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Author Question: Ashley is trying to create a small model village on the mantle of her fireplace. She bought ... (Read 26 times) |
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
Blood is approximately twice as thick as water because of the cells and other components found in it.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
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.