Exchange

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  • Created by: Kate
  • Created on: 25-11-12 12:10

Features of exchange surfaces

Exchange surface-Is a specialised area that is adapted to make it easier for molecules to cross from one side of the surface to the other

Large surface area for molecules to pass through usually via folding.

Thin barrier to reduce diffusion distance.

Fresh supply of molecules on one side to keep concentration high and maintain a steep diffusion gradient.

Removal of required molecules on the other side to keep the concentration low.

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Features of lungs for efficient gas exchange

Large SA - Alveoli are folded and in large numbers.

Thin barrier-Alveoli are made of squamous epithelium and one cell thick

-Capillary touches alveoli

-Capillary is one cell thick and made of squamous epithelium

High supply-lungs high conc of oxygen by breathing constantly.

Demand side-capillary - low conc of carbon dioxide by pumping blood around body - deoxygenated blood brought to the lungs.

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Functions of parts of the lungs

Cartilage-supports trachea and bronchi/ lumen

Cillia-wafts mucus up the lumen to the throat

Smooth muscle-Contracts to constict the lumen , relaxes to dilate.

Elastic fibres-Stretches during inhalation and recoils during exhalation

Goblet cells-Secrete mucus to trap bacteria smokers secrete more mucus

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Inhaling and exhaling

Inhaling  Diaphragm contracts to become flatter and pushes digestive organs down.

External intercostal muscles contract to raise ribs

Volume of chest cavity increases.

Pressure in chest cavity drops below atmospheric pressure.

Air moves into lungs.

Exhaling  Diaphragm relaxes and is pushed up by displaced organs underneath

External intercostal muscles relax and ribs fall.

Volume of chest cavity decreases.

Pressure in lungs increases and rises above atmospheric pressure

Air moves into lungs

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All terms associated with spirometers

Tidal volume-the volume of air moved in and out of the lungs with each breath when you're at rest.

Ventilation rate-The amount of air going in and out of your lungs per minute - tidal volume x breaths per minute

Vital capacity-the larger volume of air that can be moved in and out of lungs in any one breath

Oxygen uptake-the volume of air extracted from the lungs in 1 minute

Residual volume-The volume of air that always remains in the lungs

Inspiratory reserve volume-how much air can be breathed in above and beyond the tidal volume

Expiratory-how much more air can be breathed out and over and above the amount that is breathed ina tidal volume breath.

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