The Human Body: An Orientation
or repair. Reproduction of the human organism, or making a
whole new person, is the major task of the reproductive system.
When a sperm unites with an egg, a fertilized egg forms and
develops into a baby within the mother’s body. Te reproduc-
tive system is directly responsible for producing oﬀspring, but its
function is exquisitely regulated by hormones of the endocrine
system (Figure 1.3e).
(g) Lymphatic System/Immunity
Picks up fluid leaked from blood vessels
and returns it to blood. Disposes
of debris in the lymphatic stream.
Houses white blood cells (lymphocytes)
involved in immunity. The immune
response mounts the attack against
foreign substances within the body.
(h) Respiratory System
Keeps blood constantly supplied with
oxygen and removes carbon dioxide.
The gaseous exchanges occur through
the walls of the air sacs of the lungs.
Breaks down food into absorbable units
that enter the blood for distribution to
body cells. Indigestible foodstuffs are
eliminated as feces.
Eliminates nitrogenous wastes from the
body. Regulates water, electrolyte and
acid-base balance of the blood.
(k) Male Reproductive System
Overall function is production of offspring. Testes produce sperm and male sex hormone,
and male ducts and glands aid in delivery of sperm to the female reproductive tract. Ovaries
produce eggs and female sex hormones. The remaining female structures serve as sites for
fertilization and development of the fetus. Mammary glands of female breasts produce
milk to nourish the newborn.
Female Reproductive System
the blood to the lungs, where it leaves the body in exhaled air
occurs at the cellular and the organismal level.
In cellular reproduction, the original cell divides, producing two
identical daughter cells that may then be used for body growth