Blood Vessels and Circulation Flashcards
Arteries
Carry blood away from the heart
Arterioles
Smallest artery branches leading to capillaries
Capillaries
Where diffusion between blood and interstitial fluid takes place
Venules
Unite to form larger veins that return blood to heart
Path of blood
Heart > arteries > arterioles > capillaries > venules > veins > heart
Where does blood leave the heart through?
Pulmonary trunk (right ventricle) > pulmonary arteries > lungs
Aorta (left ventricle) > systemic arteries > all other organs
Vessel wall structure in arteries and veins
- Tunica intima
- Tunica media
- Tunica externa
Tunica intima
- Inner layer
- Endothelial lining and a surrounding layer of connective tissue with a variable number of elastic fibres
- Thick layer of elastic fibres (internal elastic membrane) in arteries
Tunica media
- Middle layer
- Concentric sheets of smooth muscle tissue in a framework of loose connective tissue
- Typically thickest layer
- Smooth muscle cells encircle endothelium that lines the lumen
What separates tunica media and tunica externa?
External elastic membrane
Tunica externa
- Outer layer
- Connective tissue sheath
Vasa vasorum
Blood vessels in the walls of large vessels
Why do large vessels contain vasa vasorum?
Because the vessel walls are too thick for diffusion
Differences between arteries and veins
- Artery walls thicker
- Arteries keep shape in sectional view
- Arteries have folds in sectional view
- Veins have valves
3 main types of arteries
- Elastic
- Muscular
- Arterioles
What gives arteries their elasticity and contractility?
Thick, muscular walls
Vasoconstriction
When stimulated, arterial smooth muscles contract, constricting the arteries
Vasodilation
When arterial smooth muscles relax, the diameter of the lumen increases
What do vasoconstriction and vasodilation affect?
- Afterload on heart
- Peripheral blood flow
- Capillary blood flow
Elastic arteries
Pulmonary trunk and aorta and their major branches
Muscular arteries
Distribute blood to the body’s skeletal muscles and internal organs
Arterioles
Smaller than muscular arteries
Resistance vessels
Arterioles
Aneurysm
Bulge in the weakened wall of an artery
When local blood pressure exceeds the capacity of the elastic component of the arterial walls
Types of capillaries
- Continuous capillaries
- Fenestrated capillaries
- Sinusoids
Continuous capillaries
- The endothelium is a complete lining of the lumen
- Tight junctions and desmosomes connect endothelial cells
Fenestrated capillaries
Contain pores in the wall due to an incomplete or perforated endothelial lining
Sinusoids
Discontinuous endothelium
Capillary bed
Interconnected collective network
Precapillary sphincter
Surrounds the entrance of a capillary and controls arterial blood flow to the tissues
Thoroughfare channel
Central passageway in the arteriole system
What happens when a precapillary sphincter constricts?
Blood is diverted into other branches of the network
Collaterals
Multiple arteries that supply blood to a capillary bed
Arterial anastomosis
The fusion of two collateral arteries that supply an arterial bed
Arteriovenous anastomoses
Direct connections between arterioles and venules
What happens when an arteriovenous anastomosis is dilated?
Blood bypasses the capillary bed and flows directly into venous circulation
Angiogenesis
Formulation of new blood vessels from preexisting vessels