The lungs (Exchange cells and breathing: F211)

Notes on the lungs from the specification F211 (OCR)

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The lungsoverview
Tissue: a group of one or a few similar types of cell that carry out a specific function.
E.g. blood, phloem etc.
Organ: two or more tissues working together to perform a specific function E.g. muscle
Tissues in the breathing system:
Epithelium this is a lining tissue which forms sheets which cover surfaces. Almost all organs in the body
has some kind of epithelial tissue involved. Simple epithelia are one cell thick. Cells rest on a basement
membrane which is a network of collagen and glycoprotein, secreted by the underlying cells and that holds
the epithelial cells in position ­ found in alveoli.
Squamous epithelia cover many surfaces in the body including the cheeks, blood vessels and alveoli and
capillaries. The individual cells are smooth, flat and thin. Their thinness allows rapid diffusion due to a short
diffusion distance which is found in the alveoli.
Ciliated epithelia are lined with cilia they have tiny hair like structures projecting from their membrane. The
cilia wafts back and forthwafting mucus up the airway to the back of throat to be swallowed the acidity in
the stomach will kill any bacteria.
Goblet cells (look like a wine glass) are under the epithelium and make and secrete mucus onto the
surface to trap any tiny particles from the air including: pollen, bacteria and dust. So that the cilia can then
waft the mucus out of the airway trapping bacteria so that it can be removed this will reduce the risk of an
infection.
Cartilage is a strong tissue, which helps to support the walls of the trachea and bronchi. The bronchioles
do not contain cartilage. Cshaped rings of cartilage in the walls of trachea and bronchi, help to hold these
tubes open them and prevent them from collapsing when the air pressure inside is low due to inspiration. As
the cartilage does not form a complete ring, it allows for some flexibility, allowing you to make retch without
constricting your airways.
Smooth muscle is found in the walls of the trachea, bronchi and bronchioles. It contracts and relaxes to
control the diameter of the airway smooth muscle contracts it will constrict the airways making the lumen of
the airway narrower. This contraction is involuntary and smooth muscle is made up of a collection of spindle
shaped cells. Smooth muscle is used in the bronchus as they can be made wider during exercise in order
to get more air in and out of the lungs, more rapidly. In asthma sufferers the smooth muscle can contract
and retract the airways in response to substances from the air making it difficult to breathe.
Elastic fibres are found in the walls of all of the airways, trachea, bronchi, bronchioles, alveoli etc. They are
made of elastic fibres called Elastin. They are especially important around the alveoli as during inspiration
the alveoli expand stretching the elastic fibres. During expiration the fibres recoil helping to decrease the
volume inside of the lungs and forcing air out. Also in the trachea, bronchus and bronchioles, when smooth
muscle contracts and reduces the diameter of the lumen of the airway the elastic fibres distant but when the
smooth muscle starts to relax the elastic fibres recoil to their original shape and size to help dilate the
airways.
Where would I find these in the lung?
Trachea Bronchus Bronchiole Alveolus
Tissue

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Smooth muscle
Elastin
Cartilage
Epithelium
Alveoli:
Goblet cells:…read more

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Squamous epithelium:…read more

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