AN69.1-3 | Blood Vessels — Summary & Reflection

KEY TAKEAWAYS

Key histological points to carry forward:

1. All blood vessels (except capillaries) have three tunics: intima (endothelium), media (smooth muscle ± elastic), adventitia (collagen/fibroblasts)
2. Elastic arteries (aorta): multiple concentric elastic lamellae in the media — buffer pressure
3. Muscular arteries: prominent internal elastic lamina + thick smooth muscle media — regulate flow
4. Capillaries: endothelium + basement membrane only; three types — continuous (BBB), fenestrated (kidney/gut), sinusoidal (liver/spleen)
5. Veins: thin wall, larger lumen, valves in limbs; tunica media less developed than arteries
6. Ultrastructure highlights: Weibel-Palade bodies (endothelium), type IV collagen in basement membrane, gap junctions in media, dense bodies in smooth muscle

Indian clinical hook: Hypertensive arteriosclerosis (hardening of muscular arteries due to smooth muscle hypertrophy and intimal fibrosis) is an epidemic in India. Histology = concentric laminar fibrosis of the intima, smooth muscle hyperplasia of media — directly traceable to the three-layered wall structure.