8964301 Respiratory Physiology All and Complete

7/30/2019 8964301 Respiratory Physiology All and Complete

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Respiratory Physiology

Dr Sherwan R Shal

2006-2007

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Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Respiration

Ventilation:Action of breathing with muscles and lungs.

Gas exchange:Between air and capillaries in the lungs.

Between systemic capillaries and tissues of thebody.

02 utilization:Cellular respiration in mitochondria.

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Ventilation

Mechanical process thatmoves air in and out of thelungs.

Diffusion of

O2: air to blood.

C02: blood to air.

Rapid:

large surface area

small diffusion distance.

Insert 16.1

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Conducting Zone

Conducting zone:

All the structures air

passes throughbefore reaching therespiratory zone.

Mouth,nose, pharynx,trachea, glottis,larynx, bronchi.

Insert fig. 16.5

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Conducting Zone

Conducting zone

Warms and humidifies until inspired air becomes:

37 degreesSaturated with water vapor

Filters and cleans:

Mucus secreted to trap particlesMucus/particles moved by cilia to be expectorated.

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Respiratory Zone

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Respiratory Zone

Alveoli

Air sacs

Honeycomb-like clusters

~ 300 million.Large surface area (6080 m2).

Each alveolus: only 1 thin cell layer.

Total air barrier is 2 cells across (2 mm) (alveolarcell and capillary endothelial cell).

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Respiratory Zone

Alveolar cells:

Alveolar type I: structural cells.

Alveolar type II: secrete surfactant.

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C i ht Th M G Hill C i I P i i i d f d ti di l


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Mechanics of breathing

Gas: the more volume, the less pressure (Boyles law).

Inspiration:

lung volume increase ->

decrease in intrapulmonary pressure, to just belowatmospheric pressure ->

air goes in!

Expiration: viceversa

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Copyright The McGraw Hill Companies Inc Permission required for reproduction or display


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Pleura

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Compliance: lungs can stretch when under tension.

Elasticity: they recoil (to original shape).

- elastin

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Copyright The McGraw-Hill Companies Inc Permission required for reproduction or display


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Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.


Quiet breath: +/- 3 mmHgintrapulmonary pressure.

Forced breath:

Extra muscles, including abs

+/- 20-30 mm Hg intrapulmonary pressure

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Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.

Problems

Pneumothorax: a hole in chest can causeone lung to collapse.

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Copy g t e cG a Co pa es, c e ss o equ ed o ep oduct o o d sp ay

Surface tension

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py g p , q p p y

Surface Tension

Very thin film of fluid in alveoli.

Absorb: Na+

active transport.Secrete: Cl- active transport.

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py g p , q p p y

Surface Tension

Surface tension:

H20 molecules at the surface are attracted to

other H20 molecules rather than to air.

Surface tension-> hard to expand the

alveoli.Small alveoli, more resistance to expansion.

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Measuring pulmonary function

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Pulmonary Function

Spirometry:

Breathe into a closed system, with air,water, moveable bell

Insert fig. 16.16

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Lung capacities

Vital capacity (VC): the most you can actuallyever expire, with forced inspiration andexpiration.

VC= IRV + TV + ERV

Total lung capacity: VC plus residual volume

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Pulmonary disorders

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Pulmonary disorders Stop

Restrictive disorder:

Vital capacity is reduced.

Less air in lungs.

Obstructive disorder:

Rate of expiration is reduced.

Lungs are fine, but bronchi are obstructed.

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Disorders

Restrictive disorder:

Black lung from coal mines.

Pulmonary fibrosis: too much connective tissue.

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Pulmonary Disorders

COPD (chronic obstructive pulmonarydisease):

AsthmaEmphysema

Chronic bronchitis

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Disorders

Asthma:Obstructive

Inflammation, mucus secretion, bronchial

constriction.Provoked by: allergic, exercise, cold and dry air

Anti-inflammatories, including inhaled epenephrine(specific for non-heart adrenergic receptors),anti-leukotrienes, anti-histamines.

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Disorders

Emphysema:

Alveolar tissue is destroyed.

Chronic progressive condition

Cigarette smoking stimulates macrophages and WBCto secrete enzymes which digest proteins.

Or: genetic inability to stop trypsin (which digestsproteins).

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Blood gases

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Blood gases

Barometers use mercury (Hg) asconvenience to measure total atmosphericpressure.

Sea level: 760 mm Hg (torr)

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Blood gases

Total pressure of a gas mixture is = to the sum of theindependent, partial pressures of each gas (DaltonsLaw).

In sea level atmosphere:

PATM = 760 mm Hg = PN2+ P02+ PC02 + PH20

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Blood gases

But inside you, the air is saturated with water vapor.PH20 = 47 mm Hg at 37 degrees

So, inside you, there is less P02:P02 = 105 mm Hg in alveoli.

In constrast, alveolar air is enriched in CO2, ascompared to inspired air.

PCO2 = 40 mm Hg in alveoli.

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Blood gases

Insert fig. 16.20

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Blood gases

Gas and fluid in contact:

[Gas] dissolved in a fluid depends directly on its partialpressure in the gas mixture.

With a set solubility, non changing temp.(Henrys law)

So

P02 in alveolar air ~ = P02 in blood.

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Blood gases

O2 electrodes can measure dissolved O2 in a fluid.(also CO2 electrodes.)

Good index of lung function.

Arterial P02 is only slightly below alveolar P02

Arterial P02 = 100 mm HgAlveolar P02 = 105 mm Hg

P02 level in the systemic veins is about 40 mm Hg.45



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Blood gases

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Blood gases

Most O2 is in hemoglobin

.3 ml dissolved in plasma +

19.7 ml in hemoglobin

20 ml O2 in 100 mls blood!

But: O2 in hemoglobin-> dissolved -> tissues.

Breathing pure O2 increases only the dissolvedportion.

- insignificant effect on total O2

- increased O2 delivery to tissues47



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Pulmonary Circulation

L ventricle pumps to entire body, R ventricleonly to lungs.

Both ventricles pump 5.5 L/min!

Pulmonary circulation: various adaptations.as a mellow river, doesnt spill over the banks

low pressure, low resistance.

prevents pulmonary edema.

pulmonary arteries dilate if P02 is low (opposite of systemic)

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Neural control

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Neural control

Respiratory centers

In hindbrain

- medulla oblongata

- pons

automatic breathing

Insert fig. 16.25

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Neural control

Also: voluntary breathing controlled by

cerebral cortex.

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Neural control

Ondines curse: only voluntary breathing.

Ondine: water nymph, punished by gods, must stay awake in orderto breath.

Or: she so cursed her philandering husband, after she gave upimmortality to join him, and he promised to love her with everywaking breath

http://www.silentpartners.org/sleep/sinfo/miscl/ondine.htm

Gene mutation in fetus:http://news.bbc.co.uk/1/hi/health/2996791.stm

Description:

http://www.medterms.com/script/main/art.asp?articlekey=9634

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http://www.silentpartners.org/sleep/sinfo/miscl/ondine.htmhttp://news.bbc.co.uk/1/hi/health/2996791.stmhttp://www.medterms.com/script/main/art.asp?articlekey=9634http://www.medterms.com/script/main/art.asp?articlekey=9634http://www.medterms.com/script/main/art.asp?articlekey=9634http://news.bbc.co.uk/1/hi/health/2996791.stmhttp://news.bbc.co.uk/1/hi/health/2996791.stmhttp://news.bbc.co.uk/1/hi/health/2996791.stmhttp://news.bbc.co.uk/1/hi/health/2996791.stmhttp://news.bbc.co.uk/1/hi/health/2996791.stmhttp://www.silentpartners.org/sleep/sinfo/miscl/ondine.htm


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Chemoreceptors

Oxygen: large reservoir attached to hemoglobin.

So chemoreceptors are more sensitive to changes in

PC02 (as sensed through changes in pH).

Ventilation is adjusted to maintain arterial PC02of 40mm Hg.

Chemoreceptors are located throughout the body (inbrain and arteries).

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chemoreceptors

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Hemoglobin

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Hemoglobin

Each hemoglobin has 4 polypeptide chains (2 alpha,2 beta) and 4 hemes (colored pigments).

In the center of each heme group is 1 atom of ironthat can combine with 1 molecule 02.

(so there are four 02 molecules per hemoglobinmolecule.)

280 million hemoglobin molecules per RBC!57


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Hemoglobin

Oxyhemoglobin:

Ferrous iron (Fe2+) plus 02.

Deoxyhemoglobin:

Still ferrous iron (reduced).

No 02.

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Hemoglobin

Carboxyhemoglobin:

carbon monoxide (CO) binds to heme insteadof 02

- smokers

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Hemoglobin

Can tell % of types of hemoglobin by color!

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Hemoglobin

Loading:

Load 02 into the RBC.

Deoxyhemoglobin plus 02 -> Oxyhemoglobin.

Unloading:

Unload 02 into the tissues.

Oxyhemoglobin -> deoxyhemoglobin plus 02.

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Hemoglobin

Loading/unloading depends on:

- P02

- Affinity between hemoglobin and 02- pH

- temperature

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Hemoglobin

Dissociation curve: % oxyhemoglobinsaturation at different values of P02.

Describes effect of P02 on loading/unloading.Sigmoidal

At low P02 small changes produce large

differences in % saturation and unloading.Exercise: P02 drops, much more unloading from veins.

At high P02 slow to change.

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O hemoglobin Dissociation


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Oxyhemoglobin DissociationCurve

Insert fig.16.34

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Hemoglobin

Affinity between hemoglobin and 02:

- pH falls -> less affinity -> more unloading

(and viceversa if pH increases)

- temp rises -> less affinity -> more unloading

exercise, fever

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Hemoglobin

Arteries: 97% saturated (i.e. oxyhemoglobin)

Veins: 75% saturated.

Arteries: 20 ml 02 /100 ml blood.

Veins: ~ 5 ml less

Only 22% was unloaded!Reservoir of oxygen in case:

- dont breathe for ~5 min

- exercise (can unload up to 80%!)68



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Hemoglobin

Fetal hemoglobin (F):

- gamma chains (instead of beta)

- more affinity than adult (A) hemoglobin

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Anemias

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Hemoglobin

Anemia:

[Hemoglobin] below normal.

Polycythemia:

[Hemoglobin] above normal.

Altitude adjustment.

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Disorders

Sickle-cell anemia:fragile, inflexible RBC

inherited change: one base pair in DNA -> one aa in

beta chainshemoglobin S

protects vs. malaria; african-americans

Thalassemia:

defects in hemoglobin

type of anemia

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Disorders

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RBC

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RBC

RBC

no nucleus

no mitochondria

Cannot use the 02 they carry!!!

Respire glucose, anaerobically.

(note: androgens stimulate erythropoiesis)

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Transport of CO2

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C02 Transport

H20 + C02

carbonic acid bicarbonate

H2C03 H+ + HC03

-

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C02 transported in the blood:

- most as bicarbonate ion (HC03-)

- dissolved C02- C02 attached to hemoglobin

(Carbaminohemoglobin)

C02 Transport

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C02 Transport

Carbonic anhydrase in RBC promotes usefulchanges in bloodPC02

H20 + C02 -> H2C03 ->HC03-

high PC02

CA

H20 + C02


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C02 Transport

Chloride shift:

Chloride ions help maintain electroneutrality.

HC03- from RBC diffuses out into plasma.

RBC becomes more +.Cl- attracted in (Cl- shift).

H+

released buffered by combining withdeoxyhemoglobin.

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Acid-base balance

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Acid-Base Balance

Ventilation is normally adjusted to keep pacewith metabolic rate, so homeostasis of bloodpH is maintained.

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Acid-Base Balance

Hyperventilation -> PC02 down -> pH of CSF up ->vasoconstriction -> dizziness.

If hyperventilating, should you breath into paperbag? Yes! It increases PC02!

Metabolic acidosis can trigger hyperventilation.

Diarrhea -> acidosis.

Vomit -> alkalosis.

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Adaptations

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Exercise

During exercise, breathing becomes deeper and more rapid.

Yet blood gas levels instantly stay about the same. Huh?!

Neurogenic: sensory response from muscles?

Humoral: homones?

Local differences we cant sense in a lab?

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Adaptations

Frequent exercise, or high altitudes ->series of changes in oxygenconsumption, or [hemoglobin], etc.

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8964301 Respiratory Physiology All and Complete

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