Breathing and Gas Exchange

Breathing and Respiration

Respiration is the oxidation of glucose

Breathing is the exchange of gasses in the lungs

Ventilation

Not Really The Respiratory System

Proper term should be the

Gas Exchange System

Composition of Air

Inhaled

Oxygen – 21%, Carbon dioxide – 0.04%, Nitrogen – 79%

Exhaled

Oxygen – 17%, Carbon dioxide – 4%, Nitrogen – 79%

Composition of Air

Exhaled is also saturated with 6% water vapour

Basic Structure

Larynx

Trachea

Bronchus

Bronchioles

Alveolus

Pleural membrane

Pleural fluid

Diaphragm

Basic Structure

The are found in the thorax of the body

You may be wondering why they are C-shaped and not full circles.

You can think of the trachea as a

tube lined with C-shaped supporting

rungs.

.

These rings are made

of a tough material

called cartilage. They

help to hold the tube

open.

Diagram of trachea with cartilage rungs

Organ 2 Organ 1

FRICTION

This friction could damage the tissue and kill cells.

Therefore, a protective bag called the pleural membrane surrounds the

lungs, which are likely to rub against other organs during the breathing

process.

Danger of friction

pleural membrane

lung

fluid

The pleural membrane

A fluid is found within this bag, surrounding the lungs.

This fluid lubricates the lining of the lungs and stops friction being

generated.

The Lungs

Regulate breathing

A route for water loss and heat elimination

Removal of CO2

Maintains acid-base balance

Enables speech, singing, etc.

Serves as defense mechanism

Affect chemical signals

Breathing

When you breathe in (inhale), your hands move up and outwards.

When you breathe out (exhale), your hands move down and inwards.

Take a breath

When we inhale, our lungs fill with air.

As they fill, they become enlarged.

The ribs must then move upwards and outwards to make

more room in the thorax.

The overall effect of this is that our chest expands.

Inhaling: chest expansion

Breathing

Air moves into and out of the lungs by changing volume

Volume is increased by the contraction of the diaphragm and the intercostal muscles

Intercostal Muscles

Your diaphragm is located beneath the lungs, which means that it separates

the thorax from the abdomen.

It is a sheet of muscle that

spans the width of the body.

inhaling

The diaphragm

Before we inhale, it is found in a dome shape.

As we inhale, it contracts and flattens.

The result of this change in shape is a

change in the volume of the thorax.

Low

High

Diaphragm flattens

Air pressure drops

Thorax volume increases

High air pressure outside

Low air pressure inside

Air diffuses into the lungs

As the volume of the thorax increases, the internal air pressure drops.

This means that the air pressure outside the lungs is greater than the air

pressure inside the lungs.

These changes can be summarised in the table below...

Feature Inhaling Exhaling

diaphragm shape flat domed

ribs up and out down and in

diaphragm muscle contracted relaxed

rib muscle contracted relaxed

lungs inflated deflated

Features of inhalation and exhalation

Click on the “Air Drawn In” buttons

Click on the “Passage of air” buttons

Control of Respiration

Chemoreceptors in the carotid arteries monitor pH of the blood

Control of Respiration

When CO2 production increases blood pH decreases.

Chemoreceptors sends a message to the diaphragm and intercostal muscles to increase breathing rate

Air Breathed

Tidal air – quiet breathing, ½ litre

Vital capacity – forced breathing, 3.5 litre

Residual air – can’t expelled, 1.5 litre

The lungs

Keeping Airways Clean

Cilia hairs

Mucus

ciliated cells

mucus being made by the ciliated cells

microbes travelling

down the trachea

within inhaled air

microbes become stuck

within the mucus

The presence of mucus and cilia on the lining of the trachea

ensures that the air we breathe is clean and free from disease.

.

swallowed

coughed out

Elevator action

Once the microbes are stuck in the mucus, the cilia move the mucus

upwards using a wafting action. The mucus passes up to the top of the

trachea where it can either be swallowed or coughed out of the body

Actually, each air sac is found to

be a bundle of air sacs.

Together, they are known as an

alveolus.

We can look inside the alveolus to get some idea of why they

are shaped the way they are.

The outside of the alveolus is

covered with tiny blood vessels.

Oxygen makes its way to special air sacs.

Inside an alveolus

Alveoli (air sacs)

provide large surface area for gas exchange

one lung equivalent to a tennis court of surface area using alveoli

Features of Alveoli for efficient

gas exchange

large surface area to absorb oxygen.

moist surface to allow oxygen to dissolve.

thin lining to allow easy diffusion of gases.

dense network of blood capillaries for easy gas exchange.

oxygen (O2) gas

passes through here

This O2 is then

able to dissolve in

a small moist

lining.

epithelial lining

of the alveolus

A cross-section of an alveolus

O2 O2

O2

O2

dissolve

dissolve

moist lining

This moist lining also stops the alveolus from drying and cracking. It

lubricates the insides of the air bag.

Keeping the environment right

Diffusion at work

After the oxygen dissolves it also diffuses.

O2 O2 O2 O2 cell lining of

alveolus

cell lining of

capillary

blood

D I F F U S I O N

The oxygen molecules must diffuse through both the lining of the alveolus

and the lining of the blood capillary.

They are eventually picked up by red blood cells.

Oxygen diffusion into red blood cells

Features of capillaries for

efficient gas exchange

dense network to carry CO2 and O2

Large surface area to transport gases

Lining is one cell thick so gases can pass through quickly and easily.

Carbon Dioxide

CO2 is transported as dissolved bicarbonate ions (HCO3) in the plasma

This formation occurs in the red blood cells.

Hemoglobin (Hb)

Four protein fractions

O2 binds to the iron heme group

Hemoglobin (Hb)

Binding increased by many different conditions:

Increase in pH

Decrease in Temperature

Increase in CO2

High altitude

Diffusion into Tissue

Why Do You Breath Faster When You Exercise?

Lung Diseases

Pollution

Cystic fibrosis

Bronchitis

Enemia

Lung Diseases

Smoking

Emphysema

Lung cancer

Carbon monoxide