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Exchange Surfaces – Module 3.1

Exchange Surfaces By Esha Sandhu Exchange and Transport Module 3.1

Esha Sandhu

Exchange Surfaces – Module 3.1

Specialised Exchanged Surfaces Organisms exchange substances with their environment: 

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Every organism needs to exchange things with its environment o Cells need to take in things like oxygen and glucose for aerobic respiration and other metabolic reactions o They also need to excrete waste products from these reactions, such as Carbon dioxide and urea How easy the exchange of substance is depends on the organisms SA:V ratio

Surface Area : Volume Ratios:  

Smaller animals have bigger SA:V Ratio A mouse has a bigger SA:V ratio then hippos, this can be proven mathematically

Single Celled Organisms:  

Substances can diffuse directly in or out of the cell across the cell surface membrane Diffusion rate is quick, because of the small distances the substances have to travel

Multicellular Organisms: 

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Diffusion across the outer membrane is too slow, this is due to several reason such as: o Some cells are deep within the body, so there is a greater distance between them and the outside environment o Larger animals have a lower SA:V ratio – so its harder to exchange enough substances to a large volume with a small surface area o Multicellular organisms have a higher metabolic rate than single-celled organisms, so they use up oxygen and glucose faster Therefore multicellular organisms need Specialised Exchange surfaces

Esha Sandhu

Exchange Surfaces – Module 3.1

Special Features of Exchange surfaces: 

Exchange surfaces have special features, which enables them to improve the efficiency

1. Large Surface area For Example: ROOT HAIR CELLS    

Root hair cells have long ‘root hairs’ which project into the soil These Each branch of root will be covered with millions of microscopic hairs This will increase the SA:V ratio Which increases the rate of absorption of water (Osmosis) and mineral ions (Active Transport) from the soil

2. Thin For Example: THE ALVEOLI     

Gas exchange system in the lungs Each alveolus is made from a single layer of thin, flat cells called the alveolar epithelium Oxygen diffuses out of the Alveolar space and into the blood Carbon dioxide diffuses out of the blood and into the alveolar space The thinness of the alveolar epithelium helps to decrease the distance that the oxygen and carbon dioxide has to travel, which increases the rate of diffusion

3. Good Blood supply/Ventilation For Example: ALVEOLI     

The alveoli are surrounded by a network of capillaries So each alveoli has its own blood supply This ensures that the blood is constantly taking away oxygen from the alveoli, and bringing in carbon dioxide The lungs are ventilated, so this means the air in each alveolus is constantly replaced Theses features help to maintain the concentration gradients of oxygen and carbon dioxide

FISH GILLS     

The gills are the gas exchange system in fish In the gills oxygen and carbon dioxide are exchange through the fishes blood and surrounding water The gills contain a large network of capillaries , Which keeps them well supplied with blood Fish also are well ventilated, as fresh water constantly passes over them These features help to maintain the concentration gradient of oxygen, Which increases the rate of which oxygen diffuses into the blood

Esha Sandhu

Exchange Surfaces – Module 3.1

The Gaseous Exchange System In Mammals Lungs: In mammals the lungs are the Exchange Organs 1. As you breathe in, the air goes down the trachea (Wind pipe) 2. Then the trachea splits into two bronchi, going into each lung 3. The bronchi’s split into smaller tubes called bronchioles 4. And at the end of the bronchioles there is a ‘air sac’, known as the alveoli. This is where gas exchange takes place 1. The ribcage, intercostal muscles and diaphragm all work together to move air in and out

Structures in the gaseous exchange system: 1. GOBLET CELLS o Line the airway o Secrete mucus o Mucus traps microorganism and dust particles from reaching the alveoli 2. CILIA o Cilia is on the surface of the lining o Cilia beats the mucus o Mucus contains dusts and microorganisms o Pushes the mucus up and away from the alveoli towards the throat , where it is swallowed o This helps to prevent lung infection 3. ELASTIC FIBRES o In the Trachea, bronchi, bronchioles and alveoli, o Helps the process of breathing out o When breathing in, the lungs inflate and the elastic fibres stretch o When exhaling, the elastic fibres recoil to help push out the air 4. SMOOTH MUSCLE o In the trachea, bronchi and bronchioles o allows diameter to be controlled o During exercise the smooth muscle relaxes, o Which widens the air way, o which means there is less resistance. o So air can flow easily in and out of the lungs 5. RINGS OF CARTILAGE o In the trachea and bronchi o Provide support o Strong but flexible o Prevents the trachea and bronchi collapsing, when you breathe in and the pressure drops Esha Sandhu

Exchange Surfaces – Module 3.1

Parts Found in the system:

Esha Sandhu

Exchange Surfaces – Module 3.1

Ventilation In Mammals    

Ventilation in mammals consists of inspiration and expiration Inspiration = Breathing in Expiration = Breathing out Ventilation is controlled by the movements of the internal and external intercostal muscles, the diaphragm and the ribcage

Inspiration Inspiration is an active process, which requires energy 1. The external intercostal and diaphragm contract 2. Causing the ribcage to move up and outwards 3. Causing the diaphragm to flatten 4. So the thorax volume increases, and the pressure in the lungs decreases 5. Which allows air to flow into the lungs

Expiration Expiration is a passive process, so ir does not require energy 1. The external intercostal and diaphragm relax 2. Causing the diaphragm to curve again 3. So the thorax pressure decreases, which increases the Air pressure 4. Which forces the air out of the lungs Forced Expiration: 1. Internal intercostal muscle contracts 2. Causing the ribcage to move down and out

Respiratory Volumes: Tidal Volume: The volume of air in each breath. Usually 0.4 dm3 Vital Capacity: The greatest possible volume that can be expelled from the lungs after taking the deepest possible breath Breathing Rate: How many breaths are taken. Usually per minute Oxygen Uptake: The volume of oxygen absorbed by the lungs in one minute Residual Volume: The amount of air that remains in the lungs after forced expiration

Esha Sandhu

Exchange Surfaces – Module 3.1 How a spirometer works: 1. A spirometer contains a oxygen chamber, with a moveable lid 2. A person breathes into a tube which is attached to the oxygen chamber 3. As the person breathes in and out the lid of the chamber moves up and down Movements can be recorded via:

    

1. A pen attached to the lid of the chamber, that writes on a rotating drum, creating a spirometer trace 2. Or it could be hooked up to a motion sensor, which creates electronic signals, that are picked up by a data logger The soda lime in the tube which the person breaths into absorbs the carbon dioxide The total volume of gas in the chamber decreases over time As the carbon dioxide is being absorbed by the soda lime Which leaves only oxygen in the chamber The oxygen will be used up during respiration, so the total volume will decrease#

Ventilation in Fish and Insects As there is a low concentration of oxygen in the water than the air, Fish have specialised adaptations that make sure they get enough oxygen.

Esha Sandhu

Exchange Surfaces – Module 3.1 Water containing oxygen, enters the fish via the mouth an passes out through the gills

Gills: 

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Gills are made out of thin branches called gill filaments or primary lamella o This has a large surface area for the exchange of gases Attached to the gill filaments/primary lamella is loads of tiny structures called gill plates or secondary lamella o This also increases the surface area further Each gill is supported by a gill arch

Fish’s Counter-Current System:    

Blood flows over the gill plates in one direction, and water flows over in the other direction. This is known as the counter current system This maintains a large concentration gradient between the water and blood The concentration of oxygen in the water is always higher than the concentration of oxygen in the blood Therefore the water is constantly diffusing as much oxygen as possible into the blood

Ventilation in Fish: Operculum: Each gill is covered by a bony flap called the operculum, The increase of pressure in the cavity, forces the operculum to open and release water 1. Fish opens mouth 2. Floor of buccal cavity is lowered 3. The volume increases in the cavity, decreasing the pressure in the cavity 4. Which causes water to be sucked into the cavity

1. Fish closes the mouth 2. Which causes the floor of the buccal cavity to raise 3. The volume decreases inside the cavity, increasing the pressure in the cavity 4. Water is then forced out of the operculum

Esha Sandhu

Exchange Surfaces – Module 3.1

Ventilation in insects: The Trachea are microscopic air filled pipes, which insects use for gas exchange Spiracle: Pores on the surface of the insect Oxygen diffuses down the concentration gradient into the cells. Carbon dioxide diffuses on its own concentration gradient moving towards the spiracle, to be released into the environment. 1. Air moves into the trachea through the spiracle 2. The trachea splits into smaller tubes called tracheoles 3. The tracheoles contains tracheal fluid which oxygen can dissolve in i. The tracheoles have thin permeable walls, which go into individual cells 4. The oxygen in the fluid, diffuses into the blood of the insect i. Carbon dioxide moves in the opposite way Insects use rhythmical abdominal movements to change the volume of their bodies, and move air in and out of the spiracles. When larger insects fly, they use their wings to pump their thoraxes...