Bma Illustrated Medical Dictionary

Jakob–Creutzfeldt diseaseSee Creutz-

feldt–Jakobdisease.

jaundiceYellowing of the skin and the

whites of the eyes, caused by an accu-

mulation of bilirubin in the blood.

Jaundice is the chief sign of many disor-

ders of the liverand biliary system.

Many babies develop jaundice soon

after birth (see jaundice, neonatal).

Bilirubin is formed from haemoglobin

when old red cells are broken down,

mainly by the spleen. It is absorbed by

the liver, where it is made soluble in

water and excreted in bile.

There are 3 main types of jaundice:

haemolytic, hepatocellular, and obstruc-

tive. In haemolytic jaundice, too much

bilirubin is produced for the liver to

process. This is caused by excessive

haemolysisof red cells, which can have

many causes (see anaemia, haemolytic).

In hepatocellular jaundice, bilirubin

accumulates because its transfer from

liver cells into the bile is prevented,

usually due to acute hepatitis (see hep-

atitis, acute) or liver failure.

In obstructive jaundice, also known as

cholestatic jaundice, bile cannot leave

the liver because of bile duct obstruc-

tion. Obstructive jaundice can also

occur if the bile ducts are not present

(as in biliary atresia) or if they have been

destroyed by disease. Cholestasisthen

occurs and bilirubin is forced back into

the blood. For all types of jaundice,

treatment is for the underlying cause.

jaundice, neonatalYellowing of the

skin and whites of the eyes in newborn

babies, due to accumulation of bilirubin

in the blood. It usually results from the

liver being immature and unable to

excrete bilirubin efficiently.This form of

jaundice is usually harmless and disap-

pears within a week. Rarely,severe or

persistent neonatal jaundice is caused

by haemolytic disease of the newborn,

G6PD deficiency, hepatitis, hypothyroid-

ism, biliary atresia, or infection.

Jaundiced babies usually require extra

fluids and may be treated with photo-

therapy. Exchange transfusion (see blood

transfusion) may be needed in severe

cases. If severe neonatal jaundice is not

treated promptly, kernicterusmay occur.

jawThe mobile bone of the face, also

known as the mandible. The term some-

times includes the maxilla. The mandible

bears the lower teeth on its upper sur-

face and is connected to the base of the

skull at the temporomandibular joints.

Muscles attached to the jaw allow move-

ments needed in chewing, biting, and

side-to-side and downward movement.

jaw, dislocatedDisplacement of the

lower jawfrom one or both temporo-

mandibular joints. A dislocated jaw is

usually due either to a blow or to yawn-

ing. There is pain in front of the ear on

the affected side or sides, and the jaw

projects forwards. The mouth cannot be

fully closed, making eating and speak-

ing difficult. Dislocation tends to recur.

Surgery may be carried out to stabilize

the joint but is often unsuccessful.

jaw, fracturedA fracture of the jaw,

most often caused by a direct blow. A

minor fracture may cause tenderness,

pain on biting, and stiffness. In more

severe injuries, teeth may be loosened

or damaged, jaw movement may be sev-

erely limited, and there may be loss of

feeling in the lower lip. Minor fractures

are normally left to heal on their own.

For severe fractures with displacement

of the bones, surgical treatment is nec-

essary. To allow healing, the jaw is

immobilized, usually by wiring the upper

JAKOB–CREUTZFELDT DISEASE JAW, FRACTURED

J

JAW

Maxilla

(upper

jaw)

Tooth

Temporo-

mandibular

(TM) joint

Skull

Mandible (lower jaw)

J