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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.
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.
This year, an estimated 1.4 million Americans will have a new or recurrent heart attack.
The Centers for Disease Control and Prevention has released reports detailing the deaths of infants (younger than 1 year of age) who died after being given cold and cough medications. This underscores the importance of educating parents that children younger than 2 years of age should never be given over-the-counter cold and cough medications without consulting their physicians.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.