Test 2 Vascular System Flashcards
What cell lines a blood vessel?
endothelial cells- form barrier against blood movement
What are the 3 layers of blood vessels?
- Tunica Externa (adventitia)
- Strong outer covering of arteries and veins
- Consists of connective tissues (collagen and elastic fibers of external elastic lamina) - Tunica Media (media)
- Middle layers of smooth muscle and elastic fibers
- Thicker in arteries than veins - Tunica Intima (intima)
- Inner layer in direct contact with the blood
- Elastic basement membrane (inner elastic lamina) covered by endothelial cells
What separates the layers of blood vessels?
Each layer separated from the next by elastic lamina (external and internal)
Primary difference between arteries and veins is amount of ____ and _____.
smooth muscle (more in arteries) and elastic lamina (thicker in arteries)
Walls of large and medium sized arteries contain a large amount of ____ and _____.
smooth muscle (media) and elastic tissue (thick elastic lamina)
Laminas passively stretch during _____ and recoil during _____.
systole; diastole
Vascular smooth muscle is influenced by____, which means there is no ____innervation.
SNS (constrict);
PNS
What are the major site of vascular resistance (blood pressure regulation)? What does this do to BP?
arterioles
***Active constriction increases
BP, dilation decreases BP
Arteriolar smooth muscle contraction results in ____, increasing pressure in the proximal arteries (i.e., overall increased BP) while reducing blood flow through distal capillaries (i.e., reduced tissue perfusion)
increased vascular resistance
Most capillaries are between ____ µm in diameter
5 and 10
Capillaries are sufficient to permit ____ (~5 µm) to squeeze through in “single file“
red blood cells
Capillaries can ____ dilate with increased arteriolar pressure
passively
The entrance into capillary beds are surrounded by smooth muscle, called ______
precapillary sphincters
Precapillary schinters respond to _____ substances (locally released or circulating)
vasoconstrictor
What do the precapillary schinters control through capillary beds?
blood flow
Is the pressure inside capillaries high or low?
low
therefore flow is slow and continuous
Only ___ % of all blood volume is in capillaries
5
What do capillaries carry?
Exchange of gases, nutrients, and wastes
Capillaries allow movement from blood into tissue spaces in 3 ways:
- Vesicle movement (“continuous” capillaries, e.g., BBB)
- Fenestrations (pores) between cells (e.g., glomerular)
Fenestrations regulate size of molecules passing through them - Fenestrations and incomplete basement membranes (“Sinuosoidal” capillaries, e.g., liver and many lymphoid organs)
O2, CO2 and other gases are readily permeable or impermeable across all capillary endothelial cells and basement membranes
permeable
Nutrients (FA, AA, vitamins, minerals) freely move across ____ and _____ (except continuous, only by receptor-mediated vesicular transport)
fenestrated and sinusoidal capillaries
____ are metabolized by endothelial cell lipoprotein receptors and enzymes (e.g., lipoprotein lipase)
Lipoprotein particles
____ and _____ are held inside capillary lumen (except when specifically transported or with “leaky” capillary walls)
cells and most proteins
_____ are only slightly thicker than capillary walls, easily distended
Venule walls
Veins contain relatively little smooth muscle but can constrict with what?
with sympathetic stimulation and cytokines
Midsize and large veins have ______ to prevent retrograde (backward) blood flow
one-way valves
____ are not present in the very small veins and venules or in the “great” veins (e.g., vena cava), or the veins from the brain and viscera
valves