1.2.3 The Lungs and Investigating Lung Function

OCR specifiaction based notes for AS Human Biology

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1.2.3 The Lungs and Investigating Lung Function
(a) Tissues and Organs
A tissue is a group of similar cells specialised to carry out the same function.
An organ is a structure made up of different kinds of tissue.
(b) Relationships Between Cells
Epithelial tissue is arranged in single or multi-layered sheets and covers the internal and external
surfaces of the body. The cells are held together by special junctions and a carbohydrate based
cementing substance between the cells.
Epithelium rests on a basement membrane which is a connective tissue matrix containing collagen fibrils.
This helps to stabilise and hold the epithelium to
underlying tissues.
(c) Cell Structure
(d) Photomicrograph of The Lung

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Surface to Area Ratio
(f) Gas Exchange Surface
Large Surface Area
The bronchioles are branched
Millions of alveoli in each lung
The alveoli are folded
Thin Surface Area
The squamous cells are very thin
Capillary walls are only one cell thick
Steep Diffusion Gradient
The blood circulation carries oxygenated blood away and brings deoxygenated back
Ventilation brings oxygen rich air and air rich in carbon dioxide is removed
The surrounding capillaries are very narrow slowing blood flow allowing time for efficient
exchange.…read more

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(j) Causes of Respiratory Arrest
respiratory disorder such as asthma
An obstruction in the trachea or bronchi such as food or a small object
Overdosing on drugs that suppress the respiratory system
Respiratory arrest may also occur following cardiac arrest.
(k) First Aid
Roll onto back, lift chin, check for blockages, pinch nose shut, make a seal over their mouth with yours,
breath out and check that chest rises, give one breath every 5 seconds.…read more


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