Page 25 - Human anatomy COMPLETELY DONE1

BLOOD FUNCTIONS
In humans, blood is constantly moving through a closed system of blood vessels.
Most of the functions of the blood are associated with the transfer of substances, so they
are often combined into one common transport function. Blood carries metabolic
products, hormones, enzymes, heat. Humoral regulation of the body with biologically
active substances is carried out with the participation of blood. It provides the body's
protective reactions against infections and maintains a constant body temperature.
-Respiratory – carries oxygen, taking it in the lungs from the air, to all the cells
of the body, and in the opposite direction carries carbon dioxide into the lungs, which
is exhaled into the external environment.
-Nutritious – carries throughout the body those nutrients that are absorbed from
digested food in the intestine.
-Excretory – removes metabolic products from tissues to those organs that
remove them from the body, that is, into the kidneys or liver.
-Thermoregulatory – heating up, the blood transfers heat from the place of its
formation, that is, from the skeletal muscles and liver, to those organs that need to be
warmed (skin, brain).
-Protective – cells, which are an integral part of the blood, kill foreign agents that
enter the body and cause diseases. The protective function of the blood also includes
the formation of a blood clot – a blood clot in the place where the vessel is damaged.
This process protects the body from deadly blood loss.
-Regulatory – maintaining the relative constancy of the chemical composition
and physical properties in the body by transferring a number of biologically active
substances.
The internal environment of the body
The blood itself does not directly come into contact with most cells. However, a

certain amount of the liquid component of blood passes through the walls of thin blood
vessels and forms a watery membrane around the cells – tissue fluid.
Part of the tissue fluid, which is called lymph, is collected in the thinnest tubes
with blindly closed ends – lymphatic capillaries. Further, the lymphatic capillaries pass
into thin-walled lymphatic vessels. In those places where several lymphatic vessels
merge, lymph nodes are formed. It is these structures that form the lymphatic system
through which the lymph circulates.
Thus, the internal environment includes blood, lymph and tissue fluid.
The internal environment of the body ensures the interconnection of all cells of
the body with the environment, acts as an intermediary in the implementation of
metabolism. It provides the cells with the substances necessary for their work, and
through it the decay products are removed.
Pathogenic microorganisms are destroyed in the lymph. Thus, the main function
of the lymph is protective.
In addition, the lymph ensures the return of tissue fluid to the bloodstream.

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