The Circulatory System

by **OrjoWan** Fri Jan 28, 2011 5:36 am

The Circulatory System
The Cardiovascular System

The circulatory system

is an organ system that passes nutrients
(such as amino acids, electrolytes and lymph),
gases, hormones, blood cells, etc.
to and from cells in the body to help fight diseases
and help stabilize body temperature and pH
to maintain homeostasis.

This system may be seen strictly as a blood distribution network,
but some consider the circulatory system as composed
of the cardiovascular system, which distributes blood,
and the lymphatic system, which distributes lymph.
While humans, as well as other vertebrates,
have a closed cardiovascular system
(meaning that the blood never leaves the network of arteries,
veins and capillaries)
, some invertebrate groups have an open cardiovascular system.
The most primitive animal phyla lack circulatory systems.
The lymphatic system, on the other hand, is an open system.

Two types of fluids move through the circulatory system:
blood and lymph.
The blood, heart, and blood vessels form the cardiovascular system.
The lymph, lymph nodes, and lymph vessels form the lymphatic system.
The cardiovascular system and the lymphatic system collectively
make up the circulatory system.

Human cardiovascular system
The main components of the human cardiovascular system
are the heart the veins, and the blood vessels.

It includes: the pulmonary circulation,
a "loop" through the lungs where blood is oxygenated;
and the systemic circulation, a "loop" through the rest of the body
to provide oxygenated blood.
An average adult contains five to six quarts
(roughly 4.7 to 5.7 liters) of blood,
which consists of plasma, red blood cells,
white blood cells, and platelets.
Also, the digestive system works with the circulatory system
to provide the nutrients the system needs
to keep the heart pumping.