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The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
There are more bacteria in your mouth than there are people in the world.
Long-term mental and physical effects from substance abuse include: paranoia, psychosis, immune deficiencies, and organ damage.
For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
![The absorption of cerebrospinal fluid from the subarachnoid space (blue) into a major sinus. Note ...](https://biology-forums.com/gallery/30/medium_548020_02_06_17_12_10_51_30203561.png)
![Absorption of a drug through cell membranes into the bloodstream (systemic circulation). The drug ...](https://biology-forums.com/gallery/31/medium_398119_17_07_17_9_59_15_319381276.jpeg)