This page outlines information on the cardiovascular system. Separate pages describe the types and structures of arteries, characteristics of blood flow, and information on lipoproteins .
The human cardiovascular system is composed of a heart which pumps blood through a closed system of blood vessels. The heart is composed mostly of cardiac muscle, or myocardium. Its primary function is to transport nutrients, water, gases, wastes, and chemical signals throughout the body. More information on the heart as a pump, blood flow and control of blood pressure, and components of blood will be discussed in related pages.
The cardiovascular system transports materials throughout the body:
1. Materials entering the body, such as oxygen via the lungs and nutrients
and water via the intestinal tract, are carried to all cells.
2. Materials moved from cell to cell (intercellular communication)
including:
a) wastes products from some cell cells to the liver for processing;
b) immune cells that are present in the blood continuously for other
cells,
c) hormones from endocrine cells to their target cells
d) stored nutrients from liver and adipose tissue to all cells.
3. Materials that are expelled from the body, such as metabolic wastes,
heat, and carbon dioxide that are removed via the kidneys, skin, and
lungs, respectively.
As a general overview, the cardiovascular system is composed of the heart,
the blood vessels (or vasculature), and the cells and plasma of the blood.
1. Arteries are blood vessels that carry blood away from the heart and
veins return the blood to the heart. A system of valves in the heart and
veins ensures that the blood flows in one direction.
2. The heart is anatomically divided into two halves by a central wall, or
septum, into left and right halves. Each half is composed of an atrium
which receives blood returning to the heart and a ventricle that pumps the
blood out into the blood vessels that serve the body. The atria and
ventricles and exiting blood vessels are separated by closable valves.
Functionally, the heart serves as a pump in series that generates pressure
to propel the blood through the system.
3. The lungs are were oxygen is picked up and carbon dioxide is expelled.
The pulmonary circulation goes from the right side of the heart
(deoxygenated blood) and returns it to the left side of the heart, with
oxygenated blood.
4. The systemic circulation consists of the vessels that go from the left
side of the heart to the tissues and back to the right side of the heart.
The systemic circulation and the pulmonary circulation can be traced
together:
Deoxygenated blood returning from body enters the heart in the right
atrium. From the right atrium the blood passes through the tricuspid
valves to enter the right ventricle. The blood is then pumped into the
pulmonary arteries, passing the pulmonic valves, where it goes to the
lungs. After becoming oxygenated in the lung's capillaries, the blood is
carried by the pulmonary veins to the left atrium. It then passes through
the bicuspid or mitral valves into the left ventricle, where it is pumped
into the aorta through the aortic valves. The aorta branches into smaller
and smaller arteries that finally lead to capillary beds in the tissue.
Here oxygen is exchanged for carbon dioxide and returned via veins which
join into the inferior vena cava (veins coming from the lower body) and
superior vena cava (from the upper body). The IVC and the SVC empty into
the right atrium.