3.7 exchange surfaces and breathing

do small organisms or large organisms have a larger SA:V ?

• small organisms

why is it it good that single celled organisms have a large SA:V?

• sufficient diffusion across the cell membrane to meet the needs of the organism

why do large multicellular organisms have exchange surfaces?

• have small SA:V

• not enough substances can diffuse in and out to supply the whole organism

what are root hair cells specialised for?

• absorbing water and minerals

what are a few adaptations of root hair cells

• large surface area so can absorb water and minerals

• mitochondria for respiration

how is the spongy mesophyll adapted?

• air spaces

• to increase the rate of diffusion of gases

how is the lower epidermis adapted?

• lots of stomata

• for gas exchange as CO₂ diffuses into leaf and CO₂ diffuses out

how is the alveoli adapted?

• each alveoli is made of a single layer of flat cells, providing a short diffusion distance

a good blood supply maintains a concentration gradient by taking the O₂

what are features of an efficient exchange surfaces?

• thin for short diffusion distance

• large surface area so lots of a substance can diffuse at once

• good blood supply to maintain a concentration difference

what does goblet cells do?

• secrete mucus to trap microbes and dust

what does cilia do?

• waft the trapped mucus

what are structural parts of the trachea?

• ciliated epithelium with goblet cells

• elastin fibres

• c-shaped cartilage

• smooth muscle

what are structural parts of the bronchi?

• ciliated epithelium with goblet cells

• elastin fibres

• smooth muscle

• small piece of cartilage

what are structural parts of the bronchiole?

• ciliated epithelium with some goblet cells

• smooth muscle and elastin fibres

what are structural parts of the alveoli?

• elastin fibres

• alveolar epithelium

• capillary

what is the purpose of cartilage?

• strong and flexible

• prevent them collapsing when the pressure drops when you breathe out

what is the purpose of smooth muscle?

• allows the diameter to be controlled

what is the purpose of elastin fibres?

• when you breathe in elastin fibres are stretched

• these recoil to help push the air out during exhalation

what sizes of bronchioles have smooth muscle?

• large

• medium

what sizes of bronchioles have elastin fibres?

• large

• medium

• small

what sizes of bronchioles have goblet cells?

• large

what sizes of bronchioles have epithelium with cilia?

• large

• medium

what is inspiration?

• breathing in

what is the process of inspiration?

1. external intercostal and diaphragm muscles contract

2. ribcage moves up and out, increasing the volume of the thorax

3. the lung pressure decreases

4. air is forced into lungs

This is an active process and requires energy

what is expiration?

• breathing out

what is the process of expiration?

1. external intercostal and diaphragm muscles relax

2. ribcage moves down and in

3. thorax volume decreases causing pressure to increase

4. air is forced out of lung

A passive process - no energy is required

what is forced expiration?

• active process

• internal intercostal muscles contract pulling ribcage down and in

what are parts of a spirometer?

why is a spirometer trace slanting down into successive cycles?

• O₂ is removed from spirometer

• CO₂ that you breathe out is absorbed so the chamber doesn’t rise as high

what is tidal volume?

• volume of air in each breath (about 0.4 dm³) at rest

what is vital capacity?

• the maximum volume of air that can be breather in or out

what is breathing rate (ventilation rate)?

• how many breaths are taken per unit of time (usually per minute)

what is oxygen uptake?

• the rate at which person uses up oxygen (dm³/min)

label a lung volume graph

what is pulmonary ventilation?

• measure of lung function

• the volume of air taken into the lungs in one minute

what is the equation for pulmonary ventilation?

why do fish have to pass large volumes of water over their gas exchange systems relative to volume of air ventilated by land animals?

• air has 20.9% oxygen

• water has 0.5% oxygen

• therefore more water is needed than air to get the same amount of oxygen

what is the suction pump phrase?

• inspiration

• water in

• buccal cavity extended

what is the pressure pump phase?

• expiration

• water out

• buccal cavity closed

why can fish extract as much as 80% of available oxygen though gills?

• very large surface area for gaseous exchange

• short diffusion distance across the gaseous exchange systems

• high concentration gradient between the blood in the gills and water passing over them

label this

• operculum flap (gill cover)

label this

• gill filaments

• usually 4 gill arches on each side of the fish

label this

label this

why are gill lamellae very thin?

• short diffusion distance between blood and seawater

how is concentration gradient maintained in exchange system in fish? (counter current exchange)

why is counter current exchange system good?

• relatively constant rate of diffusion

• concentration gradient is maintained along the whole length of lamellae

• always favours the movement of oxygen from water into blood

concurrent exchange (parallel) is used in dogfish why is this bad?

• blood and water moves in same direction so only 50% of oxygen is absorbed

do fish blood contain haemoglobin?

• yes

why do fish blood contain haemoglobin?

• helps to carry oxygen away from he gills and maintain a high concentration gradient

is the cuticle permeable or impermeable?

• impermeable

what is the purpose of the cuticle?

• prevent water loss from the body cells to the surroundings

what is the problem with the cuticle? How can it be solved?

• oxygen and carbon dioxide are unable to move through it

• spiracles

what are spiracles?

• small holes in he cuticle for gas exchange

label this of insect gas exchange structure

what do tracheoles contain?

• tracheal fluid

what happens related to tracheoles as activity increases?

• fluid is removed form tracheoles as muscle cells produce lactic acid which lowers water potential of the cells

• meaning gas exchange occurs nearer the cell=faster

how is the concentration gradient created in a insect gas exchange system?

• when cells are actively respiring, O₂ is used up

• the conc of O₂ towards the end of tracheoles falls

• this creates a diffusion gradient for O₂ towards the cells

what do CO₂ produced by cells make a diffusion gradient with?

• atmosphere

how does expiration take place for larger insects?

• muscles contract and flatten the body

• volume of the tracheal system decreases

• air is forced out

how does inspiration take place for larger insects?

• passive

• when body segments return to original shape

• air is forced in

why do some insects have ability to close spiracles using valves?

• reduce water loss

• or prevent excess oxygen from entering their cells

why is there a limit on the size of insects?

• due to tracheal system, all oxygen is obtained by diffusion

• efficient over small distances but only effective up to 1cm