin) and covers the glans. The prepuce is
sometimes removed by a surgical procedure called a
LEARNING OBJECTIVE: Recall the parts
of the female reproductive system and their
The organs of the female reproductive system are
specialized to produce and maintain the female sex
cells, or egg cells; to transport these cells to the site of
fertilization; to provide an environment for a
developing offspring; to move the offspring outside;
and to produce female sex hormones. The primary
female reproductive organs are the ovaries. The other
structures of the female reproductive system are
considered accessory reproductive organs. The