Bio B3 and B4 Review Flashcards
Define Gas exchange
the exchange (diffusion) of oxygen and carbon dioxide to and from the blood at the alveoli and the respiring tissues.
Define ventilation
the movement of air into and out of the lungs in two stages: inspiration and expiration. This is controlled by the movement of the diaphragm and ribcage.
State the location of gas exchange in humans
internally, which allows for gas exchange with the blood
Outline the mechanism of gas exchange in humans.
gas exchange occurs in small air sacs called alveoli inside the lungs
Describe how the structure of the alveoli increases surface area for gas exchange.
millions in number each with own netowkr of capillaries, membranes of alveoli and capillaries are very thin so diffusion path is short, surfaces are wet so gasses are dissolved.
Properties of gas-exchange surfaces
Permeable → oxygen and carbon dioxide can diffuse across freely
Large → the total SA is large in relation to the volume of the organism
Moist → the surface is covered by a film of moisture in terrestrial organisms so gasses can dissolve
Thin → the gasses must diffuse only a short distance, in most cases through a single layer of cells
maintenance of concentration gradients
Diffusion evens out concentration gradients, which could slow –>
In small aerobically respiring organisms, it is cell respiration that maintains concentration gradients
rate of ventilation
adjusted according to the carbon dioxide concentration of the blood
Fish:
Take in fresh water through their mouth and pump it over their gills then out through the gill slits
Outline the flow of air into the lungs.
the lungs in the trachea and bronchi and then to the alveoli in bronchioles
State the role of smooth muscle fibres in the bronchioles.
allows the width of airways to vary
bronchus and bronchioles
the bronchus branches repeatedly to form bronchioles
alveoli from bronchioles
Alveolar ducts branch off from the bronchioles, each leading to a group of five or six alveoli (air-sacs)
alveoli
surrounded by a dense capillary network, capillary wall is extremely thin –> air and blood are short distance
monolayer on the surface of the moisture lining the alveoli
Molecules form a monolayer on the surface of the moisture lining the alveoli, with the hydrophilic heads facing the water and the hydrophobic tails facing the air
This reduces the surface tension and prevents the water from causing the sides of the alveoli to adhere when air is exhaled from lungs
Prevents collapse of the lung