Arteriole : lecture note

 

Arteriole

The greatest change in blood pressure and velocity of blood flow occurs at the transition of arterioles to capillaries. An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries

Arteriole is also known as resistance vessels . Most arterioles can dilate 60% to 100% from their resting diameter, and they can maintain as much as 40% constriction for a long time. Therefore, a large decrease or increase in vascular resistance has a direct effect on distribution of blood flow and systemic arterial pressure.

Arteriole About 10 percent of the total blood volume is in the systemic arterial system at any given

If all the arteries, veins, and capillaries were laid end to end, the total length would be  100,000 km

The diameter of arterioles  are in between  100  to 300 µm.

Arteriole: Like any other blood vessels arteriole is made by three concentric layers (within outward )

Tunica intima ,Tunica media and Tunica adventitia

Tunica intima of arteriole  contain

1. endothelium & its basement membrane

2. Subendothelial connective tissue is formed by loose connective tissue which contain smooth muscle cells

3. Large arteriole contain internal elastic lamina but small arteriole contain no  internal elastic lamina

Tunica media of arteriole contain Circularly arrange smooth muscle cells layers(1-2 cells layer)  with variable amounts of elastin, reticular fibers, and proteoglycans are interposed between the smooth muscle cells

Arteriole  has tunica adventitia which  is composed of collagenous & elastic connective tissues, whose thickness approaches that of the tunica media.

Large arteriole contain external elastic lamina but small arteriole contain no  external elastic lamina  

Arterioles control blood flow to capillary networks by contraction of the smooth muscle cells. Arterioles serve as flow regulators for the capillary beds. In the normal relationship between an arteriole and a capillary network, contraction of the smooth muscle in the wall of an arteriole increases the vascular resistance and reduces or shuts off the blood going to the capillaries.

Arteriole is also known as resistance vessels . Most arterioles can dilate 60% to 100% from their resting diameter, and they can maintain as much as 40% constriction for a long time. Therefore, a large decrease or increase in vascular resistance has a direct effect on distribution of blood flow and systemic arterial pressure.