The Lungs
Teacher recommended
?- Created by: Eleanor Izzard
- Created on: 12-12-12 19:05
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- The Lungs
- Organ of Exchange
- Air passes into the lungs through thenose and along the trachea, bronchi and bronchioles, and finally to the alveoli
- Inspiration
- diaphragm contracts - flatter, pushing digestive organs down
- External Intercostal muscles contract to raise ribs
- Volume of chest cavity increases
- Pressure decreases to below atmospheric pressure
- Air moves into the lungs, from high to low pressure
- Pressure decreases to below atmospheric pressure
- Volume of chest cavity increases
- External Intercostal muscles contract to raise ribs
- diaphragm contracts - flatter, pushing digestive organs down
- Expiration
- Diaphragm relaxes, pushed up by displaced organs underneath
- External intercostal muscles relax and ribs fall
- volume ofchest cavity decreases
- pressure rises above atmospheric pressure
- Air moves out of lungs
- pressure rises above atmospheric pressure
- volume ofchest cavity decreases
- External intercostal muscles relax and ribs fall
- Diaphragm relaxes, pushed up by displaced organs underneath
- Gas Exchange
- the movement of gases by diffusion between an organism and its environment across a barrier
- through the walls of the alveoli and capillaries
- Adaptations
- Permeable barrier of plasma membranes to O2 and CO2
- Thin Barrier - reduce diffusion distance: alveoli and capillary wall 1 sqaumous cell thick, narrow capillaries only allow 1 red blood cell through at once, total barrier less then 1micrometre
- Moisture lines alveoli - evaporates as we breathe out. Lungs must produce surfactant to reduce the cohesive forces between the water molecules and stop the alveolus collapsing
- alveoli lined with capillaries to decrease diffusion distance
- Large surface area - so many alveoli(100-300µm) that they combine to make approx. 70m²
- Concentration Gradient
- needs to be maintained for quick diffusion - lots of molcules on one side and few on the other
- so there needs to be a removal system and a fresh supply
- achieved by the blood bringing CO2 from the tissues to the lungs and carrying O2 away from the lungs
- the breathing movements of the lungs ventilate the lungs - replacing used air with fresh, oxygen filled air - and removing CO2
- needs to be maintained for quick diffusion - lots of molcules on one side and few on the other
- Roles of Tissue
- Elastic Fibres
- smooth muscle cannot reverse the narrowing effect. When it constricts it deforms the elastic fibres
- as the muscle relaxes, the elastic fibres recoil to their original size and shape - helping to dilate the airway
- Smooth Muscle
- can be important if there are harmful substances in the air - involuntary reaction
- can contract, constricting the airway (narrower lumen) - restricting the air flow
- Goblet Cells/Glandular tissue
- under the epithelium the tissue can secrete mucus to trap tiny particles from the air
- removal can reduce the risk of infection
- Cartilage
- structural - holds the trachea and bronchi open, preventing collapse when pressure is low in inhilation
- C shaped to allow some flexability - movementof neck and expansion of oesophagus
- Ciliated Epithelium
- ciliated cells have tiny hair like extensions - cilia - that move in a synchronised pattern
- waft mucus up airway to back of throat to be swallowed for stomasch acid to destroy bacteria
- Elastic Fibres
- Where are the tissues
- Bronchioles - much narrower than bronchi, some may have cartilage but many have none. Wall mostly smooth muscle and elastic fibres. Smallest bronchioles have clusters of alveoli at their ends
- Trachea and Bronchi- lots of cartilage, inside surface of cartilage contains elastic fibres, smooth muscle and blood vessels. Inner lining is epithelium layer containing cilia and goblet cells
- Bronchi are smaller than Trachea
- Alveoli - elastic fibres for stretch and recoil function
- Organ of Exchange
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