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Martini’s VisualAnatomy and Physiology

First Edition

Martini Ober

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Chapter 20 - Respiratory System

Lectures 12 & 13

Midterm GradesYour midterm grades (due March 28) will be calculated as follows:Lec 1 Exam 100 pointsLec 2 Exam 100 pointsLab 1 Exam 100 pointsLaboratory Grade 25-35 points (5-7 labs so far)

Extra Credit 4 points

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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.

Mid-term CheckupBased 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

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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:

Points desired (see syllabus) – Total points so far

350 (if no grade dropped) or 450 (if low grade dropped)

Average grade needed on remaining exams* =

*This formula assumes you will have 50 pts for lab and 6 XC pts at the end of the course

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Points and Grades (from Syllabus) - RevisedGrade 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

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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) = x; x = 0.79 (79%) Average on upcoming exams350

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 XCpoints:

574 – (83 + 90 + 50 + 6) = x; x = 0.76 (76%) Average on upcoming exams450

D 60-67 420-475 0.7

F less than 60 less than 420 0.0

Lecture Overview

• Lectures 12 & 13– The breathing mechanism (ventilation)

– Respiratory volumes and capacities

– Nonrespiratory air movements

Alveolar gas exchange

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– Alveolar gas exchange

– Transport of O2 and CO2 in the blood

– Control of breathing

– Factors affecting breathing

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

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• 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

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Air Movements

• Moving the Figure from:

If Volume increases, pressure decreases and vice versa

Stated mathematically: P 1/V (Boyle’s Law)

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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

gSaladin, Anatomy & Physiology, McGraw Hill, 2007

Lungs at RestWhen lungs are at rest, the pressure on the inside of the lungs is equal to the pressure on the outside of the thorax

Think of pressure differences as difference in the “concentration” of gas

Figure from: Hole’s Human A&P, 12th

edition, 2010

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gmolecules and use the rules of diffusion.

Higher pressure means higher concentration (ignoring temperature difference)

Normal Inspiration• Intra-alveolar (intrapulmonary) pressure decreases to about 758 mm Hg as the thoracic cavity enlarges

An active process

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• Atmospheric pressure (now higher than that in lungs) forces air into the airways

• Compliance – ease with which lungs can expand

Phrenic nerves of the cervical plexus stimulatediphragm 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.

Figure from: Hole’s Human A&P, 12th

edition, 2010

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Maximal (Forced) InspirationThorax during normal inspiration

Thorax during maximal inspiration• aided by contraction ofsternocleidomastoid and pectoralis minor muscles

Compliance decreases as lung volume

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increases

Costal (shallow) breathing vs. diaphragmatic (deep) breathing

Figure from: Hole’s Human A&P, 12th

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

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lungs (elastic rebound) and abdominal organs

- surface tensionbetween walls of alveoli (what keeps them from collapsing completely?)

Figure from: Hole’s Human A&P, 12th

edition, 2010

Maximal (Forced) Expiration

• contraction of abdominal wall muscles

• contraction of posterior

Figure from: Hole’s Human A&P, 12th

edition, 2010

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posterior (expiratory) internal intercostal muscles

• An active, NOT passive, process

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Terms Describing Respiratory Rate

• Eupnea – quiet (resting) breathing

• Apnea – suspension of breathing

• Hyperpnea – forced/deep breathing

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• Dyspnea – difficult/labored breathing

• Tachypnea – rapid breathing

• Bradypnea – slow breathing

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

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p

• 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

Alveoli and Respiratory Membrane• consists of the walls of the alveolus and the capillary, and the basement membrane between them

1) cells of alveolar wall are tightly

Mechanisms that prevent alveoli from filling with fluid:

Figure from: Hole’s Human A&P, 12th

edition, 2010

15Surfactant resists the tendency of alveoli to collapse on themselves.

) g yjoined 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

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Just a Quick Review!

• Atmosphere is composed of several gases, each exerting its own partial pressure, PO2

• P 1/V (Boyle’s Law)

• InspirationN l

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– Normal

– Forced or maximal

• Expiration– Normal

– Forced or maximal

• The respiratory membrane for gas exchange

Blood Flow Through Alveoli

• 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

Mechanisms that prevent alveoli from filling with fluid:

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Low pressure circuit

Figure from: Hole’s Human A&P, 12th

edition, 2010

Diffusion Across Respiratory Membrane

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Figure from: Hole’s Human A&P, 12th

edition, 2010

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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, 12th

edition, 2010

19At a given temperature, the amount of a particular gas in solution is directly proportional to its partial pressure outside the solution (Henry’s Law)

Composition of Inspired and Alveolar Air

21From: Saladin, Anatomy & Physiology, McGraw Hill, 2007

Factors Affecting O2 and CO2 Transport

• O2 and CO2 have limited solubility in plasma

• This problem is solved by RBCs

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p y– Bind O2 to hemoglobin

– Use CO2 to make soluble compounds

– Reactions in RBCs are• Temporary

• Completely reversible

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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, 12th

edition, 2010

23But what special properties of the Hb molecule allow it to reversibly bind O2?

Lungs

Tissues

Review of Hemoglobin’s Structure

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Figure From: Martini, Anatomy & Physiology, Prentice Hall, 2001

The O2-Hb Dissociation Curve

Recall that Hb can bind up to 4 molecules of O2 = 100% saturation

At 75% saturation, Hb binds 3 molecules of O2

Figure from: Hole’s Human A&P, 12th

edition, 2010

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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

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Oxygen ReleaseAmount 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)

th

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Figure from: Hole’s Human A&P, 12th

edition, 2010

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

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H2CO3 ↔ H+ + HCO3-

CO2 exchange in TISSUES

Figure from: Hole’s Human A&P, 12th

edition, 2010

Chloride Shift• bicarbonate ions diffuse out RBCs• chloride ions from plasma diffuse into RBCs• electrical balance is maintained

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Figure from: Hole’s Human A&P, 12th

edition, 2010

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Carbon Dioxide Transport in Lungs

Figure from: Hole’s Human A&P, 12th

edition, 2010

29CO2 exchange in LUNGS

Control of Respiration

• Homeostatic mechanisms intervene so that cellular gas exchange needs are met

• Control occurs at two levels

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– 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

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

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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

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Factors Affecting Resistance to Airflow

• Diameter of bronchioles– Bronchodilation (epinephrine, sympathetic

stimulation)

– Bronchoconstriction (parasympathetic ti l ti hi t i ld i h i l

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stimulation, histamine, cold air, chemical irritants)

• Pulmonary compliance

• Surface tension of alveoli and distal bronchioles.

Neural Control of Respiration

Neural control of respiration has an autonomic as well as a

Figure from: Hole’s Human A&P, 12th

edition, 2010

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autonomic as well as a voluntary component

Respiratory Center – Autonomic Control

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2 sec / 3 sec

-

Figure from: Hole’s Human A&P, 12th

edition, 2010

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Respiratory centers can be facilitated (caffeine, amphetamines) or depressed (opioids, barbiturates)

Apneustic area

+

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Factors Affecting Breathing

Central chemoreceptors

Respond to PCO2 and pHof the CSF

Eff t i t ll d t

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Effect is actually due to [H+] as follows:

CO2 + H2O ↔ H2CO3

H2CO3 ↔ H+ + HCO3-

Carbonic acidBicarbonate

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Factors Affecting Breathing

Decreased blood PO2 or pH (or increased CO2) stimulates peripheralchemoreceptors in the carotid and aortic

Both central and peripheral chemoreceptors are subject to adaptation

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bodies

Stimulation leads to anincrease in the rate and depth of respiration

CO2 is the most powerful respiratory stimulantFigure from: Hole’s Human A&P, 12

thedition, 2010

Control of Respiration

• Control of respiration is accomplished by:1) Local regulation

2) Nervous system regulation

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• Local regulation– alveolar ventilation (O2), Blood flow to alveoli

– alveolar ventilation (O2), Blood flow to alveoli

– alveolar CO2, bronchodilation

– alveolar CO2, bronchoconstriction

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Control of Respiration

• Nervous System Control– Normal rhythmic breathing -> DRG in medulla

– Forced breathing -> VRG in medulla

• Changes in breathing

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g g– 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

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

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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!

Clinical Application

The Effects of Cigarette Smoking on the Respiratory System

• cilia disappear• excess mucus produced• lung congestion increases lung i f ti

Figure from: Hole’s Human A&P, 12th

edition, 2010

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infections• lining of bronchioles thicken• bronchioles lose elasticity• emphysema fifteen times more common• lung cancer more common• much damage repaired when smoking stops

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Clinical Application

43Figure from: Martini, “Fundamentals of Anatomy & Physiology”, Pearson Education, 2006

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., …)

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pressure (14.7 lbs/in ,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

Review

• Normal inspiration– An active process

– Phrenic nerve and diaphragm

– External (inspiratory) intercostal muscles

– Role of the lung pleura

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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

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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

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in alveoli and tissues

– Several factors can increase the release of O2 from Hb

• Increased PCO2

• Increased [H+] (decreased pH)

• Increased temperature of blood

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

-

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• Carbonic anhydrase in RBCs accelerates interconversion between CO2 and HCO3

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• 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

Review

• The respiratory membrane– Simple squamous epithelium of the alveoli and

capillaries

– Basement membrane between them

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Basement membrane between them

• Terms used to describe breathing (know these)

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Control of Respiration

• Control of respiration is accomplished by:1) Local regulation

2) Nervous system regulation

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• Local regulation– alveolar ventilation (O2), Blood flow to alveoli

– alveolar ventilation (O2), Blood flow to alveoli

– alveolar CO2, bronchodilation

– alveolar CO2, bronchoconstriction

Control of Respiration

• Nervous System Control– Normal rhythmic breathing -> DRG in medulla

– Forced breathing -> VRG in medulla

• Changes in breathing

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g g– 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