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When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.
The types of cancer that alpha interferons are used to treat include hairy cell leukemia, melanoma, follicular non-Hodgkin's lymphoma, and AIDS-related Kaposi's sarcoma.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.