Vessels and Circulation Flashcards
Anastomosis
-Convergence of two or more vessels
-Veins anastomose with each other more
-End arteries do not form anastomoses
Companion vessels
Arteries and veins that lie next to each other
Lumen
A lumen is a cavity or channel within a tube or tubular organ in the body
- Tunica Interna
– tunica intima
– Innermost layer
– Endothelium
– Slick surface minimizes friction
– Supported by connective
tissue in large vessels
- Tunica Media
- Middle layer
- Smooth muscle with sheets of elastin
- Influences blood flow and blood pressure by controlling vasoconstriction and vasodilation
- Tunica Externa
– tunica adventia
– Connective tissue
– Anchors and protects blood vessels
Elastic arteries
– Thick walled
– Elastin in all 3 tunics
– From heart to medium
sized arteries E.g., Aorta
– Inactive in vasoconstriction
Muscular arteries
– Distal to elastic arteries
– Includes most named arteries e.g.,
brachial, femoral
– Thick tunica media
– Active in vasoconstriction
Arterioles
– Smallest arteries
– Single layer of smooth muscle
around endothelium
Capillaries
– Smallest blood vessels
– Average length = 1mm
– Red blood cells pass single file
– Exchange materials
– Capillary beds are interweaving networks of capillaries
Capillary Bed Structure
Look at slide 12
Continuous Capillaries
-Endothelial cells form a complete lining
-Tight junctions
-Most common type
-In muscle and brain
Fenestrated Capillaries
-Endothelial cells contain pores
-Allow fluid exchange between blood and interstitial fluid
-In small intestine and kidney
Sinusoid Capillaries
-Large gaps between endothelial cells
-Discontinuous (or absent) basement membrane
-Allows transport of large molecules and cells to and from blood
-In bone marrow and liver
Venules
– Formed where capillaries unite
– Almost entirely endothelium
– Porous: facilitate nutrient and waste
exchange
