gas exchange surfaces Flashcards
(21 cards)
why does a high SA:V ration increase exchange of substances
- the alge surface area allows for maximum absorption of nutrients and gases and secretion of waste products
- the small volume means the diffusion distancee to all organelles is short
adaptions of the alveoli for gas exchange
- short diffusion distance because walls of alveoli are only one cell thick and these cells are flattened
- large number of alveoli - increases surface area available for diffusion
- extensive capillary network, allows for constant flow of blood which maintains the concentration gradient necessary for gas exchange
- ## good ventilation - breathing moves air in and out of the alvelo, helping maintain steep diffusion gradients
features of the human gaseous exchange system
- nasal cavity
- trachea
- bronchus
- bronchioles
- alveoli
features of the naval cavity
- large surface area with a good blood supply, which warms the air to body temperature
- a hairy lining, which secrets mucus to trap dust and bacteria
- moist surfaces, which increases the humidity of the incoming air, reducing evaporation from the exchange surface
features of the trachea
- wide tube supported by incomplete rings of strong, flexible cartilage, which stop the trachea from collpasing
- trachea and its branches are lined with ciliated epitelium with goblet cells between and below epithilial cells
—> goblet cells secrete mucus onto the lining of the trachea to trap dust and microorganisms that have escaped the nose lining
–> the cilia beat and move the mucus along with any trappped dirt and microorganisms, away from the lungs
bronchus features
similar in structure to the trachea, with the same supporting rings of cartilage but they are smaller
bronchioles features
- no cartilage rings, the walls contain smooth muscle
–> when the smooth muscle contracts, the bronchioles constrict and when it relaxes, the bronchioles dilate. <- this changes the amount of air reaching the lungs - ## lined with a thin layer of flattened epithlium, making some gaseous exhance possible
what happens during inspiration
- external intercostal mucles contract
- internal intercostal mucles relax
- ribcage moves up and out
- diaphragm contracts and flattens
- volume of thorax increases
- pressure inside thorax decrease
- air is drawn in
what happens during exhalation
- external intercostal muscles relax
- internal intercostal muscles contract
- ribcage moves down and in
- diaphragm relaxes and becomes dome-shaped
- volume of the thorax decreases
- pressure inside thorax increase
- air is forced out
explain ventilation mechanism in fish
- when the fish opens their mouth, they lower the floor of the buccal cavity
- this causes the volume inside the buccal cavity to increase, which casues a decrease in pressure within the cavity
- the pressure is higher outside the mouth of the fish and so water flows into the buccal cavity
- the fish then raises the floor of the buccal cavity to close its mouth, increasing the pressure within the buccal cavity
- water flows from the buccal cavity (HP) into the gill cavity (LP)
- as water enters, pressure begins to build up in the gill cavity and causes the operculum (a flap of tissue covering the gills) to be forced open and water to exit the fish
- the operculum is pulled shut when the floor of the buccal cavity is lowered at the start of the next cycle
what do goblet cells do for the gas exchange
goblet cells which line the airways secrete mucus.
the mucus traps microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli
what do cilia do for the gas exchange system
cilia are hair like structures on the surface of epithelial cells lining the airways
they beat mucus secreted by the goblet cells
this moves mucus (plus microorganisms and dust particles that its trapped) upward awat from the alveoli towards the throat, where its swallowed
this helps prevent lung infection
how do elastic fibres help in the gas exchange system
- elastic fibres in the walls of the trachea, bronchi, bronchioles and alveoli help the process of breathing out
- on breathing in, the lungs inflate and the elastic fibres are stretched. then, the fibres recoil to help push the air out when exhaling
how does smooth muscle help in the gas exchange system
allows vessels diameters to be controlled
during exercise the smooth muscle relaxes, making the tubes wider
this means theres less resistance to air flow and air can move in and out of the lungs more easily
how does cartilage help in the gas exchange system
rings of cartilage in the walls of the trachea and bronchi provide support. its strong and flexible - it stops the trachea and bronchi collapsing when you breath in and the pressure drops
what can a spirometer give readings of
- tidal volume (the volume of air in each breath, this is usually about 0.4dm3)
- vital capacity (the maximum volume of air that can be breathed in or out)
- breathing rate (how many breaths are taken per unit time)
- oxygen uptake (the rate at which a person uses up oxygen)
how do you use a spirometer
- a spirometer has an oxygen-filled chamber with a moveable lid.
- the person using the spirometer berathes through a tube connected to the oxygen chamber
- as the person breathes in and out, the lid of the chamber moves up and down
- these movements are recorded by a pen attached to the lid of the chamber - this writes on a rotating drum, creating a spirometer trace
- or the spirometer can be hooked up to a motion sensor which use the movements to produce electronic signals which are picked up by a data logger
- the soda lime in the tube the subject breathes into absorbs carbon diocide
why does the total volume of has in the chamber of a spirometer decrease over time
because the air that’s breathed out is a mixture of oxygen and carbon dioxide
the carbon dioxide is absorbed by the soda lime - so there’s only oxygen in the chamber which the subject inhales from
as this oxygen gets used up by respiration, the total volume decreases
how can you ensure validity of a spirometer reading
- the person using it must wear a nose clip
- this ensures that they can only breathe in and out through their mouth
- the machine must also be airtight
explain the structure of gills
- each gill is made of lots of thin plates called gill filaments or primary lamellae which gives a big surface area for exchange of gases (and so increase the rate of diffusion)
- the gill filaments are covered in lots of tiny structures called gill plates or secondary lamellae which increase surface area even more
- each gill is supported by a gill arch
- the gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion between the water and the blood
explain gas exchange and ventilation in insects
- insects have microscopic air filled pipes called trachaea which they use for gas exchange
- air moves into the trachea through pores on the surface called spiracles
- oxygen tavels down the concentration gradient towards the cells
- carbon dioxide from the cells moves down its concentration gradient towards the spiracles to be released into the atmosphere
- the trachea branch off into smaller tracheoles which have thin permeable walls and go to individual cells
- the tracheoles also contain fluid which oxygen dissolves in
- the oxygen then diffuses from this fluid into body cells
- carbon dioxide diffuses in the opposite directon
