An enzyme is a protein that speeds up the rate at which a chemical reaction occurs. Enzymes are substrate specific, meaning that each type of enzyme has a specific type of molecule that it affects. The human body needs enzymes to influence the rates at which biological processes occur.

Cells within the human body contain thousands of genes, proteins and other chemicals enclosed within cellular membranes. Each cell responds to chemical signals from the body or the environment and modifies its behavior in response to signals.

Excessive fluid buildup around the heart, known as pericardial effusion, can be diagnosed on fetal ultrasound. Pericardial effusion can interfere with the heart’s ability to pump blood to the rest of the body, affecting growth and vitality of the fetus.

A child's developmental milestones depend on two main factors: nature and nurture. Nature refers to the child's genetic makeup -- her DNA -- a conglomeration of traits handed down to the child by her parents. Nurture is the environment in which the child lives, plays and learns.

The arteries are blood vessels that carry blood away from your heart and branch out into smaller arteries going toward your different organs to supply fresh, oxygen-rich blood.

The heart is a muscle surrounded by a fibrous sac containing sheath called the pericardium. There is normally 2 to 3 ccs of fluid between the heart and the pericardial lining. If excessive fluid builds up in the space between the pericardium and the heart, this is called a pericardial effusion.

Clogged arteries, medically known as arteriosclerosis or atherosclerosis, refers to a condition in which fatty substances called cholesterol build up in your blood vessel walls.

Numerous diseases can cause a change in hair texture and volume. According to the U.S. National Library of Medicine and the National Institutes of Health, or NIH, the lips, palms and soles of the feet are the only parts of the body on which hair does not grow.

An artery becomes clogged when a buildup of plaque forms on the inner walls. Plaque consists of calcium, fat, cholesterol and cellular waste. If you have clogged arteries due to poor diet and lifestyle choices, you are at an increased risk of having a heart attack, stroke or suffering from heart failure.

The typical American diet, which is high in animal-based and processed fats, contributes to a buildup of plaque in the arteries. If you have -- or suspect you have -- buildup of arterial plaque, you should take steps to try to clear it away. Certain vitamins may help a bit, but other measures are more effective.

A normal heart rhythm has the ability to pump blood to and from the heart without undue stress. Tachycardia is a rhythmic disorder of the heart that causes it to beat at a faster rate than normal.

Many people have had an electrocardiogram, or EKG, at some point in their lives. Although it is one of the simplest medical tests to perform, it can give doctors a wealth of information, some of which could ultimately prove lifesaving. Many conditions can cause an abnormal EKG result.