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Lesson Overview

The Respiratory System

Lesson Overview

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Lesson Overview

The Respiratory System

THINK ABOUT IT

When medics examine an unconscious accident victim, one of the first things they do is check whether the person is breathing. This is one way to determine whether there is still a life to save. Why is there such a close connection between breathing and life?

All cells in our body, especially brain cells, require a constant supply of oxygen for cellular respiration. Without oxygen, many cells begin to die within minutes.

The respiratory system works together with the circulatory system to provide our cells with oxygen. Any interruption in that vital

function can be fatal.

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Lesson Overview

The Respiratory System

Structures of the Respiratory System

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Lesson Overview

The Respiratory System

Structures of the Respiratory System

What is the function of the respiratory system?

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Lesson Overview

The Respiratory System

Structures of the Respiratory System

For organisms, respiration means the process of gas exchange

between a body and the environment.

The human respiratory system picks up oxygen from the air we inhale and releases carbon dioxide into the air we exhale.

The circulatory system links the exchange of gases in the lungs with our body tissues.

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Lesson Overview

The Respiratory System

Nose

To keep lung tissue healthy, air entering the respiratory system must be filtered, moistened, and warmed.

Hairs lining the entrance to the nasal cavity start the filtering process by trapping large particles.

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Lesson Overview

The Respiratory System

Pharynx, Larynx, and Trachea

Air moves through the nose to a cavity at the back of the mouth called the pharynx, or throat, which serves as a passageway for both air and food.

Air moves from the pharynx into

the trachea, or windpipe.

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Lesson Overview

The Respiratory System

Pharynx, Larynx, and Trachea

Between the pharynx and the trachea is the larynx, which contains two highly elastic folds of tissue known as the vocal cords.

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Lesson Overview

The Respiratory System

Pharynx, Larynx, and Trachea

Mucus produced in the trachea continues to trap inhaled particles.

Cilia lining the trachea sweep both mucus and trapped particles away from the lungs toward the pharynx, where they can be

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Lesson Overview

The Respiratory System

Lungs

From the trachea, air moves into two large tubes in the chest cavity called bronchi. Each bronchus leads to one lung.

Within each lung, the large bronchus divides into smaller bronchi, which lead to even smaller passageways called bronchioles.

Bronchi and bronchioles are surrounded by smooth muscles, controlled by the autonomic

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Lesson Overview

The Respiratory System

Lungs

The bronchioles continue to divide until they end at a series of tiny air sacs

called alveoli.

Alveoli are grouped in clusters, like bunches of grapes. A network of

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Lesson Overview

The Respiratory System

Gas Exchange and Transport

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Lesson Overview

The Respiratory System

Gas Exchange and Transport

How are oxygen and carbon dioxide exchanged and transported throughout the body?

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Lesson Overview

The Respiratory System

Gas Exchange

When air enters alveoli,

oxygen dissolves in the moisture on their inner surface and then diffuses across thin capillary walls into the blood.

Oxygen diffuses in this

direction because the oxygen concentration is greater in the alveoli than it is in the blood.

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Lesson Overview

The Respiratory System

Gas Exchange

The air you inhale usually contains 21 percent oxygen and 0.04 percent carbon dioxide.

Exhaled air usually contains less than 15 percent oxygen and 4 percent carbon dioxide.

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Lesson Overview

The Respiratory System

Transport

Diffusion of oxygen from alveoli into capillaries is a passive process that stops when oxygen concentration in the blood and alveoli is the same.

Hemoglobin actively binds to dissolved oxygen, removing it from

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Lesson Overview

The Respiratory System

Transport

When carbon dioxide diffuses from body tissues to capillaries, most of it enters red blood cells and combines with water, forming carbonic acid. The rest of it dissolves in plasma or binds to hemoglobin and proteins in plasma.

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Lesson Overview

The Respiratory System

Breathing

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Lesson Overview

The Respiratory System

Breathing

What mechanisms are involved in breathing?

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Lesson Overview

The Respiratory System

Inhalation

The lungs are sealed in two sacs, called pleural

membranes, inside the chest cavity.

At the bottom of the chest cavity is a large dome-shaped muscle known as the

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Lesson Overview

The Respiratory System

Inhalation

When you inhale, the

diaphragm contracts and flattens. Muscles between the ribs also contract, raising the rib cage.

These actions increase the volume of the chest cavity and create a partial vacuum inside the cavity.

Atmospheric pressure fills the lungs as air rushes into the

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Lesson Overview

The Respiratory System

Exhalation

During exhalation, both the rib cage and the diaphragm relax, decreasing the volume of the chest cavity and making air pressure in the chest cavity greater than atmospheric pressure.

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Lesson Overview

The Respiratory System

Exhalation

Exhalation is usually a passive process, but to blow out a candle, speak, sing, or yell, you need

more force than passive exhalation provides.

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Lesson Overview

The Respiratory System

Exhalation

Breathing works only because the chest cavity is sealed.

If a wound punctures the

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Lesson Overview

The Respiratory System

Breathing and Homeostasis

You have some conscious control over your breathing—when you swim or play an instrument, for example—but breathing is not purely voluntary.

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Lesson Overview

The Respiratory System

Breathing and Homeostasis

Breathing is initiated by the

breathing center in the part of the brain stem called the medulla oblongata.

Sensory neurons in or near the medulla and in some large blood vessels gather information about carbon dioxide levels in the body and send the information to the breathing center.

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Lesson Overview

The Respiratory System

Smoking and the Respiratory System

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Lesson Overview

The Respiratory System

Smoking and the Respiratory System

How does smoking affect the respiratory system?

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Lesson Overview

The Respiratory System

Effects on the Respiratory System

Three of the most dangerous substances in tobacco smoke are nicotine, carbon monoxide, and tar.

Nicotine is an addictive stimulant that increases heart rate and blood pressure.

Carbon monoxide is a poisonous gas that blocks hemoglobin from binding with oxygen, thus interfering with oxygen transport in blood.

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Lesson Overview

The Respiratory System

Effects on the Respiratory System

Tobacco smoke paralyzes cilia in the trachea, allowing inhaled particles to stick to the walls of the respiratory tract or enter the lungs, and smoke-laden mucus to become trapped along airways.

Irritation from accumulated particles and mucus triggers a cough to clear the airways.

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Lesson Overview

The Respiratory System

Diseases Caused by Smoking

Damage to the respiratory system from smoking can become permanent and lead to diseases such as chronic bronchitis, emphysema, and lung cancer.

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Lesson Overview

The Respiratory System

Chronic Bronchitis

In chronic bronchitis, the bronchi become inflamed and clogged with mucus.

Smoking even a moderate number of cigarettes on a regular basis can produce chronic bronchitis.

Affected people often find simple activities, like climbing stairs, difficult.

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Lesson Overview

The Respiratory System

Emphysema

Long-term smoking can lead to emphysema, the loss of elasticity and eventual breakdown of lung tissue.

People with emphysema cannot get enough oxygen to the body tissues or rid the body of excess carbon dioxide.

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Lesson Overview

The Respiratory System

Lung Cancer

Lung cancer is particularly deadly because, by the time it is detected, it usually has spread to other areas of the body.

Few people diagnosed with lung cancer live more than five years.

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Lesson Overview

The Respiratory System

Other Effects of Smoking

Smoking also negatively affects the circulatory system. It raises blood pressure by constricting blood vessels, which forces the heart to work harder to deliver enough oxygen.

Nonsmokers exposed to secondhand smoke are also at greater risk for respiratory and circulatory system disease.

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Lesson Overview

The Respiratory System

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Lesson Overview

The Respiratory System

Other Effects of Smoking

Whatever the age of a smoker, and no matter how long that person has smoked, his or her health can be improved by quitting.

Nicotine is a powerful drug with strong addictive qualities that make it very difficult to quit smoking.

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