27. The Reproductive System
This is the only system not required for the life of the individual.
Rather, it is required for the
continued existence of the species.
The reproductive system in an individual produces, stores,
nourishes, and transports either male or female
The female reproductive system is also
responsible for protecting, supporting, and nourishing a developing fetus.
The reproductive system includes the following components:
are organs that produce gametes and reproductive hormones.
Accessory reproductive organs
include (1) ducts that provide passages for transport of the
gametes, (2) various glands that secrete fluids required by the reproductive system, and (3)
perineal structures that are important during copulation.
(Perineal structures are also referred to
I will probably not review the information in the paragraph that follows.
However, you should
be familiar with this information to better understand the concepts of Chapter 27.
All cells in your body, except gametes, have two copies of all your genes.
These cells are called
, and they may be referred to as
) to indicate the presence of two
copies of the genes.
Each gamete has only one copy of your genes, and gametes may be referred
) to indicate the presence of only a single copy of each gene.
In order for a
new individual to form, two 1n gametes must fuse to form a 2n
, a process called
The zygote then divides by
to form an embryo, which may eventually
grow into an adult human.
Gametes are produced from 2n cells via the process of
which reduces the amount of genetic material by half (2n
I. Anatomy of the Male Reproductive System
The basic structures of the male reproductive system are shown in Fig. 27.1.
The male gonads
The male duct system begins with the
, which leads to the
, and finally the
Accessory glands include the
, and the
Perineal structures include
During early development, testes form inside the body near the kidneys.
Prior to birth, the testes
typically descend into the scrotum.
The scrotum is a sac made of a layer of skin and an
underlying layer of tissue called the
Bands of skeletal muscle, called the
, lie deep to the dermis of the scrotum.
Contraction of the cremaster muscle pulls the testis close to the body wall.
relaxation allows regulation of temperature of the testes, which should be about 1ºC cooler than
core body temperature for normal sperm development.