• Do not perform this activity if you have any breathing problems. Working with a partner, count the number of breaths you take in 15 seconds. Multiply that number by 4 for the number of breaths per minute. Your partner will act as the timer/recorder. Repeat the procedure three times and take an average. Now, take a deep breath and hold it for as long as you can. Have your partner record your time. Repeat the procedure three times and take an average. Switch roles with your partner and repeat the procedure. Exchange data with other groups and answer the following questions.

1. What was the range of breathing rates?

2. Why are there differences in breathing rates among members of the class?

3. What was the average length of time classmates could hold their breath?

4. What factors might affect how long you could hold your breath?

5. A child having a tantrum declares she is going to hold her breath “until I turn blue!” Do you think this is possible? Explain your answer.

The Respiratory

System

Respiration

Respiration is the exchange of gases between an organism and the environment

• In humans, as with most organisms, it is the release of carbon dioxide and the uptake of oxygen

The Respiratory System

• The basic function performed by the respiratory system in humans is to bring about the exchange of oxygen and carbon dioxide between the blood, the air, and tissues

Parts of the Respiratory System

• The respiratory system consists of the nose/mouth, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli

• Several blood vessels are included in the respiratory system, especially the pulmonary artery, pulmonary vein, and capillaries.

Movement of Oxygen and Carbon Dioxide In and Out of the

Respiratory System

Oxygen and carbon dioxide exchange at

alveoli

Oxygen-richair from

environment

Bronchioles

Nasalcavities

Pharynx Trachea Bronchi

BronchiolesAlveoli

Pharynx Nasalcavities

Carbon dioxide-rich

air to the environment

Bronchi

Trachea

Structures (cont’d)

• Nose/Mouth –– Air enters the respiratory system through

these two structuresAir is filtered, warmed, and moistened

The Human Respiratory System

• A thin layer of mucus is produced on the lining of the tubes of the respiratory systemThis thin layer traps particles of dust or

smoke

Cilia clean the passageways by sweeping the dirt away from the lungs

Structures (cont’d)

• Pharynx –– Back of mouth

• Found behind the uvula– Serves as a passageway for

both air and food

Structures (cont’d)• Larynx –

– Voice box, Adam’s apple– Contains vocal cords

• 2 loose flaps of tissue– Top of the trachea

Structures (cont’d)• Trachea –

– Windpipe• Tube made of cartilage that carries air to the lungs

– Contains cells that produce mucus • Mucus traps dirt found in air

– Contains cilia • Tiny hairs that move dirt out of the tubes

Structures (cont’d)• Bronchi –

– 2 branches that come off of trachea– Each tube leads to lungs

• Bronchioles – – Branches of the bronchi– Found inside lungs

• Each tube is surrounded by smooth muscle which helps control size of passageways

• Bronchitis inflammation and irritation of bronchi and bronchioles

Review• What is the function of the Respiratory

system?• After the pharynx air passes through the

blank , blank and blank to reach the alveoli. Fill in the blanks.

• What is the function of the mucus and cilia?• Where are the vocal cords found?• What keeps food from entering the trachea?• Where is the site gas exchange going to

occur?

Structures (cont’d)

• Alveoli – – Small structures at the end of each bronchiole– Occur in clustersPlace where gas exchange occurs

• Oxygen into blood, carbon dioxide into lungs• Each is surrounded by capillaries

Gas Exchange and Hemoglobin

• 300 million alveoli are in a healthy lung– Provides a large surface area for gas exchange

Oxygen dissolves in the moisture in the alveoli– It can then diffuse into the capillaries– Carbon dioxide diffuses in the opposite direction

• Hemoglobin binds with so much oxygen that it increases the oxygen carrying capacity of the blood more than 60 times

Gas Exchange and Hemoglobin

• Hemoglobin binds with so much oxygen that it increases the oxygen carrying- capacity of the blood more than 60 times

Breathing

• Breathing is the movement of air into and out of the lungs

Force that drives breathing is air pressure– No muscles are directly connected to the lungs

Breathing

• Lungs sit in two sacs = pleural membranes

• At the bottom of the chest cavity is the diaphragm

Inhaling

• When you inhale, the diaphragm contracts and expands the volume of the chest cavity

• Because the chest cavity is tightly sealed, this creates a partial vacuum inside the cavity– Air rushes into the lungs as a result

Exhaling

• Exhaling is a passive event

• Diaphragm relaxes and lungs return to normal size, placing pressure on the lungs– Air rushes out of the lungs

Air inhaled

Diaphragm

Rib cage rises

Air exhaled

Diaphragm

Rib cage lowers

Inhalation ExhalationFigure 37-15 The Mechanics of Breathing

Breathing Control

• Breathing is voluntary to a point, then it becomes involuntary– Nervous system will take over– Medulla oblongata in the brain reads the

amount of carbon dioxide in the bloodIf the level of carbon dioxide gets too high, the

diaphragm will increase contractions