Respiratory sys

7/30/2019 Respiratory sys

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RESPIRATORYSYSTEM


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Energy obtained through aerobic mechanisms that require oxygen and producecarbon dioxide

2 system that cooperate to supply O2 & remove CO2

cardiovascular & respiratory

Living cells need energy for:

maintenance

growthdefensereplication


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CARDIOVASCULAR SYSTEM

transports the respiratory gases.

circulating blood carries O2from the lungs >>>> peripheral tissues;

transports the CO2 >>>>>>> lungs

RESPIRATORY SYSTEMS

confined inside the lungs

provides for gas exchange difussion of gases between the air and the blood.


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It takes place in 3 basic steps:-

Pulmonary Ventilation

Gas Exchanged

Diffusion of O2& CO2between;

lungsblood[external respiration]

blood tissues [internal respiration]

exchange of gases betweenthe atmosphere, blood & cells.

Gas Transport

Transportation of O2and CO2


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FUNCTIONS OF THE RESPIRATORY SYSTEM

5 basic functions:-

Providing an extensive area for gas exchange between the air

and the circulating blood

Moving air to and from the exchange surfaces of the

lungs

Protecting respiratory surfaces from dehydration, temperature changes,or

other environmental variations and defending the respiratory system and

other tissues from invasion by pathogens

Producing sounds involved in speaking, singing, and

nonverbal communication

Providing olfactory sensations


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The respiratory system can be divided int

upper respiratory system

lower respiratory system

Nose, nasal cavity, paranasal sinuses, and pha

larynx (voice box), trachea (windpipe), bronchi,

bronchioles, and alveoli of the lungs

- filter, warm, & humidify the incoming air - cool &dehumidify outgoing air --- --protecting the moredelicate surfaces of the lower respiratory system

ORGANISATION OF THE RESPIRATORY SYSTEM

1bronchi

Larynx

Nose

Nasalcavity

Trachea

Lungs

Pharynx


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By the time air reaches the alveoli, most foreign particles and pathogens have beenremoved, and the humidity and temperature are within acceptable limits.

The success of this "conditioning process" is due primarily to the properties of therespiratory mucosa

The respiratory tract can be divided into

conducting portion

respiratory portion

- nose pharynx larynx trachea bronchi bronchioles(conduct air into the lungs)

- respiratory bronchioles the alveoli(gas exchange surface)

Filtering, warming, and humidification - begin at the entrance and continue throughout trest of the conducting system.


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The respiratory mucosa lines the conducting portion of the respiratory system

consists of an epithelium (ciliated with numerous goblet cells ) and loose connectivetissue

The Respiratory Mucosa

Goblet cell

Cillia

Stem cell


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the primary passageway for air entering the respiratory system made of cartilage & sk

Air normally enters through the paired external nares, or nostrils, which open into the ncavity.

The Nose and Nasal Cavity

Fn:- warming, moistening & filtering the incoming air; receiving olfactory stimuli; & servinglarge, hollow resonating chamber to modify speech sounds.

The vestibule - space contained withthe nose - contains coarse hairs thaextend across the external nares.

-- Large airborne particles, such as s

sawdust, or even insects, are trappedthese hairs and are thereby preventfrom entering the nasal cavity

The olfactory region, includes the arlined by olfactory epithelium (recept

provide sense of smell.


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a muscular chamber shared by the digestive and respiratory systems.

It extends between the internal nares and the entrances to the larynx and esophagus.

It can be divided into 3 anatomical regions:-

The nasopharynx fn/ in respiration

The oropharnxy

The laryngopharynx

The Pharynx

passageway that connects the pharynx with the trachea

Three large, unpaired cartilages form the body of the larynx:

the thyroid cartilage (Adams apple)

the cricoid cartilage connect larynx & trachea

the epiglottis - preventing the entry of liquids or solid food into respiratory tra

The Larynx

Serving as passageways for both air & food

Th l t i l f ld ( l d ) d d


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The larynx contains vocal folds (vocal cords) produce sound

The pitch of the sound produced depends on the diameter, length, and tension in the vocafolds.

children - slender, short vocal folds - voices tend to be high-pitched.

At puberty, the larynx of a male enlarges > a female. The true vocal cords of an adult male - thicker and longer - produce lower tones

# other structures are necessary for converting the sound into recognisable speech


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The Trachea

a tough, flexible tube - a diameter of about 2.5 cm & a length of ~ 11cm

extends from the larynx to the 1 bronchi

composed of smooth muscle & C-shaped cartilagciliated epithelium

cartilage rings keep the airway open & prevent itcollapse

The cilia sweep debris away from the lungs & bato the throat to be swallowed

Heimlich maneuver, or abdominal thrust tracheostomy & intubation


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The Primary (1) Bronchi

The trachea divides into the right & left primary bronchi.

A ridge called the carina marks the line of separation between the two bronchi

The bronchial tree consists of;

Trachea, 1 Bronchi, 2 Bronchi, 3 Bronchi, Bronchioles & Terminal Bronchioles

Walls of bronchi contains cartilage rings

Walls of bronchioles dominated by smooth musc


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Each tertiary bronchus branches several times giving rise to multiple bronchioles.

These branch further into the finest conducting branches, called terminal bronchioles.

Roughly 6500 terminal bronchioles are supplied by each tertiary bronchus.

The walls of bronchioles, which lack cartilaginous supports, are dominated by smooth mustissue.

Varying the diameter of the bronchioles provides control over the amount of resistance t

airflow and the distribution of air within the lungs. The ANS regulates & controls the diameter of the bronchioles.

Sympathetic - bronchodilation ( diameter)

Parasympathetic bronchoconstriction ( diameter)

Bronchoconstriction also occurs during allergic reactions such as anaphylaxis, in responsehistamine released by activated mast cells and basophils.

The Bronchioles


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Alveolus

Bronkus 3

Bronkus 1

Bronkus 2

Bronkiol

Rawan

Trakea


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o Paired organs located in the thoracic cavity; enclosed & protected by the pleural membra

- Parietal pleura (outer layer) attached to the wall of the thoracic cavity

- Visceral pleural (inner layer) covering the lungso Between the pleurae the pleural cavity filled with lubricating fluid

o Each lung is a blunt cone, with the tip, or apex, pointing superiorly.

o The lungs have distinct lobes separated by deep fissures.

The right lung - three lobes separated by 2 fissuresThe left lung - two lobes separated by 1 fissure + a depression, the cardiac notc

The Lungs

Al l D t d Al li


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Respiratory bronchioles are connected to individual alveoli and to multiple alveoli alongregions called alveolar ducts.

These passageways end at alveolar sacs, common chambers connected to multiple individu

alveoli

Alveolar Ducts and Alveoli

Alveoli are tiny thin-wall sacs where gas exchanoccurs.

Each lung contains about 150 million alveoli,and their abundance gives the lung an open,

spongy appearance.

An extensive network of capillaries is associatewith each alveolus.

The capillaries are surrounded by a network of elastic fibers.


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p y

This elastic tissue helps maintain the relativepositions of the alveoli and respiratorybronchioles.

Recoil of these fibers during exhalationreduces the size of the alveoli and helpspush air out of the lungs.

ALVEOLI & PULMONARY CAPILLARIES


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ALVEOLI & PULMONARY CAPILLARIES

The PULMONARY ARTERIEScarry deoxygenated blood from the heart to the lungs

These blood vessels branch repeatedly, eventually forming dense networks of capillaries t

completely surround each alveolus.

Oxygen and carbon dioxide are exchanged between the air in the alveoli and the blood in pulmonary capillaries.

Blood leaves the capillaries via PULMONARY VEINS, which transport oxygenated bloodback to the heart.

STRUCTURE OF AN ALVEOLUS

Alveoli contains 3 types of cells:-

Simple squamous epithelium cells (Type I cells)

Alveolar marcophages (dust cells)

Surfactant-secreting cells (Type II cells / septal cells)


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The wall of an alveolus is primarily composed of simple squamous epithelium cells (Type Icells).

They usually very thin & delicate.

Gas exchange occurs easily across this very thin epithelium.

Roaming alveolar macrophages patrol the epithelium phagotising any particulate matter thhas eluded the respiratory defenses & reached the alveolar surface.

Surfactant-secreting cells are scattered among squamous cells.

These large cells produce an oily secretion, or surfactant.

Surfactant lowers the surface tension of alveolar fluid, preventing the collapse of alveolwith each expiration.

* *Surface tension is due to the strong attraction between H2O molecules at the surface of liquid, whdraws the H2O molecular closer together.**

THE RESPIRATORY MEMBRANE


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At the respiratory membrane, the total distance separating the alveolar air and the bloocan be as little as 0.1 m.

Diffusion across the respiratory membrane proceeds very rapidly, because:

(1) the distance is small and

(2) both oxygen and carbon dioxide are lipid-soluble.

THE RESPIRATORY MEMBRANE

Gas exchange occurs across the respiratory membrane of the alveoli.

The respiratory membrane is a composite structure consisting of three parts:

The squamous epithelial cell lining the alveolus.

The endothelial cell lining an adjacent capillary.

The fused basement membranes that lie between the alveolar and endothelial c


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RESPIRATORY MUSCLES


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diaphragm

External

intercostals

RESPIRATORY MUSCLES

the most important respiratory muscles - the diaphragm and the external intercostals(inspiratory muscles).

These muscles are involved in normal breathing atrest.

The accessory respiratory muscles become activewhen the depth and frequency of respiration mustbe increased markedly.

rectus

abdominis

Serratus

anterior

sternocleidomasto

PULMONARY VENTILATION


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PULMONARY VENTILATION ~ physical movement of air into & out of the respiratory tract.

The primary function :-

# to maintain adequate alveolar ventilation (air movement into

& out of the alveoli)

Alveolar ventilation prevents the buildup of CO2 in the alveoli & ensure a continuous supply of O

Relationship between pressure & volume is important to understand this mechanical process

The pressure is related to the volume

Volume Pressure

Volume Pressure


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Gas pressure (P) is inversely prop ort ion alto volume (V)V - P

V - P

This relationship,

is called Boyles law, (Robert Boyle, 1600s)

Air flow area higher pressure area of lower pressure.

A single respiration cycle consists of :-

# Inspiration (inhalation)

# Expiration (exhalation)

P = 1/V


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Inhalation & exhalation involve changes in the volume of the lungs

These changes create pressure gradients that move air into & out of the respiratory tract.

Movements (contraction / relaxation) of the chest wall & diaphragm also have direct effect onthe volume of the lungs.

A respiratory cycle is a single cycle of inhalation and exhalation.

The tidal volume is the amount of air you move into or out of your lungs during a single respir

cycle.

It is related to changes in the intrapleural and intrapulmonary pressures

The Respiratory Cycle

INSPIRATION


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INSPIRATION

The volume of the thoracic cavity is change by muscle contraction

& relaxation.

During quite inspiration, the diaphragm & the external intercostal

muscles contract.

The diaphragm flattens & moves downward, while the external

intercostal muscles elevate rib cage & move the sternum forward.

These actions enlarge the thoracic cavity,

increasing the volume

decreasing the pressure within the thoracic

cavity & the lungs.


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air flows in

Volume

Poutside > Pinside

EXPIRATION


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Quite expiration is a passive process, in which;

As the diaphragm relax, it moves inward & as the external intercostal muscle relax ;

rib cage & sternum return to resting position.

the diaphragm & the external intercostal muscle relax

the elastic lungs &thoracic wall recoil inward.

These actions,

decreasing the volume

increasing the pressure within the thoracic cavity & the lungs.


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air flows out

Volume

Poutside < Pinside

Respiratory Rates


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Respiratory Rates

Respiratory rate is the number of breaths per minute.

The normal respiratory rate of a resting adult ranges from 12 to 18 breaths per minute

Children breathe more rapidly, at rates of about 18-20 breaths per minute.

INTRAPULMONARY PRESSURE (IPP) CHANGES


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( )

The direction of airflow - determined by the relationship between atmospheric pressurintrapulmonary pressure.

IPP/intra-alveolar pressure = the pressure measure within the alveoli

Between breaths, it equals atmospheric pressure - 760 mmHg at sea level.

~ generally refers as 0, when refer to the respiratory pressure.

On inhalation, the lungs expand, and the IPP drops to about 759 mmHg (negative pressu

Because the IPP is 1mm Hg below atmospheric, it is generally reported as -1 mmHg.

Since air moves from area of high pressure area of low pressure, air flows into the lu

At the end of the respiration, when the IPP = the atmospheric pressureair flows stop.


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On exhalation, the lungs recoil, and the IPP rises to 761 mm Hg, or +1 mm Hg (positivepressure)

Following pressure gradient, air flows out of the lungs until at the end of exhalation, whethe IPP = the atmospheric pressure.

INTRAPLEURAL PRESSURE

pressure in the space between the parietal & visceral pleurae.

Always negative (~ -4 mm Hg) - acts like a suction to keep the lungs inflated.

The negative pressure is due to 3 main factors:-

Surface tension of alveolar fluid

the surface tension of the alveolar fluid tends to pull each of the alveoli inward &therefore pulls the entire lungs inward.

>>>surfactant reduces this force


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Elasticity of the lungs

The abundant elastic tissues in the lungs tend to recoil & pull the lungs inward.

As the lungs moves away from the thoracic wall, the cavity becomes slightly larger,

decreasing the pressure The negative pressure acts like a suction to keep the lung inflated.

Elasticity of the thoracic wall

The elastic thoracic wall tends to pull away from the lung, further enlarging the pleucavity & creating this negative pressure.

The surface tension of pleural fluid resist the actual separation of the lungs & thorawall.

INTRAPLEURAL PRESSURE CHANGES


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As the thoracic wall moves outward during inspiration,

volume of the pleural cavity

intrapleural pressure

As the thoracic wall moves inward/recoils during expiration,

volume of the pleural cavity

intrapleural pressure

EFFECT OF PNEUMOTHORAX !!!!

What will happen to a lung if you cut through the thoracic wall????????

>>The lung will collapse IN THIS CASE when there is no pressure difference - there is no suction >>>lung collapse


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>> IN THIS CASE, when there is no pressure difference there is no suction >>>lung collapse.

INHALATION EXHALATION

+1

+2

0

-1

-2

-3

-4

-5

-6

Intrapulmonary

pressure

(mm Hg)

Intrapleural

pressure

(mm Hg)

SUMMARYINSPIRATION

EXPIRATION


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SUMMARY

AIR FLOW INTOTHE LUNGS

Lungs expandintrapulmonary pressure

drops (to -1mm Hg)

Intrapleural pressurebecome > negative

Thoracic cavityvolume increases

Inspiratory musclescontract (diaphragmdescends; rib cage

rises)

AIR FLOW OUTTHE LUNGS

Lungs recoilintrapulmonary pressure

rises (to +1mm Hg)

Intrapleural pressurebecome < negative

Thoracic cavityvolume decreases

Inspiratory musclesrelax (diaphagm

rises; rib cage descends)

FACTORS AFFECTING VENTILATION


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2 other important factors play roles in ventilation:-

resistance within the airways

lungs compliance

Resistance within the airways

As air flows into the lungs, the gas molecules encounter resistance when they strike t

walls of the airway.

Therefore, the diameter of the airway affects resistance.

What will happen when bronchiole constrict (diameter)????>>the resistance increases


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AIRFLOW =( )

RESISTANCE (R)

P - pressure difference between atmosphere

& intrapulmonary pressure.

in healthy lungs, the airways typically offer little resistance,so airflow flows easily into & out of the lungs.

Factors affecting airways resistance

Parasympathetic neurones released the Ach, which constricts bronchioles

>> resistance > resistance


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bronchioles

>> resistance >> occur in some pathologicalcondition such as fibrosis, in which increasing amount of less flexible

connective tissues developed.

(2) The level of surfactant production


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(2) The level of surfactant production

The collapse of alveoli on expiration, due to inadequate surfactant, as in

respiratory distress syndrome, reduces compliance.

without surfactant, alveoli have high surface tension, & they tend to collapse

(3) The mobility of the thoracic cage.

Arthritis or other skeletal disorders that affect the articulations of the ribs orspinal column will also reduce compliance.

GAS EXCHANGE


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Pulmonary ventilation ensures that alveoli are supplied with oxygen (O2), and it removes

the carbon dioxide (CO2) arriving from bloodstream.

The actual process of gas exchange occurs between the blood and alveolar air across threspiratory membrane.

O2 & CO2 diffuse between the alveoli & pulmonary capillaries in the lungs, & between t

systemic capillaries & cells throughout the body.

Things to consider:-

(1) the partial pressures of the gases involved and

(2) the diffusion of molecules between a gas and a liquid.

DALTONS LAW OF PARTIAL PRESSURE


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The air that we breathe is not a single gas but a mixture of gases :-

OXYGEN (O2)

- 2nd most abundant, ~ 20.9%

CARBON DIOXIDE (CO2)

- 0.04%

NITROGEN (N2)

- the most abundant, accounting for ~ 78.6% of the atmospheric gas molecules.

WATER (H2O)

- 0.46%

The combined pressure of these gases equals atmospheric pressure.

At sea level, atmospheric pressure is 760 mm Hg, represents the combined effects of

collisions involving each type of molecule in air.

Each gas within the atmospheric is responsible for part of that pressure in proportion

to its percentage in the atmosphere.

The pressure exerted by :-


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>

20.9% x 760 mm Hg = 159 mm Hg

This value is known as the partial pressu

O2 & it is written as Po2.

>

0.04% x 760 mm Hg = 0.3 mm Hg

>

78.6% x 760 mm Hg = 597 mm Hg

>

0.46% x 760 mm Hg = 3.5 mm Hg

The partial pressures of the 4 gases added together equal the total pressure exerted by

the gas mixture.

PO2 + PCO2 + PN2 + PH2O = 760 mm Hg

This relationship is known as Daltons law

Atmospheric pressure decreases with increasing altitude.


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eg. At altitude above 10 000, atmospheric pressure drops to ~ 440 mm Hg.

>

20.9% x 440 mm Hg = 92 mm Hg (PO2

at sea level = 159 mm H

- lower atmospheric pressure > fewer gas molecules & fewer oxygen molecules areavailable.

# that explained why you may gasp for breath at hig h alt i tude / feel l ight-headed #

>

0.04% x 440 mm Hg = 0.2 mm Hg

>

78.6% x 440 mm Hg = 346 mm Hg

>

0.46% x 440 mm Hg = 2 mm Hg

At high altitudes, the partial pressures of all gases are lower than at sea level.

HENRYS LAW : DIFFUSION BETWEEN LIQUIDS AND GASES


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Within the lungs, O2 & CO2 diffuse between the air & the alveoli & the blood,

i.e. between the gas & the liquid.

This movement is governed by Henrys law, which states that the amount of gas whichdissolves in a liquid is proportional to both :

the partial pressure of the gas

the solubility of the gas

At equilibrium, the pressure of O2 in the air is the same as in the liquid, with the gas

molecules diffusing at the same rate in both directions.


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The actual amount of a gas in solution at a given partial pressure and temperature

depends on the solubility of the gas in that particular liquid.

Carbon dioxide is very soluble, oxygen is somewhat less soluble, and nitrogen has very

limited solubility in body fluids.

pressure pressure

SITES OF GAS EXCHANGE


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Blood that is low in O2 (deoxygenated blood) is pumped from the right side of the hear

through the pulmonary artery to the lungs.

CO2 diffuses from the pulmonary capillaries into the alveoli.

O2 diffuses from the alveoli into the pulmonary capillaries.

EXTERNAL RESPIRATION (occur within the lungs at respiratory membrane)

O2

-rich blood (oxygenated blood) leaves the lungs & transported through pulmonary

vein to the left side of the heart.

From here, it is pumped through the systemic circuit to tissues throughout body.

INTERNAL RESPIRATION (occur within tissues)

CO2 diffuses from the tissues/cells into the capillaries

O2 diffuses from the capillaries into the tissues/cells.


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FACTORS INFLUENCING EXTERNAL RESPIRATION


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Gas exchange at the respiratory membrane is efficient for the following five reasons

The fusion of capillary and alveolar basement membranes reduces the distance to average of 0.5 m.

Inflammation of the lung tissue or fluid buildup inside the alveoli will increase the

diffusion distance and impair alveolar gas exchange.

The distances involved in gas exchange are small

the 300 millions alveoli covered with dense network of pulmonary capillaries provid

an enormous surface area for efficient gas exchange.

The total surface area is large

Both oxygen and carbon dioxide diffuse readily through the surfactant layer and t

alveolar and endothelial cell membranes.

The gases are lipid-soluble

The differences in partial pressure across the respiratory membrane


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This fact is important because the greater the difference in partial pressure, the faster

the rate of gas diffusion.

Conversely, if the PO2 in the alveoli decreases, the rate of oxygen diffusion into the

blood will drop.

Blood flow and airflow are coordinated.

This arrangement improves the efficiency of both pulmonary ventilation and pulmonar

circulation.

e.g., blood flow is greatest around alveoli with the highest PO2 values, where oxygenuptake can proceed with maximum efficiency.

If the normal circulation is impaired, as occurs in a pulmonary embolism, or the norma

airflow is interrupted, as in various forms of pulmonary obstruction, this coordination

lost, and respiratory efficiency decreases.

Partial Pressures in the Alveolar Air and Alveolar Capillaries


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Blood arriving in the pulmonary arteries has a lower PO2 and a higher PCO2 than does

alveolar air.

Diffusion between the alveolar mixture and the pulmonary capillaries thus elevates the Pof the blood while lowering its PCO2.

By the time the blood enters the pulmonary venules, it has reached equilibrium with the

alveolar air, so it departs the alveoli with a PO2 of ~ 100 mm Hg and a PCO2 of ~ 40 mm

Diffusion occurs very rapidly.

At rest, a red blood cell moves through one of pulmonary capillaries in ~ 0.75 sec.

During exercise, that passage takes less than 0.3 second.


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pulmonary capillary

Partial Pressures in the Systemic Circuit


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The oxygenated blood leaves the alveolar capillaries and returns to the heart, to be

discharged into the systemic circuit.

As it enters the pulmonary veins, the oxygenated blood from the alveolar capillariesmixes with blood that flowed through capillaries around conducting passageways.

The partial pressure of oxygen in the pulmonary veins therefore drops to ~ 95 mm Hg

& no further changes in partial pressure occur until the blood reaches the peripheral

capillaries.

Normal interstitial fluid has a PO2 of 40 mm Hg.

oxygen diffuses out of the capillaries and carbon dioxide diffuses in, until the capipartial pressures are the same as those in the adjacent tissues.

Blood entering the systemic circuit normally has a PCO2 of 40 mm Hg.

Inactive peripheral tissues normally have a PCO2 of about 45 mm Hg.

As a result, carbon dioxide diffuses into the blood as oxygen diffuses out.


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PO2=40


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PO2=40

Pco2=45

PO2=100

Pco2=40

PO2=100

Pco2=40

PO2=95

Pco2=40

PO2=40

Pco2=4PO2=40

Pco2=45

GAS TRANSPORT


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O2 & CO2 have limited solubility in blood plasma.

The limited solubilities of these gases are a problem because peripheral tissues need

more oxygen and generate more carbon dioxide than the plasma can absorb and trans

The problem is solved by th e red bloo d cel ls either bind them (in the case of oxygeor use them to manufacture soluble comp oun ds (in the case of carbon dio xide).

The important thing about these reactions is that they are

(1) temporary

(2) completely reversible.

Of the O that diffuses from the alveoli:

Oxygen transport


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1.5 % dissolves in plasma

98.5 % combines with hemoglobin (Hb) in red blood cells

Of the O2 that diffuses from the alveoli:-

each Hb molecule can bind 4 molecules of oxygen, forming oxyhemoglobin.

This is a reversible reaction can be summarised as :

Hb + O2 HbO2

lungs

tissues

~ 280 million molecules of hemoglobin in each RBC & since each hemoglobin moleculecontains four heme units,

each RBC potentially can carry more than a billion molecules of oxygen

C b di id i t d b bi t b li i i h l ti

Carbon Dioxide Transport


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Carbon dioxide is generated by aerobic metabolism in peripheral tissues.

After entering the bloodstream, a CO2 molecule may be

(1) converted to a molecule of carbonic acid,

(2) bound to the protein portion of hemoglobin molecules within RBCs, or

(3) dissolved in the plasma

All three are completely reversible reactions.

- Carbon dioxide is converted to carbonic acid through the activity of the enzyme

carbonic anhydrase within RBCs.

- The carbonic acid molecules immediately dissociate into a hydrogen ion and a

bicarbonate ion.

Carbonic acid formation

- Most of the carbon dioxide absorbed by the blood (~ 70 percent of the total) will be

transported as molecules of carbonic acid.

carbonic


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anhydraseCO2 + H2O H2CO3 H

+ + HCO3

~ 23 % of the carbon dioxide carried by your blood will be bound to the globular prote

portions of the Hb molecules inside RBCs.

These carbon dioxide molecules are attached to exposed amino groups (--NH2) of the molecules.

The result is called carbaminohemoglobin, HbCO2

Hemoglobin Binding

CO2 + HbNH2 HbNHCOOH (HbCO2)

Plasma becomes saturated with carbon dioxide quite rapidly and only about 7 % of the

Plasma Transport


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Plasma becomes saturated with carbon dioxide quite rapidly, and only about 7 % of the

carbon dioxide absorbed by peripheral capillaries is transported in the form of dissolv

gas molecules.

The rest is absorbed by the RBCs for conversion by carbonic anhydrase or storage ascarbaminohemoglobin

SUMMARY OF THE PRIMARY GAS TRANSPORT MECHANISMS


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CONTROL OF RESPIRATION

Normal breathing - rhythmic, involuntary


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g y , y

The respiratory muscles, however, are under voluntary control

The control of respiration is tied to the principle of homeostasis.

Body maintained homeostasis through homeostatic control mechanisms which have 3

basic components:-

RECEPTORS

CONTROLCENTERS

EFFECTORS

The principle factors that control respiration are chemical factors in the blood.

Changes in arterial PCO2, PO2 & pH are monitor by sensory receptor called

chemoreceptors.

The chemoreceptors send sensory inputs to respiratory centers in the brainstem,which determine the the appropriate respond to the changing variables.

Th t th d i l t th ff t th i t l t t


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The centers then send nerve impulses to the effectors, the respiratory muscles to contr

the force & frequency of contraction.

These changes the ventilation, the rate & depth of breathing.

Ventilation changes restored the arterial blood gases & pH to normal range.

Arterial PCO2, PO2 & pH

Chemoreceptors

RESPIRATORY

CENTERS

Respiratory muscles

ventilation

RESPIRATORY CENTER


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The basic rhythms of breathing is controlled by respiratory centers located in medulla &

pons of the brainstem.

Within the medulla, a pair group of neurones known as the inspiratory center/ dorsal

respiratory group (DRG) sets the basic rhythms by automatically initiating inspiration.

A 2nd group of neurone in the medulla, the expiratory center/ ventral respiratory group

appear to function mainly during forced expiration, stimulating the internal intercostal &

abdominal muscles to contract.

The neurones in the pneumotaxic area of the pons continously transmit impulse that

inhibit the inspiratory originating from DRG.

Respiratory sys

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