Ultrastructure of Blood Vessels Flashcards
What are the three main sections of blood vessel walls, from innermost to outermost?
Tunica intima
Tunica media
Tunica adventia
What are the four main types of arteries, in order of decreasing size?
Large elastic (conducting) arteries
Medium muscular (distributing) arteries
Arterioles
Metarterioles
What is the structure of the tunica intima of large arteries?
Endothelial cells
Thin subendothelium of connective tissue
Discontinuous elastic laminae
What is the structure of the tunica media of large arteries?
40-70 fenestrated elastic membranes
Smooth muscle cells and collagen between lamellae
Thickest section
What is the structure of the tunica adventia of large arteries?
Thin layer of connective tissue containing
- Lymphatics
- Nerves
- Vasa vasorum
What are the vasa vasorum?
Blood vessels that supply blood to artery
What is the structure of the tunica intima of medium arteries?
Endothelium
Subendothelial layer
Thick elastic lamina
What is the structure of the tunica media of medium arteries?
40 layers of smooth muscle connected by gap junctions - allow coordinated contraction
What is the structure of the tunica adventia of medium arteries?
Thin layer of connective tissue containing
- Minor vasa vasorum
- Lymphatics
- Nerve fibres
What is the structure of arterioles?
Diameter <0.1mm
3 layers of smooth muscle cells
Absent internal elastic lamina
What do metarterioles supply?
Capillary bed
What is the structure of metarterioles?
No continuous layer of smooth muscle
Intermediate rings of smooth muscle located at certain points = precapillary sphincters > contract to control blood flow to capillary bed
What is the structure of capillaries?
One layer of endothelium + basement membrane
What are the three types of capillaries?
Continuous
Fenestrated
Sinusoidal
What are the types of veins, in order of ascending size?
Postcapillary venules
Venules
Veins
Into which type of vessel does tissue fluid drain?
Postcapillary venules
What is the structure of postcapillary venules?
Endothelial lining
Associated pericytes
Diameter of 10-30 micrometres
From which vessel type do white blood cells migrate?
Postcapillary venules
What is the structure of venules?
Endothelium
Associated pericytes/thin smooth muscle cells > form very thin wall
Diameter of up to 1mm
Contain valves
How does a vein differ from its accompany artery in structure?
Larger diameter
Thinner wall
More connective tissue
Fewer elastic and muscle fibres
What is the structure of small and medium veins?
Well developed tunica adventia
Thin tunica intima and media
What is the structure of large veins?
Diameter >10mm
Thicker tunica intima
Well developed longitudinal smooth muscle in tunica adventia
Circular smooth muscle in tunica media
What is the function of valves within veins?
Prevent retrograde blood flow
Act together with muscle contraction to propel blood towards heart
What are venae comitantes?
Deep paired veins wrapped together with an artery in one sheath
