Computerized Axial Tomography, CAT, or Computed Tomography, CT Terms +

The belly or that part of the body that contains all of the structures between the chest and the pelvis: The abdomen is separated anatomically from the chest by the diaphragm, the powerful muscle spanning the body cavity below the lungs.

Referring to something that deviates from the usual structure, position, condition, or behavior: In referring to a growth, an abnormal development may mean that it is cancerous or premalignant; that is, likely to become cancer.

In pharmacology, any unexpected or dangerous reaction to a drug: An adverse reaction is an unwanted effect caused by the administration of a drug.

The onset of the adverse reaction may be sudden or develop over time.

1. A misguided reaction to foreign substances by the immune system: Carol suffered from an allergy, and this condition of hypersensitivity to some unknown substance totally baffled the doctor.
2. The body system of defense against foreign invaders, particularly pathogens (the agents of infection): The reaction to a foreign substance that is normally harmless can result in an allergy.

The substances that can trigger allergies are called "allergen".. Examples include pollens, dust mite, molds, danders, and certain foods.

People who are prone to allergies are said to be "allergic" or "atopic".

1. The study of form: Gross anatomy involves structures that can be seen with the naked eye and is the opposite of microscopic anatomy, or histology, which involves structures seen under the microscope.

Traditionally, both gross and microscopic anatomy are studied in the first year of medical school in the U.S.

The most celebrated textbook of anatomy in the English-speaking world is >Gray's Anatomy, which is still a useful reference book.
2. Etymology: from the Greek ana- meaning "up" or "through" + tome meaning "a cutting".

Anatomy was once a "cutting up" because the structure of the body was originally learned through dissecting it, that is "cutting it up".

A drugs that combat the histamine released during an allergic reaction by blocking the action of the histamine on the tissue: Antihistamines do not stop the formation of histamine; therefore, antihistamines do not stop the allergic reaction but protect tissues from some of its effects.

Antihistamines frequently cause mouth dryness and sleepiness. Newer "non sedating" antihistamines are generally thought to be somewhat less effective.

Antihistamine side effects that occasionally occur include urine retention in males and a fast heart rate.

The largest artery in the body: The aorta arises from the left ventricle of the heart, goes up (ascends) a little way, bends over (arches), then goes down (descends) through the chest and through the abdomen where it ends by dividing into two arteries called the common iliac arteries that go to the legs.

The familiar red vital fluid in the body that contains white and red cells, platelets, proteins, and other elements: Blood is transported throughout the body by the circulatory system.

Blood functions in two directions: arterial and venous. Arterial blood is the means by which oxygen and nutrients are transported to body tissues while venous blood is the means by which carbon dioxide and metabolic by-products are transported to the lungs and kidneys respectively for removal from the body.

The substance that forms the skeleton of the body: Bones are composed chiefly of calcium phosphate and calcium carbonate.

Bones also serves as a storage area for calcium, and plays a large role in calcium balance in the blood.

The process of respiration: Breathing takes place when air is inhaled into the lungs through the mouth or nose due to muscle contraction, and then exhaled as a result of muscle relaxation.

A picture of a structure within the body created by a computer that takes the data from multiple X-ray images and turns them into pictures on a screen.

The computerized axial tomography (CAT) scan can reveal some soft-tissue and other structures that cannot even be seen in conventional X-rays.

Using the same dosage of radiation as that of an ordinary X-ray machine, an entire slice of the body can be made visible with about 100 times more clarity with the CAT scan.

The "cuts" (tomograms) for the CAT scan are usually made five or ten millimeters (mm) apart. The CAT machine rotates 180 degrees around the patient's body; hence, the term "axial".

The machine sends out a thin X-ray beam at 160 different points. Crystals positioned at the opposite points of the beam pick up and record the absorption rates of the varying thicknesses of tissue and bone. The data are then relayed to a computer that turns the information into a 2-dimensional cross-sectional image.

CAT scanning was invented in 1972 by the British engineer Godfrey N. Hounsfield (later Sir Godfrey) and the South African (later American) physicist Alan Cormack.

CAT scanning was already in general use by 1979, the year Hounsfield and Cormack were awarded the Nobel Prize in Medicine or Physiology for its development.

The area of the body located between the neck and the abdomen: TThe chest contains the lungs, the heart, and part of the aorta.

The walls of the chest are supported by the dorsal vertebrae, the ribs, and the sternum.

A projection radiograph of the chest: Chest X-rays are commonly used to detect abnormalities in the lungs, but it can also detect abnormalities in the heart, aorta, and the bones of the thoracic area.

In medicine, an additional problem that arises following a procedure, treatment, or illness and is secondary to it: A complication is a condition of a disorder or disease that coexists with and alters the first disease, but it is not consequently linked with it.

The term condition has a number of biomedical meanings including the following:

An unhealthy state, such as in "this is a progressive condition".
• A state of fitness, such as "getting into condition".
• Something which is essential to the occurrence of something else; essentially, a "precondition".
• As a verb: to cause a change in something so that a response that was previously associated with a certain stimulus becomes associated with another stimulus; to condition a person, as in behavioral conditioning.