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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
There are more sensory neurons in the tongue than in any other part of the body.
Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
Children with strabismus (crossed eyes) can be treated. They are not able to outgrow this condition on their own, but with help, it can be more easily corrected at a younger age. It is important for infants to have eye examinations as early as possible in their development and then another at age 2 years.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
![Internal view of the heart illustrating the heart chambers, heart layers, and major blood vessels as](https://biology-forums.com/gallery/47/medium_14755_10_09_12_7_22_08_851775.jpeg)
![Aneurysm. Photograph of the aorta, the large blood vessel arising from the heart, with a large bulge](https://biology-forums.com/gallery/47/medium_14755_11_11_12_7_14_25_100201378.jpeg)