The first heart sound consists of two components: mitral  and tricuspid.  These two components are separated by a short interval which creates an audible narrow splitting of S1.  Here, you can find more information and a good example of the normal splitting of S1.

A lot of information is enciphered in heart sound.  There are two main problems:  it is difficult to perceive this sound because it is too faint, and it is not simple to interpret reaped information.  The later is some kind of understanding a foreign language.  Let us continue our talk about the language of the heart.

I am going to publish a series of posts about issential heart sound and murmurs. I will try to be explicit and breaf. And I will try to give information relevant to clinical use.
The first heart sound will be the first. This is natural, isn't it?