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Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
Prostaglandins were first isolated from human semen in Sweden in the 1930s. They were so named because the researcher thought that they came from the prostate gland. In fact, prostaglandins exist and are synthesized in almost every cell of the body.
Over time, chronic hepatitis B virus and hepatitis C virus infections can progress to advanced liver disease, liver failure, and hepatocellular carcinoma. Unlike other forms, more than 80% of hepatitis C infections become chronic and lead to liver disease. When combined with hepatitis B, hepatitis C now accounts for 75% percent of all cases of liver disease around the world. Liver failure caused by hepatitis C is now leading cause of liver transplants in the United States.
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.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
![Injecting an IV push (bolus) medication; C, another type of needleless syringe and needleless IV acc](https://biology-forums.com/gallery/47/medium_18099_26_09_12_4_39_03.jpeg)
![A replaceable PROM used in an older General Motors computer. Notice that the sealed access panel ...](https://biology-forums.com/gallery/29/medium_548020_30_05_17_8_05_55_298772489.png)