Respiratory System

The Respiratory System

Animals cells require a regular supply of oxygen to survive. Oxygen is needed in order for cells to be able to carry out the complex chemical reactions necessary to maintain life.

The respiratory system provides the body with the ability to take oxygen from the air (or water in the case of aquatic animals.) The respiratory systems also provides animals with a way to get rid of waste carbon dioxide gas which is toxic to animal cells.

Watch Brain Pop Respiratory System

The diaphragm, a dome-shaped sheet of muscle that separates the chest cavity from the abdomen, is the most important muscle used for breathing.

As the diaphragm contracts, it pulls down on the lungs increasing their length and diameter. This cause air to be drawn into the lungs. This is inhalation.

When the diaphragm relaxes, the lungs return to their resting size and air goes out of them. This is exhalation.

Air enters the body through the nasal passage and mouth.

The air passages through a series of tubes (pharynx, larynx, and trachea). A small flap known as the epiglottis prevents food and drink from accidentally entering the respiratory tract.

Air enters the lungs through the trachea and enters a series of branching tubes known as bronchial tubes that get increasingly smaller as they fan out through the lungs.

At the ends of the smallest bronchial tubes, air enters small sacs known as alveoli. A healthy human lung contains about 300 million alveoli. This is where gas exchange occurs- the alveoli release oxygen into tiny blood vessels called capillaries. At the same time, they receive waste CO2 from the capillaries. This exchange occurs through a combination of osmosis and diffusion.

Oxygen gas is in higher concentration in the alveoli than in the blood and so it diffuses into the blood through this thin layer of cells. Carbon dioxide is in higher concentration in the blood than the alveoli and so it diffuses into the alveoli through this thin layer of cells.

Old blood low in oxygen flows back to the lungs.

Blood newly refreshed with oxygen leaves the lungs and heads for the heart so it can be pumped back into the body.

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MSB Air in, Air Out

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Diseases of he Respiratory System

Pathogenic (Infectious)

Respiratory illnesses can be the result of pathogens, environmental hazards, and inherited traits.

Pathogenic diseases include invasion by viruses such as influenza and rhinovirus (common cold) which target the cells lining the respiratory tract. In addition to damage caused by the virus, the excess mucous created by the illness can make the respiratory system a ripe breeding ground for secondary bacterial infections like sinusitis, tonsillitis, bronchitis (the suffix itis essentially means “an infection of”) and pneumonia.

rhinovirus

Influenza

Tuberculosis is thought to be the disease that has killed more people throughout history than any other disease. By some estimates, as much as 1/3 of the world population has been exposed to the bacteria that causes TB, but only 1 in 10 people actually develops the disease. Most TB is treatable, but in the areas of the world where TB is prevalent people cannot afford the antibiotics. TB is extremely contagious. The bacteria can become airborne when the infected person coughs, spits, or sneezes.

Left untreated, each person with active TB disease will infect on average between 10 and 15 people every year. But people infected with TB bacilli will not necessarily become sick with the disease. The immune system "walls off" the TB bacilli which, protected by a thick waxy coat, can lie dormant for years. When someone's immune system is weakened, the chances of becoming sick are greater.

Environmental

Respiratory illnesses can also be caused by environmental hazards such as smoking tobacco products; inhaling coal dust, asbestos, or other hazardous substances. Smoking is the number one cause of environmental respiratory disease. Smoking destroys the lung tissue and can cause cancer. Compare the image of this healthy lung to the lung of smokers.

Smoking can lead to other pulmonary (lung) diseases such as lung cancer, emphysema, and Chronic Obstructive Pulmonary Disorder (COPD).

Lung cancer

Bullous emphysema causes large fluid sacs to grow on the lungs.

Sections of lung with emphysema

Ideopathic pulmonary fibrosis is a terminal disease of the lung with no known cause, though it is thought to be environmental. Lung tissue must be soft, moist, and elastic in order to work. IPF causes the alveoli to become hard and stiff so that they cannot expand to accept the incoming oxygen. IPF can be caused by exposure to environmental hazards such as asbestos or other dusts. Hundreds of rescue workers who were present at the World Trade Centers on 9/11/01 are now suffering from Pulmonary Fibrosis from breathing the toxic dusts of the bombing site. Hundreds of others have been ill with types of cancers presumed to be caused by exposure to the dust at the site. Within the first five years of that disaster, the deaths of over 240 rescue workers have been attributed to their role as rescuers and as members of the clean up crew at the site of the World Trade Center bombings.

Coal miners are exposed to small particles of coal dust in the air. Over time, this accumulates in the lungs causing a condition known as Black Lung Disease.

Asbestos is a substance that was used as an insulation material for pipes and for many other things. Tiny particles of the asbestos become airborne and lodge in the lungs. This can cause a disease known as asbestosis or mesothelioma (there are actually several diseases caused by asbestos. Mesothelioma is a form of cancer.

Asbestos particles

Inherited Pulmonary (lung) Diseases

The most common inherited respiratory disorder is asthma. Asthma is a disease where the bronchial tubes become narrow making it difficult for a person affected with asthma to get enough oxygen. While the physical traits for asthma are usually inherited, environmental factors such as airborne allergens can trigger asthmatic attacks.

Cystic fibrosis is the most common cause of chronic lung disease in children and young adults, and the most common fatal hereditary disorder affecting Caucasians in the U.S. CF is a hereditary disease affecting the mucous glands of the lungs, liver, pancreas, and intestines. The lungs become filled with large amounts of mucous and thus become extremely vulnerable to infections. The mucous also impairs the ability of the lung to function properly.