Biol. 12
THE RESPIRATORY SYSTEM KEY
1.
2.
Label the diagram of the respiratory system with the following structures.
Give the function and special structural characteristics of each part.
a.
Larynx : Found at the entrance of the trachea. Triangular
section of cartilage, the front of which forms the Adam’s apple.
Referred to as the voice box since the vibrations of the vocal cords,
which are stretched across the top of the larynx, creates our “voice”.
b.
Pharynx: Chamber where air and food channels cross (common
passage). Food is prevented from entering larynx by the epiglottis.
c.
Trachea: Wind pipe; surrounded by C-shaped cartilaginous
rings to maintain opening of tube. Allows the passage of air to
the bronchi.
d.
Bronchus: (bronchi pl.) 2 branches form from trachea that
enter the right and left lung; continues the path for continuous
column of air.
e. Bronchioles: smaller branches off of the bronchus; walls become
very thin with no cartilage.
f.
Alveoli: air pockets at the end of bronchioles are the exchange
site for gases.
g.
Diaphragm: dome-shaped muscle that forms the floor of the
thoracic cavity separating it from the abdominal cavity. Aids
in breathing.
h.
Pleural membranes: inner membrane surrounds and is fused to
the lungs. Outer membrane is fused to the rib cage and the
diaphragm. Very little space between the two, which is filled with a
film of fluid. Aids in breathing and reduces friction between lungs
and thoracic wall.
i. Lungs: Made up of millions of alveoli, the lungs are the respiratory
surfaces where gases are exchanged.
j.
Thoracic Cavity: That part of the coelom that houses the lungs
and heart. Divided from the abdominal cavity by the diaphragm.
k.
Ribs: Bones that surround lungs to give support and
protection to them. They play a major role in breathing.
List 4 ways alveoli structure lends itself to their particular function? The aveloli
are microscopic sacs that are only 1 layer of squamous epithelial cells thick,
surrounded by capillaries. This makes for very efficient gas exchange since
the gasses must only diffuse through 2 layers of cells and there is a huge
surface area. They also secrete surfactant, which allows the alveoli to refill
with air once they collapse and helps keep the surfaces moist allowing
diffusion to occur.
2
3. Where would you find cilia and mucus in the respiratory tract? What are each of
their functions? Cilia are found in the nasal, trachea and bronchi passages.
They keep debris out of the lungs. Mucus is important to moisten air before
it reaches the lungs and to trap dirt, bacteria and other debris to protect the
lungs. It can be found at all levels of the respiratory system.
4. Read carefully pg. 276-277
Explain what occurs during INSPIRATION and EXPIRATION to the rib cage,
the diaphragm and the pressure in the lungs. (Diagram on pg. 276 will help). Use
terms such as partial vacuum and negative pressure. Inspiration: The
intercostal muscles of the rib cage contract causing the ribs to move up and
out. The diaphragm also contracts, flattening out. Both these processes
cause the thoracic cavity to expand. This will cause the lungs to expand as
the plural membranes are pulled outward with the ribs, thus creating a
negative pressure, i.e. one lower than atmospheric pressure within the lungs.
Air will rush into this partial vacuum in order to balance the pressures.
Expiration: The muscles of the ribs and diaphragm will relax (ribs move
down and in, the diaphragm moves up), the lungs “rebound”, creating a rise
in pressure, which will force the air out of the lungs.
5. Explain how the respiratory center of the medulla oblongata is involved in
inspiration and expiration (identify the afferent nerve, nerve leading to the lung
and efferent nerve). The medulla oblongata monitors and maintains regular
breathing by sending nerve impulses along the phrenic nerve and the
intercostal nerve (afferent nerves) at a rate of about 15 breaths per minute.
These stimuli cause both the diaphragm and intercostal muscles to contract.
As the lungs fill with air, the medulla stops sending impulses to the muscles
of the thoracic cavity and expiration occurs as the muscles relax. The
medulla can be inhibited when either the concentration of carbon dioxide
falls or stretch receptors in the alveoli respond by sending an inhibitory
impulse to the medulla along the vagus nerve (efferent nerve) causing the
muscles to relax and expiration to occur.
6. What is the role CO2 and H+ ions play in breathing? Explain where their
concentrations are detected (3 chemoreceptor sites in the body) and the effect
rising concentrations have on breathing. It is the concentration of these 2
substances in the blood, not O2, that regulate breathing. They are detected
by chemoreceptors in the medulla oblongata. There are also chemoreceptors
that detect these substances (and O2 levels) within the carotid bodies on the
carotid artery and within aortic bodies on the aorta. As the concentrations of
CO2 and H+ rise in the blood (due to an increase in the metabolic rate of the
cells) the medulla sends impulses to the intercostal muscles to increase the
rate and depth of breathing, and so match breathing to heart rate and
oxygen needs.
3
7. What is the role the pleural membranes play in breathing? Because the
membranes are fused to the lungs and the surrounding tissues they maintain
a closed system within the thoracic cavity. As the ribs move outward they
pull both membranes and therefore the lungs with them. This increases the
volume of the thoracic cavity creating a negative pressure within the lungs.
Also, the fluid between the membranes has a pressure less than that of the
atmosphere. This situation allows the lungs to expand with the ribs. If the
membranes were pierced then air from the outside, with the greater
pressure, would force the lungs to collapse.
8. Define the following:
a.
reduced hemoglobin hemoglobin that carries hydrogen = HHb.
Helps as a buffer by picking up excess H+.
b.
carbominohemoglobin hemoglobin that carries carbon dioxide
= CO2 .
c.
oxyhemoglobin hemoglobin that carries oxygen.
d.
bicarbonate ion main molecule for the transport of carbon
dioxide in the blood. Forms from the dissociation of carbonic
acid, a chemical created when water and carbon dioxide are
joined.
e.
carbonic anhydrase an enzyme needed for the efficient union of
water and carbon dioxide in the red blood cells. (also catalyzes
the breakdown of that union)
9. Name and explain the four parts of respiration. Breathing = the taking of air
into the lungs.
External respiration = the exchange of gases between environment
and blood of the lungs.
Internal respiration = the exchange of gases between the blood and
the cells of the body.
Cellular respiration = the use of oxygen and glucose to generate
energy for the formation of ATP.
10. Discuss the events of external respiration. Include two pertinent equations in your
discussion.
External Respiration: the exchange of gases between air and blood. The
partial pressure of O2 is lower in the blood than the air, therefore O2 will
diffuse into the blood, and since the opposite partial pressures exists for CO2,
diffusion will occur out of the blood and into the alveoli. As CO2 leaves the
blood additional CO2 comes out of solution from its major transferred state
i.e. bicarbonate ion. It will combine with free H+ ions to form carbonic acid,
which quickly decomposes (with the aid of carbonic anhydrase), into water
and carbon dioxide. Losing H+ increases the pH, which makes the uptake of
O2 more efficient (the cooler temperature of lung tissues also increases the
uptake of oxygen). Here is the equation showing the loss of CO2 from the
blood.
4
H+ + HCO3-  H2CO3  H2O + CO2
The loss of CO2 from the blood drives this reaction continuously to the right.
The hemoglobin that is freed when both CO2 and H are released from it, is
immediately bonded to the O2 diffusing into the red blood cells.
The equation showing this process is:
Hb + O2   HbO2
11. What two equations pertain to the exchange of gases during internal respiration?
During internal respiration the process is reversed due to changes in partial
pressures of CO2 and O2. Of course conditions are also different at the
tissues to encourage the loss of O2 from the blood to the tissues i.e. pH is
lower and temperatures are warmer.
From cells to blood:
CO2 + H2O  H2CO3  H+ + HCO3At the same time the cells will absorb O2.
HbO2  Hb + O2
12. State 3 factors that influence hemoglobin’s O2 binding capacity and relate them to
the environmental conditions in the lungs and tissues.
Hemoglobin is bonded more easily with oxygen at lower temperatures,
higher pH and higher partial pressure. Each of these conditions is more
favorable at the lungs so oxygen is taken up by hemoglobin. The opposite
conditions exist at the tissues so oxygen is released by hemoglobin.
1.
13.
Why is it better to give a non-breathing person a mixture of oxygen and
carbon dioxide rather than pure oxygen? You would not give a NONBREATHING person pure oxygen because you need CO2 to trigger the
breathing center to send the nerve impulse to initiate breathing.