Exchange surfaces and breathing

what are the important features of the nasal cavity

• large SA

• good blood supply→ warms the air to body temperature

• hairy lining→ secretes mucus to trap dust and bacteria- protects lungs from irritation and infection

• moist surfaces→ increases humidity in air- reduces evaporation from the exchange surfaces

what does the trachea do

• main airway carrying clean, warm, moist air from the nose to the chest

• branches are lined with ciliated epithelium with goblet cells

describe the structure of the trachea

• wide tube

• supported by incomplete (c-shaped) rings of strong, flexible cartilage- stops the trachea from collapsing

• rings are incomplete so food can easily move down the oesophagus behind the trachea

what do goblet cells do

• secrete mucus onto the lining of the trachea

• traps dust and microorganisms that have escaped the nose lining

• cilia then beat to move the mucus away from the lungs→ most of this goes to the throat and is swallowed and digested

describe bronchus

• trachea divides to form the left bronchus leading to the left lung

• right bronchus leads to the right lung

• similar structure to the trachea with the same supporting cartilage

describe bronchioles

• no cartilage rings

• walls contain smooth muscle→ contracts to constrict the bronchioles

• when muscle relaxes→ bronchioles dilate

• changed the amount of air reaching the lungs

• lined with a thin layer of flattened epithelium- making gas exchange possible

describe alveoli

• tiny air sacs

• main gas exchange surfaces of the body

describe the structure of alveoli

• thin layer of flattened epithelial cells

• contains collagen and elastic fibres

• elastic tissues allow the alveoli to stretch as air is drawn in

• elastic recoil of the lungs- alveoli return to resting size to squeeze the air out

• coated with lung surfactant→ makes it possible for alveoli to remain inflated- 02 dissolved in water before diffusing into blood

what are the adaptations of alveoli

• large SA→ large area for gas exchange

• thin layers→ walls of one layer of single epithelial cells- diffusion distance is very short

• good blood supply→ constant flow of blood brings CO2 and carries of O2- maintains steep conc. gradient

• good ventilation→ maintains steep diffusion gradient between blood and air in lungs

describe the ventilation of lungs

• air is moved in and out of lungs due to pressure changes

what is the thorax

• chest cavity

• lined with pleural membranes- which surround the lungs

• space between the membranes is filled with a thin layer of lubricating fluid so the membranes can easily slide over each other as you breath

describe the rib cage

• semi-rigid case which protects the lungs

• pressure can be lowed with respect to air outside

describe the diaphragm

• broad, domed sheet of muscle

• forms the floor of the throax

what is inspiration

• taking air in

• active process

what is expiration

• breathing out

• passive process

describe forcible exhale

active process

describe the movement during inhalation

• diaphragm contracts, flattens and lowers

• intercostal muscles contract

• ribs move up and out

• volume of thorax increases- pressure is reduced

• air drawn in- equalises pressures inside and outside of chest

describe movement during exhalation

• diaphragm relaxes and moves up to become dome shaped

• intercostal muscles relax

• ribs move down and inwards

• elastic fibres of alveoli return to normal length

• volume of thorax decreases

• air moves out of lungs- pressure inside and out is equal again

describe what happens during an asthma attack

• cells lining the bronchioles release histamines- makes the epithelial cells become inflamed and swollen

• goblet cells make excess mucus

• muscles in bronchiole walls contract

• airways narrow and fill with mucus making it difficult to breath

describe the treatment of asthma

• relievers→ immediate relief of symptoms- chemicals similar to adrenaline

• attach to the active sites on surface membranes to muscle cells of bronchioles- making them dilate the airways

• preventers→ steroids, taken every day to reduce the sensitivity of the lining of airways

how can you use a peak flow meter to measure capacity of lungs

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

• often used by people with asthma to monitor how well their lungs are working

how can vitalographs be used to monitor capacity of lungs

• more sophisticated versions of peak flow meters

• patient breaths out as quickly as they can through mouthpiece- instrument produces a graph of the amount of air they breath out

what does a spirometer do

• commonly used to measure different aspects of lung volume or to investigate breathing patterns

what is tidal volume

• volume of air that moves into and out of the lungs with each resting breath

• usually about 500cm3

• uses about 15% of the vital capacity of the lungs

what is vital capacity

• the volume of air that can be exhaled when the deepest possible intake of breath is followed by the strongest possible exhalation

what is the inspiratory reserve volume

• maximum volume of air you can breathe in over and above a normal inhalation

what is expiratory reserve volume

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

what is residual volume

• the volume of air that is left in your lungs when you have exhaled as hard as possible

• cannot be directly measured

• usually 1 litre

what is total lung capacity

• the sum of the vital capacity and the residual volume

describe breathing rhythms

• the pattern and volume of breathing changes as the demands of the body changes

what is breathing rate

• the number of breaths taken per minute

what is ventilation rate

• the total volume of air inhaled in one minute

• ventilation rate= tidal rate x breathing rate

describe what happens during exercise to breathing rate

• tidal volume can increase from 15% to as much as 50% of the vital capacity

• breathing rate increases

• oxygen uptake during gas exchange increases to meet the demands of the tissues

describe how you read the graph of a spirometer

• inhale- trace goes down

• exhale- trace goes up

• oxygen in the tank decreases over time so overall line goes down

describe how to use a spirometer

1. person breaths in + out in tube- connected to tube of o2

2. exhaled air passes through a drum of soda lime (absorbs co2)

3. as the person breaths, the floating container of o2 floats and falls

4. a pen is attached to the floating tank- traces the movement onto a rotating drum of paper

5. oxygen in the chamber gradually used up over time

6. on a graph- inhale would go up, exhale would go down

why is diffusion alone enough to supply the needs of single celled organisms

• low metabolic activity

• o2 and co2 demands and production are low

• SA:V ratio is high

why do insects need a different way to exchange gases

• little to no gases can exchange in the exoskeleton

• don’t have blood pigments to carry oxygen

describe spiracles

• small openings

• located along the thorax and abdomen

what is the function of spiracles

• air enters and leaves the system

• water is also lost

• can be open and closed by sphincters

• kept closed as much as possible to minimise water loss- increases efficiency

whats the function of sphincters

• open and close the spiracles

describe the trachea in insects

• largest tubes in the respiratory system

• carry air into the body

• tubes are lined by spirals of chitin- keeps them open

describe chitin

• lines the trachea of insects

• makes up the cuticle

• relatively impermeable so little gas exchange takes place in the trachea

describe the tracheoles in insects

• an elongated cell with no chitin lining

• freely permeable

• run between individual cells in the insect

• give a large SA for gas exchange

describe tracheal fluid in insects

• limits the penetration of air for diffusion

describe what happens in insects when oxygen demands increase

e.g. during flying

• a lactic acid build up in the tissues leads to water moving out of the tracheoles by osmosis- exposes more SA for gas exchange

describe mechanical ventillation in insects

• air is actively pumped into the system by the muscular pumping movements of the thorax and abdomen

• changes the vol. of the body to change the pressure to draw air in

• done when there is a higher oxygen demand

describe collapsible enlarged tracheae or air sacs in insects

• act as air reservoirs

• increase the amount of air moved through the gas exchange system

• usually inflated and deflated by the ventilating movements of the thorax and abdomen

• done when there is a higher demand for o2

describe gills

• large surface area

• good blood supply

• thin layers needed for gas exchange

describe the operculum

• a protecting ayer over the gills

• active in maintaining a flow of water over the gills

how is gas exchange maintained at all times by fish

• fish need to maintain a continuous flow of water over the gills

how do fish maintain a flow of water over the gills

• opening their mouth and operculum

• buccal cavity is lowered which increases the vol. - pressure is lowered and water moves in

• floor of the buccal cavity moves up so the water moves over the gills

what are the adaptations to gills to increase gas exchange

• tips of the gill filaments overlap to increase resistance to flow of water- slows it down for more time for gas exchange to take place

• water move over the gills and blood in the gill filaments move in opposite directions- maintains steep conc. gradient for fast diffusion -countercurrent system

how do you dissect a fish head

• cut off the operculum using scissors

• cut out the gill arches out- observe the colour

• place the gill arch in water and observe the structures

describe the countercurrent exchange system in fish

• blood and water flow in opposite directions

• so oxygen concentration gradient between the water and blood is maintained along the gil

• oxygen can diffuse down the gradient so a much higher level of oxygen saturation of the blood is achieved

describe a parallel exchange system

• blood in the gills and water flowing over the gills travels in the same direction

• gives an initial steep oxygen concentration gradient between blood and water

• diffusion takes place until the oxygen conc. between the blood and water are at equilibrium- so then there is no net movement of oxygen into the blood