I. Respiratory System notes
1. General Anatomy - air entering the respiratory system comes in
contact with the following structures in order:
a. Nose -Inspiration and expiration usually occurs through the
nose. The nose has main two functions: The cilia and hairs which line the nasal
cavities trap dust and other foreign particles and the rich supply of blood
surrounding the cavities warms the air before it enters the lungs.
b. Pharynx - allows for separation of food and air. The epiglottis
closes the trachea when we eat and opens when we breathe.
c. Larynx - this structure sits on top of the trachea. Air rushing
across two ligaments causes sounds that we shape into speech. Also called the
voice box.
d. Trachea - Also called the windpipe
e. Bronchi - the trachea branches into two forks each called a
bronchi
f. Bronchioles - the smaller and smaller passageways that come off
the bronchi
g. Alveoli - these are the small air sacs where actual gas
exchange takes place.
Be able to identify and label the parts in the above list on the diagram below
2. The Mechanics of Breathing
-Air flows into or out of the lungs when air pressure in the alveoli differs
from the pressure of the surrounding air. eg. Alveolar pressure higher than air
pressure = air flows out of lungs, alveolar pressure lower than air pressure =
air flows into the lungs
-Air pressure in the lungs is changed by changing the volume of the thoracic
cavity.
a. During inhalation
-the diaphragm contracts (becomes less dome shaped)
-the rib muscles contract
-the rib cage moves up and out.
These movements, enlarge the volume of the thoracic cavity, causing the pressure
in the lungs to become lower than air pressure, and air will move into the
lungs.
b. During exhalation
-diaphragm relaxes (becomes more domed shaped)
-the rib muscles relax
-the rib cage moves down and in
These movements decrease the volume of the thoracic cavity, causing the pressure
in the lungs to become greater than air pressure and air is forced out of the
lungs.
3. Control of Breathing by the Nervous system
-Rate and depth of breathing is controlled by the breathing centre located in
the Medulla oblongata of the brain.
-When the breathing centre is stimulated (by increased Hydrogen ion and carbon
dioxide concentration in the blood.) it sends messages to the diaphragm and rib
muscles to contract and breathing occurs. If these levels are high, depth and
rate of breathing will increase until enough CO2 is exhaled and the blood
chemistry returns to normal.
-When the breathing centre is inhibited (by stretch receptors in the alveoli)
the muscles relax and breathing out occurs.
4. How the Structure of the Alveoli is Related to its Function
-The alveoli function to exchange gases from the blood to the air and vice versa
-The following structures of the Alveoli facilitate its function:
a. each alveolus is 0.1 to 0.2 millimeters in diameter - This small size
maximizes surface area and allows for faster exchange of gases.
b. The walls of the capillaries and the alveoli are each made up of a single
layer of cells. This means the distance that the gases have to diffuse,( into
and out of) is short and gases can be exchanged more quickly
c. A film of lipoprotein covers the alveoli. This lowers surface tension and
prevents the alveoli from collapsing.
d. There is a lot of blood supplied to the alveoli via capillaries. This allows
for faster exchange of gases
e. There are approximately 150 million alveoli. The large number increases
surface area.
The diagram below shows alveoli, bronchioles and blood vessels. Be able to
label.
5. Gas Exchange
i. External respiration - exchange of gases between the air in the
lungs and the blood in the alveoli.
Things that occurs during External Respiration
-Bicarbonate ions react with hydrogen ions to form carbon dioxide and water and
are exhaled
-Other forms of carbon dioxide (carbaminohemoglobin and carbon dioxide dissolved
in the plasma) are converted to carbon dioxide gas and exhaled
-Oxygen bonds with hemoglobin forming oxyhemoglobin
-Reduced hemoglobin releases the hydrogen ions it is carrying forming hemoglobin
The following chemical reactions occurs
a. Oxygen
Hemoglobin bonds with oxygen according to the following reaction:
Hb + O2 -----> HbO2
Hemoglobin + oxygen oxyhemoglobin
b. Carbon Dioxide
i. Bicarbonate ions react with the Hydrogen ions that are released from reduced
hemoglobin and are converted to water and carbon dioxide, according to the
reaction below. The enzyme Carbonic Anhydrase catalyzes the reaction. The water
and carbon dioxide are then exhaled.
carbonic
anhydrase
HCO3- + H+
-----> H2CO3 -----> CO2 (exhaled) +
H2O (exhaled)
Bicarbonate ion + Hydrogen ion -----> Carbonic Acid -----> Carbon
Dioxide + water
c. Hemoglobin
i. Hemoglobin carrying Hydrogen ions is called reduced hemoglobin.
Hemoglobin releases the Hydrogen ions it is carrying according to the following
reaction:
HHb -----> Hb
+ H+
reduced hemoglobin hemoglobin hydrogen ions
ii. Hemoglobin carrying Carbon Dioxide is called carbaminohemoglobin.
Hemoglobin releases the Carbon Dioxide it is carrying according to the following
reaction:
HbCO2 --------> Hb
+ CO2 (exhaled)
carbaminohemoglobin hemoglobin Carbon
Dioxide
ii. Internal Respiration - exchange of gases between the blood
capillaries and the tissues.
Things that occurs during Internal Respiration
-Carbon dioxide and water diffuse into the blood from the tissue cells and are
converted to Hydrogen ions and bicarbonate ion.
-Carbon dioxide bonds to hemoglobin forming carbaminohemoglobin
-Carbon dioxide dissolves in the plasma
-Oxyhemoglobin releases the oxygen it is carrying forming hemoglobin. The oxygen
diffuses into the tissue cells from the blood.
-Hemoglobin bonds with hydrogen ions
The following chemical reactions occurs
a. Oxygen
HbO2 -----> Hb
+ O2
oxyghemoglobin -----> hemoglobin oxygen
b. Carbon Dioxide - About 9% is carried in the blood as dissolved
CO2, another 25% is carried bound to hemoglobin and called
carbaminohemoglobin, and the remaining 65% is carried as Bicarbonate ion ( HCO3-).
The bicarbonate ion is produced in two stages:
carbonic
anhydrase
1st stage: Carbon Dioxide + water <------->
Carbonic Acid
CO2 + H2O
<-------> H2CO3
carbonic
anhydrase
2nd stage: Carbonic Acid <-------> Bicarbonate ion +
Hydrogen ion
<-------> HCO3-
+ H+
c. Hemoglobin
Hb + H+
--------> HHb
hemoglobin hydrogen ions reduced hemoglobin
Hb + CO2
--------> Hb CO2
hemoglobin carbon dioxide
carbaminohemoglobin
The red blood cells contain an enzyme called Carbonic Anhydrase that catalyzes
the reaction of carbonic acid to bicarbonate and hydrogen ion. As more carbon
dioxide is taken up by the blood the blood becomes increasingly acid. As the
acidity increases, the hemoglobin gives up its oxygen more readily. The
hemoglobin then binds with the excess H+ ions and carries them to the
lungs. Therefore as CO2 enters the blood, more oxygen is given off
and taken in by the tissues.
6. Function of the Pleural Membranes
- A thin membrane called the pleura surrounds each lung and lines the thoracic
cavity.
- The pleura secretes a small amount of fluid that lubricates each surface, so
that they slide past one another as the lungs expand and contract
7. Function of cilia in the respiratory tract
-beat continuously , pushing mucus and foreign particles embedded in
mucus up towards the pharynx where it is swallowed
II.
Respiratory system Quiz Questions
1. Name the structures in the lungs where gases are exchanged
2. Name the structure separates the chest cavity from the abdominal cavity
3. What is the name of the breathing control centre
4. What is the name of the membrane which lines the lungs and chest cavity?
5. Be able to identify the parts of the respiratory system from a diagram and
define their functions
6. The concentration of what gas controls the breathing movements
7. What is the function of the epiglottis
8. What is the function of the pleural membranes
9. What will be the effect of increased pressure in the thoracic cavity
10. What will be the effect of decreased pressure in the thoracic cavity
11. What is the function of the diaphragm
12. Most of the carbon dioxide in the blood is carried as what chemical
13. What is the name of the air sacs where gas exchange takes place
14. What is the definition of breathing
15. What is Carbonic Anhydrase
16. Name the 3 ways Carbon Dioxide is carried in the blood
17. What is the name of the chemical which carries oxygen in the blood
18. What is carbaminohemoglobin
II. Respiratory System Written Questions
1. Explain the mechanical process of breathing in. Include in your answer the
names of the structures involved, the roles they play and the reasons why the
lungs inflate.
2. Describe what happens as the following gases are exchanged at the tissue
capillaries (internal respiration)
a.) oxygen
b.) carbon dioxide
3. Describe what happens as the following gases are exchanged at the lung
capillaries (external respiration)
a.) oxygen
b.) carbon dioxide
4. Explain the mechanical process of breathing in. Include in your answer the
names of the structures involved, the roles they play and the reasons why the
lungs inflate.
5. Name
three characteristics of the alveolus and describe how these characteristics
assist in the function of gas exchange.
6. Breathing rate increases
during exercise. Using your knowledge of cellular metabolism and the respiratory
system, explain why.
7. List the structures, in the correct sequence through which a molecule of air
would pass from the point of entry into the respiratory system until it reaches
the air sacs in the lungs. (4 marks: 1/2 mark each for the structures and 1
marks for the order)
