Histology: Circulatory System Flashcards
What are the 3 layers of vessels?
Tunica intima
Tunica media
Tunica adventitia
What are the components of the tunica intima?
- Endothelium
- Subendothelium
- Internal elastic lamina (IEL) in arteries
What are the components of the tunica media?
- Smooth muscle layer
- External elastic lamina (EEL) in arteries
What are the components of the tunica adventitia?
- Connective tissue and fibroblasts
- Longitudinal smooth muscle in veins
- Vasovasorum in large vessels
What is a unique structure found only in veins?
Valves
What vessel part is very large in large arteries?
Tunica media
What is the major cell type that dominates medium arteries?
Smooth muscle (AKA muscular artery)
What is the difference between small and medium arteries?
Generally have same structure as medium artery but have a smaller diameter and no external elastic lamina. The tunica media also has fewer layers of smooth muscle cells.
What is the difference between the arterioles and other blood vessels?
Only two layers of smooth muscle cells. Internal elastic lamina, external elastic lamina, and subendothelial layers usually absent.
Continuous, Fenestrated and Discontinuous Capillaries
Continuous - no holes at all
Fenestrated - holes on the endothelium
Discontinuous - holes on the endothelium AND basal lamina
What layer generally dominates in veins?
Tunica adventitia which is at least as wide as the media, and often even wider.
What layer are the valves in veins formed from?
Tunica media
Where are the vasa vasorum found?
Tunica adventitia
What are the differences in the lumen of arteries and veins?
Arteries are smaller and rounder with prominent internal elastic lamina while veins are larger and flatter
What are some of the features of the lymphatic vessels?
- Have large lumens and relatively thin walls
- Single layer of endothelium
- Connective tissue outer layer with few smooth muscle cells
- Also have valves
