Transcript Gaseous Exchange File

GASEOUS EXCHANGE
AS PE
LEARNING OBJECTIVES
By the end of this lesson you will:
 Recap the mechanics of breathing and lung volumes
 Understand the process of diffusion
 Know how gaseous exchange takes place at the lungs and the muscles
RECAP
Complete the worksheet provided , explaining the processes of inspiration and
expiration both at rest and during exercise
1.
Is the process active or passive?
2.
Muscles involved and their role
3. Changes from rest to exercise
4. Additional muscles involved
Inspiration
Expiration
Air into the lungs
Rest
1. Diaphragm contracts downwards
2. External intercostals contract (between the ribs/outside
of them) – pull the ribs upwards and outwards –
ribcage
3. Combined movements above mean that thoracic cavity
area increases – air rushes in from outside environment
(high pressure) to lungs (now lower pressure due to
enlarged chest cavity)
Air out of the lungs
Rest
1. Passive process – does not need muscle contraction
2. Diaphragm and external intercostal muscles relax – rib
cage falls back inwards, recoils – thoracic volume
decreases – pressure increases – air flows out of the
lungs
3. Pressure inside chest higher than outside of body
During exercise
1. Active process
During exercise
2. Internal intercostals (inside of the ribs) – contract and
1. Diaphragm and external intercostals contract
pull the ribs down and in – thoracic volume smaller
2. Additional muscles help – pectoralis minor (contracts to 3. Diaphragm relax and create a dome shape
help top ribs move up and out to assist increasing area) 4. Abdominals – contract to aid diaphragm relaxing –
– sternocleidomastoid/scalenes – neck muscles (attach
decrease chest cavity quicker
on top sets of ribs – increase area)
5. Pressure builds inside thoracic cavity and air rushes out
3. Aim to make thoracic chest cavity greater, larger
volume of air in lungs
RECAP
In pairs, match the lung volume or capacity with the correct definition, value at rest
and the changes that take place during exercise
Complete the blank spirometer chart
LUNG VOLUMES AND CAPACITIES
GASEOUS EXCHANGE
Gaseous exchange is the exchange of gases at different parts of the body. There are two
sites for this:
1.
Between the air in the alveoli of the lungs and the blood surrounding alveolar capillaries
2.
Between the tissues / muscles of the body and the surrounding blood capillaries
The object of this exchange is to convert deoxygenated blood returning from the body into
oxygenated blood
PARTIAL PRESSURE (P)
Partial (part) pressure (p) is the pressure exerted by an individual gas when it exists
within a mixture of gases
The gas exerts a pressure that is proportional to its concentration within the whole gas
E.g. atmospheric pressure is composed of nitrogen (79%), oxygen (21%) and carbon
dioxide (0.03%) – together they exert a barometric (atmospheric) pressure of
760mmHg
P02 = 760mmHg x 0.21 = 159.6mmHg
DIFFUSION
Gases move from areas of high pressure to areas of low pressure
Diffusion is the movement of gases from areas of a higher partial pressure to a lower
partial pressure until equilibrium is reached
The difference in high and low partial pressure creates a pressure or diffusion
gradient
The larger the gradient, the greater the diffusion
GASEOUS EXCHANGE AT THE ALVEOLI
https://www.youtube.com/watch?v=AJpur6XUiq4
This process involves movement of oxygen and carbon dioxide between the alveoli of
the lungs and the surrounding capillaries
As blood circulates through the alveolar capillaries, oxygen is picked up from the
alveoli and carbon dioxide is lost to them so that it can be expired
GASEOUS EXCHANGE AT THE ALVEOLI
Blood entering the alveolar capillaries has a low partial pressure of oxygen
(40mmHg), compared to that in the alveoli (104mmHg)
Diffusion gradient = 104mmHg – 40mmHg = 64mmHg
What happens?
Oxygen diffused from the alveoli into capillary blood
GASEOUS EXCHANGE AT THE ALVEOLI
In the meantime, the partial pressure of carbon dioxide within the blood entering the
alveolar capillaries is relatively high (46mmHg), compared to that in the alveoli
(40mmHg)
What is the diffusion gradient?
46mmHg – 40mmHg = 6mmHg
What happens?
Carbon dioxide diffuses from the capillary blood into the alveoli until the pressure on
both sides of the respiratory membrane becomes equal
GASEOUS EXCHANGE AT THE MUSCLES / TISSUES
OXYGEN
Capillary membranes surrounding the
muscles, the p02 in the blood (105mmHg)
p02 in the muscle tissues is 40mmHg
Q: Where will the oxygen move from and
to?
CARBON DIOXIDE
The partial pressure of the carbon dioxide
from the heart arriving at the muscles is
40mmHg
The partial pressure of the Carbon dioxide in
the muscle is 46mmHg
Q: Where will the carbon dioxide move
from and to?
Move from the blood into the muscle tissue
Move from the muscle into the blood
GASEOUS EXCHANGE PROCESS
THE PROCESS OF GASEOUS EXCHANGE
OXYGEN IS INHALED AND DIFFUSES INTO THE BLOOD BECAUSE THE PRESSURE IS HIGHER IN THE
ALVEOLI THAN IN THE BLOOD
THE OXYGENATED BLOOD IS THEN PUMPED BY THE HEART TO THE WORKING MUSCLES WHERE IT
IS USED TO PRODUCE ENERGY
CARBON DIOXIDE ON THE OTHER HAND IS THE WASTE PRODUCT FROM ENERGY PRODUCTION
IN THE MUSCLES AND THEREFORE THE CONCENTRATION IN THE MUSCLES IS HIGH.
THE CARBON DIOXIDE MOVES FROM THE MUSCLE INTO THE BLOOD AND IS PUMPED BY THE
HEART TO THE ALVEOLI WHERE IT DIFFUSES INTO THE ALVEOLI AND IS THEN EXHALED
FACTORS INCREASING THE EFFICIENCY OF
DIFFUSION
 Large number of alveoli
 Large surface area of each alveoli
 Diameter of capillaries is very narrow – forces blood cells to travel through them
slowly – maximises diffusion of gases across the cell
 Short diffusion pathway – capillary walls one cell thick
 Large blood supply to the capillary network surrounding each alveoli and the
muscle cells
 Layer of moisture - allows the gases to dissolve and diffuse quicker
HOMEWORK
1. Complete the exam question provided
2. Create an information poster on gaseous exchange (use diagrams to support) –
pages 46-48 in your textbook. Your poster must have 3 questions (with answers)
on it that can be asked to the rest of the class to check their understanding of
gaseous exchange