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The Respiratory System
Pulmonary Anatomy and
Physiology
Chapter 15: 393-423
What is Respiration?
 Closely Matched to Activity
 Includes:
 Breathing:
Moving air into lungs
 Gas Exchange: Between lungs and
blood
 Gas Transport: By the blood
 Gas Exchange: Between blood and
tissues
 Cellular Respiration: O2 use
Pulmonary Overview:
 Structure and Function
 Mechanics of Breathing
 Lung
Volumes and Capacities
 Gas Exchange
 Gas Laws: Partial Pressures
 O2, CO2, and pH Homeostasis
 Control of Ventilation
 Special Issues: Exercise/Disease
The Lungs and
Homeostasis!
 The primary effector in Maintaining
constant blood gases:
 O2
 CO2
 pH (H+ and HCO3-)
 You Guessed it! Exercise causes a
blood gas homeostatic
emergency!
Pulmonary Anatomy
 Upper Respiratory Tract:
 Nose,
Nasal Cavity,Pharynx etc.
 Lower Respiratory Tract:
 Larynx,
Trachea, Bronchi
 Lungs
 Pleural Membrane
 Circulation and Lymphatics
Structure and Function:
 Ventilation: Breathing –
airways/respiratory muscles
 Gas Exchange: Interface
between air/blood
 Alveoli
 Pulmonary
capillaries
 VERY thin diffusion distance
 VERY great surface area
Assignment:
 Read pages 393-406
 Note: How do pressure
gradients affect breathing (page
402-403)
 What is surfactant?
 What is a “pneumothorax”?
Horace Pippin: “Cabin in the Cottonfields”
1930’s
Gases and Gases in
Solution
 Oxygen is a gas!
 Atmospheric Gases:
Concentrations:
 Oxygen:
21%
 Nitrogen: 78+%
 Carbon Dioxide: 0.03%
Concentration vs. Partial
Pressure
 Concentration (content) reflects
the relative amount of gas in a
gas mixture
 Pressure: The force of
“bouncing” gas molecules
against the walls of any
container (lungs, atmosphere,
balloons)
Speaking of Balloons!
 Let’s fill this
balloon with
expired air from
our lungs:
 What are the
gases?
 Put in the fridge
Pressure and Partial Pressure
 Pressure: The force of ALL the
gas molecules as they “bounce
of the walls”
 Partial Pressure: The force of
one particular TYPE of gas
molecule as they bounce…
 In
this room: Partial Pressure
of guys vs. girls…
Gas Laws: The effect of T
and V on P…
 What happens to molecular
movement when they heat up?

T =
P
 What happens to the force
exerted against the walls, when
the walls close in?

V=
P
General Gas Law:
•PV = T
Or:
P = T/V
P = 1/V
P = T
 Let’s check out the balloon…
Temperature and Volume
 What happened
to the cooled
balloon?
 Why “Hot Air
Balloons?
 Hot air
molecules
“expand”…
Calculating Partial
Pressures
 The atmospheric pressure at
sea level is 760 mm Hg:
 21% of that pressure force is
from oxygen molecules:
 760 mmHg X .21 = 160 mmHg
Pressure and Diffusion:
 Gas Molecules move from
levels of high pressure to lower
pressure
 PRESSURE GRADIENT
 The pressure gradient of O2
between the alveoli and
pulmonary capillary DRIVE O2
into the blood
Oxygen “Gradients” in
the Lung:
105
 Pulmonary
Capillary

40
= 40 mmHg
 Alveolus
=
105 mmHg
 When the blood
leaves the lung
=
105 mmHg
105
105
105
Gas Pressures: mmHg
Atm
PO2 160
PCO2
0.3
Alv
Deoxy
Blood
Oxy
Tissue
Blood Cells
105 40
105 40
40
40
45
45
Oxygen and Tissues
 The relative
pressures of
CO2 and O2
drive oxygen
into the
tissues and
CO2into the
blood
Ventilation:
 Inspiration: Breathing in
 Diaphragm
contracts
 Thorax Expands
 Increased Volume = Decreased
Pressure compared to the air
 Air Moves from high to low
pressures
Ventilation:
 Expiration: Breathing out
 Diaphragm
relaxes
 Thorax recoils
 Decreased Volume = Increased
Pressure compared to outside
air
 Air moves out of the lungs
Surfactant:
 Lungs Expand: Pleural
membranes pull lungs out
during inspiration
 Alveoli Expand: Surfactant
coats the inner surface of the
alveoli, and reduces surface
tension –which keeps the
alveoli from collapsing during
exhalation
The Purpose of Ventilation:
 To Get Oxygen from the
atmosphere to the needy
tissues
 Gas enters the blood only
from the alveoli.
 The remainder of the
respiratory tract is “Dead
Space”
Gas Exchange:
 Efficiency Depends on:
 Pressure
Gradients between
alveoli and capillary PO2
 Solubility constant:(O2 is OK)
 Diffusion Distance: 2 cells thick
 Surface Area: All those alveoli
increase the surface area of the
lungs to 70 m2
The Hemoglobin Assist!
 Hemoglobin in Red Blood
Cells increases the O2 carrying
capacity of the blood
 Hemoglobin has a “heavy
attraction” (affinity) to oxygen
 Hemoglobin carries ~98.5% of
the O2 in the blood
Hemoglobin-Oxygen
Dissociation Curve:
Carbon Dioxide:
 Highest in the tissues
 High solubility and diffusion
 7% dissolved in plasma
 23% combine with hemoglobin
70% combine with H2O
CO2 + H2O
H2CO3
Bicarbonate and pH
 At physiologic conditions
(tissues):
H2CO3
+
H
+ HCO3
-
 So CO2 causes a decrease in
pH
 CARBONIC ANHYDRASE is
the enzyme catalyst
Breathing and pH
 In the lung, the reaction
reverses:
H2CO3
H2O + CO2
 So Exhaling blows off CO2 …
 AND reduces H+
 RESPIRATORY
COMPENSATION (of acidosis)
Assignment:
 Read Pages: 406-410
 Read Lab for Monday
 Have a good weekend!