Everything about Arterioles totally explained
An
arteriole is a small diameter
blood vessel that extends and branches out from an
artery and leads to
capillaries.
Arterioles have thin
muscular walls (usually only one to two layers of smooth muscle) and are the primary site of
vascular resistance.
Blood pressure in the arteries supplying the body is a result of the work needed to pump the
cardiac output (the flow of blood pumped by the heart) through the
vascular resistance, usually termed
total peripheral resistance by physicians and researchers.
Natural fluctuation
The up and down fluctuation of the
arterial blood pressure is due to the pulsatile nature of the
cardiac output and determined by the interaction of the
stroke volume versus the volume and elasticity of the major arteries.
In a healthy vascular system the
endothelium, inner lining of arterioles and other blood vessels, is smooth and the vessel is relaxed.
This healthy condition is promoted by the ample production of
nitric oxide in the endothelium, which biochemical reaction is regulated by a complex balance of
polyphenols, various
nitric oxide synthase enzymes and L-
arginine. In addition there's direct communication via gap junctions between the endothelial cells and the vascular smooth muscle
Pathology
Any pathogen which constricts blood flow, such as
stenosis, will increase total peripheral resistance and lead to
hypertension.
Medication
The muscular contraction of arterioles is targeted by drugs that lower blood pressure (
antihypertensives), for example the
dihydropyridines (
nifedipine and
nicardipine), which block the
calcium conductance in the muscular layer of the arterioles, causing relaxation.
This decreases the resistance to flow into peripheral vascular beds, lowering overall systemic pressure.
Metarterioles
A "
metarteriole" is an arteriole which bypasses capillary circulation.
Further Information
Get more info on 'Arterioles'.
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