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The familiar sounds of your heart are made by the heart's valves as they open and close.
Signs of depression include feeling sad most of the time for 2 weeks or longer; loss of interest in things normally enjoyed; lack of energy; sleep and appetite disturbances; weight changes; feelings of hopelessness, helplessness, or worthlessness; an inability to make decisions; and thoughts of death and suicide.
There are actually 60 minerals, 16 vitamins, 12 essential amino acids, and three essential fatty acids that your body needs every day.
Chronic marijuana use can damage the white blood cells and reduce the immune system's ability to respond to disease by as much as 40%. Without a strong immune system, the body is vulnerable to all kinds of degenerative and infectious diseases.
Once thought to have neurofibromatosis, Joseph Merrick (also known as "the elephant man") is now, in retrospect, thought by clinical experts to have had Proteus syndrome. This endocrine disease causes continued and abnormal growth of the bones, muscles, skin, and so on and can become completely debilitating with severe deformities occurring anywhere on the body.
![Otitis media. This illustration shows an inflamed tympanic cavity, which is the most common source o](https://biology-forums.com/gallery/47/medium_14755_14_10_12_6_37_46_94012321.jpeg)
![In the summer of 1793, a yellow fever epidemic struck Philadelphia, killing nearly 4,000. Tens of th](https://biology-forums.com/gallery/47/medium_374628_16_08_15_9_52_07_222511109.jpeg)