3.1 exchange surfaces and breathing Flashcards
what 3 factors affect the need for exchange surfaces
size
surface area to volume ratio
level of activity
why can’t large organisms rely on diffusion only?
This is because they have a small surface area to volume ratio so cells in the center of the organism wouldn’t receive enough oxygen or nutrients due to the longer diffusion pathway.
Diffusion is too slow to enable a sufficient supply to the innermost cells
how does surface area to volume ratio change as the organism gets larger?
As size increases volume rises more quickly than surface area so a small organism may have a small surface area but an even smaller volume whereas in a large organism the surface area is relatively small compared to the volume
What does the surface area to volume ratio indicate?
A large SA:V means the surface area is large enough to supply all their cells with sufficient oxygen
how does the need for exchange surfaces change with level of activity
Metabolic activity uses energy from food and requires oxygen to release energy in aerobic respiration.
The cells of an active organism require a good supply of nutrients and oxygens to supply energy for movement.
What are the features of a good exchange system?
A large surface area to volume ratio
a thin barrier/ small diffusion distance
A good blood supply
how do you calculate surface area and volume in a cylinder?
volume = πr2 * height
surface area = (2πr*height)+2πr
How do you calculate the volume and surface area of a sphere
volume = 4/3πr3
surface area = 4πr2
describe how air enters the lungs
Air passes along the trachea, bronchi, bronchioles and finally reaches the alveoli
Describe what surrounds the lungs
The lungs are protected by the ribcage which are held together by the intercostal muscles.
The action of these muscles and the diaphragm helps to produce breathing motions
Describe gaseous exchange in the lungs
Gasses pas by diffusion through the thin walls of the alveoli. Oxygen passes from the air in the alveoli to the blood capillaries and carbon dioxide passes from the blood to the alveoli.
How are the lungs adapted for gas exchange?
barrier is permeable to O2 and CO2
thin barrier - short diffusion distance
A good blood supply
ventilation
Describe the barriers in the lungs
alveolus wall is one cell thick
capillaries are one cell thick
both walls consist of squamous cells
capillaries are in close contact with the alveoli
narrow capillaries causes the red blood cells to squeeze against its wall making them closer to the air in the alveoli
describe inspiration
Inhalation -
1- The diaphragm contracts to move down and become flatter
2- the external intercostal muscles contract to raise the ribs
3- the volume of the chest cavity is increased
4- the pressure in the chest cavity drops below atmospheric pressure
5- air is moved into the lungs
Describe expiration
Exhalation
1- the diaphragm relaxes and is pushed up by the displaced organs underneath
2- the external intercostal muscles relax and the ribs fall
3- the volume of the chest cavity is decreased
4- the pressure in the lungs increases above the pressure in the surrounding atmosphere
4- air is moved out of the lungs
What happens during coughing or sneezing
external intercostal muscles relax but internal intercostal muscles can contract to help push air out more forcefully
What are the airways and what are the 4 things they require to be effective?
trachea, bronchi, bronchioles
Be large enough to allow sufficient air flow without obstruction
supportive to prevent collapse during inspiration wen pressure is low
flexible in order to allow movement
the airways are lined with ciliated epithelium and goblet cells to trap pathogens
Describe the structure of the trachea and bronchi
They have a similar structure but the bronchi are narrower. These airways are supported by cartilage which prevent collapse
Cartilage in the trachea is C-shaped which allows flexibility and space for food to pass down the esophagus
Describe the structure of the bronchioles
Much narrower than bronchi and larger bronchioles may contain cartilage but the smaller ones do not.
They’re composed of a wall of mostly smooth muscle and elastic fibers
Describe the structure of the lung tissue
Comprised of alveoli with squamous epithelium and surrounded by blood capillaries
The alveolus walls contain elastic fibers to stretch during inspiration and recoil
Describe the function of the smooth muscle
They can contract and constrict airways controlling flow of air if there are harmful substances in it.
however, it is not a voluntary act and can’t reverse on its own
Describe the function of the elastic fibers.
Elastic fibers elongate the smooth muscle and dilate the airways.
When the muscle contracts it deforms the elastic fibers and as the fibers recoil it causes the muscle to relax
What is a spirometer
It is used to measure lung volume
What are the 4 precautions with using a spirometer
Subject should be healthy and asthma free
soda lime should be fresh and functioning
should be no air leaks in the machine
mouthpiece should be sterilised
Define tidal volume
The volume of air that moves in and out of the lungs with each resting breath
avg= 0.5dm3 500cm3
Define vital capacity
largest volume that can be inhaled and exhaled in one breath
inspiratory reserve volume + expiratory reserve volume
avg=5dm3
Define residual volume
volume of air left in the lungs when you have exhaled as much as you can
Define total lung capacity
sum of vital capacity and residual volume
Explain why the air in the spirometer drops slowly
Because the CO2 being exhaled is being absorbed by the soda lime but the student continues to inhale and absorb oxygen
what is the buccal cavity
The fish’s mouth
What are filaments
Slender branches of issue that make up the gill and are often called primary lamellae
What are the lamellae
folds of the filament to increase surface area
What is the operculum
Bony flap that covers and protects the gills
what is a spiracle
an external opening or pore that allows air in or out of the trachea
What is tracheal fluid
Fluid found at the end of tracheoles in the tracheal system in insects
What is the tracheal system
a system of air filled tubes in insects
What is special about the blood and water flow in a fish relating to gas exchange
It has countercurrent flow to maximise absorption of oxygen from the water
Describe the ventilation in bony fish
Bony fish keep water moving over the gills by changing pressure in the buccal cavity
When the fish opens it mouth the volume in the buccal cavity increases and pressure decreases so water is drawn in. The mouth closes and water is pushed through the gills
Movements of the operculum are co ordinated with movement of the buccal cavity
As water is pushed from the buccal cavity the operculum moves outwards reducing pressure in the opercular cavity helping water to flow through the gills
How does an insect inspire and expire
air enters the system via a spore in each segment called a spiracle and is then transported into the body with trachea which then divide into smaller tubes called tracheoles which contain tracheal fluid where gas exchange occurs
What happens to an insects tracheal fluid when more oxygen is required
The amount of tracheal fluid decreases in the tracheoles in order to increase the surface area of the tracheole wall exposed to air
in terms of energy how do inspiration and expiration differ
inspiration is an active process but expiration is passive
describe gaseous exchange at the alveoli
oxygen moves into the lungs and thus alveoli down a pressure gradient, red blood cells slow down as they move around the alveoli increasing diffusion time and oxygen will diffuse down it’s concentration gradient, from the alveolus cavity across two layers of epithelium and into the capillary, red blood cells are flattened against the capillary walls to reduce the diffusion distance and CO2 moves in the opposite direction, movement of air in and out of the lungs helps to maintain the concentration gradient
what is the purpose of residual volume
prevents airway collapse
what should tidal volume be able to do
should provide enough oxygen to tissues at rest
what are the gas exchange tissues and what is their purpose
ciliated epithelial cells and goblet cells trap and waft pathogens
elastic fibres stretch to expand lungs and recoil to push air out
smooth muscle controls diameter of airways by contracting and relaxing
cartilage provide support and prevents airway collapse
describe how to use a spirometer to find tidal volume
subject breathes normally and not through nose, measure amplitude of waves from the trace
(as you breathe in lid goes down and as you breathe out lid goes up )
measure at least three waves and calculate mean
how does smoking lead to development of a smokers cough
tar causes singeing of ciliated cells and more mucus is produced which accumulates and cannot be removed
How can excess coughing damage the lungs
it inflames alveoli and the elastic fibres, causing formation of scar tissue, airway walls thicken and the lumen narrows restricting air flow
