Respiratory Physiology

VentilationGas exchange

Oxygen uptake & utilization & removal of carbondioxide

From this study you should be able to:Describe the need to breath as a part of a metabolic process

Describe the function of the respiratory conducting zone

Describe pulmonary ventilation

Briefly explain how surface tension arises & is stabilized

Define lung volumes & lung capacities

Explain gas movement during external & internal respiration

Briefly describe neurological control of breathing with description of the stimulation of central chemoreceptor

State the role of Haemoglobin in gas movement

Explain how O2 & CO2 are carried in the blood

The Need to Breath The Primary function of the respiratory system is to supply oxygen

to the tissues of the body and to remove carbondioxide and to regulate acid base balance

Oxygen helps us to release energy from food we eat

Every cell in the body needs energy

Glucose + Oxygen = Energy + Carbondioxide + water + Heat (ATP)

From the atmosphere

Waste products of

energy production

Dealing with waste products

Carbondioxide + water

CO2 plus H2O= COO + HHO

H2 CO3

A weak acid substance

CARBONIC ACID

RespirationVentilation:

Breathing.

Gas exchange: Occurs between air and blood in the lungs. Occurs between blood and tissues.

Oxygen (02 ) utilization: Cellular respiration and removal of

carbondioxide

Respiratory System

Mucocilliary escalator

Mucocilliary escalator Covers most of the trachea, bronchi,

bronchioles and nose- consists of goblet cells and ciliated columnar epithelium

There is synchronous regular beating of cilia of the mucous membrane

Wafts mucous and adhered particles (dust, bacteria etc) up towards the larynx

Mucous is then expectorated or swallowed. Involved in non-specific immunity What happens in people who smoke?

The Pleura2 layers- Visceral & Parietal.

Intrapleural space

-a film of fluid-secreted by the pleura & NO AIR

The lungs remain in contact with the chest wall –allowing them to move with the thoracic cavity

Pleura

Pulmonary Ventilation:Inspiration and expiration

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Quiet Inspiration - Process

Contract your diaphragm, to achieve vertical expansion of your lungs.

Contract your Intercostal Muscles, to increase thoracic volume laterally.

Muscles of respiration

% of gases in inspired air

Oxygen-- 20-21 Carbondioxide – 0.04 Nitrogen - 78 Inert gases – 1% Water vapour - variable

% of expired air

Oxygen – 16 Carbondioxide- 4 Nitrogen = 78 Inert gases – 1 Water vapour – more on expiration

Pressure changes on Quiet InspirationAtmospheric pressure (at sea level) = 760 mmHg

The chest expands (actively)

Intrapulmonary press 757 mmHg so

air moves into the lungs

Pulmonary pressure rises by + 3 mm Hg.

Expiration Hold your breath-

After stretching the lungs (by contracting both diaphragm and thoracic muscles), the diaphragm and thoracic muscles relax & the thorax and lungs recoil

The decrease in lung volume raises the pressure inside to above 763mmHg This is greater than atmospheric pressure- so air moves out of the lungs.

Are your respiratory muscles getting tired?

Recap

Inspiration

Figure 22.13.1

Expiration

Inspiratory muscles relax and the rib cage descends due to gravity

Thoracic cavity volume decreases Elastic lungs recoil passively and intrapulmonary

volume decreases Intrapulmonary pressure rises above

atmospheric pressure (+1 mm Hg) Gases flow out of the lungs down the pressure

gradient until intrapulmonary pressure is 0

Lung expansion

BOYLE’S LAW.

THE RELATIONSHIP BETWEEN

THE PRESSURE AND VOLUME OF GASES

IS GIVEN BY BOYLE’S LAW.

IT STATES THAT WHEN THE

TEMPERATURE IS CONSTANT, THE

PRESSURE OF A GAS VARIES

INVERSELY WITH ITS VOLUME

PRINCIPLE 1Boyle’s Law

Changes in intrapulmonary pressure occur as a result of changes in lung volume.(Pressure of gas is inversely proportional to its volume).

Increase in lung volume decreases intrapulmonary

(alveolar) pressure. Air goes in.

Decrease in lung volume, raises intrapulmonary pressure above atmosphere. Air goes out.

animation

Dead SpaceAir passes thro’ 150 ml of space before reaching the respiratory zone.

Air is Warmed and humidified, Filters and cleaned: (Mucous traps particles )

Mucous moved by cilia to be expectorated.

Lung Volumes

Tidal volume

Volume of gas inspired/expired in an unforced breath

Inspiratory reserve volume

The maximum volume of air that can be inspired during

forced breathing

Expiratory reserve volume

The maximum volume of gas that can be expired during

forced breathing

Residual volume

The volume of gas remaining in the lungs after a maximum

expiration

Lung CapacitiesTotal lung capacity

The total amount of gas in the lungs after a maximum inspiration

Vital capacity

The maximum amount of gas that can be expired after a maximum inspiration

Inspiratory capacity

The maximum amount of gas that can be inspired after a normal tidal expiration

Functional residual capacity

The amount of gas remaining in the lungs after a normal tidal expiration

Peak Expiratory Flow Rate

The maximum flow at the outset of forced expiration

Spirometry

In obstructive lung disease, the FEV1 is reduced due to obstruction to air escape due to obstruction to air escape

Thus, the FEV1/FVC ratio will be reduced.. A diagnosis of airflow obstruction can be made if the FEV1/FVC < 0.7 (i.e.

70%) and FEV1 < 80% predicted. (NICE 2004)

Respiratory Zone

Where gas is exchanged between air and blood.

Gas exchange occurs by diffusion.

AlveoliClustered like a honeycomb.300 million air sacs.

Large surface area (60 – 80 m2).

Each alveolus is 1 cell thick.

2 types of cell:Alveolar type I:

Structural cells.Alveolar type II:

Secrete surfactant.

Lung alveoli and capillaries

Production of surfactant

Surface Tensiona property of the surface of a liquid that allows it to resist an external force

H20 molecules at the surface are attracted to other H20 molecules by attractive forces.

What could happen to alveoli if this was not corrected?

en.wikipedia.org/wiki/File:Amenbo_06f5520sx.jpg

Surfactant- reduces surface tension

A phospholipid produced by alveolar type II cells.

Function: Lowers surface tension.

Think of a detergent

Reduces attractive forces between H20 molecules.

As alveoli radius decreases, surfactant’s ability to lower surface tension increases- so the alveolus does not collapse

Principle 2 Gases move from an area of high concentration to

an area of low concentration

This movement is termed diffusion ( a passive process)

Gas movement relies on concentration gradients

Diffusion of gases

If I set off a stink bomb in the lecture theatre, those unfortunate to be near the front (an area of high concentration) would smell it. After a while the gases would attempt to fill the whole lecture theatre- the gases would diffuse from an area of high concentration to an area of low concentration (e.g. the back of the lecture theatre) when this occurs the molecules would be so far apart that no one would smell it.

Principle 3

Gas Exchange: Dalton’s Law Total pressure of a gas mixture is = to the sum of

the pressures that each gas in the mixture would exert independently.

Think of being in a crowded lift

Now think of Partial Pressure

43

Diffusion Gradients of Respiratory Gases at Sea Level

Total 100.00 760.0 760 760

H2O 0.00 0.0 47 47

O2 20.93 159.1 105 40

CO2 0.03 0.2 40 46

N2 79.04 600.7 569 573

Partial pressure (mmHg)

% in Dry Alveolar VenousGas dry air air air blood

NB. CO2 is ~20x more soluble than O2 in blood => large amounts move into & out of the blood down a relatively small diffusion gradient.

44

PO2 and PCO2 in Blood

External Respiration

Haemoglobin and 02 Transport

Each haemoglobin has 4 protein chains and 4 hemes.

Each heme has 1 atom iron that can combine with an 02 molecule.

C02 transported in the blood:

HC03- (70%).

Dissolved C02 (10%).

Carbaminohemoglobin (20%).

CO2 is ~20x more soluble than O2 in blood. There for

large amounts of CO2 move into & out of the blood more easity

C02 Transport

Internal Respiration

Recap-Blood P02 & PC02

P02 in systemic veins is about 40 mm Hg.

PC02 in systemic veins is 46 mm Hg.

After gas exchange, Arterial blood P02 is normally about 100 mm Hg & PC02 is 40mm Hg

Regulation of Breathing Neurons in the medulla

oblongata forms the rhythmicity center: Controls automatic

breathing. Brain stem respiratory

centers: Medulla. Pons.

Chemoreceptor Control

C02 + H2O

H+ cannot cross the blood brain barrier.

C02 can cross the blood brain barrier and will form Carbonic acid & then H+

H+H2C03HC03

What is this?Bicarbonate

H+ is the trigger for the chemoreceptors

This is Carbonic acid

Clinical relevance point 1Haemoglobin production controlled by

erythropoietin.

(Produced re P02 delivery to kidneys).

Loading/unloading of gas on Hb depends on: Hb level & capacity in the blood Enzymes: ↑ 2,3 DPG - increases unloading of O2 Temp: ↑Heat increases unloading of O2 Acid/base: ↓pH increases unloading of O2

This enzyme is produced when Hb is low

Questions What are the three functions of the respiratory system? In order, list all of the components of the respiratory system What is the function of epiglottis? What is the function of the cilia in the trachea? What surrounds the trachea and helps to keep it open? What is the role of surfactant in the lungs? What is the composition of air in %. Which law governs movement of gases in out of the lungs? A) Boyles law

or b) process of diffusion Where are the chemo-receptors situated? How does the respiratory system respond to increase in CO2 in the blood? In what form, can carbondioxide be carried in the blood? – see slide no 49

for answer In what form can Oxygen be carried in the blood? – see slide no 49 for

answer What is the name of chemical produced by the kidneys which stimulates

production of Red Blood Cells from Red Marrow?