Exchange surfaces and breathing Flashcards
Why are exchange surfaces necessary and what are three factors affecting need?
supply nutrients and remove waste, large organisms need exchange surfaces for more and efficient exchange
What are three factors affecting need for exchange surfaces?
sa:v ratio - cant supply enough nutrients from surface alone, diffusion pathway too far
level of activity - higher level requires more energy and oxygen
size - small animals diffusion through the surface can supply the whole body
Features of a good exchange surface (3)
Large surface area for more space for diffusion
Thin barrier which reduces diffusion distance
A good blood supply to maintain concentration gradient
Describe the pathway of air into the lungs
Through nose, along trachea, bronchi and bronchioles to the alveoli
What muscles/tissues protect and ventilate the lungs?
protected by ribcage, which is held together by intercostal muscles, and the diaphragm helps produce breathing movements
Describe gas exchange in the lungs
in the alveoli, oxygen passes into the blood and carbon dioxide diffuses out of blood into alveoli to be exhaled
State and explain the adaptations of the lungs for gas exchange (6)
Millions of alveoli give surface area
surfactant which counters cohesive forces preventing collapse and dissolves gases
Barrier permeable to carbon dioxide and oxygen
Diffusion distance reduced, capillary close to alveoli, rbcs squeeze through capillary, both have one cell thick walls which are squamous (flattened)
Good blood supply to maintain concentration gradient
Well ventilated maintaining concentration gradient
What is the role of the layer of surfactant in the alveoli?
counters cohesive forces preventing collapse, dissolves gases
How is the diffusion distance reduced in the alveoli?
capillaries close to alveoli, rbcs squeezed through capillary, walls one cell thick and squamous
How is the concentration gradient maintained in the alveoli?
good blood supply, always deoxygenated blood, good ventilation
Describe the process of inspiration (5)
inhaling -
diaphragm contracts, lowers and flattens, displacing digestive organs;
external intercostal muscles contract raising ribs;
volume of chest cavity increases;
pressure drops below atmospheric pressure;
air moves into lungs
Describe the process of expiration
exhaling -
diaphragm relaxes, digestive organs push up;
external intercostal muscles relax and ribs move down;
volume of chest cavity decreases;
pressure rises to above atmospheric levels;
air moves out of lungs;
internal intercostal muscles contract during exercise/coughing/sneezing to push air out
Describe the tissues in the lungs
alveoli comprised of squamous epithelium, surrounded by blood capillaries, walls contain elastic fibres, stretch during inspiration and recoil to help push air out during expiration
What is the role of elastic fibres in the alveoli?
stretch during inspiration and recoil to push out air during expiration
Describe the role of ciliated epithelium and goblet cells
line airways, goblet cells release mucus, traps pathogens, cilia wafts mucus to top of airway where swallowed and pathogen killed
Three requirements of the airways
large enough for sufficient air flow;
supported to prevent collapse
flexible to allow movement
Structure of trachea and bronchi
similar but bronchi narrower;
contain rings of c-shaped cartilage, allows flexibility and room for food to pass down the oesophagus
Structure of the bronchioles
Much thinner, some cartilage but mostly smooth muscle and elastic fibres
Role of smooth muscle and elastic fibres in the airways
smooth muscles can contract to restrict air flow, can be important when harmful substances in the air, elastic fibres recoil, dilating the airway
When would airways be constricted?
when harmful substance in air, during allergic reaction, during asthma attack
What is a spirometer and how is this used?
float chamber on top of water trough, moves up/down as person breathes, soda lime absorbs carbon dioxide and vol. of air slowly falls
What does a spirometer measure?
lung volume
Precautions for using a spirometer (5)
Subject healthy and asthma free;
soda lime fresh;
no air leaks for accurate results;
mouthpiece sterilised;
water chamber not overfilled
