The HUMAN RESPIRATORY SYSTEM

Take a nice deep breath.  Inhale through the nose, exhale through your mouth.
Aaaaahh........... Inhale, exhale.  Inhale, exhale.  Inhale, exhale.

Hey --- wake up !  Time to learn about the system of organs that's responsible for taking in oxygen and getting rid of carbon dioxide ... the respiratory system.
 


First, allow me to list the structures and organs that together make up the respiratory system.  Your job is to write them down in the order that air passes through them as it is inhaled. OK?

 
 

alveoli, bronchiole, bronchus, larynx, lung, pharynx, nasal cavity, nostril, trachea

cLick HeRe to see THe RiGHT ordER



















Now let's take a look at what those respiratory structures look like. 

Can you identify those same organs that we listed just a minute ago? 
Go ahead, give it a try.

alveoli (air sacs)
bronchioles
bronchus

diaphragm
larynx
lung
pharynx

nasal cavity
nostril
trachea

Notes:

  • the esophagus is part of the digestive system. it is the tube leading to the stomach.
  • the epiglottis is a flab of flesh (tissue) that covers the trachea (windpipe) when you swallow so that food doesn't "go down the wrong pipe". in other words, the epiglottis prevents choking.
  • the lungs lie (well protected) behind the ribs in the chest cavity.
  • a membrane called the pleura surrounds each lung

Click <here> to see answers

 

  


Here is a summary of the functions of each Respiratory Structure

STRUCTURE

FUNCTION

nose / nasal cavity

 warms, moistens, & filters air as it is inhaled

pharynx (throat)

 passageway for air, leads to trachea

larynx

 the voice box, where vocal chords are located

trachea (windpipe)

 tube from pharynx to bronchi
 rings of cartilage provide structure, keeps the windpipe "open"
 trachea is lined with fine hairs called cilia which filter air before it reaches the lungs

bronchi

 two branches at the end of the trachea, each lead to a lung

bronchioles

 a network of smaller branches leading from the bronchi into the lung tissue & ultimately to air sacs

alveoli

 the functional respiratory units in the lung where gases (oxygen & carbon dioxide) are exchanged (enter & exit the blood stream)

Let's take a closer look at the air sacs (alveoli) in the lungs.

As the bronchioles branch out into smaller & smaller & smaller & smaller & smaller tubes, they eventually lead to microscopic clusters of alveoli, which are referred to as air sacs.  You can think of the air sacs as a bunch of grapes, with each individual grape representing a single alveolus.  Like this:

 A close-up of the air sacs, which are located at the ends of the bronchioles.  Each "air sac" is comprised of a cluster of alveoli. 

The red structures represent blood vessels leading to & from the air sacs.

An even closer look at an alveolus. 

Notice that the wall of an alveolus is only one cell thick.  This allows gases to diffuse into & out of the alveoli.

Also notice that the alveoli are surrounded by capillaries so that oxygen and carbon dioxide can be exchanged between the lungs & the blood.  Oxygen in the alveolus can diffuse into the bloodstream (& be transported throughout the body) and carbon dioxide in the bloodstream can enter the alveoli (& then be exhaled).


And now a few words about breathing ...........

There are no muscles in your lungs.  They do not actively pump air in & out, in & out.  The muscle responsible for breathing actually lies below the lungs.  It is like a rubber sheet that separates your chest cavity & your abdominal cavity.  It's name is diaphragm.

When you inhale, the diaphragm contracts & moves downward, which creates more space in your chest cavity & draws air into the lungs.  When you exhale, the diaphragm relaxes & moves upward, forcing air out of the lungs.

A common demonstration of the mechanics behind breathing involves a bell jar, some glass tubing, and a couple of balloons.  Like so:

If you look closely at the right side of the diagram, which represent exhaling, you can see how the Heimlich maneuver works. The Heimlich maneuver is the "bear hug" that helps to dislodge food from the windpipe of a choking victim.  By pushing upwards below the victims ribs, the diaphragm is forced up & air is forced out of the trachea, hopefully with enough "UmmppHH" to remove the blockage.  See, biology can save you life.

One more tidbit: hiccups are muscle spasms in the diaphragm.


 

Malfunctions & Diseases of the Respiratory System

asthma

severe allergic reaction characterized by the constriction of bronchioles

 bronchitis

inflammation of the lining of the bronchioles

emphysema

condition in which the alveoli deteriorate, causing the lungs to lose their elasticity

pneumonia

condition in which the alveoli become filled with fluid, preventing the exchange of gases

lung cancer

irregular & uncontrolled growth of tumors in the lung tissue

Keep your lungs happy & healthy --- keep them SMOKE FREE. 



It's REVIEW TIME !
Jot down your answers to the following questions. Try to answer them without peeking back.
And NO LOOKING AT THE ANSWERS until you're all done.

1. Which choice lists the structures adapted for permitting air flow from the external environment to the human lungs in the correct order?
a) nasal cavity, bronchi, bronchioles, pharynx, trachea
b) nasal cavity, trachea, pharynx, bronchi, bronchioles
c) nasal cavity, pharynx, trachea, bronchi, bronchioles
d) nasal cavity, bronchioles, trachea, pharynx, bronchi

2. A structural difference between the trachea and esophagus that prevents the trachea from collapsing is the presence of:
a) smooth muscle
b) skeletal muscle
c) respiratory cilia
d) rings of cartilage

3. In order for gas exchange to take place, alveoli must be closely associated with:
a) capillaries
b) villi
c) veins
d) arteries

4. Deposits from cigarette smoke interfere with the normal functioning of cilia in the:
a) trachea
b) esophagus
c) bronchioles
d) pharynx

5. The exchange of air between the human body and the environment is the result of coordinated contractions of the muscles of the rib cage and the:
a) lung
b) diaphragm
c) heart
d) pleura

6. The site of gas exchange in humans is the:
a) nasal cavity
b) trachea
c) pleura
d) alveoli

7. A disease involving the breakdown of the air sacs in the lungs is:
a) asthma
b) emphysema
c) pneumonia
d) bronchitis

Base your answers to questions 8 through 11 on the diagram below:

8. The process responsible for gas exchange between areas "B" & "D" is:
a) breathing
b) diffusion
c) osmosis
d) peristalsis

 

 

 

 

 

9. The type of blood vessel shown in the diagram is:
a) an artery
b) a capillary
c) a vein
d) none of the above

10. At which location would blood with a low oxygen content and a high carbon dioxide content be found?
a) A     b) B     c) C     d) D

11. This diagram is based on structures found in which respiratory organ?
a) the bronchi
b) the lungs
c) the pharynx
d) the nasal cavity

Base your answers on questions 12 through 20 on the diagram over there =>

12. Which structure warms & filters air as it is inhaled?
13. Bronchitis effects which two structures?
14. Which structure is referred to as the "voice box"?
15. What are two names for structure #9?
16.  What is the number and name of the muscle responsible for breathing?
17. What is the importance of the epiglottis?
18. Where does the actual exchange of oxygen and carbon dioxide take place?
19. What is the name of the membrane surrounding structure #5?
20. In what direction does structure #6 move during inhalation?

Check your answers by clicking ----------------------> HERE.
 
 
 
 
 

 

Return to List of Bio Topics.

Please e-mail questions, comments, or site problems to mr.lubey

WHY the site is here / site USE / site MISUSE

Lubey's
BioHELP!
1999-today


 
 
 
 
 
 
 


THE ANSWER AREA - NO PEEKING !

Answers to the "Order" of Respiratory Structures
The respiratory organs in the right order are:

nostril, nasal cavity, pharynx, larynx, trachea, bronchus, lung, bronchioles, alveoli

Air goes in through the nostril & into the nasal cavity.  The pharynx is the area in the back of the throat, the larynx (voice box) is just below (posterior) to that.  Air then travels down the windpipe (trachea), which branches into two bronchi (one bronchus leads to each lung).  Once inside the lung the bronchi branch out into smaller tubes called bronchioles which lead to clusters of air sacs.  The air sacs are called alveoli.

< BACK TO WORK
 
 
 
 

 


 

Answers to the Respiratory System Diagram
Here are the numbers from the diagram with the names of each organ.

1 - nasal cavity
2 - pharynx (throat)
3 - (blue) alveoli or air sacs
4 - (yellow) bronchioles
5 - (pink) lung
6 - (red) diaphragm
7 - nostril
8 - (orange) larynx or voice box
9 - (green) trachea
10 - (light green) bronchus

<back to diagram


 


 
 

Answers to the Review Questions:  Correct response are in green.

1. Which choice lists the structures adapted for permitting air flow from the external environment to the human lungs in the correct order?
a) nasal cavity, bronchi, bronchioles, pharynx, trachea
b) nasal cavity, trachea, pharynx, bronchi, bronchioles
c) nasal cavity, pharynx, trachea, bronchi, bronchioles
d) nasal cavity, bronchioles, trachea, pharynx, bronchi

2. A structural difference between the trachea and esophagus that prevents the trachea from collapsing is the presence of:
a) smooth muscle
b) skeletal muscle
c) respiratory cilia - these are present in trachea but their function is to filter air
d) rings of cartilage

3. In order for gas exchange to take place, alveoli must be closely associated with:
a) capillaries - these are the only blood vessels thin enough to allow gases to pass through
b) villi
c) veins
d) arteries

4. Deposits from cigarette smoke interfere with the normal functioning of cilia in the:
a) trachea
b) esophagus
c) bronchioles
d) pharynx

5. The exchange of air between the human body and the environment is the result of coordinated contractions of the muscles of the rib cage and the:
a) lung
b) diaphragm
c) heart
d) pleura

6. The site of gas exchange in humans is the:
a) nasal cavity
b) trachea
c) pleura
d) alveoli

7. A disease involving the breakdown of the air sacs in the lungs is:
a) asthma
b) emphysema
c) pneumonia
d) bronchitis

Base your answers to questions 8 through 11 on the diagram below:

8. The process responsible for gas exchange between areas "B" & "D" is:
a) breathing
b) diffusion
c) osmosis - this is the diffusion of water
d) peristalsis - this refers to the muscular contractions of the alimentary canal (digestive system)

9. The type of blood vessel shown in the diagram is:
a) an artery
b) a capillary
c) a vein
d) none of the above

10. At which location would blood with a low oxygen content and a high carbon dioxide content be found?
a) A - the blood is just arriving to the alveolus from the body cells which means it would have more carbon dioxide & less oxygen
b) B
c) C
d) D

11. This diagram is based on structures found in which respiratory organ?
a) the bronchi
b) the lungs
c) the pharynx
d) the nasal cavity

Base your answers on questions 12 through 20 on the diagram below:

12. Which structure warms & filters air as it is inhaled? #1 - nasal cavity
13. Bronchitis effects which two structures? #10 (bronchi) & #4 (bronchioles)
14. Which structure is referred to as the "voice box"? #8 - larynx
15. What are two names for structure #9? trachea & windpipe
16.  What is the number and name of the muscle responsible for breathing? #6 - diaphragm
17. What is the importance of the epiglottis? covers & blocks the opening of the trachea when food is swallowed (prevents choking)
18. Where does the actual exchange of oxygen and carbon dioxide take place? #3 - air sacs (alveoli)
19. What is the name of the membrane surrounding structure #5? the pleura
20. In what direction does structure #6 move during inhalation? down (draws air in)
 
 
 
 

<Back to Review Questions

the end