C7 - Exchange surfaces and breathing

Module 3

surface area

total surface over which substances and heat can be exchanged

volume of an organism determines

number of substances need to be taken in and transported out

• larger volume = more materials needed for metabolism

surface area to volume ratio

decreases with increasing organism size

large surface area

allows more of a substance to diffuse at the same time

• large sa:v in prokaryotes

• small sa:v in eukaryotes (much larger)

• eukaryotes need specialist organelles to meet needs (mitochondria)

adaptations to overcome decrease in sa:v

• thin membrane = reduces diffusion distance

• transport systems = creates higher conc. gradient e.g. blood vessels

• adaptations for heat transfer = large vascularised ears

exchange in single celled organisms

• obtain substances from their environment to be used in cell processes

• remove waste substances to avoid harm

body surface exchange in single celled organisms

• exchange substances using membrane

• can increase rate by inc. sa:v ratio

• can adapt to be wide+flat or have folds to increase ratio

• rapid diffusion rate

gas exchange surfaces

parts of the body/organism specialised for gas exchange

gas exchange surface in insects

tracheal system

• networks of tracheoles (small tubes) and spiracles

• most efficient gas exchange system in active animals

how does the tracheal system work

• tracheole tubes branch into cells

• tracheoles contain fluid, gases dissolve into it

• tracheal fluid moves further into the tissue when the insect is active

• so gas exchange happens closer to respiring cells

what improves the efficiency of the tracheal system (insects)

• thoracic and abdominal movements that moneys gases

• as diffusion doesn’t supply oxygen quick enough

spiracles

openings along the thorax and abdomen of insects that allow gas diffusion

• through spiracles into tracheoles

• or out of spiracles

gas exchange system in fish

• gills - thin tissue, highly branched and folded into lamellae

• operculum - covers gills

• buccal cavity

countercurrent system

process of gas exchange in fish

• gills have large sa for exchange

• fish mouth opens, filling buccal cavity (which inc in volume)

• opercula remains closed

• mouth closes, volume decreases, operculum opens

• water forces across gills

• oxygen in water diffuses into bloodstream

works due to counter current system

how does the counter current system work

blood flows through the lamellae the opposite direction of water through the girls

• maintains steep conc. gradient

lung system structure

• air enters from the trachea

• sa maximised

• trachea held open by cartilage (gap at back for oesophagus)

• trachea divides into 2 bronchi (cartilage and smooth muscle)

• bronchus divides into many bronchioles

• branch into alveoli (air sacs)

control of ventilation (mammals)

• ribcage

• intercostal muscles

• external intercostal muscles

• diaphragm

move to allow air in/out lungs

alveoli structure

• surrounded by capillaries = large sa to bloodstream

• alveolar epithelium is 1 cell thick = short diffusion distance

• quick transport of gases in bloodstream = maintains steep gradient

steps of human inspiration

• external intercostals contract

• diaphragm contracts, moves down

processes use energy

• ribcage moved up and out

• thoracic cavity vol. inc.

• lung pressure decreases

• creates pressure gradient

• air flows into lungs down gradient

steps of human expiration

• external intercostals relax

• diaphragm relaxes and moves up

• internal intercostals contract

contraction uses energy

• ribcage moves in and down

• diaphragm moves up

• thoracic cavity volume decreases

• lung pressure increases

• creates pressure gradient

• air flows out (down gradient)

what is used to measure lung function

a spirometer

what is a spirometer

measures the volume of air that is inspired/expired by an individual

• measures lung function

• measures tidal volume, breathing rate, forced expiratory volume, vital capacity and oxygen uptake

tidal volume

the volume of air in a normal breath at rest

• average 0.4 dm³ − 0.5 dm³

breathing rate

number of breaths a person takes per minute at rest

• average is 15 breaths per minute

forced expiratory volume

maximum volume an individual can expire in one second (not more than total gas volume in lungs)

• residual air always remains, keeps alveoli open

vital capacity

maximum volume of air that can be breathed in/out the lungs

oxygen uptake - VO2

maximum oxygen uptake a person is capable of

= oxygen consumption per Kg when exercising at highest capacity

• higher VO2 = fitter person.

• dangerous if person is unwell, pushes them too far

pulmonary ventilation rate equation

PVR = tidal volume x breathing rate

how does lung damage effects function

• decreases tidal volume

• causes shortness of breath

• occurs to smokers

residual air

The small volume of air that cannot be expired. This ensures the alveoli do not close.

what are the required practicals

dissections

features of nasal cavity

• large sa, good blood supply (warms air to body temp)

• hairy lining, secretes mucus to trap bacteria and protect delicate lung tissue

• moist, inc. humidity of incoming air, reducing evaporation from surface

means air enters lungs at similar temp and humidity to air already there

what is the trachea lined with

ciliated epithilium - goblet cells between

• goblet cells = secrete mucus to trap microorganisms

• cilia = best to move mucus away from lungs, to be digested

features of bronchioles

• smaller ones (1mm diameter or less) have no cartilage

• walls contain muscle

• muscle contracts = bronchioles dilate

• muscle relaxes = bronchioles restrict

• changes air reaching lungs

• contain some flattened epithelium for gas exchange

features of alveoli

• diameter 200-300um

• layer of thin epithelial cells and elastic fibres

• alveoli stretch when air drawn in, use elastic recoil to return to resting size

lung surfactant

the substance that makes it possible for alveoli to remain inflated, covers the inner surface of the alveoli (along with water and salts)

inspiratory reserve volume

maximum volume of air you can breathe in, over a normal inhalation

expiratory reserve volume

the extra amount of air you can force out your lungs over pr above the normal tidal volume of air you breathe out

ways to measure lung capacity

• peak flow meter

• vitalograph

• spirometer

what is a peak flow meter

measures the rate at which air can be expelled from the lungs

• used by people with asthma to measure lung function

what is a vitalograph

• more sophisticated than peak flow meter

• patient breaths out as quick as possible through a mouthpiece, instrument ctreyaes graph

• records amount of air and how quickly air is breathed out

= forced expiratory volume in 1 second

how a spirometer works

• nose clip and mouthpiece

• patient breaths in/out until all oxygen used up

• there is an airtight chamber filled with oxygen

• co2 produced is removed by canister of soda lime

• a trace is drawn on a revolving drum as the lid moves up and down

ram ventilation

ramming water past the gills, used in primitive cartilaginous fish e.g. sharks