血管

#血blood

##动脉Arteries

###毛细血管Capillaries 

##静脉Vein

High-oxygen blood in your arteries looks bright red.

$\color{#FF0000}{In reality, low-oxygen bllood in your veins looks dark red. }$

注： 本文练习Markdown语法，可是还没成功调出红色。 努力中...