M01.10.07 Arteriole and Venules

Histology of Arterioles and Venules

Arterioles:

• Structure: Arterioles are small arteries with a thick muscular layer relative to their size. They have three layers:
  • Tunica Intima: Endothelial lining with a thin subendothelial layer.
  • Tunica Media: Dominated by smooth muscle cells that regulate blood flow and pressure.
  • Tunica Adventitia: Thin and consists mostly of connective tissue.
• Function: Arterioles regulate blood flow into capillaries by constricting or dilating. They play a major role in controlling systemic vascular resistance and thus blood pressure.

Arteriole and Venule

Normal arteriole and venule with peripheral nerve

medium power microscopic

Venules:

• Structure: Venules are small veins that collect blood from capillaries. They have a thinner wall than arterioles, with:
  • Tunica Intima: Single layer of endothelial cells.
  • Tunica Media: Thin smooth muscle layer.
  • Tunica Adventitia: Contains collagen fibers and some smooth muscle.
• Function: Venules allow for the return of blood from the capillaries to larger veins. Their walls are less muscular and more distensible than those of arterioles.

Key Points:

• Arterioles are more muscular and play a role in regulating blood pressure.
• Venules have thinner walls and are involved in blood collection and return.