3.1 exchange surfaces and breathing Flashcards
what do cells need to survive
supply of oxygen
nutrients
remove waste products so they don’t build up and become toxic
what does and doesn’t need a specialised exchange system
small organisms don’t need one because their cytoplasm is close to the environment so diffusion is sufficient
large organisms need one because they have multiple layers of tissues so diffusion is not sufficient
what factors affect the need for a exchange system
size
surface area to volume ratio
level of activity
how does size affect the need for a transport system
small organisms cytoplasm is close to the environment so diffusion is sufficient
multicellular organisms have multiple layers of cells so the diffusion pathway is too long and too slow for supply to the inner cells
how does surface area to volume ratio affect the need for a transport system
small organisms have large SA/V ratio- SA is larger than V so diffusion is sufficient
Large organisms have small SA/V ratio- SA not sufficient for diffusion
Some organisms can adopt shapes to increase SA
Animals can’t bc they have a range of tissues and larger volume
how does level of activity affect the need for a exchange system
metabolic energy uses energy from food and oxygen
cells of active organisms need a good supply of O2 and nutrients for movement
energy is also needed to keep warm
some organisms are more active than others
what makes a good exchange surface
large surface area- space for molecules to pass thru
thin barrier- decrease diffusion distance
good blood supply- steep conc. gradient, diffusion fast
what is gas exchange like in animals
lungs and airways carry air in and out
AIR- NOSE-TRACHEA-BRONCHI-BRONCHIOLE-LUNGS
gas exchange takes place at alveoli (tiny air filled sacs)
lungs are protected by rubs and ribcage
intercostal muscles and diaphragm help produce breathing movements
how does gas exchange happen in the lungs
gas passes by diffusion through thin walls of alveoli
O2 passes from alveoli to blood in capillaries
CO2 passes from blood to air in alveoli
lungs maintain steep conc. gradient to continue diffusion
why are lungs a good exchange surface
surface area- alveoli is small but lots of them (high SA)
permeability- plasma membrane of alveolus and capillaries allow diffusion
Thin barrier- alveolus and capillary are 1 cell thick, squamous cells
Blood supply- blood system transports CO2 from tissues to lungs (CO2 in blood diffuses into alveoli) , blood transports oxygen away from lungs (lower than alveoli so O2 diffuses into blood)
Describe mammalian ventilation
breathing ventilates lungs and replaces old air w fresh air
gets rid of CO2 and brings in more O2
Conc of O2 is higher in alveoli than in blood
Conc of CO2 is lower in alveoli than in blood
conc gradient maintained
describe airways
large enough for sufficient air flow
supported to prevent collapse when air pressure is low
flexible for movement
goblet cells in epithelium release mucus to trap pathogens
describe trachea and bronchi
similar structure but bronchi are smaller
supported by C-shaped rings of cartilage- prevent collapse and allow flexibility and space for food to move down oesophagus
describe bronchioles
narrower than bronchi
they have a wall of smooth muscle and elastic fibres
smallest ones end in cluster of alveoli
describe alveoli
squamous epithelium
surrounded by blood capillaries
contain elastic fibres which stretch in inspiration and recoil in expiration
alveolus wall is thing
describe smooth muscle and elastic tissue
action of smooth muscle constricts the airway as lumen narrows which restricts flow or air
contraction of smooth muscle not voluntary (allergy)
smooth muscle elongated again by elastic fibres
muscle contraction deforms elastic fibres but when it relaxes, they recoil to their original shape and size
describe inspiration
diaphragm contracts and moves down and flatter
external intercostal muscles contract and raise ribs
volume of thoracic cavity increases
describe expiration
diaphragm relaxes and is pushed up
externcostal muscles relax and ribs fall
volume of thoracic cavity decreases
what do you measure lung volume with
spirometer
how does a spirometer work
consists of chamber of air floating on a tank of water
CO2 ruch air is passed through the chamber of soda lime which absorbs it- allows measurement of O2 consumption
what precautions should you take when using a spirometer
subject is healthy, free of asthma
soda lime fresh
nor air leave in apparatus
mouthpiece sterilised
water chamber not overfilled
what direction does the graph on a spirometer go
inspiring- down
expiring- up
why does the overall trace of the spirometer graph go down
soda lime absorbs CO2
when breathing we use up the O2 from the tank and the CO2 we breathe out is absorbed by the soda lime
gas volume of tank decreases over experiment by participant
explain tidal volume
volume of air that moves in and out of lungs with each resting breath
500cm3 in average adult
15% of vital capacity
explain vital capacity
the maximum volume of air that can be moved by the lungs in one breath
what factors does vital capacity depend on
size of person
age and gender
level of regular exercise
explain residual volume
volume of air that remains in lungs after forced expiration
approximately 1.5dm3
what does increased oxygen uptake result from
increased breathing rate
deeper breaths
describe fish ventilation
mouth opens (operculum closed)
buccal cavity floor is lowered- increases volume + decreases pressure of buccal cavity
water rushes into mouth down pressure gradient
opercular cavity expands
buccal cavity floor is raised- pressure in buccal cavity higher than opercular cavity
water moves from buccal cavity over gills into opercular cavity
mouth closes and operculum opens
sides of opercular cavity move inwards- increase pressure
water rushes out fish through operculum
what is the operculum
bony flag that covers and protects gills
define countercurrent flow
where two fluids flow in opposite directions and this maintains a favourable concentration gradient
define tracheal system
system of air filled tubes in insects
describe ventilation in insects
air enters system via spiracle (external opening)
air is transported into body via tracheae (series of tubes)
tracheae divined into smaller tubes- tracheoles which are open and filled w fluid called tracheal fluid
gaseous exchange happens between air in the tracheole and tracheal fluid
how can larger insects also ventilate their tracheal system
movements of the body
examples of how insects ventilate through movements of their body
- some have sections of their tracheal system which is expanded and flexible and repetitive expansion and contraction ventilates the system
- movements of the wings alter the volume of the thorax and when it increases the pressure drops so air is pushed in
- some can alter the volume of their abdomen by opening and closing valves in the spiracles which causes air to enter the tracheal system
