chapter 10 respiration

RESPIRATION

What Is Respiration?

We know that living cells need food in order to sustain life.

Food provides energy for the cell.The process of breaking down food

molecules to RELEASE energy in living cells is called respiration.

The main food substance used to provide energy is glucose

Anaerobic respiration does not require oxygen.

From these equations, we can see why living things take in oxygen and give out carbon dioxide.

Aerobic respiration requires oxygen.

Oxygen is taken in from the surroundings, and carbon dioxide is given out.

This is called gaseous exchange.In simple organisms like the Amoeba,

which consists of only one cell, the process is very simple.

Gaseous Exchange

Why Do We Need To Breathe?

Humans are large organisms made up of millions of cells.It is not practical for oxygen and carbon dioxide to diffuse

freely between the environment and all our cells.We have evolved a special system of organs to bring

these gases in and out of our bodies.The mechanism of this exchange of gases is also known

as external respiration to distinguish it from what happens in the cells, which is called cellular respiration.

This exchange of gases by the body is known as breathing.

The need for a respiratory system

The Human Respiratory System

Trachea (‘windpipe’)

Lungs

Diaphragm - separates chest from abdomen

Nasal cavity

Larynx (‘voice box’)

Pharynx

Structures of Chest in ContextThe expanded lungs fit neatly into the thoracic cavity, against the ribcage

with its intercostal muscles, and the diaphragm below. The pulmonary arteries bring deoxygenated blood from the right heart, and oxygenated blood returns to the left heart via the pulmonary veins

larynx

right pulmonary vein

branches of right pulmonary artery

right lung cut open to show structures inside

trachea

ribs

intercostal muscles

diaphragm

right bronchus

left lung

location of heart (removed)

A Look at Mr Q’s beautiful rib cage! WoW!


Trachea (‘windpipe’) which is supported by C-shaped rings of cartilage

Inside the lungs the bronchi divide further into a network of progressively smaller ‘tubes’ called bronchioles

Each bronchiole ends in a cluster of grape-like structures called alveoli

Branches into 2Right main bronchus leading to right lungLeft main bronchus leading to left lung

Passage of inspired air


Lung tissue is like a ‘sponge’, made up of thousands of tiny air sacs called alveoli.The alveolus is where gaseous exchange actually takes place.

The bronchioles leads to clusters of alveoli which look like grapes.

The whole structure of the lungs is designed to provide a very large surface area for gaseous exchange.

The wall of each alveolus is only one cell thick.

The inner surface is coated with a thin film of moisture.

It is supplied by a capillary whose wall is also only one cell thick.

This is the site where exchange of gases takes place!


3D Look at Alveolus!

A model of the breathing mechanism

The jar is sealed tight to create a vacuum, like the chest cavity.

When the rubber diaphragm is pulled down, the balloons expand, sucking in air from the outside due to negative pressure.

glass tube (trachea)

glass tube (bronchus)

balloon (lung)

rubber sheet (diaphragm)

bell jar (thoracic wall)

A model of the breathing mechanismTo take this example further, imagine each alveolus like a tiny balloon so the lung is a collection of many, many balloons all connected to the same network of tubes

Full expirationvery little air left in lungs. Alveoli collapse, lung is shrunken, diaphragm

pulled upwards

EquilibriumSome air in

lungs

Full inspiration-lungs (alveoli) fully inflated, diaphragm

pushed down

vertebral column

stemum

Internal intercostal musclesrib

external intercostal muscles

A model of the breathing mechanism

This model is not perfect because the rib cage is not representedUnlike the rigid gas jar, the rib cage can move to a certain extent, expanding and contracting the thoracic cavity with each breath

These diagrams illustrate how the ribs are able to move

position when breathing in

position when breathing out

stemum

external intercostal muscles

Mechanism of Breathing

rib

sternum

vertebral column

Front view Side view

When you breathe in or inspire, the following events take place:

Movement of rib cage during inspiration

rib cage


rib

sternum

vertebral column


• Your diaphragm contracts and flattens.


diaphragm contracts and flattens

rib cage


rib

sternum

vertebral column


• Your external intercostal muscles contract while your internal intercostal muscles relax.


rib cage



ribs and sternum raised

rib

sternum

vertebral column


Rib cage swings upwards and outwards

• Your ribs and sternum move upwards and outwards.


rib cage





rib

sternum

vertebral column


• The volume of your thoracic cavity increases.


rib cage



volume of thorax increases and lungs expand




rib

sternum

vertebral column


• Expansion of your lungs causes the air pressure inside them to decrease.

Movement of rib cage during inspirationSide view

rib cage



lungs expand, causing air pressure inside lungs to decrease




rib

sternum

vertebral column

Front view

• Atmospheric pressure is now higher than the pressure within your lungs. This causes air to rush into your lungs.


rib cage



lungs expand, causing air pressure inside lungs to decrease

air enters lungs

Side viewSide view


Mechanism of BreathingWhen you breathe out or expire, the following events take place:

rib

sternum

vertebral column

Side viewFront viewMovement of rib cage during expiration

rib cage

Mechanism of Breathing• Your diaphragm relaxes and arches upwards.

rib

sternum

vertebral column


rib cage diaphragm relaxes and arches upwards

Mechanism of Breathing• Your internal intercostal muscles contract while your external intercostal muscles relax.

rib

sternum

vertebral column




ribs and sternum lowered

rib

sternum

vertebral column

Ribs swing down

• Your ribs move downwards and inwards. Your sternum also moves down to its original position.

Front viewMovement of rib cage during expiration

Side view


ribs and sternum returned to original position



rib

sternum

vertebral column

Ribs swing down and decrease volume of thorax

• The volume of your thoracic cavity decreases.

volume of thorax decreases


Side view





rib

sternum

vertebral column


• Your lungs are compressed and air pressure inside them increases as the volume decreases.


lungs are compressed, causing air pressure inside lungs to increase

Side view





rib

sternum

vertebral column

Front view


Movement of rib cage during expiration

• Air pressure within the lungs is now higher than atmospheric pressure. The air is forced out of your lungs to the exterior.

lungs are compressed, causing air pressure inside lungs to increase

Side view


air expelled from lungs

Mechanism of BreathingWhat happens to your intercostal muscles when you are breathing?


When you inhale, you…

Relax your Internal intercostal muscles and Contract your External intercostal muscles

R

IC

E

What happens to your intercostal muscles when you are breathing?


When you inhale, you…

Relax your Internal intercostal muscles and Contract your External intercostal muscles

R

IC

E

&

ERI

C

What happens to your intercostal muscles when you are breathing?

When you exhale, your…

External intercostal muscles Relax and your Internal intercostal muscles Contract

The Mechanics of Breathing

Side view of movements in the thorax during inspiration and expiration

air in

rib cage is raised

volume of thorax increases, so air is drawn into the lungs

diaphragm contracts and flattens down

spinal column

Inspiration Expiration

rib cage drops down

volume of thorax decreases, forcing air out of the lungs

diaphragm relaxes and arches up

air out

spinal column

Inspired and Expired air

Inspired Air Expired AirOxygen 21% 16.4%Carbon dioxide

0.03% 4.0%

Nitrogen 78.0% 78.0%Water vapour

Variable Saturated

Temperature

Variable Body temperature

Dust particles

Variable Little, if any

Gaseous Exchange in the Alveolus

Adaptations for Gaseous Exchange in the Alveolus

1) Thin film of moisture

allows oxygen to dissolve in it diffusion of oxygen into blood capillaries is more efficient

2) Extensive network of blood capillaries

maintain concentration gradient as blood is brought towards and away from the capillaries quickly allows diffusion to gases into and out of alveoli / blood capillaries is more efficient

3) One celled thick capillary wall & one celled thick alveolar wall

reduce distance for movement of gases hence faster diffusion of gases into and out of the alveoli /blood capillaries

4) Numerous alveoli

increase surface area to volume ratio hence faster diffusion of gases into and out of the alveoli /blood capillaries


Deoxygenated blood carrying carbon dioxide

Oxygen-rich blood

Oxygen

Carbon dioxide

(which will go back to the

heart and enter the systemic circulation)

Inhaled oxygen

Carbon dioxide to be exhaled

capillary

alveolus

Oxygen dissolved in

mucous layer

diffuses through

alveolar and capillary

wallscapillary

alveolus

Carbon dioxide

gas to be exhaled

Binds to haemoglobin in red blood cells to

form oxyhaemoglobin

HCO3- ions in

plasma of blood

converted back to CO2 which

diffuses across barrier


Transport of O2 and CO2 in the blood

Oxygen is transported by haemoglobin in red blood cells. Haemoglobin is a protein which contains iron. Each Hb molecule can bind up to 4 oxygen molecules in a reversible reaction.

Oxygen Concentration and Haemoglobin

The binding of oxygen to haemoglobin molecules is dependent on the concentration of oxygen in the surroundings. In oxygen-rich areas (such as in the lungs), oxygen binds to Hb to form oxyhaemoglobin. In surroundings where the oxygen concentration is low (other organs eg muscles), the process is reversed and oxygen molecules are released.

This allows efficient transporting and distribution of oxygen

Low O2 concentration

High O2 concentration

Transport of O2 and CO2 in the blood

Carbon dioxide is transported in the plasma. The enzyme carbonic anhydrase converts the dissolved CO2 to form hydrogen carbonate ions, also in a reversible reaction.

More about aerobic and anaerobic respiration

What is the difference between the 2 equations?

Why does anaerobic respiration produce a smaller amount of energy per glucose molecule?

More about aerobic and anaerobic respiration (Explanation)

The energy released in respiration comes from the oxidation of glucose.

In aerobic respiration, the glucose molecule is completely used up. All 6 carbon atoms are oxidised to carbon dioxide.

In anaerobic respiration, the glucose is partially oxidised to ethanol. Not all the energy is released, as ethanol can actually be oxidised further.

Why use anaerobic respiration if it is less efficient?

The Uses of Anaerobic RespirationOrganisms such as yeast and bacteria may predominantly

respire anaerobically. This may come about because their habitat contains little oxygen

Anaerobic respiration of yeast cells is used in the baking of bread. Mixed in the dough, the yeast cells respire, using up the sugar present, and replicate at high speed. The carbon dioxide gas given off forms ‘pockets’ of gas in the bread, causing it to ‘rise’ and be light and spongy in texture

Yeast are also used in alcoholic fermentation to make beer, wine and other alcoholic drinks

Lactobaccillus bacteria is added to milk to make yoghurt. The lactic acid produced ‘separates’ the milk solids and gives the characteristic sour taste

Anaerobic Respiration in Humans

Why do our muscles ache after vigorous exercise?

What makes the pain go away after some time?

When exercised vigourously, muscles need a lot of energy. Even though we breathe faster and deeper than usual, they may not be able to receive enough oxygen fast enough to meet the demand for aerobic respiration

What happens then is that the muscle cells respire anaerobically

Anaerobic Respiration in Humans

Anaerobic respiration in human cells produces lactic acid. Lactic acid builds up in the muscle cells and causes muscle pain (called fatigue) when it reaches a certain concentration. This way of obtaining energy cannot be sustained for long.

The lactic acid must be removed by oxidation. This requires oxygen, thus the body is said to have incurred an oxygen debt.

During a period of rest, the body cells continue working ‘overtime’ to oxidise all the lactic acid thus ‘repaying’ the ‘debt’ and relieving the pain.

Energy is released Energy is stored in carbohydrate molecule

Oxygen is used, carbon dioxide and water are given off.

Carbon dioxide and water is used, oxygen is given off.

Occurs at all times in all cells, independent of chlorophyll and sunlight.

Occurs only in cells containing chlorophyll and in the presence of sunlight.

Results in a loss in dry masses.

Results in a gain of dry masses.

Differences between

Respiration and Photosynthesis

Function of Cilia

• Form a lining on the thin epithelium lining

• Cilia helps to sweep dust particles and bacteria up the bronchi and trachea into the pharynx to get swallowed into the oesophagus

Harmful Substances in Cigarette Smoke

Chronic bronchitis

Due to prolonged breathing of irritants

Chronic bronchitis

Inflammation of trachea, bronchi, bronchioles (airways)Cilia along the epithelium lining being paralysedIrritants are trapped in the mucus lining the

airwaysLeads to inflammationAirways become blocked, making breathing

difficultPersistent coughing, in order to clear airwaysThere is an increased risk of getting lung

infections

Emphysema

Due to persistent and violent coughing

Emphysema

Violent coughing breaks the partition walls between the alveoliSurface area for gaseous exchange will

decrease

Lungs also lose their elasticityAir is trapped in the lungs

Breathing becomes difficultPerson will wheeze and suffer from severe

breathlessness

What happens when a person suffers BOTH chronic bronchitis and emphysema?

This person is suffering from COPD!Chronic Obstructive Pulmonary Disease lah!

chapter 10 respiration

Health & Medicine

movement of rib cage

view rib cage swings

breathing mechanism

mechanism of breathing

rubber diaphragm

mr qs beautiful rib

inspiration lungs alveoli

external respiration