why do we cry when we're sad

so lately for some reason I was wondering why people cry when sad, it just seems weird when you really think about it. So I looked it up and this is what I came up with ( I just copied and pasted it so these aren't my words). It makes a lot of sense and now I know why people cry

Crying is a more complicated process than one would at first imagine. First of all, there are really three different types of tears. Basal tears keep our eyes lubricated constantly. Reflex tears are produced when our eyes get irritated, like with onions or when something gets into our eyes. The third kind of tear is produced when the body reacts emotionally to something. Each type of tear contains different amounts of chemical proteins and hormones. Scientists have discovered that the emotional tears contain higher levels of manganese and the hormone prolactin, and this contributes in a reduction of both of these in the body; thus helping to keep depression away. Many people have found that crying actually calms them after being upset, and this is in part due to the chemicals and hormones that are released in the tears.

How then actually do we cry? The psychic tears (or emotional tears) require an emotional response, or trigger to be activated. This response can be caused by an outside source, either pain or loss of love, etc., or from an inside source (self-realization of one's life and others). When emotions affect us, the nervous system stimulates the cranial nerve, in the brain and this sends signals to the neurotransmitters to the tear glands. Thus, we cry .The largest tear gland, the lacrimal gland produces the tears of emotion and reflex. Many believe that the body, in times of emotional stress, depends on this gland to release excess amounts of chemicals and hormones, returning it to a stable state.