Exchange Surfaces and Breathing Flashcards
Why don’t single celled organisms need exchange surfaces?
They have a high surface area to volume ratio.
They are small so demand for O2/ CO” removal is low.
The diffusion distance is small and particles cross this in enough time to meet demands.
Why do multicellular organisms need exchange surfaces?
The have a small surface area to volume ratio.
They have high demands for O2/ CO2 removal.
The diffusion distance is too great; particles can’t cross this in enough time to meet demands.
Describe the features of an efficient exchange surface with reference to an alveolus.
Alveoli produce a large surface area for the diffusion of O2 and CO2 into/out of the blood.
The squamous epithelium of the alveoli is very thin providing a short diffusion distance.
The alveoli have capillaries running over their surface delivering CO2 to be removed and allowing O2 to be carried away.
Describe the features of the alveoli of a mammalian lung that make it efficient for gas exchange?
Alveoli have a thin squamous epithelium and the surrounding capillaries have a thin endothelium which provides a short diffusion distance.
How do the epithelial cells of the alveoli make the mammalian lung efficient for gas exchange?
The epithelial cells of the alveoli produce a surfactant which reduces the surface tension and prevents the alveoli collapsing when the pressure changes.
How do erythrocytes make the mammalian lung efficient for gas exchange?
Erythrocytes transport oxygen and carbon dioxide from and to the alveoli.
How do the intercostal muscles and the diaphragm make the mammalian lung efficient for gas exchange?
The diaphragm and intercostal muscles maintain a concentration gradient.
How do the ciliated epithelial cells make the mammalian lung efficient for gas exchange?
The ciliated epithelial and goblet cells remove dust / bacteria / pollen / spores.
How does cartilage make the mammalian lung efficient for gas exchange?
Cartilage holds the airway open.
How does smooth muscle make the mammalian lung efficient for gas exchange?
Smooth muscle can constrict and control the diameter of the airway.
How do elastic fibres make the mammalian lung efficient for gas exchange?
Elastic fibres recoil aiding ventilation by helping to expel air.
How do macrophages and neutrophils make the mammalian lung efficient for gas exchange?
Macrophages and neutrophils engulf and destroy pathogens.
Describe the structure of the trachea and bronchi.
Bronchi are narrower than the trachea.
Thick walls made of several layers of tissue
Much of the wall consists of cartilage
Regular C-rings in the trachea and less regular in the bronchi..
On the inside surface of the cartilage is a layer of glandular tissue, connective tissue, elastic fibres, smooth muscle and blood vessels.
The inner layer is an epithelium layer than has two types of cells. Most of the cells are ciliated epithelium, and there are goblet cells amongst them (secrete mucus).
Describe the structure of the bronchioles.
Much narrower than the bronchi
Larger bronchioles have some cartilage, but the smaller ones don’t.
The wall is made mostly of smooth muscle and elastic fibres.
Describe the structure of the alveoli.
Wall is one cell thick.
100-300μm diameter.
Good blood supply.
