9. Gas Exchange Flashcards
What is the human gas exchange system adapted to? (4)
-clean and warm the air that enters during breathing
-maximize the surface area for diffusion of oxygen and carbon dioxide between the blood and atmosphere
-minimize the distance for this diffusion
-maintain adequate gradients for this diffusion
How does diffusion of oxygen take place in single celled organisms?
From the fluid outside the cell through the cell surface membrane and into the cytoplasm.
Where is the gas exchange surface in humans?
Alveoli in the lungs
Why is it important for the alveoli to have a huge surface area?
- So that a large number of oxygen and carbon dioxide molecules can diffuse the the surface at any moment giving a high rate of gas exchange.
- Oxygen is not very soluble in water, so an increased surface area allows the oxygen to diffuse effectively across the respiratory membrane into the bloodstream where it binds to hemoglobin in red blood cells for transport.
What is the trachea and how is it adapted for its function?
It is the large tube that carries air from the throat down to the lungs
1. Rings of cartilage keep the airway open
2. Smooth muscle can contract or relax to constrict or dilate the airway and change airflow
3. Elastic tissue contains elastic fibers with elastic that allows stretching and recoiling
4. Lined with ciliated epithelial cells and goblet cells.
How is desiccation prevented inside the lungs?
As air flows through the nose and the trachea it is warmed to body temperature and moistened by evaporation from the lining.
What is mucin?
Any glycoprotein that forms parts of of the mucus secreted by goblet cells and mucous cells.
What is a ciliated epithelium?
An epithelium that consists of goblet cells, these produce and secrete mucus that traps dust and microbes.
The cilia, which waft the mucus upward to the mouth so it can be swallowed.
And macrophages, which patrol the surfaces of the airways engulfing and destroying debris and microbes.
Describe the pathway of air through the respiratory system.
- Air first enters the trachea
- Air travels into the two bronchi, with one bronchus going to each lung
- Air travels into smaller airways called bronchioles
- Air travels into clusters of air sacs called alveoli at the end of the bronchioles.
What are the bronchi and how are they adapted for their function?
They are two main branches extending from the trachea that carry air into each lung.
1. Reinforced with cartilage to keep the airway open.
2. Smooth muscle can contract or relax to constrict or dilate the airway and change airflow.
3. Elastic tissue contains elastic fibers with elastic that allows stretching and recoiling.
4. Lined with ciliated epithelia cells and goblet cells.
What are the bronchioles and how are they adapted for their function?
They are smaller airways branching from the bronchi that carry air to the alveoli.
1. No cartilage, can change shape.
2. Smooth muscle can contract or relax to constrict or dilate the airway and change airflow.
3. Elastic tissue contains elastic fibers with elastic that allows stretching and recoiling.
4. Simple squamous epithelium
Explain how the alveoli carry out gas exchange.
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.
Oxygen therefore diffuses down its concentration gradient from the air in the alveoli to the blood, and carbon dioxide diffuses down its concentration gradient in the opposite direction.
How are alveoli adapted for gas exchange?
- Wall consists of one layer of squamous epithelial cells, this allows for rapid diffusion.
- Large surface area, this increases rate of gas exchange.
- Elastic fibers, which stretch during inspiration and recoil during expiration to help force air out.
- Collagen fibers, these contain strong collagen that prevents alveoli from bursting and limits overstretching.
- Moist inner surface, this allows gases to dissolve and lung surfactant helps alveoli remain inflated.
Why is it a good thing that there is no cartilage in the bronchioles?
Allows the lumen size to change, when the smooth muscle relaxes, the lumen gets larger this allows more air to go into the alveoli, so that more oxygen can diffuse into the blood.
Why is the squamous epithelium one cell thick?
In order to minimize the diffusion distance.
The smaller the distance the easier and faster diffusion can happen
