Why do multicellular organisms need specialised exchange surfaces and single-celled organisms do not?
Because they are multicellular they have a smaller surface area:vol ratio. Exchange of substances via direct diffusion is too slow. So a transport system is needed to move substances to and from cells quickly.
1 of 9
Describe the features of an efficient exchange surface.
Large S/A. Thin (often 1 layer of epithelial cells) = short diffusion pathway. Maintains steep concentration gradient of gases. Good blood supply.
2 of 9
What are the features of the mammalian lung that adapt it to efficient gaseous exchange?
Many alveoli= large S/A for diffusion. Alveolar epithelium and capillary endothelium, only one cell thick=short diffusion pathway. Good blood supply to alveoli, constantly take 02, bring c02, air always refreshed, maintains concentration gradient.
3 of 9
What are the roles of each component of the lungs?
Goblet cells-secrete mucus, trap bacteria. Cilia- waft mucus up to throat, swallowed and killed by stomach acid. Elastic fibres- stretch and recoil during ventilation. Smooth muscle- controls diameter of tubes. Cartilage- prevent bronchi collapsing.
4 of 9
Describe inspiration.
Intercostal & diaphragm muscles contract, ribcage moves up and out, diaphragm flattens increasing vol of thorax, so lung pressure decreases below atmospheric level and air flows into lungs (active process).
5 of 9
Describe expiration.
Intercostal muscles relax, ribcage moves down and in, diaphragm becomes curved, thorax vol decreases, so air pressure increases (above atmospheric pressure), air forced out of lungs (passive process).
6 of 9
What is meant by tidal volume and vital capacity?
Tidal vol (TV)- vol of air in each breath, usually about 0.4dm3. Vital capacity- the maximum vol of air that can be breathed in or out.
7 of 9
How and what can a spirometer measure?
An 02 filled chamber (movable lid), subject breathes into tube, lid moves up&down, movement recorded by pen attached to lid, writes on rotating drum, creates spirometer trace (Soda lime-c02) Reads tidal vol, vital capacity, breathing rate & 02 uptake
8 of 9
What are the precautions of using a spirometer?
Mouth piece must be sterilised. Medical grade 02 must be used. People with asthma can't use them. Can't be done for long periods of time- vol of gas decreases, air breathed out=mix of 02+c02, c02 absorbed by soda lime, only 02 left (respiration).
9 of 9
Other cards in this set
Card 2
Front
Describe the features of an efficient exchange surface.
Back
Large S/A. Thin (often 1 layer of epithelial cells) = short diffusion pathway. Maintains steep concentration gradient of gases. Good blood supply.
Card 3
Front
What are the features of the mammalian lung that adapt it to efficient gaseous exchange?
Back
Card 4
Front
What are the roles of each component of the lungs?
Comments
No comments have yet been made