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Martini’s Visual
Anatomy and Physiology
First Edition
Martini w Ober
Chapter 20 - Respiratory System
Lectures 12 & 13
1
Midterm Grades
Your midterm grades (due March 28) will be calculated as follows:
Lec 1 Exam
100 points
Lec 2 Exam
100 points
Lab 1 Exam
100 points
Laboratory Grade
25-35 points (5-7 labs so far)
Extra Credit
4 points
Total points possible so far...329-339 points
Your grade… (Ex., Total points you have / 330) * 100
Note: No grades will be dropped for calculation of midterm grade.
2
Mid-term Checkup
Based on the three (3) grades you have received so far, you should do a
mid-term checkup.
To find your average so far total the following points:
Lec Exam 1 + Lec Exam 2 + Lab Exam 1 + Lab points (6 labs)
Example: (83 + 67 + 90 + 26)  330 = 0.80 (80%)
Dropping the low grade: (83 + 90 + 26)  230 = 0.86 (86%)
To figure out what you need to AVERAGE for the next lecture and/or
lab exam and the final COMBINED to get a particular grade:
Average grade
needed on
remaining exams*
Points desired (see syllabus) – Total points so far
=
350 (if no grade dropped) or 450 (if low grade dropped)
*This formula assumes you will have 50 pts for lab and 6 XC pts at the end of the course
3
Points and Grades (from Syllabus) - Revised
Grade for Course
Grade as %
Points (of a possible 700)
Quality Points
A
92-100
644-700
4.0
A-
90-91
630-643
3.7
B+
88-89
616-629
3.3
B
82-87
574-615
3.0
B-
80-81
560-573
2.7
C+
78-79
546-559
2.3
C
70-77
490-545
2.0
D+
68-69
476-489
1.0
D
60-67
420-475
0.7
F
less than 60
less than 420
0.0
Example 1: To get a grade of B for the course, using the example grades on previous slide, and
not dropping lowest grade (50), and assuming 50 pts for lab and 6 XC points:
574 – (83 + 67 + 90 + 50 + 6)
350
= x;
x = 0.79 (79%) Average on upcoming exams
Example 2: To get a grade of B for the course, using the example grades on previous slide, and dropping lowest grade (67), and assuming 50 pts for lab and 4 XC
points:
574 – (83 + 90 + 50 + 6)
450
= x;
x = 0.76 (76%) Average on upcoming exams
4
Lecture Overview
• Lectures 12 & 13
–
–
–
–
–
–
–
The breathing mechanism (ventilation)
Respiratory volumes and capacities
Nonrespiratory air movements
Alveolar gas exchange
Transport of O2 and CO2 in the blood
Control of breathing
Factors affecting breathing
5
Gases and Pressure
• Our atmosphere is composed of several gases and
exerts pressure
– 78% N2, 21% O2, 0.4% H2O, 0.04% CO2
– 760 mm Hg, 1 ATM, 29.92” Hg, 15 lbs/in2,1034 cm H2O
• Each gas within the atmosphere exerts a pressure of
its own (partial) pressure, according to its
concentration in the mixture (Dalton’s Law)
– Example: Atmosphere is 21% O2, so O2 exerts a partial
pressure of 760 mm Hg. x .21 = 160 mm Hg.
– Partial pressure of O2 is designated as PO2
6
Air Movements
If Volume increases,
pressure decreases and
vice versa
Stated mathematically:
P  1/V (Boyle’s Law)
• Moving the
plunger of a syringe
causes air to move in
or out
• Air movements in
and out of the lungs
occur in much the
same way
Figure from:
Saladin, Anatomy &
Physiology,
McGraw Hill, 2007
7
Lungs at Rest
When lungs are at rest, the pressure on the inside of the
lungs is equal to the pressure on the outside of the thorax
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Think of pressure
differences as
difference in the
“concentration” of gas
molecules and use the
rules of diffusion.
Higher pressure
means higher
concentration
(ignoring temperature
difference)
8
Normal Inspiration
• Intra-alveolar
(intrapulmonary)
pressure decreases to
about 758 mm Hg as
the thoracic cavity
enlarges
• Atmospheric
pressure (now higher
than that in lungs)
forces air into the
airways
• Compliance – ease
with which lungs can
expand
An active process
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Phrenic nerves of the cervical plexus stimulate
diphragm to contract and move downward and
external (inspiratory) intercostal muscles contract,
expanding the thoracic cavity and reducing
intrapulmonary pressure.
Attachment of parietal pleura to thoracic wall pulls
visceral pleura, and lungs follow.
9
Maximal (Forced) Inspiration
Thorax during normal
inspiration
Thorax during maximal inspiration
• aided by contraction of
sternocleidomastoid and pectoralis minor
muscles
Compliance
decreases as
lung volume
increases
Costal (shallow)
breathing vs.
diaphragmatic
(deep) breathing
10
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Normal Expiration
• due to elastic recoil of the lung tissues and abdominal organs
• a PASSIVE process (no muscle contractions involved)
Normal expiration is
caused by
- elastic recoil of the
lungs (elastic rebound)
and abdominal organs
- surface tension
between walls of alveoli
(what keeps them from
collapsing completely?)
11
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Maximal (Forced) Expiration
• contraction of
abdominal wall
muscles
Figure from: Hole’s Human A&P, 12
th
edition, 2010
• contraction of
posterior
(expiratory)
internal intercostal
muscles
• An active, NOT
passive, process
12
Terms Describing Respiratory Rate
• Eupnea – quiet (resting) breathing
• Apnea – suspension of breathing
• Hyperpnea – forced/deep breathing
• Dyspnea – difficult/labored breathing
• Tachypnea – rapid breathing
• Bradypnea – slow breathing
13
Know these
Nonrespiratory Air Movements
• coughing – sends blast of air through glottis and clears upper
respiratory tract
• sneezing – forcefully expels air through the nose and mouth
• laughing – deep breath released in a series of short convulsive
expirations
• crying – physiologically same as laughing
• hiccupping – spasmodic contraction of diaphragm against
closed glottis
• yawning – deep inspiration through open mouth
• valsalva maneuver – expiration against a closed glottis
14
Alveoli and Respiratory Membrane
• consists of the walls of the alveolus and the capillary,
and the basement membrane between them
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Mechanisms that prevent alveoli
from filling with fluid:
1) cells of alveolar wall are tightly
joined together
2) the relatively high osmotic
pressure of the interstitial fluid
draws water out of them
3) there is low pressure in the
pulmonary circuit
Surfactant resists the tendency of alveoli to collapse on themselves.
15
Just a Quick Review!
• Atmosphere is composed of several gases, each
exerting its own partial pressure, PO2
• P  1/V (Boyle’s Law)
• Inspiration
– Normal
– Forced or maximal
• Expiration
– Normal
– Forced or maximal
• The respiratory membrane for gas exchange
16
Blood Flow Through Alveoli
Mechanisms that prevent alveoli from filling with fluid:
• cells of alveolar wall are tightly joined together
• the relatively high osmotic pressure of the interstitial fluid
draws water out of them
• there is low pressure in the pulmonary circuit
Low
pressure
circuit
Figure from: Hole’s Human A&P, 12
th
edition, 2010
17
Diffusion Across Respiratory Membrane
18
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Diffusion Through Respiratory Membrane
The driving for the exchange of gases between alveolar air
and capillary blood is the difference in partial pressure
between the gases.
Figure from: Hole’s Human A&P, 12
th
edition, 2010
At a given temperature, the amount of a particular gas in solution is directly
proportional to its partial pressure outside the solution (Henry’s Law)
19
Composition of Inspired and Alveolar Air
From: Saladin, Anatomy & Physiology, McGraw Hill, 2007
21
Factors Affecting O2 and CO2 Transport
• O2 and CO2 have limited solubility in
plasma
• This problem is solved by RBCs
– Bind O2 to hemoglobin
– Use CO2 to make soluble compounds
– Reactions in RBCs are
• Temporary
• Completely reversible
22
Oxygen Transport
• Most oxygen binds to hemoglobin to form oxyhemoglobin (HbO2)
• Oxyhemoglobin releases oxygen in the regions of body cells
• Much oxygen is still bound to hemoglobin in the venous blood
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Tissues
Lungs
But what special properties of the Hb molecule allow it to reversibly bind O2?
23
Review of Hemoglobin’s Structure
Figure From:
Martini, Anatomy
& Physiology,
Prentice Hall, 2001
24
The O2-Hb Dissociation Curve
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Recall that Hb can bind
up to 4 molecules of O2 =
100% saturation
At 75% saturation, Hb
binds 3 molecules of O2
on average
Sigmoidal (S) shape of
curve indicates that the
binding of one O2 makes
it easier to bind the next
O2
This curve tells us what the percent saturation of Hb will be at
various partial pressures of O2
25
Oxygen Release
Amount of oxygen released from oxyhemoglobin increases as
• partial pressure of carbon dioxide increases
• the blood pH decreases and [H+] increases (Bohr Effect; shown below)
• blood temperature increases (not shown)
• concentration of 2,3 bisphosphoglycerate (BPG) increases (not shown)
Figure from: Hole’s Human A&P, 12
th
edition, 2010
26
Carbon Dioxide Transport in Tissues
• dissolved in plasma (7%)
• combined with hemoglobin as carbaminohemoglobin(15-25%)
• in the form of bicarbonate ions (68-78%)
CO2 + H2O ↔ H2CO3
H2CO3 ↔ H+ + HCO3Figure from: Hole’s Human A&P, 12
th
edition, 2010
27
CO2 exchange in TISSUES
Chloride Shift
• bicarbonate ions diffuse out RBCs
• chloride ions from plasma diffuse into RBCs
• electrical balance is maintained
Figure from: Hole’s Human A&P, 12
th
edition, 2010
28
Carbon Dioxide Transport in Lungs
Figure from: Hole’s Human A&P, 12
CO2 exchange in LUNGS
th
edition, 2010
29
Control of Respiration
• Homeostatic mechanisms intervene so that
cellular gas exchange needs are met
• Control occurs at two levels
– Local regulation
• Lung perfusion (blood flow; ~5.5 L/min)
• Alveolar ventilation (~4.2 L/min)
• Ventilation/perfusion coupling (matching)
– Respiratory center of the brain
30
Local Control of Respiration
• Local Control regulates…
– Efficiency of O2 pickup in the lungs
• Lung perfusion (blood flow)
– Alveolar capillaries constrict when local PO2 is low
– Tends to shunt blood to lobules with high PO2
• Alveolar ventilation (air flow)
– High PCO2 (hypercapnia) causes bronchodilation
– Low PCO2 (hypocapnia) causes bronchoconstriction
– Directs airflow to lobules with higher PCO2
– Rate of O2 delivery in each tissue
• Changes in partial pressures
• Local vasodilation in peripheral tissues
31
Factors Affecting Resistance to Airflow
• Diameter of bronchioles
– Bronchodilation (epinephrine, sympathetic
stimulation)
– Bronchoconstriction (parasympathetic
stimulation, histamine, cold air, chemical
irritants)
• Pulmonary compliance
• Surface tension of alveoli and distal
bronchioles.
32
Neural Control of Respiration
Figure from: Hole’s Human A&P, 12
th
edition, 2010
Neural control of
respiration has an
autonomic as well as a
voluntary component
33
Respiratory Center – Autonomic Control
Figure from: Hole’s Human A&P, 12
th
edition, 2010
2 sec / 3 sec
+
Apneustic area
Respiratory centers can be
facilitated (caffeine,
amphetamines) or depressed
(opioids, barbiturates)
34
Factors Affecting Breathing
Central chemoreceptors
Respond to PCO2 and pH
of the CSF
Effect is actually due to
[H+] as follows:
CO2 + H2O ↔ H2CO3
H2CO3 ↔ H+ + HCO3Carbonic acid
Bicarbonate
35
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Factors Affecting Breathing
Both central and
peripheral
chemoreceptors are
subject to adaptation
Decreased blood PO2 or
pH (or increased CO2)
stimulates peripheral
chemoreceptors in the
carotid and aortic
bodies
Stimulation
leads to an
increase in
the rate and
depth of
respiration
Figure from: Hole’s Human A&P, 12
th
edition, 2010
CO2 is the most powerful respiratory stimulant
36
Control of Respiration
• Control of respiration is accomplished by:
1) Local regulation
2) Nervous system regulation
• Local regulation
–
–
–
–
 alveolar ventilation (O2),  Blood flow to alveoli
 alveolar ventilation (O2),  Blood flow to alveoli
 alveolar CO2, bronchodilation
 alveolar CO2, bronchoconstriction
38
Control of Respiration
• Nervous System Control
– Normal rhythmic breathing -> DRG in medulla
– Forced breathing -> VRG in medulla
• Changes in breathing
– CO2 is most powerful respiratory stimulant
– Recall: H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3– Peripheral chemoreceptors (aortic/carotid bodies)
•  PCO2,  pH ,  PO2 stimulate breathing
– Central chemoreceptors (medulla)
•  PCO2,  pH stimulate breathing
39
Breathing Reflexes
• Protective Reflexes
– Sneezing - Triggered by an irritation of the nasal cavity
– Coughing – Triggered by an irritation of the larynx,
trachea, or bronchi
– Both sneezing and coughing involve
• A period of apnea
• Forceful expulsion of air from lungs opening the glottis (up to
100 mph or more!!)
– Laryngeal spasms – chemical irritants, foreign objects,
or fluids into the area around glottis
• Temporarily closes the airway
• Some stimuli, e.g., toxic gas, can close the glottis so
powerfully that it doesn’t open again!
40
Clinical Application
The Effects of Cigarette Smoking on the
Respiratory System
Figure from: Hole’s Human A&P, 12
th
edition, 2010
• cilia disappear
• excess mucus produced
• lung congestion increases lung
infections
• lining of bronchioles thicken
• bronchioles lose elasticity
• emphysema fifteen times more
common
• lung cancer more common
• much damage repaired when
smoking stops
42
Clinical Application
Figure from: Martini, “Fundamentals of Anatomy & Physiology”, Pearson Education, 2006
43
Review
• The atmosphere is composed of a mixture
of gases
– Each gas exerts a partial pressure (Pg)
– Sum of all partial pressures = atmospheric
pressure (14.7 lbs/in2,760 mm Hg., …)
• Gases move from a higher concentration
(pressure) to a lower concentration
(pressure)
• Function of the diaphragm is to create a
lower intrpulmonary pressure so that
atmospheric gases flow into the lungs
44
Review
• Normal inspiration
–
–
–
–
An active process
Phrenic nerve and diaphragm
External (inspiratory) intercostal muscles
Role of the lung pleura
• Normal expiration
– A PASSIVE process
– Due to elasticity of lung/abdominal organs and alveolar
surface tension
• Forced inspiration
• Forced expiration
45
Review
• Oxygen travels in the blood bound to Hb
– Four O2 molecules can be bound to 1 Hb
– O2 bound to Hb - oxyhemoglobin
– Uptake and release of O2 is dependent upon PO2
in alveoli and tissues
– Several factors can increase the release of O2
from Hb
• Increased PCO2
• Increased [H+] (decreased pH)
• Increased temperature of blood
46
Review
• Carbon dioxide can travel in several ways
– Dissolved in plasma (7%)
– As carbaminohemoglobin (15-25%)
– As HCO3- ion (70%)
• Recall: H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3• Carbonic anhydrase in RBCs accelerates
interconversion between CO2 and HCO3• H+ combines with or dissociates from Hb
• HCO3- diffuses into plasma or into RBCs
• Cl- diffuses into RBC (chloride shift) as HCO3- exits
• Diffusion of CO2 is related to PCO2 in alveoli
and tissues
47
Review
• The respiratory membrane
– Simple squamous epithelium of the alveoli and
capillaries
– Basement membrane between them
• Terms used to describe breathing (know
these)
48
Control of Respiration
• Control of respiration is accomplished by:
1) Local regulation
2) Nervous system regulation
• Local regulation
–
–
–
–
 alveolar ventilation (O2),  Blood flow to alveoli
 alveolar ventilation (O2),  Blood flow to alveoli
 alveolar CO2, bronchodilation
 alveolar CO2, bronchoconstriction
49
Control of Respiration
• Nervous System Control
– Normal rhythmic breathing -> DRG in medulla
– Forced breathing -> VRG in medulla
• Changes in breathing
– CO2 is most powerful respiratory stimulant
– Recall: H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3– Peripheral chemoreceptors (aortic/carotid bodies)
•  PCO2,  pH ,  PO2 stimulate breathing
– Central chemoreceptors (medulla)
•  PCO2,  pH stimulate breathing
50