3.1.1 exchange surfaces Flashcards
why don’t unicellular organisms need specialised exchange surfaces
big SA compared to volume and shorter distance from outside to middle
substances can diffuse across a short diffusion pathway straight into the cell
why do multicellular organisms need specialised exchange surfaces
they have a lower SA:V ratio as they are bigger
higher metabolic rate
longer distance from outside to middle
so need a specialised system for efficient exchange
what are the features needed for efficient gas exchange
large SA
thin wall for short diffusion pathway
good blood/gas supply to maintain steep conc. gradient
what is fick’s law
(large SA x steep conc. gradient)/short diffusion distance
what are the features of the mammalian gas exchange system
trachea
bronchi
bronchioles
alveoli
lungs
ribs
intercostal muscles
diaphragm
what does cartilage do
prevents collapse of the trachea, bronchi and lungs during exhalation
what is the trachea and it’s function
the ‘windpipe’
made of:
incomplete c-shaped rings of cartilage
ciliated epithelium with goblet cells
smooth muscle that can stretch and recoil the lumen due to elastic fibres
what are the bronchi
2 extensions of the trachea
cartilage within their walls
narrower and lined with loose tissue and elastic fibres
what are the bronchioles
narrower than bronchi
made of smooth tissue and some cartilage
what are the alveoli
site of ventilation
small air sacs with walls of squamous epithelium (short diffusion distance)
provides large SA
step concentration gradient, surrounded by capillaries
what do the ribs do
protect lungs
what do the intercostal muscles do
contract and relax to raise or lower the ribcage
what are the lungs used in
inspiration and expiration
what does the diaphragm do
contracts and relaxes
separates lungs from abdomen
what does ciliated epithelium do
moves mucus along
what do goblet cells do
secrete mucus
what does smooth muscle do
controls diameter and airflow into alveoli
what do elastic fibres do
stretch in inhalation and recoil in exhalation
describe the process of inspiration
diaphragm contracts
external intercostal muscles contract / internal intercostal muscles relax
ribcage raises
volume of thoracic cavity increases
pressure in thoracic cavity decreases below atmospheric pressure
air flows into the lungs down the pressure gradient
describe the process of expiration
diaphragm relaxes
external intercostal muscles relaxes / internal intercostal muscles contract
ribcage lowers
volume of chest cavity decreases
pressure in chest cavity increases above atmospheric pressure
air flows out of the lungs down the pressure gradient
what is a bell jar
apparatus used to demonstrate the process of inspiration and expiration in mammals
balloons = lungs
glass pipe = trachea
elastic sheet = diaphragm
glass jar = ribcage
how does ventilation work in the alveoli
oxygen rich air is delivered by air and goes into the blood by diffusion across the squamous epithelium and endothelial cells
carbon dioxide is delivered by the blood by diffusion and removed by expiration
what is a spirometer
apparatus used to measure lung volume e.g. volume of air inhaled/exhaled
what are the components of a spirometer
airchamber containing water
soda-lime in a canister to absorb carbon dioxide
mouthpiece
