http://www.ck12.org Chapter 1. Human Biology
FIGURE 1.61
Asthma occurs when the bronchioles swell and the muscles around the bronchioles contract.Pneumonia
Pneumoniais an illness that occurs when the alveoli, the tiny sacs in the lungs where gas exchange takes place,
become inflamed and filled with fluid. When a person has pneumonia, gas exchange cannot occur properly across
the alveoli. Pneumonia can be caused by many things. Infection by bacteria, viruses, fungi, or parasites can cause
pneumonia. An injury caused by chemicals or a physical injury to the lungs can also cause pneumonia. Symptoms of
pneumonia include cough, chest pain, fever, and difficulty breathing. Treatment depends on the cause of pneumonia.
Bacterial pneumonia is treated with antibiotics.
Pneumonia is a common illness that affects people in all age groups. It is a leading cause of death among the elderly
and people who are chronically and terminally ill.
Tuberculosis
Tuberculosis (TB)is a common and often deadly disease caused by a genus of bacterium calledMycobacterium.
Tuberculosis most commonly attacks the lungs but can also affect other parts of the body. TB is a chronic disease,
but most people who become infected do not develop the full disease. Symptoms include a cough, which usually
contains mucus and coughing up blood.
The TB bacteria are spread in the air when people who have the disease cough, sneeze, or spit, so it is very
contagious. To help prevent the spread of the disease, public health notices, such as the one pictured below (Figure
1.62), remind people how to stop the spread of the disease.
Cancer
Lung canceris a disease in which the cells found in the lungs grow out of control. The growing mass of cells can
form a tumor that pushes into nearby tissues. The tumor will affect how these tissues work. Lung cancer is the most
common cause of cancer-related death in men, and the second most common in women. It is responsible for 1.3
million deaths worldwide every year (Figure1.63). The most common symptoms are shortness of breath, coughing