Anat: Lung Respiration
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How is surface tension reduced in the lungs?
The use of surfactant
What problems would the lungs have without surfactant?
In spaces with small diameters, such as an alveolus, any water on the alveolar surface would exert strong capillary forces which would inhibit the expansion of the lung
Where can surfactant be found?
A thin layer around the whole lung due to it being so surface active. This allows the lung to be expanded with modest energy
What does the thorax consist of?
• 12 ribs (costae) all joined posteriorly to one of the 12 thoracic vertebrae • Anteriorly, three bones join together to form the sternum • The ribs are linked to the sternum by bars of cartilage, which is somewhat flexible but prevents overexpansion of lungs
What is pleura?
A thin, tough layer that covers the surface of the lungs. Layer covering the lung = visceral pleura Layer covering the cavity = parietal pleura
What is the need for pleura in the lungs?
Between both pleura layers is a thin layer of slippery fluid. This fluid causes adherence of the two layers to each other. This means that as the diaphragm contracts, the parietal pleura is pulled down which pulls the visceral pleura down causes an expansion of the lungs
What part of the diaphragm moves and what happens when it contracts?
The tendinous plate in the middle moves downwards. This causes an extension of the lungs, compression of intestines and abdomen and there is a slight widening of the lowest ribs
What happens to the ribs during forced inspiration and expiration?
• Ribs are normally curved downwards. • Forces inspiration lifts them up which widens thorax • Forced expiration lowers them and narrows thorax
What do the intercostal muscles do?
They tense lightly during resting respiration and more intensly during forced respiration
How are the abdominals involved in respiration?
When activated, they pull the lower ribs downward to lower the volume of the lungs (key to forced expiration)
What are the other accessory muscles used for forced respiration?
Sternocleidomastoideus (neck strap muscles) Pectoralis minor -For maximal respiration, the abdominals relax, the intercostals and accessory muscles contract to create largest volume in lungs
What are the hollow spaces in facial bones called? what are they important for?
Sinuses -They render the air warm and moist when it hits alveoli of the lung
What happens during inspiration through the nose?
-Air goes through our nasal cavity and turbinate bones create turbulance in the air causing a much enhances surface to air volume ratio.