Well let me first say that your hair is dead with know feelings it’s not alive, I thought I would throw that in. We have have follicles on our head and each day our hair releases a certain about of hair strands so that new ones can grow in. Depending on what condition your scalp is in. That plays and important role on how fast and how much of hair grows, so try and keep your scalp healthy. Sometimes when some of those follicle get damage then the hair don’t grow in those spots and as you get older some of those follicles die and you hair appears thinner.