Exchange surfaces Flashcards
(33 cards)
Required for an exchange surface
-Large surface area.
-Short diffusion distance.
-Steep concentration gradient.
-Protection from drying up.
Inhalation process
-Diaphragm contracts and flattens.
-External intercostal muscles contract.
-Rib cage moves up and out.
-Volume of chest cavity increases.
-Pressure of chest cavity decreases.
-Air moves down the pressure gradient into the lungs.
Exhalation process
-Diaphragm relaxes.
-External intercostal muscles relax.
-Ribs go down and in.
-Volume of chest cavity decreases.
-Pressure of chest cavity increases.
-Air moves down the pressure gradient out of lungs.
Pleural cavity
-Space within the pleural membrane, a double membrane that encloses the lungs.
-Filled with fluid that lubricates the lungs.
-Sticks the outer walls to the thoracic cavity by water cohesion, so the lungs expand with the chest while breathing.
Nasal cavity
-Where air enters the body.
-Has a hairy lining to trap dust and bacteria.
-Has moist, warm surfaces to increase the humidity and warmth of air to reduce water loss.
Trachea
-Supported by layer of c-shaped rings made of cartilage that prevent collapse in low pressure during inhalation, and allow it to bend.
-Lined with goblet cells that produce mucus to trap dust and bacteria.
-Also lined with ciliated epithelial cells that move dust into the oesophagus where they can be digested.
Bronchus
-Extend from trachea.
-Split into left and right lung.
-Very similar structure to trachea with c-shaped rings and goblet cells but smaller.
Bronchioles
-Branch off from bronchi.
-Very small, 1mm in diameter.
-Do not have cartilage, are held open by smooth muscle which allows them to contract.
-Lined with thin layer of epithelial tissue which allows for some gas exchange.
Alveoli
-Tiny (200-300um) air sacs at the end of bronchioles.
-Made up of a one cell (0.5um) thick layer of flattened (squamous) epithelial cells.
-Also contain collagen and elastic fibres which allow recoil to move air out of the alveoli.
Lung surfactant
-A phospholipid.
-Prevents collapse during low pressure (inhalation) by coating the surface of the lungs.
-This stops the alveoli from creating a surface tension.
Cartilage
-Resistant to tension and compression.
-Prevents collapse in trachea and bronchi during low pressure in inhalation.
-Incomplete ring allows for some flexibility.
Smooth muscle
-In the trachea, bronchi, and bronchioles.
-Able to contract and narrow the lumen.
-In bronchioles can restrict air to the alveoli in the event of harmful substances entering.
Elastic fibre
-Found in all airways.
-Used to reverse the constriction of the lumen by smooth muscle.
-As muscle relaxes elastic fibres recoil to original shape and size.
-Allows expiration to be a largely passive process.
Goblet cells/glandular tissue
-Found between ciliated cells in the trachea, bronchi and large bronchioles.
-Secrete mucus to trap particles from the air, therefore reducing the risk of infection.
Ciliated epithelium
-Many hair like structures called cilia.
-Waft mucus up the airway to the back of the throat.
Perfusion
-Allowing blood to flow adjacent to the alveoli.
Spiracles (insects)
-Small holes where gas enters the insects.
-Water can also be lost through them.
-This means they are only open during high oxygen demand.
Tracheae (insects)
-Carry air from the spiracles through the body.
-Lined by impermeable chitin.
Tracheoles
-Where tracheae lead to.
-Ends are filled with tracheal fluid that increases the diffusion gradient.
-Run throughout the tissue.
How insects increase ventilation
-Can actively move their thorax to change volume and pressure.
-Flying insects can gain air by flying fast.
-Locusts can open spiracles at the front of their body and close them at the back. Once air flows in the front ones are closed and the back opened, causing a flow of air.
Gill structure (fish)
-Gills are where gas exchange occurs.
-Supported by gill bars/arches made of bone or cartilage.
-The space between each bar is called the gill slit.
-Each bar has two rows of filaments.
-Each filament is covered in folds called lamellae. This is where exchange from water occurs.
Ventilation in cartilaginous fish
-Cartilaginous fish employ passive ventilation by swimming forward with their mouths open and facing the current.
Ventilation in bony fish
-The buccal floor in the mouth opens and the operculum across the gills closes.
-This means pressure decreases and water flows in.
-The mouth then closes and the buccal floor raises so pressure increases and water is pushed through the gills.
-Operculum opens to let water be pushed out.
Parallel flow
-Blood and water flow the same direction
-The concentration gradient stops at 50% saturation.
