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Vein Histology
Vein Histology
Key points:
- Vessel diameter increases as we near the heart.
- Walls tend to be collapsed, which helps to distinguish from arteries.
- Travel within adipose tissue
General Tunics:
- Outer tunica adventitia
- Tunica media (smooth muscle)
- Tunica intima faces lumen
Details:
Small venules
- Carry blood from the capillaries
- Little to no tunica media
Muscular venules
- Travel with the muscular arteries
- Smooth muscle holds it slightly open
Large veins
- Includes the venae cavae, which drain into the heart.
- Vasa vasorum
- Small blood vessels, may course through the thick adventitia
- Smooth muscle fibers can be found in the adventitia
- In larger veins, including some muscular veins, the tunica intima projects into the lumen as valves to prevent blood backflow; this is of particular importance in the extremities, where semi-lunar projections that act as valves to maintain unidirectional blood flow.
Clinical Correlation:
- Valve failure causes stretching of the vessel wall and varicose veins and can lead to stasis dermatitis.