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Unit L: Respiration
I Respiratory structures
and functions:
i)
Nasal Cavity: moistens,
warms and cleans air
ii) Pharynx: joins mouth and
nasal passages
iii) Larynx: Contains vocal
chords for sounds
Nasal cavity
Pharynx
iv) Trachea: passage way for air. Larynx
Trachea
v) Lung: site of gas exchange
vi) Bronchus: divides trachea to Lung
Bronchus
each lung
vii) Bronchiole: takes air to
alveoli
Bronchiole
viii) Diaphragm: Muscle for
inhalation and exhalation
Diaphragm
Alveoli: Specialized structures
for gas- exchange.
• Millions of alveoli are
found at end of
bronchioles.
• Alveoli are 1 cell thick
to allow diffusion.
• Covered with
lipoprotein: acts as a
surfactant to prevent
walls sticking together.
• Stretch receptors inside
tell brain when they are
full of air.
• Moist to help gas
diffusion.
• Many capillaries on
outside.
II. Respiration is divided
into three types:
• External respiration: In the lungs:
O2 is absorbed from the external atmosphere
into the blood in capillaries. CO2 is removed
from blood and moved into atmosphere.
• Internal Respiration: In the body’s tissues:
Blood releases O2 to the tissues and
absorbs CO2 at the capillaries.
• Cellular respiration: In the cell’s
mitochondria.
C6H12O6 + O2  CO2 + H2O and ATP’S!
III. External Respiration:
Inhalation
• Inhalation requires the movement of the
diaphragm downwards, intercostal muscles
move ribs outwards.
• The enlargement of the thoracic cavity
causes a negative pressure to develop, air
rushes in to fill the vacuum, inflating the
lungs.
• **The lungs DO NOT have their own
muscles for inflation!**
Exhalation:
• Stretch receptors in alveoli indicate that they
are full, sends a signal to brain to initiate the
relaxing of muscles.
• Diaphragm relaxes and moves upwards, rib
cage moves down and inwards.
• A positive air pressure develops, causing air
to rush out of body.
• CO2 detectors in medulla oblongata of brain
detect rising levels and begin the inhalation
process by activation of breathing muscles.
External Respiration: gas
exchange at alveoli.
• Gas exchange occurs at the walls of the alveoli.
Gases diffuse easily across the cell membranes:
O2 into blood and RBC’s- binds to hemoglobin.
CO2 out of plasma and through alveoli walls into
bronchi passage for exhalation.
V. Gas Exchange Reactions:
i) Oxygen is carried on hemoglobin, the
human respiratory pigment:
At the lungs:
Hb + O2  HbO2
Hemoglobin + oxygen  oxyhemoglobin
**Caused by pH= 7.4 and temp. = 37 C**
At the tissues the reverse reaction:
HbO2 
oxyhemoglobin 
Hb
+
O2
Hemoglobin + oxygen
**Caused by pH= 7.3 and temp. = 38 C**
V. Gas Exchange cont’d
ii) Carbon dioxide is carried in three important ways:
1) Small percentage dissolved as a gas in the plasma
2) Some reacts with free hemoglobin in RBC’s at tissues:
CO2 + Hb  HbCO2.
Carbon dioxide + hemoglobin  carbaminohemoglobin.
3) Most reacts with water to form bicarbonate, which is
carried in the plasma.
CO2 + H2O 
H2CO3
 H+ + HCO3-1
Carbon dioxide+watercarbonic acidhydrogen+bicarbonate
This requires a special enzyme: carbonic anhydrase.
4) Extra H+ ions are reacted with hemoglobin & carried in
RBC’s:
H+ + Hb  HHb.
Hydrogen ion + hemoglobin  Reduced hemoglobin
(remember GER?)
VI. Gas Reactions at Lungs are
reversed…
1) The small percentage of CO2 dissolved as a gas in the
plasma is released from blood to alveoli.
2) Hemoglobin releases CO2 due to changes in pH and T:
HbCO2.  CO2 + Hb
carbaminohemoglobin Carbon dioxide + hemoglobin
3) Hydrogen ions are released from Hemoglobin as well.
HHb  Hb + H +
The Hb can now pick up O2 coming into blood.
4) Bicarbonate is converted back to CO2 and H2O due the
free H+ ions driving the reaction….
H+ + HCO3-1 
H2CO3  CO2 + H2O
This still requires a special enzyme: carbonic anhydrase.
CO2 Reactions:
HbCO2  Hb + CO2
HHb  Hb + H+
H+ + HCO3-H2O + CO2
Hb + CO2HbCO2
H2O + CO2  H+ +HCO3-
Hb +
H +
HHb
O2 Reactions:
Hb + O2 HbO2
pH= 7.4
T= 37 C
HbO2  Hb + O2
pH= 7.3
T= 38 C