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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
There are more sensory neurons in the tongue than in any other part of the body.
The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.
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.
Although not all of the following muscle groups are commonly used, intramuscular injections may be given into the abdominals, biceps, calves, deltoids, gluteals, laterals, pectorals, quadriceps, trapezoids, and triceps.