9.5 Alveoli Flashcards
What do the alveolar walls contain?
Elastic fibres
What are elastic fibers?
Bundles of fibrous protein last thing which can stretch and recoil like a elastic bands
How much can a elastic fibres stretch before breaking
Up to twice their length
How do the elastic fibres act during inspiration and expiration?
They stretch during inspiration and recall during expiration to help force out the air.
What is the benefit of the elasticity of the alveoli?
It allows the alveoli to expand according to the volume of air breathed in
How does the expanding of alveoli help more oxygen into the body?
When the alveoli are expanded, the surface area for diffusion increases and the air is expelled efficiently when the elastic fibre recoil during exhalation
The alveoli walls also contains some collagen fibre. What is the benefit of them?
They provide support and help prevent a alveoli from bursting
Describe what the alveoli walls are like
They are extremely thin walls, each consisting of a single layer of squamous epithelial cells.
What are squamous epithelial cells like?
These cells are like fried eggs. The nucleus is like the yolk surrounded by a thin layer cytoplasm which is only 25 nm thick.
No part of the squamous epithelial cell is more than _______ thick
0.5 µm
What is pressed closely against the alveoli walls?
Blood capillaries that are led by anterior cells which are also also very thin
What is the benefit of the cells being so thin near alveoli
Oxygen and carbon dioxide molecules diffuse quickly between the air and the blood because the distance is very small
How is the steep concentration gradient maintained between the alveoli and blood
By breathing and the movement of blood. Breathing brings supplies of fresh air into the lungs with a relatively high oxygen concentration gradient and relatively low carbon dioxide concentration. Blood is brought to the lungs with a lower concentration of oxygen and a higher concentration of carbon dioxide than the air in the alveoli. The blood is constantly flowing through and out of the lungs so as the oxygenated blood leaves, more deoxygenated blood enters to maintain the concentrated gradient with each new breath.
What is the percentage of oxygen in the deoxygenated blood from pulmonary artery?
70% saturated with oxygen
What is the amount of oxygen in oxygenated blood going to the pulmonary vein?
95% saturated with oxygen
