Gas ExchangeGas Exchange

IB Learning Objectives

• Distinguish between ventilation, gas exchange and cell respiration

All Living things Respire.

Why living things must respire (breathe):

– Cellular Respiration – controlled release of energy in the form of ATP from organic processes in the cell

CC66HH1212OO66 + O + O22 ---> 6CO ---> 6CO22 + 6H + 6H220 + ATP0 + ATP

– Gas Exchange -- Exchange of gases (Oxygen, Carbon Dioxide) between an organism and it environments

– Ventilation - process of "changing" or replacing gas (Oxygen, Carbon Dioxide) in a space (ex: lungs)

IB Assessment Statement

• Explain the need for a ventilation system

6.4.2 Explain the need for a ventilation system.(3)

• A ventilation system is needed to maintain concentration gradients in the alveoli

• The steep concentration gradient across the respiratory surface is maintained in two ways: by blood flow on one side and by air flow on the other side. The ventilation system replaces diffuses oxygen (keeping the concentration high) and removes carbon dioxide (keeping the concentration low).

• This means oxygen can always diffuse down its concentration gradient from the air to the blood, while at the same time carbon dioxide can diffuse down its concentration gradient from the blood to the air.

IB Learning Objective

• Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli

Gas exchange in multicellular animals (i.e. Mammals)

• A ventilation system is a pumping mechanism that moves air into and out of the lungs efficiently, thereby maintaining the concentration gradient for diffusion.

Ventilation System of Mammals

• Lungs are housed in the thorax

• Thorax – an airtight chamber formed by the rib cage.

• The thorax is housed by ribs and its muscles called intercostal muscles.

Ventilation System of Mammals

• Diaphragm – A sheet of muscle that separated the thorax from the abdomen

• Pleural Membrane- internal surface of thorax, which secretes pleural fluid

• Pleural Fluid - is a lubricating fluid from blood plasma that protects the lungs from friction during breathing movements

LE 42-24

Rib cageexpands asrib musclescontract

Airinhaled

Lung

Diaphragm

INHALATIONDiaphragm contracts

(moves down)

Rib cage getssmaller asrib musclesrelax

Airexhaled

EXHALATIONDiaphragm relaxes

(moves up)

Ventilation System of Mammals

• Lungs connect to the mouth via the trachea

• The trachea divides into 2 bronchi, on to each lung

• Within the lungs the bronchi divide into even smaller bronchioles

LE 42-23

Branchfrompulmonaryvein(oxygen-richblood)

Terminalbronchiole

SEM

Nasalcavity

50 µ

m

Leftlung

Heart

Larynx

Pharynx

EsophagusTrachea

Rightlung

Bronchus

Bronchiole

Diaphragm

Ventilation System of Mammals

• The smallest bronchioles end in air sacs called alveoli. LE 42-23

Branchfrompulmonaryvein(oxygen-richblood)

Terminalbronchiole

Branchfrompulmonaryartery(oxygen-poorblood)

Alveoli

50 µ

m

Colorized SEMSEM

Nasalcavity

50 µ

m

Leftlung

Heart

Larynx

Pharynx

EsophagusTrachea

Rightlung

Bronchus

Bronchiole

Diaphragm

The Human Respiratory System

• Bronchioles subdivide into millions of tiny air sacs called alveoli.

Alveoli

Bronchiole

The Human Respiratory System

• Alveoli are grouped in clusters.

• Alveoli have thin, moist walls

• A network of capillaries surrounds each alveolus.

Pulmonary vein

Capillaries

Pulmonary artery

• Gas Exchange

• Gas exchange takes place in the alveoli.

Capillary

LE 42-23

Branchfrompulmonaryvein(oxygen-richblood)

Terminalbronchiole

Branchfrompulmonaryartery(oxygen-poorblood)

Alveoli

50 µ

m

Colorized SEMSEM

Nasalcavity

50 µ

m

Leftlung

Heart

Larynx

Pharynx

EsophagusTrachea

Rightlung

Bronchus

Bronchiole

Diaphragm

IB Learning Objective

• Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli

IB Learning Objective

• Describe the features of alveoli that adapt them to gas exchange.

• Gas Exchange

• Gas exchange takes place in the alveoli.

Capillary

LE 42-23

Branchfrompulmonaryvein(oxygen-richblood)

Terminalbronchiole

Branchfrompulmonaryartery(oxygen-poorblood)

Alveoli

50 µ

m

Colorized SEMSEM

Nasalcavity

50 µ

m

Leftlung

Heart

Larynx

Pharynx

EsophagusTrachea

Rightlung

Bronchus

Bronchiole

Diaphragm

Cellular Respiration and Gas exchange

Diffusion:

– Gas exchange between an individual cell and its environment takes place by diffusion

– Gases will diffuse (move) across the cell membrane from an area of high concentration to an area of low concentration.

• Gas Exchange

• Gas exchange takes place in the alveoli.

Capillary

LE 42-23

Branchfrompulmonaryvein(oxygen-richblood)

Terminalbronchiole

Branchfrompulmonaryartery(oxygen-poorblood)

Alveoli

50 µ

m

Colorized SEMSEM

Nasalcavity

50 µ

m

Leftlung

Heart

Larynx

Pharynx

EsophagusTrachea

Rightlung

Bronchus

Bronchiole

Diaphragm

Gas Exchange inside a cell example

• Gas Exchange

• Gas exchange takes place in the alveoli.

• Oxygen diffuses into the blood.

Capillary

O2

Gas Exchange inside a cell example

• Carbon dioxide in the blood diffuses into the alveolus.

Capillary

O2

CO2

Features of the Alveolus that make it great for gas exchange

• Large total surface area – 700 million in our lungs, providing 70m2 in total surface area. 30-40 times greater than the surface area of our skin

• Surface Area – greater the surface area faster the rate of diffusion.

Features of the Alveolus that make it great for gas exchange

• Walls of alveoli very thin, consisting of a single layer of flattened cells,

• Thin walls decrease the length of the diffusion path. The shorter the diffusion path the greater the rate of diffusion

• Thus the respiratory path must be as thin as possible.

• Walls of the alveoli have elastic properties meaning they can stretch during inhalation and then shrink back to their original size during exhalation.

Features of the Alveolus that make it great for gas exchange

• Surface of alveoli walls are covered with a film/ layer of moisture

• Oxygen gas dissolves in water lining of alveoli. Oxygen diffuses into the blood when it is dissolved in solution.

• Prevents the walls of the alveoli from sticking together

• Surrounded by a dense network of capillaries.

Features of the Alveolus that make it great for gas exchange

Alveoli is surrounded by a dense network of capillaries.

• Network of capillaries around each alveolus supplied deoxygenated blood from pulmonary artery and draining into pulmonary veins.

• This maintains the concentration gradient of O2 and CO2.

Gas exchange occurs across capillaries, whose walls are one cell thick

We have 50,000 miles of them

Red blood cells

Capillary wall

Few human cells are > 100 μm from a capillary

6.4.3 Describe the features of alveoli that adapt them to gas exchange.(2)

• Large surface area due to the combined spherical shape (600 million alveoli = 80 m2)

• Flattened epithelial cells of alveoli and close association with capillaries

• Short diffusion distance from alveoli to blood (0.5-1.0 um)

• Dense capillary network

• Moist surface for the solution of gases

Gas exchange Animations

Ventilation

•http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP15104

Gas exchange:

•http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter25/animation__gas_exchange_during_respiration.html

Repiratory system tutorials

http://www.getbodysmart.com/ap/respiratorysystem/menu/menu.html

Lung Transplant Ted Talk

https://www.youtube.com/watch?v=T2EmuyHoMAI

Opera Sing with a lung transplant

https://www.youtube.com/watch?v=cvO9i0QkQbE

IB Learning Objective

• Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal, muscles, the diaphragm and abdominal muscles

Breathing ventilates the lungs

The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air

LE 42-24

Rib cageexpands asrib musclescontract

Airinhaled

Lung

Diaphragm

INHALATIONDiaphragm contracts

(moves down)

Rib cage getssmaller asrib musclesrelax

Airexhaled

EXHALATIONDiaphragm relaxes

(moves up)

How a Mammal Breathes

• Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs

• The thorax is an air tight chamber, thus as volume changes in the lungs, so does pressure.

– Boyles Gas Law = P1V1=P2V2

How a Mammal Breathes

Inhalation (inspiration) – Volume increases

•Lung volume increases as the:

– External rib muscles (external intercostal muscles) contract and cause the rib cage to move up.

– and diaphragm contract (moves downs)

– Internal rib muscles (internal intercostal muscles) relax.

How a Mammal Breathes

Inhalation (inspiration) – Volume increases

•Ribs will move upwards & outwards increasing volume

•Diaphragm moves down increasing volume

•Increasing Volume, Lowers Pressure (Boyles Law)

•Air moves from high pressure to low pressure. Thus air will move from the atmosphere into the lungs.

How a Mammal Breathes

Exhalation – Expiration – Decreasing Volume

Lung volume decrease as the

– Internal rib muscles ( internal intercostal muscles) contract moving the rib cage up and out

– and diaphragm relaxes (moves up)

– Internal rib muscles (external intercostal muscles) relax.

• Decrease volume/ increases the pressure in the lungs and air is forced out

How a Mammal Breathes

Exhalation – Expiration – Decreasing Volume

• The ribs move downwards and inwards, and the diaphragm moves up.

• Volume is decrease

• Decreasing Volume, increasing Pressure (Boyles Law)

• Air moves from high pressure to low pressure. Thus, air from the lungs will be pushed towards the atmosphere.

LE 42-24

Rib cageexpands asrib musclescontract

Airinhaled

Lung

Diaphragm

INHALATIONDiaphragm contracts

(moves down)

Rib cage getssmaller asrib musclesrelax

Airexhaled

EXHALATIONDiaphragm relaxes

(moves up)

The respiratory system

When the diaphragm contracts, the chest cavity expands, and the lungs fill with air

Fig. 42.24