Chapter #21: Blood Vessels & Circulation Flashcards
The largest blood vessels attached to the heart
-Pulmonary trunk
-Aorta
Types of Blood Vessels
-Arteries
-Arterioles
-Capillaries
-Venules
-Veins
Arteries
carry blood away from (comes out of left ventricle)
Arterioles
smallest branches of arteries that lead to capillary beds
Capillaries
-Smallest blood vessels with thin walls
-Location of exchange between blood and interstitial fluid
Venules
smallest branches of veins that collect blood from capillaries
Veins
return blood to heart
How many layers do blood vessel walls have?
three layers
What are the three layers of vessel walls?
- Tunica intima (inner layer)
- Tunica media (middle layer)
- Tunica externa (outer layer)
** know diagram on slide 9
Tunica Intima
-inner layer
-includes: the endothelial lining and internal elastic membrane (in arteries which contain elastic fibers)
-usually rippled due to muscle constriction (in arteries)
-usually rippled due to vessel constriction (in veins)
Order of blood exchange
arteries –> arterioles –> capillaries –> venules –> veins
Why are elastic fibers important in the internal elastic membrane in your arteries?
-stretch and return back to normal size
-expansion/contraction of the vessel to absorb shock and keep capillaries from bursting
-closer the vessels are to the heart, the more elastic fibers they’ll have due to the absorbance of shock
Tunica Media
-middle layer
-contains smooth muscle
-external elastic membrane (in arteries)
Tunica Externa
-outer layer
-Anchors vessel to adjacent tissues
-Contains: collagen fibers, elastic fibers, smooth muscle cells (in veins)
Differences between arteries and veins
-Arteries have thicker walls and higher blood pressure than veins
-A constricted artery has a small, round lumen
-A vein has a large, irregular lumen
-The endothelium of a constricted artery is folded
-Arteries are more elastic than veins
-Veins have valves
Structure and function of arteries
-Elasticity allows arteries to absorb pressure waves that come with each heartbeat
-Contractility
-Vasoconstriction
-Vasodilation
Contractility in arteries
-Arteries change diameter
-Controlled by sympathetic division of ANS
Vasoconstriction in arteries
Contraction of arterial smooth muscle
Vasodilation in arteries
-Relaxation of arterial smooth muscle
-Enlarges the lumen
Effects of Vasoconstriction and vasodilation
-Afterload on heart
-Peripheral blood pressure
-Capillary blood flow
Afterload on heart
-if vessels are constricted, the afterload will be greater
-the force against which the left ventricle has to push into the arteries
Peripheral blood pressure
everything from the heart past your aorta
from arteries to capillaries, arteries change:
-from elastic arteries
-to muscular arteries
-to arterioles
Elastic Arteries
-conducting arteries
-Large vessels (e.g., pulmonary trunk and aorta)
-Tunica media has predominantly elastic fibers
-Elasticity evens out pulse force
Muscular arteries
-distribution arteries
-Most arteries are medium-sized muscular arteries
-Tunica media has predominantly muscle cells
Arterioles
-resistance vessels
-Small vessels (smallest of the arterial system)
-Have no tunica externa
-Have thin or incomplete tunica media
Aneurysm
-A bulge in an arterial wall
-Caused by weak spot in elastic fibers
-Pressure may rupture vessel
Capillaries
-Smallest vessels with thin walls
-Microscopic capillary networks permeate all active tissues
Capillary function
-Location of all exchange functions of cardiovascular system
-Materials diffuse between blood and interstitial fluid
Capillary structure
-Endothelial tube, inside thin basement membrane
-No tunica media
-No tunica externa
-Diameter is similar to that of a red blood cell
Capillary beds
-capillary plexus
-Connect one arteriole and one venule
-Precapillary sphincter
-ex) when you’re running, the capillary bed will open at your quads and close at your liver
**know diagrams on slides 22 & 23
Precapillary Sphincter
-part of capillary beds
-Guards entrance to each capillary
-Opens and closes, causing capillary blood to flow in pulses
-allows things in or out; contains smooth muscle tissue
Collaterals
-Multiple arteries that contribute to one capillary bed
-Allow circulation if one artery is blocked
Arterial anastomosis
Fusion of two collateral arteries
Arteriovenous anastomoses
-Direct connections between arterioles and venules
-Bypass the capillary bed
Veins
Collect blood from capillaries and return it to heart
Compared to arteries, veins have
-Larger diameters
-Thinner walls
-Lower blood pressure
Venules
-Very small veins
-Collect blood from capillaries
Medium-sized veins
-Very few smooth muscle cells
-longitudinal bundles of elastic fibers
Large veins
-Have all three tunica layers
-Thick tunica externa
-Thin tunica media