exchange surfaces, gaseous exchange and ventilation in mammals and spirometer

why do large multicellular organisms need a circulatory system

• so oxygen can get to the middle of the body which is not possible with just diffusion through skin

• to remove carbon dioxide

• they have high metabolic rates so need to exchange lots of materials and fast

• small surface area to volume ratio

features of an efficient gaseous exchange system

• good blood supply and ventilation

• thin epithelium

• high surface area

features of alveoli

• ventilation creates steep concentration gradient

• blood capillaries to carry away oxygenated blood and maintain concentration gradient

• one cell thick wall to decrease diffusion distance

• fluid layer to maintain the shape of the air sacks so O₂ and CO₂ can pass through

what is surfactant and what does it do

• thin layer of moisture lining alveoli

• lost in evaporation as we breath out

• produced by the lungs

• reduces surface tension

• stops alveoli walls from collapsing

thin barrier as an adaptation to increase diffusion distance

• alveoli and capillary wall both one cell thick

• both walls consist of squamous cells

• capillaries in close contact with alveoli

• narrow capillaries so red blood cells are squeezed against capillary walls

good blood supply as an adaptation to increase diffusion

• helps maintain steep concentration gradient so gases continue to diffuse

• transports co2 from tissue to lungs so the co2 conc is always higher in the blood than the air in the alveoli

• transports o2 from lungs to tissues so o2 conc is always higher in the air of the alveoli than the blood

• ventilation ensures these concentration gradients

ventilation

breathing movements ventilate the lungs replacing the used air with fresh air and bringing in more oxygen and removing carbon dioxide

inspiration

breathing in

expiration

breathing out

inspiration in mammals process

1. diaphragm contracts and flattens displacing the digestive organs downwards

2. external intercostal muscles contract to raise the ribs

3. volume of the chest cavity is increased

4. pressure in the chest cavity drops below atmospheric pressure

5. air rushes into the lungs down a pressure gradient

expiration in mammals process

1. diaphragm relaxes and is pushed up into a dome by the displaced organs below

2. external intercostal muscles relax and the ribs fall

3. internal intercostals can contract to help push out air more forcefully during exercise, coughing and sneezing

4. volume of the chest cavity decreases

5. pressure of the chest cavity increases above atmospheric pressure

6. air is forced out of the lungs

trachea diameter

1.8cm

trachea features

• c shaped rings of cartilage

• goblet cells

• ciliated cells

• smooth muscle

• elastic fibres

why does the trachea have c shaped rings of cartilage

flexibility and space for oesophagus

bronchus diameter

1.2cm

bronchus features

• o shaped rings or cartilage

• goblet cells

• ciliated cells

• smooth muscle

• elastic fibres

why do bronchi have o shaped rings of cartilage

stability

bronchiole diameter and how many present

1mm

48000 present in sytem

bronchiole features

• goblet cells

• ciliated cells

• smooth muscle

• squamous epithelium

• elastic fibres

alveolus diameter and how many present

250 micrometres

3 billion present in system

alveolus features

• squamous epithelium

• elastic fibres

cartilage

irregular blocks that give strength and prevent collapsing during inspiration

smooth muscle

• involuntarily constrict airways if harmful substances are in the air

• prevent harmful substances entering alveoli and causing damage

elastic fibres

in alveolus walls so they can stretch during inspiration and recoil during expiration to help force the air out

goblet cells

release mucous to trap pathogens

ciliated epithelium

waft mucus up to the top of the airways to be swallowed or coughed out

labelled spirometer

what happens when you breath in from a spirometer

oxygen taken from the chamber and it sinks

what happens when you breath out form a spirometer

oxygen pushed into chamber and it floats

labelled spirometer trace

spirometer

• a device that can measure the movement of air into and out of the lungs

• these movements can be recorded on a kymograph

what is a data logger for a spirometer

picks up electric signals from a motion senser connected to the spirometer

what can the data logger of a spirometer give readings of

• vital capacity

• residual volume

• tidal volume

• breathing rate

• oxygen uptake

vital capacity

maximum volume of air that can be expelled from the lungs after taking the deepest breath possible (2.5-5dm³)

residual volume

the volume of air remaining in the lungs after maximum exhalation (1.5dm3)

how to calculate total lung volume

residual volume + vital capacity = total lung volume

tidal volume

volume of air inhaled or exhaled in one breath at rest (0.5dm3)

breathing rate

number of breaths per minute

oxygen uptake

volume of oxygen absorbed by the lungs in one minute

why do males have higher vital capacities

typically larger than females and have more of a need for oxygen to reach cells

why do athletes have higher vital capacities

they regularly reach their vital capacities during exercise making the elastic tissue stretchier and intercostals and diaphragm stronger

factors affecting vital capacity

• size of the person (particularly height)

• age and gender

• level of regular exercise

why does a spirometer use sodalime

• toxic carbon dioxide would accumulate if someone is constantly breathing in and out the same air

• soda lime absorbs co2 that is exhaled

how can the oxygen uptake from a spirometer be calculated with the help of sodalime

• as co2 is removed the volume if the gas in the spirometer will decrease

• co2 breathed out is equal to the volume of o2 used up by the person

• so o2 uptake can be calculated

calculation for oxygen uptake

reduction in chamber x 60 seconds / time taken for reduction

factors affecting lung capacity readings

• wearing a nose clip or holding nose to ensure you only breath in and out through your mouth

peakflow meters

measure how hard and fast you exhale

puff bags

measure tidal volume and vital capacity

how to calculate surface area to volume ratio

divide the surface area by the volume

explaining how a spirometer works

• oxygen filled chamber with moveable lid

• person breaths through a tube connected to the oxygen chamber

• lid moves up and down as the person breaths in and out

• movements recorded by a pen attached to the lid of the chamber on a rotating drum making a spirometer trace