A tubercle is a small, round nodule that grows out of the skin, bone, or membranes. Tubercles can develop in several sites on the body, including the mouth, arms, legs, ears, and lungs. When attached to bone, tubercles serve the function of connecting ligaments to muscle. The most common of these is the tibial tubercle, which is the small bump below the kneecap. Other tubercles, such as those found in the lungs, are often sites of disease.
Tubercles in the mouth are found on the cusps of teeth, typically on the last molar in the upper jaw. They can also be found in other areas, such as on the canines. The gums usually cover a tubercle in the mouth, and while it typically doesn't cause any health problems, it can be surgically removed.
In the arms, there are two prominent tubercles: the greater tubercle and the lesser tubercle. Both are located on the humerus, the longest bone in the upper extremity of the body. The greater tubercle, while larger than the lesser, is not as prominent. They are separated by a long groove that holds the tendon of the biceps. The lesser tubercle connects a large muscle called the subscapularis to the front of the shoulder joint.
A tibial tubercle is the bony protrusion on the front portion of the tibia bone in the leg. This nodule connects a series of small bones, tendons, and muscles that allow the knee to extend in different ranges. Many times, this is the site of sports-related injuries, since jumping, running, or cycling put a strain on the point of extension. Avulsion fractures are common injuries in this area of the body, occurring when the portion of the tubercle breaks away from the tibia.
Within the membranes of the lungs, tubercles are a much more serious matter. Here, they are also known as tuberculous nodules, and develop as a result of exposure to mycobacteria that causes tuberculosis (TB). TB is an airborne virus that affects the lungs, but can also infiltrate other areas of the body. When bacteria develop within the lungs, small, hard tubercles form. Symptoms of the disease include cough with blood, fever, weight loss, and loss of appetite.
While medical treatment is available for TB, patients must undergo quarantine to prevent spread of the disease, and the treatment is often lengthy. Most medications used to treat TB will be prescribed for at least six to nine months. This is due in part to the fact that mycobacterium tuberculosis is a slow-growing organism that is difficult to eradicate.