Blood Vessels & Compossition Flashcards
What is tunica interna (or intima)?
Innermost layer of the blood vessel and adjacent to lumen (space inside)
What is tunica media?
Middle layer of blood vessel made of smooth muscle and elastic fibers (threads of protein)
What is tunica externa (or adventitia)?
Outermost layer adjacent to surrounding tissue
Does the exchange of nutrients and gases normally happen at the level of arteries/veins?
No, but they can exchange in the capillaries
What are arteries?
Medium/large vessels branching from the aorta
What are arterioles?
Arteries divide into smaller vessels called arterioles
What are capillaries?
Arterioles feed into smaller capillaries that form capillary beds in the body’s tissues. They allow O2/nutrients to go into the cell and CO2/waste to be removed.
What are venules?
Blood journeys from capillaries to small vessels called venules (the smallest veins)
What are veins?
Venules combine into veins and eventually become the inferior/superior vena cava that empties into the heart.
Arteries carry oxygenated or deoxygenated blood from the heart to the tissues?
Oxygenated
Arterial walls are…?
Elastic allowing them to absorb pressure created by the ventricles pumping
The smooth muscles in the arteries’ tunic media allow arteries to regulate…?
Arteries can regulate their diameter
What are the types of arteries? (2)
Elastic, muscular
Elastic arteries function as…?
Pressure reservoirs
What are some characteristics of elastic arteries (aka conducting arteries)? (4)
- Large diameter (aorta)
- More elastic fibers, less smooth muscle (hence the name)
- Tunica media is thick and has many elastic fibers
- Well-defined external elastic membrane
What are some characteristics of muscular arteries (aka distributing arteries)? (5)
- Medium diameter
- More smooth muscle, less elastic fibers
- Distributes blood to various parts of body
- Thick tunica media dominated by smooth muscle
- Thin external elastic membrane
What is anastomosis of arteries?
When 2 or more arterial branches supplying the same region of body join together creating an alternate blood route
When can anastomosis not occur in arteries supplying the same region?
If an end artery is blocked (necrosis can occur to that region)
What do capillaries connect together?
Arterioles and venules
Capillary walls are composed of…? (2)
Single layer of cells (endothelium) + basement membrane
Because capillary walls are thin, what can capillaries do?
Capillaries allow the exchange of nutrients and waste between blood and tissue cells
What is the precapillary sphincter?
It is a mechanism that allows a certain amount of blood and nutrients to enter the diffusion area
What does the precapillary sphincter have the ability to do? (2)
- Equalize pressure and RBC flux
- Protect downstream capillaries and brain tissue against adverse blood pressure
What are continuous capillaries?
Least permeable capillary only allowing small solutes to pass through