Blood Vessel.

Vascular Ultrastructure

Schematics of the structures of various types of blood vessels.

A. Capillaries consist of an endothelial tube in contact with a discontinuous population of pericytes.

B. Veins typically have thin medias and thicker adventitias.

C. A small muscular artery consists of a prominent tunica media.

D. Larger muscular arteries have a prominent media with smooth-muscle cells embedded

in a complex extracellular matrix.

E. Larger elastic arteries have circular layers of elastic tissue alternating with concentric rings

of smooth-muscle cells.

Vascular Cell Biology

The endothelium also participates in the local regulation of blood flow and vascular caliber.

Endogenous substances produced by endothelial cells,

such as prostacyclin, endothelium-derived hyperpolarizing factor, and nitric oxide (NO),

provide tonic vasodilatory stimuli under physiologic conditions in vivo (Table 217-1).

Vascular Smooth muscle cell

Regulation of vascular smooth-muscle cell calcium concentration

and actomyosin ATPase-dependent contraction.

NE, norepinephrine / ET-1, endothelin-1 /AngII, angiotensin II /PIP₂,phosphatidylinositol 4,5-biphosphate

PLC, phospholipase C / DAG, diacylglycerol /G, G-protein /VDCC, voltage-dependent calcium channel

IP₃, inositol 1,4,5-trisphosphate /PKC, protein kinase C /SR, sarcoplasmic reticulum / NO, nitric oxide

ANP, antrial natriuretic peptide / pGC, particular guanylyl cyclase / AC, adenylyl cyclase

sGC, soluble guanylyl cyclase /PKG, protein kinase G /PKA, protein kinase A

MLCK, myosin light chain kinase /MLCP, myosin light chain phosphatase