Chapter Seven: Exchange Surfaces And Breathing Flashcards
why are specialised exchange surfaces needed for multicellular organisms?
larger organisms will have:
- higher metabolic rate
- smaller sa:vol ratio
- longer distance from the outside of the organism is the middle
- therefore they need specialised exchange surfaces (adaptations) to increase the efficiency of exchange across their surfaces
why is diffusion enough to supply the needs of single-celled organisms?
- metabolic activity is low usually so oxygen demands and carbon dioxide production of the cell is relatively low
- SA:VOL ratio is large
what three structural features affect the rate of diffusion? give examples.
- surface area: root hair cells
- concentration gradient: ventilation, good blood supply
- length of diffusion pathway: alveoli wall (thin layer)
what are the main components of the mammalian gas exchange system?
- trachea
- bronchi and bronchioles
- alveoli
what are the features of the trachea?
- cartilage (c-shaped) for support
- ciliated epithelium with goblet cells
- smooth walls within the contract if harmful substances are in the air. this causes lumen to constrict which reduces air flow into the lungs
- when the smooth muscle relaxes, lumen dialates which allows it to stretch and recoil. this is possible due to the elastic fibres in the tracheal wall
what are the features of the bronchi and bronchioles?
- trachea splits into two tubes (bronchi)
- tubes split into smaller tubes, creating a network of bronchioles
- bronchi and bronchioles have cartilage in their walls for structural support and to keep tubes open
what are the features of alveoli?
- located at the end of the bronchioles, site of gas exchange
- oxygen diffuses from the alveoli into the blood in the capillaries, carbon dioxide diffuses from the blood in the capillaries to the alveoli
what features increase the rate of diffusion in alveoli?
- large surface area due to the amount of alveoli
- short diffusion distance due to alveoli walls ( very thin, made of squamous epithelial cells)
- maintains a concentration gradient due to all the alveoli being surrounded by a network of capillaries to quickly take away oxygen, and ventilation in the lungs is constant to quickly take away carbon dioxide
what is ventilation? what does is involve?
- the movement of air in and out of the lungs. it maintains the steep concentration gradient for gas exchange at the alveoli
- involves the diaphragm and antagonistic interactions between the external and internal intercostal muscles which bring about pressure changes in the thoratic cavity
define breathing
- the action of the muscles in the thorax to bring about pressure changes which leads to ventilation
explain the process of inspiration
- Diaphragm contracts
- Diaphragm flattens and lowers
- External intercostal muscles contract
- Ribs move up and out
- Volume of thorax increases
- Pressure in thorax decreases below atmospheric air pressure
- Air drawn in through nasal passages
- this process requires energy
explain the process of expiration
- Diaphragm muscles relax
- Diaphragm moves up
- External intercostal muscles relax
- Ribs move in and down
- Volume of thorax decreases
- Pressure of thorax increases higher than
atmospheric air pressure - Air moves out of the lungs
- passive process, doesn’t require energy
what does a spirometer do?
- measures the volume of air inhaled and exhaled
define these key terms: vital capacity, tidal volume, total lung capacity, residual volume, inspiratory reserve volume, expiratory reserve volume, breathing rate, and oxygen uptake
vital capacity: The maximum volume of air that can be breathed in or out in 1 breath, about 5dm cubed, but varies in men and women, and fitness
tidal volume: the volume of gas that moves in and out of lungs in each resting breath. About 0.5 dm cubed
total lung capacity: total volume of the lungs, about 6dm cubed
residual volume: volume of air left in lungs even after the largest possible exhalation, about 1.5dm cubed
inspiratory reserve volume: maximum volume of air breathed in over and above normal inhalation
expiratory reserve volume: maximum volume of air breathed out over and above normal exhalation
breathing rate: number of breaths taken per minute
oxygen uptake: the rate at which an organism uses up oxygen
how do you work out ventilation rate?
tidal volume x breathing rate
what is a spirometer?
- a machine that can give readings of tidal volume, vital capacity, breathing rate, and oxygen uptake
how can you analyse data from a spirometer graph? (breathing rate, tidal volume, vital capacity, and oxygen consumption)
- find out the breathing rate in the first minute
- find out the tidal volume
- find out the vital capacity on the graph
- oxygen consumption/ oxygen uptake can be read from the graph by taking the average slope of the trace
how are fish gills ventilated?
- fish opens mouth, which lowers floor of buccal cavity (space inside the mouth). volume of buccal cavity increases, pressure in cavity decreases. water is then sucked in
- fish closes mouth, floor of buccal cavity is raised again, volume inside the cavity is decreased, pressure increases in cavity, water is forced out the cavity and across the gill filaments
what is each fish gill covered by? what does it do?
- operculum
- operculum valve will shut and the operculum cavity will expand (as the fish gills are ventilated)
- this causes an increase in volume of the operculum cavity, therefore a decrease in pressure. the fish will then raise the floor of the buccal cavity which h forces the water over the gills within the operculum cavity
- finally, fish closes mouth and opens the operculum which increases pressure in the operculum cavity and forces water over the gills and out the fish’s head.
what do fish use for gas exchange?
- a counter-current system
what are the features of fish gills?
- use a diagram
- gill filament
- gill lamellae
- gill arch
- blood vessels (afferent and efferent)
what features of fish gills help aid it in gas exchange?
- large surface area: many gill filaments and lamellae stacked at right angles to each other
- short diffusion distance: gill lamellae and filaments both thin and contain a network of capillaries
- maintains steep concentration gradient using counter-current system
why do fish use the counter-current system?
- water has a lower dissolved oxygen concentration compared to the concentration of oxygen in the atmosphere, therefore for fish to be able to maintain the steep concentration gradient for diffusion they use the counter-current system
what is the counter-current system?
- where water flows over the gill lamellae in the opposite direction to the flow of blood in the capillaries.
-this ensures that water with a high concentration of oxygen always flows next to blood with a low oxygen concentration
