Keratin is a durable protein that makes which skin layer waterproof and resistant to bacteria and viruses?

What is the name given to the action produced by the forward stroking of millions of cilia?

a. Coughing b. Mucociliary escalator c. Mucus stroking d. The wave

In the precordial leads, V1's QRS complex

A) represents atrial depolarization. B) should be isoelectric. C) should be a primarily negative deflection. D) should be a primarily positive deflection.