Apgar Score

The Apgar Score is a rating system used to evaluate the health of newborn infants. The test is administered one minute after birth and again five minutes after birth.

Arc Lamp

Long before the incandescent (very bright) electric light bulb was invented, arc lamps gave birth to the science of electric lighting. When the first large batteries were being built in the early 1800s, researchers noticed that electric current would leap across a gap in a circuit, from one electrode (a terminal that conducts current, such as an anode or cathode in a battery) to the other.

Arteriography, Coronary

Coronary arteriography, the X-ray photography of coronary arteries in a living patient, is a technique researchers have tried to develop since the 1930s. The ability to view coronary arteries (the two artery "branches" from the aorta that supply blood to the heart muscle) is considered fundamental to the development of effective diagnosis and treatment of coronary artery disease (also known as arteriosclerosis, or "clogged arteries").


The arthroscope is an optical (pertaining to the eye) instrument that allows doctors to view the inner workings of a moveable joint without having to perform surgery. The instrument is a flexible narrow tube containing several bundles of hair-thin glass fibers that are covered with a reflective coating.

Artificial Blood

The hunt for a substance to replace whole blood in transfusions has been underway since the late 1960s. The search has so far been unsuccessful, but research continues because success would eliminate several major problems in using fresh blood.

Artificial Blood Vessels

Artificial blood vessels are tubes made from synthetic (chemically produced) materials to restore blood circulation. During World War I (1914-1918) French-American surgeon Alexis Carrel (1873-1944) perfected a procedure for sewing the ends of blood vessels together.

Artificial Bone

For years the main source of bone for replacement purposes was cadavers (dead bodies). In fact, the Red Cross maintains a "bone bank" for just this purpose.

Artificial Heart

The heart functions primarily as a pump to keep blood circulating through the body. Because the heart's job is so repetitive, medical researchers have long considered developing a mechanical pump to replace it.

Artificial Heart Valve

Heart valves are flaps of tissue within the heart. They open and close to allow blood to flow into the correct cardiac areas in the right direction.

Artificial Hip

Artificial limbs have been used since early history to replace arms and legs lost to injury or disease. The Greek historian Herodotus mentioned wooden feet in a writing from 500 B.C.

Artificial Kidney

The kidneys perform the vital function of filtering waste materials out of the blood. When the kidneys stop functioning, a person can die quickly from waste buildup.

Artificial Ligaments

Ligaments are bands of tough, elastic tissue that bind bones together at joints so that they can move. When a ligament is torn, it can either be repaired or replaced.

Artificial Limb and Joint

A man learns to use his artificial limbs and joints with the help of a physical therapist. Advances in replacement surgery allow many patients to enjoy greater mobility and decreased pain.

Artificial Skin

Artificial skin is a synthetic (laboratory produced) substitute for human skin that can dramatically save the lives of severely burned patients. Skin, composed of two layers called epidermis (the outer layer) and dermis (the inner layer), is the largest human organ.


Aspirin grew out of a group of drugs called "patent medicines." These medications—some of questionable quality—were very popular from the 1600s to later years of the 1800s. The name "patent" comes from the fact that when a medication was patented (or registered), its formula was owned by the patent holder and no one else could duplicate or sell it.

Atomic Force Microscope (AFM)

In recent years, tremendous advances have been made in the field of microscopy (the study of microscopes). The electron microscope (which uses a beam of electrons, or negatively charged particles, to form an enlarged image of an object) is found in most hospitals and medical laboratories.


An audiometer is an instrument used to measure how well a person hears. The ear is a complex organ.


During and shortly following World War II (1939-1945), new "miracle drugs" revolutionized the medical treatment of infections. These new drugs included several types of substances found to have antibacterial (destructive to bacteria) and antiviral (destructive to viruses) properties.


The autoclave is a device used to sterilize (deep clean) medical instruments. It did not start out as a medical instrument.

Bandages and Dressings

Prehistoric bandages and dressings (materials used to cover a wound) were most likely made from plant materials and strips of animal hide. Fabric bandages were developed later.