The Human Gaseous Exchange System

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Why can humans not rely on diffusion alone?
small SA:V ratio, high metabolic rate (Active and maintain own body temperature)
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Nasal Cavity
Large SA with good blood supply (warms up the air to body temp), Hairy lining which secretes mucus (Traps dust and bacteria), moist surfaces increasing humidity (reduces evaporation from exchange surfaces)
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Trachea
main airway which carries the moist body temp air away from the nasal cavity, made from incomplete rings of cartilage (stop the trachea from collapsing and incomplete rings to allow food to pass, lined with ciliated epithelium with goblet cells
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Bronchi (bronchus)
Trachea divides to form left bronchus and right bronchus, similar structure to the trachea however they are smaller
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Bronchioles
The bronchi split into loads of bronchioles, no cartilage rings, smooth muscle in walls instead
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The function of the smooth muscles in the bronchioles
Controls the amount of air reaching the lungs (contracts and closes the bronchioles, when it relaxes, they open)
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Alveoli
Tiny air sacs, single layer of epithelial cells with some collagen and elastic fibres (allowing them to stretch and return to natural shape)
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Name 4 main adaptions which make the alveoli effective for gaseous exchange
Large SA, thin layers, good blood supply, good ventilation
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What covers the surface of the alveoli?
Water, salts and lung surfactant
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What is lung sufactant?
A substance that allows the alveoli to remain inflated
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Why does the water play an important role in gaseous exchange with the alveoli?
Oxygen dissolves in it and then can diffuse into the capillaries and can also evaporate into the air in the alveoli
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Thorax
The chest cavity
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Rib cage
Semi-rigid case within which pressure can be changed in respect to the environment
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Diaphragm
Dome-shaped sheet of muscle, forms the floor of the thorax
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External and internal intercostal muscles
Muscles found around the ribs, directing the ribs
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Pleural membrane
Surrounds the lungs,with lubricating fluid in the cavity so lungs can slide over tissues smoothly
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Describe inspiration
Energy using process- Diaphragm contracts flattening, external intercostal muscles contract, rib cage moves up and out, volume of thorax increases and pressure is decreased so air moves in down a pressure gradient
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Describe expiration
Passive process- diaphragm relaxes returning to dome, external intercostal muscles relax, ribs move in and down, decreases the volume of thorax, increasing the pressure so air moves out down a pressure gradient
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How does forced expiration differ from normal expiration?
It uses energy, internal intercostal muscles contract pulling the ribs down hard and fast, abdominal muscles contract, forcing air out
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Other cards in this set

Card 2

Front

Nasal Cavity

Back

Large SA with good blood supply (warms up the air to body temp), Hairy lining which secretes mucus (Traps dust and bacteria), moist surfaces increasing humidity (reduces evaporation from exchange surfaces)

Card 3

Front

Trachea

Back

Preview of the front of card 3

Card 4

Front

Bronchi (bronchus)

Back

Preview of the front of card 4

Card 5

Front

Bronchioles

Back

Preview of the front of card 5
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