« U*X*L Complete Health Resource :: Body by Design V1

***
The Cardiovascular System

***
The cardiovascular system and the lymphatic system form what is collectively called the circulatory system. Together, these systems transport oxygen, nutrients, cell wastes, hormones, and many other substances to and from all cells in the body. The trillions of cells in the human body take up nutrients and excrete wastes every minute of every day. Although the pace of this exchange may increase with activity or slow with rest, it happens continuously. If it stops, so does life. Of the two systems, the cardiovascular system is the primary transport operator; the lymphatic system aids it in its function.

***
DESIGN: PARTS OF THE CARDIOVASCULAR SYSTEM

***
Cardiovascular comes from the Greek word cardia, meaning "heart," and the Latin vasculum, meaning "small vessel." The basic components of the cardiovascular system are the heart, the blood vessels, and the blood. The system can be compared to a large muscular pump (the heart) that sends a fluid (blood) through a series of large and small tubes (blood vessels). As blood circulates through the increasingly intricate system of vessels, it picks up oxygen from the lungs, nutrients from the small intestine, and hormones from the endocrine glands. It delivers these to the cells, picking up carbon dioxide (formed when cells use sugars or fats to produce energy) and other wastes in return. The blood then takes these waste products to the lungs and kidneys, where they are excreted.

***
The heart

***
The heart is a hollow, cone-shaped muscular organ located behind and slightly to the left of the sternum or breastbone. Nestled between the lungs, the heart sits within a protective, bony cage formed by the sternum, ribs, and spine. The lower tip of the heart, called the apex, points toward the left hip and rests on the diaphragm (a membrane of muscle separating the chest cavity from the abdominal cavity). The upper portion of the heart, called the base, points toward the right shoulder and lies beneath the second rib. It is from the base that the major blood vessels of the body emerge.

The heart is about the size of a clenched fist. At birth, an infant's heart and fist are about the same size. As a human body develops, the heart and fist grow at about the same rate. In adults, an average heart weighs between 9 and 11 ounces (255 and 310 grams). It is slightly larger in males than in females.

***
The Cardiovascular System: Words to Know

***
Agglutination (ah-glue-ti-NA-shun):
Clumping of blood cells brought about by the mixing of blood types.
Alveoli (al-VEE-oh-lie):
Air sacs of the lungs.
Antibody (AN-ti-bod-ee):
Specialized substance produced by the body that can provide immunity against a specific antigen.
Antigen (AN-ti-jen):
Any substance that, when introduced to the body, is recognized as foreign and activates an immune response.
Aorta (ay-OR-ta):
Main artery of the body.
Arteriole (ar-TEER-e-ohl):
Small artery.
Artery (AR-te-ree):
Vessel that carries blood away from the heart.
Atria (AY-tree-a):
Upper chambers of the heart that receive blood from the veins.
Atrioventricular (AV) node (a-tree-oh-ven-TRICK-ular):
Node of specialized tissue lying near the bottom of the right atrium that fires an electrical impulse across the ventricles, causing them to contract.
Atrioventricular (AV) valves:
Valves located between the atria and ventricles.
Blood pressure:
Pressure or force the blood exerts against the inner walls of the blood vessels.
Capillary (CAP-i-lair-ee):
Minute blood vessel that connects arterioles with venules.
Cardiac cycle (CAR-dee-ack):
Series of events that occur in the heart during one complete heartbeat.
Cholesterol (ko-LESS-ter-ol):
Fatlike substance produced by the liver that is an essential part of cell membranes and body chemicals; when present in excess in the body, it can accumulate on the inside walls of arteries and block blood flow.
Diaphragm (DIE-ah-fram):
Membrane of muscle separating the chest cavity from the abdominal cavity.
Diastole (die-ASS-te-lee):
Period of relaxation and expansion of the heart when its chambers fill with blood.
Diffusion (dif-FEW-shun):
Movement of molecules from an area of greater concentration to an area of lesser concentration.
Endocardium (en-doe-CAR-dee-um):
Thin membrane lining the interior of the heart.
Epicardium (ep-i-CAR-dee-um):
Lubricating outer layer of the heart wall and part of the pericardium.