The Respiratory System - MR. KELLECI'S SCIENCE...

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Functions of the Respiratory SystemIf you have ever held your breath, you probably took

deep breaths afterward. Those breaths were your body’s way of getting the oxygen it needs. Breathing is the movement of air into and out of the lungs. Breathing is how your respiratory system takes in oxygen and gets rid of carbon dioxide.

Taking in OxygenThink about the plumbing pipes that bring water into a

house. Your respiratory system is similar. It is a system of organs that bring oxygen into your body. Oxygen is important for life. In fact, your brain will tell your body to breathe even if you try not to breathe. Your brain responds when your body needs oxygen.

Why is oxygen so important? Every cell in your body needs oxygen for cellular respiration. Cellular respiration is a series of chemical reactions. During cellular respiration, oxygen and sugars react. This reaction releases energy that a cell can use.

Eliminating Carbon DioxideA house’s plumbing pipes also remove wastewater. In a

similar way, your respiratory system removes waste gases from your body. Carbon dioxide is one of the waste gases that your respiratory system removes. If waste gases are not removed, cells cannot function.

What do you think? Read the two statements below and decide whether you agree or disagree with them. Place an A in the Before column if you agree with the statement or a D if you disagree. After you’ve read this lesson, reread the statements to see if you have changed your mind.

Before Statement After

1. Breathing and respiration are the same.

2. Lungs are the only parts of the body that use oxygen.

Key Concepts • What does the respiratory

system do?• How do the parts of the

respiratory system work together?

• How does the respiratory system interact with other body systems?

REVIEW VOCABULARYcellular respirationa series of chemical reactions that transforms the energy in food molecules to usable energy

Identify the Main Ideas As you read, highlight the main idea of each section. Then use a different color to highlight a detail or example to help you understand the main idea. Use your highlighting to review this lesson.

Key Concept Check 1. Explain What does the respiratory system do?

Respiration and Circulation

The Respiratory System

LESSON 1

CHAPTER 14

Reading Essentials Respiration and Circulation 223

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Visual Check3. Identify Which part of the respiratory system contains bronchi?

Make an eight-tab vocabulary book. Use it to organize your notes on the organs of the respiratory system and their functions.

The RespiratorySystemMouth andNosePharynxLarynx

TracheaBronchi

LungsAlveoli

4. Apply What takes place in your respiratory system when you make sounds?

Organs of the Respiratory System The figure below shows air moving into and out of the

respiratory system. Air enters your respiratory system through your mouth and nose. Your nose warms and moistens the air. Hairs and sticky mucus in your nose help trap dust and dirt from the air.

Cilia are hairlike structures that line your nose and most other airways in your respiratory system. Wavelike motions of the cilia carry trapped particles away from your lungs. The cilia help keep harmful particles from getting very far into your respiratory system.

PharynxAfter air enters your mouth and nose, it passes into your

throat. The pharynx (FER ingks) is a tubelike passageway at the top of your throat that receives air, food, and liquids from your mouth or nose. The epiglottis (eh puh GLAH tus) is a flap of tissue at the bottom of the pharynx. It keeps food and liquids out of the rest of your respiratory system.

Larynx and TracheaAir passes from your pharynx into a triangle-shaped area called the

voice box, or larynx (LER ingks). Your vocal cords are in your larynx. They consist of two thick folds of tissue. Your vocal cords vibrate and make sounds as air passes over them.

Air moves from your larynx into your trachea (TRAY kee uh). Your trachea is a tube that is held open by C-shaped rings of cartilage.

Mouth

Nose

Pharynx

Larynx

Trachea

BronchiLungs

Diaphragm

Key Concept Check 2. Explain What function do cilia have in the respiratory system?

224 Respiration and Circulation Reading Essentials


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Bronchi and LungsYour trachea branches into two narrower tubes called bronchi

(BRAHN ki) (singular, bronchus) that lead into your lungs. Lungs are the main organs of the respiratory system. Inside your lungs, your bronchi branch into smaller and narrower tubes called bronchioles.

AlveoliIn your lungs, your bronchioles end in microscopic sacs, or

pouches, called alveoli (al VEE uh li) (singular, alveolus), where gas exchange occurs. During gas exchange, oxygen from the air you breathe moves into your blood. Carbon dioxide from your blood moves into your alveoli.

Look at the alveoli in the figure below. Alveoli look like bunches of grapes at the ends of the bronchioles. Like tiny balloons, your alveoli fill with air when you breathe in. They contract and release air when you breathe out. Notice in the figure below that blood vessels surround each alveolus. The walls of alveoli are only one cell thick. Red blood cells drop off carbon dioxide and pick up oxygen as they move through these blood vessels.

The thin walls of alveoli and the large surface areas make it possible for a high rate of gas exchange. If you could spread out all the alveoli in your lungs onto a flat surface, they would cover an area bigger than your classroom. Every time you breathe, alveoli help your body take in billions of oxygen molecules. They also help your body get rid of billions of carbon dioxide molecules.

Reading Check5. Name What gases are exchanged in the alveoli?

Visual Check 6. Locate How many layers of cells form the walls of the alveolus shown in this figure?

Red blood

cells

Blood

vessel

Wall of

alveolus

Oxygen

Carbon

dioxideAlveoli

Lung

Gas exchange in alveoli



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Breathing and Air PressureHow does your body know when to breathe? When high

levels of carbon dioxide build up in your blood, your nervous system tells your body to breathe out, or exhale. After you exhale, you breathe in, or inhale. How does this happen?

Below your lungs is a large muscle called a diaphragm (DI uh fram) that contracts and relaxes and moves air in and out of your lungs. Air moves into and out of your lungs with the help of your diaphragm. When your diaphragm moves, it changes the air pressure inside your chest. Breathing occurs because of these changes in air pressure.

When you inhale, your diaphragm contracts and moves down, as shown below. The space around your lungs gets bigger, or expands. The increased space reduces the air pressure in your chest. Air rushes into your lungs until the pressure inside your chest equals the air pressure outside it.

When you exhale, your diaphragm relaxes and moves up. The space around your lungs gets smaller, or reduces. Air pressure in your chest increases. Waste gases rush out of your lungs.

Lung

Lung

Ribs

Ribs

Diaphragm

Diaphragm

Inhalation

Exhalation

Reading Check 7. Explain What happens to the area in your chest around your lungs when you inhale?

Visual Check 8. Highlight the diaphragm in each figure.

Respiratory HealthHave you ever had a cold, allergies, or asthma? If you

have, you know what it is like to have a respiratory illness. You might have had a sore throat or a stuffed-up head that made breathing uncomfortable. Some respiratory illnesses make it hard to breathe. Serious respiratory illnesses can even cause death.

The best way to maintain good respiratory health is to stay away from irritants and air pollution. Common respiratory illnesses and their causes are listed in the table on the next page.

9. Infer Why might breathing be uncomfortable when you have a respiratory illness?



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Key Concept Check11. Describe How do the respiratory and muscular systems work together to maintain your body’s homeostasis?

Visual Check 10. Analyze According to the table, which respiratory illness involves the destruction of alveoli?

Respiratory Illnesses

Illness Causes Symptoms

Colds, flu viruses congestion, runny nose, watery eyes, coughing, sneezing

Bronchitis (brahn KI tus)

viruses, bacteria coughing and tired-ness resulting from mucus blocking the bronchi and bronchi-oles, slowing air movement

Pneumonia (noo MOH nyuh)

viruses, bacteria trouble breathing as a result of fluid in the alveoli that slows gas exchange

Asthma (AZ muh) dust, smoke, pollen, pollution

trouble breathing as a result of swollen air-ways and increased mucus

Emphysema (em fuh SEE muh)

smoking coughing, tiredness, loss of appetite, and weight loss resulting from destruction of alveoli

Lung cancer smoking coughing, trouble breathing, chest pain

The Respiratory System and Homeostasis

You have read in this lesson that the muscular system works with your respiratory system so you can breathe. The muscles and respiratory system working together bring oxygen into your lungs and remove carbon dioxide from your lungs.

In the next lesson, you will learn how the circulatory system and the respiratory system work together to bring oxygen to body cells. These systems also work to remove carbon dioxide from cells. The muscular system, the respiratory system, and the circulatory system help maintain homeostasis in your body.



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Mini Glossary

Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind?

What do you think

END OF LESSON

Log on to ConnectED.mcgraw-hill.com and access your textbook to find this lesson’s resources.

ConnectED

alveoli (al VEE uh li): the microscopic sacs, or pouches, at the ends of bronchioles in the lungs, where gas exchange occurs (singular, alveolus)

breathing: the movement of air into and out of the lungs

bronchi (BRAHN ki): the two narrower tubes branching from the trachea that lead into the lungs (singular, bronchus)

diaphragm (DI uh fram): a large muscle below the lungs that contracts and relaxes and moves air in and out of the lungs

larynx (LER ingks): a triangle-shaped area where air passes from the pharynx; also called the voice box

lungs: the main organs of the respiratory system

pharynx (FER ingks): a tubelike passageway at the top of the throat that receives air, food, and liquids from the mouth or nose

trachea (TRAY kee uh): a tube past the larynx that is held open by C-shaped rings of cartilage

1. Review the terms and their definitions in the Mini Glossary. Write a sentence that explains the relationship between the alveoli and the bronchi.

2. Fill in the blanks in the diagram below to create a “map” of your respiratory system.

3. Compare breathing and cellular respiration.

nose and

larynx

trachea

bronchi and

pharynx



The Respiratory System - MR. KELLECI'S SCIENCE...

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