40 facts about the human body that are based on reliable sources.

The internet is replete with videos that purport to reveal astonishing facts about the human body, but their veracity is not always grounded in the most reputable sources. This particular article is.

For instance, fingernails grow at twice the rate of toenails, and the pinky fingernail grows at a slower pace than all other nails. Over a decade, the human body regenerates an entirely new skeleton. Eyelashes take one to two months to reach full length, and the human body produces a liter of saliva daily. The stapes, located in the ear, is the smallest bone in the human body. The plica semilunaris, a vestigial structure, is the remnant of a third eyelid that many creatures on earth possess to clean and protect the eye between blinks. If one were to lay out their blood vessels end to end, they would wrap around the Earth four times.

The human heart can continue beating outside of the body, thanks to its internal pacemaker, as long as it has an oxygen supply. The left lung is smaller than the right lung due to the heart's placement. The enamel of human teeth is as hard as that of shark teeth. The cornea is the only part of the human body that does not receive oxygen through the blood, but rather through the air. Women's hearts beat faster than men's at rest, on average. Teeth are the only body part that cannot heal themselves.

The masseter is the strongest muscle based on its weight, and it can exert a force of up to 55 pounds on the incisors or 200 pounds on the molars. Onions produce syn-Propanetriol S-oxide, a chemical irritant that stimulates the lacrimal glands to release tears. The ovum is the largest cell in the human body, while sperm cells account for only a small fraction of the body's volume. A teratoma or dermoid cyst is a tumor that can contain tissue, hair, muscle, and even teeth.

Women's brains shrink during pregnancy. The human brain contains 100 billion neurons and 10 to 50-fold more glial cells. Stomach acid is one of the most acidic substances in the world, with a pH of 1, and it can dissolve many metals. However, the enzymes in the stomach cannot digest plastic. Digesting food accounts for 5 to 15% of the calories burned during the day. The human GI tract contains approximately 100 trillion microorganisms, including bacteria, viruses, fungi, and protozoa.

Cilia in the nose continue moving for up to 20 hours after death. Women's noses have up to 50% more neurons than men's noses, giving them a better sense of smell. In addition to the five senses, humans possess proprioception, equilibrioception, thermosetting, nociception, and chronoception. The gluteus maximus is the largest muscle in the human body. Aquagenic urticaria is a rare condition in which hives develop rapidly after the skin comes in contact with water, regardless of its temperature. There is no cure, but treatments are available. Regular exercise causes individuals to sweat sooner and more frequently than those who do not exercise.

Lingual papillae, which come in four types, contain taste buds, while filiform papillae are responsible for the tongue's sense of touch. Brain freeze, or sphenopalatine ganglioneuralgia, is a phenomenon that causes a harsh pain when biting into something cold, but its cause remains a mystery. Congenital insensitivity to pain is a rare condition in which individuals do not experience physical pain, which can be a curse rather than a blessing. The body's system of balance is determined by three small canals in the ear containing tiny hair cells that move when liquid sloshes back and forth.

The tongue has a unique print, just like the fingertips, which could be used as a means of unlocking a phone in the future. Demodex are small mites that live on eyelashes and can cause acne. Goosebumps, a vestigial reaction, raise the hair on the body, which was useful for our ancestors to keep warm and appear larger to predators. The pinky finger and its associated muscles are responsible for 50% of the hand's strength. The liver performs over 500 functions, including producing bile and cholesterol, cleaning the blood, and metabolizing toxins. A juice cleanse is not necessary; a healthy liver is all that is required.