HCA?
I believe it's "lub" and "dup". (p. 493, under "heart sounds" heading...second sentence)
Lubb dubb corresponds to the heart sounds heard during systole and diastole, respectively.
lub dub
Lub dub
Phonocardiogram
phonocardiogram
Onomatopoeia
Sounds as if you are describing graphite.
The word is spelled onomatopoeia. An onomatopoeia is a word that sounds like what it is describing. A good example of this is the word quack. The sound that a duck makes is "Quack." The word sounds like the sound it is describing.
Onomatopoeia: Where sounds are spelled out as words; or, when words describing sounds actually sound like the sounds they describe. I heard him gurgling water.
It sounds like you are describing teaching.
Sounds like you're describing a hemisphere.
There is no such thing as a Jewish number on a wrist. But it sounds like you are describing Holocaust survivors, who were tattooed by the Nazis with identification numbers during World Word II.