Bma Illustrated Medical Dictionary

function tests. Biochemical tests can

also be performed on urine (see urinaly-

sis) and other body fluids.

bioengineeringSee biomechanical eng-

ineering.

biofeedback trainingA technique in

which a person uses information about a

normally unconscious body function to

gain conscious control over that func-

tion. Biofeedback training may help in the

treatment of stress-related conditions,

including certain types of hypertension,

anxiety, and migraine.

The patient is connected to a record-

ing instrument that measures one of

the unconscious body activities, such

as blood pressure, heart-rate, or the

quantity of sweat on the skin. The

patient receives information (feedback)

on the changing levels of these activi-

ties from changes in the instrument’s

signals. Using relaxation techniques, the

patient learns to change the signals by

conscious control of the body function.

Once acquired, this control can be exer-

cised without the instrument.

biological clockA popular term for the

inherent timing mechanism that suppos-

edly controls physiological processes

and cycles in living organisms. (See

also biorhythms.)

biomechanical engineeringA disci-

pline that applies engineering methods

and principles to the body to explain how

it functions and to treat disorders. Prac-

tical applications include the design of

artificial joints and heart valves, plaster

casts, and kidney dialysis machines.

biopsyA diagnostic test in which a

small amount of tissue or cells are

removed from the body for microscopic

examination. It is an accurate method

of diagnosing many illnesses, including

cancer. Microscopic examination of tis-

sue (histology) or of cells (cytology)

usually gives a correct diagnosis.

There are several types of biopsy. In

excisional biopsy, the whole abnormal

area is removed for study. Incisional

biopsy involves cutting away a small

sample of skin or muscle for analysis. In

a needle biopsy, a needle is inserted

through the skin and into the organ or

tumour to be investigated. Aspiration

biopsy uses a needle and syringe to

remove cells from a solid lump. Guided

biopsy uses ultrasound scanningor CT

scanningto locate the area of tissue to

be biopsied and to follow the progress

of the needle. In endoscopic biopsy, an

endoscopeis passed into the organ to

be investigated and an attachment is

used to take a sample from the lining of

accessible hollow organs and struc-

tures, such as the lungs, stomach,

colon, and bladder. In an open biopsy,

a surgeon opens a body cavity to reveal a

diseased organ or tumour and removes

a sample of tissue. Prompt analysis, in

some cases by frozen section, can

enable the surgeon to decide whether

to remove the entire diseased area

immediately.

Biopsy samples

are analysed by

staining, in which

dyes are used to

to show up struc-

tures or identify

constituents such

as antibodiesor

enzymes. A tissue

sample may be

tested with speci-

fic antibodies in

the investigation

of infection and

inflammation. In

some cases, a tis-

sue culturemay

be required.

BIOENGINEERING BIOPSY

B

Line of

incision

BIOPSY

EXCISIONAL SKIN

BIOPSY

Abnormal area

Normal

skin

Sensor measures

heart rate or

sweating

Monitor displays

changes in body

activities such as

heart-rate

BIOFEEDBACK TRAINING