Limb

From ArticleWorld

Limbs are appendages or extremities on the body of many animals including mammals and humans. Limbs perform both large motor functions, such as locomotion, and small motor functions, such as grasping.

Embryology

In humans, the limb buds begin early in the second month of pregnancy. Initially the limb buds have no digits but by the third month of pregnancy the limbs are easily identifiable and are fitted with hands, feet and digits. Some babies sustain an insult that affects the growth and development of their limbs. In the 8 years since its release in 1953, thalidomide, a drug used for nausea and vomiting in pregnancy, caused at least 10,000 children to be born with disfiguring limb abnormalities, including agenesis or absence of some part of the limbs.

Function

All higher animals have at least two limbs dedicated to locomotion. Bipeds, such as humans, use two limbs as legs for walking and two limbs (the upper extremities) for many other functions other than for walking. Quadrupeds are four-legged animals that primarily use all limbs for animals. Quadrupeds have two different walking styles.

Animals like cats and giraffes move the each side of the body (i.e. the left foreleg and left hind leg) forward in unison and then put forward the legs of the other side whenever they walk. Most other animals put the foreleg of one side forward, along with the hind leg of the other side, then switch with the other alternating legs to propel forward.

Injuries

At times, a person has a severe vascular disease, a crushing injury or a cancerous lesion in one of the extremities so that an amputation of the affected extremity must be performed. The individual is often fitted with a prosthesis, an artificial limb that can perform some of the functions that a normal limb does.