There are four seasons in a year in Canada. They are spring, summer, autumn and winter. In spring, the weather is warm and sunny. I like to fly kites. In summer, it's hot. I like to swim. I often wear a pair of glasses and a hat. In autumn, it's always cool. I like to go to the park and ride down the street with my friends. In winter, it's cold and snowy. I like to go outside to skate and ski with my friends. Sometimes we make a big snowman, and then we dance and sing around it.

设向量$\overrightarrow{a}=\left(\sqrt{3}\sin x,\cos x\right),\overrightarrow{b}=\left(\cos x,\cos x\right)$，记$f\left(x\right)=\overrightarrow{a}·\overrightarrow{b}$，函数$y=f\left(x\right)$的周期是（      ）

与右心室相连通的血管是（　　）