2. Respiratory System
Every animal needs a system to take in oxygen from the environment
Why is oxygen needed?
Oxygen is required for cell respiration
Oxygen and nutrients are combined to release energy
Remember cell respiration?
Reactants: Products:
Glucose + O CO2 + H2O + Energy

3. How Does Oxygen Get Into Cells?
O2 and CO2 enter and leave the cells
(gas exchange) by diffusion
Different animals have different systems
Some examples:
Organism: Gas exchange between:
one-celled cell membrane and outside cell
earthworm skin and capillaries
insects trachea and body cells
fish gill filaments and capillaries
mammals air sacs (alveoli) and capillaries

4. Human Respiratory System
Our own pathway, in order:
Mouth/Nasal Cavity
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
Alveoli (tiny air sacs)

5. Respiratory System Tissues
Mouth/nasal cavity:
Air enters the body
Nasal hairs and mucus warm and clean the air
Pharynx and larynx:
Pharynx is the back of your mouth (say aaaaah)
Larynx is lower – this is your throat (voice box)
Trachea:
Air passageway leading to lungs
Lined with C-shaped rings of cartilage
Bronchi, bronchioles, alveoli:
Air pathway into each lung branches down and ends in millions of microscopic air sacs (alveoli)
An adult human lung has several hundred million alveoli,
each one surrounded by capillaries of your circulatory system

6. How Air Moves in and Out Inhaling: getting oxygen in
Exhaling: getting carbon dioxide out
Air is forced into and out of your lungs.
But how?
When you squeeze a plastic bottle, what does the air do? Which direction does it move?
When you let the plastic bottle spring back into shape, what does the air do? Which direction does it move now?
This is because of an important law of how gases work:
Boyle’s Law

7. Boyle’s Law Robert Boyle discovered that if:
volume decreases, pressure increases
volume increases, pressure decreases
Pressure and volume are inversely related:
If one increases, the other decreases
This is called an inverse relationship
Gases always move from:
areas of higher pressure to areas of lower pressure
Boyle’s Law explains how air is forced into and out of your lungs !

8. 1. Diaphragm & rib muscles contract
2. Rib cage expands
3. Volume in lungs increases
4. Pressure in lungs decreases
5. Air pressure outside is greater
6. Air rushes into lungs 1. 2. 3. 4. 5. 6.
Can you fill in steps 1- 6 for exhaling?

9. How Does O2 Get Into the Blood?A i r To
heart
From
heart A i r
Alveolus
(air sac) O2
CO2
Pulmonary capillary

10. How Does O2 Get Into the Blood?
Blood needs a special chemical to “carry” the oxygen:
Hemoglobin
oxygen “sticks to” or binds with hemoglobin in red blood cells
hemoglobin contains iron which binds with oxygen
Can you follow the oxygen?
In the lungs:
Oxygen diffuses from the air in the alveoli into capillaries
Oxygen passes into red blood cells and binds with hemoglobin
In the blood, oxygen remains bound to hemoglobin until it reaches your cells
At your cells:
CO2 diffuses from cells into capillaries
Hemoglobin releases oxygen and binds with CO2
Oxygen diffuses from red blood cells into your body cells

11. Respiratory System Problems
Dirt, pollen, dust, and smoke damage the system and interrupt the flow of oxygen to your cells
Respiratory System Defenses:
White blood cells
Surround, consume, and digest bacteria
Cannot consume asbestos
Cilia
Tiny hairs lining trachea
Hairs “wave” upward to expel foreign particles
Cigarette smoke paralyzes cilia
Defense against choking:
The epiglottis
Flap of tissue that closes trachea when you swallow
Makes certain food travels through esophagus instead

12. Respiratory Disorders
Asthma
Bronchial tubes become constricted
Symptoms: shortness of breath, wheezing, coughing
Causes: environmental factors: allergies, stress, certain foods
Emphysema
Alveoli lose ability to expand and contract when breathing
Alveoli stretch and rupture; scar tissue develops
Less oxygen to cells + buildup of CO2
Lung cancer
Caused by “tars” and other carcinogens in cigarette smoke
Cancerous tumors destroy lung tissue
Effects of smoking:
Short term: carbon monoxide (CO) replaces oxygen in blood
Long term: heart disease, emphysema, lung cancer
Without smoking, these disorders are a minor problem in society

13. Review Questions
Which term does not belong with the others and why not?
gills, alveoli, diaphragm, trachea
asthma, respiration, emphysema, lung cancer
gills, lungs, hemoglobin
lung cancer, asthma, emphysema
alveoli, diaphragm, trachea
Explain what happens to your diaphragm and ribcage when you inhale and exhale.
What are the reactants and products of cell respiration?
Use Boyle’s Law to explain inhaling, exhaling, and why the Heimlich Maneuver works.
Describe how gas exchange occurs in the lungs.
Why is your trachea lined with cartilage?
What is the function of your nasal cavity?
What is your epiglottis and what is it for?
Why do you have cilia inside your trachea?
Which respiratory condition can be the result of allergies?