Human Anatomy

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Scientists disagree about the number of facial expressions that humans can make. Some state that all human facial expressions are variations of four basic faces that people make, whereas other scientists suggest that 21 or more facial expressions are possible. Facial expressions are important for communication between people.

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  • What Part of the Brain Do We Use When We Dream?

    Q: What Part of the Brain Do We Use When We Dream?

    A: According to Bryn Mawr College, the pons is largely responsible for dreaming because of its role in regulating REM sleep, which is vital for dreaming. Damage to the pons can result in loss of dreaming sleep.
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  • What Are the Similarities Between Cat and Human Anatomy?

    Q: What Are the Similarities Between Cat and Human Anatomy?

    A: According to Melodie Anne Coffman for The Nest, cats and humans share many anatomical similarities within the lungs, heart, digestive system, urinary tract and sex organs. Cats also share very basic elements of anatomy with humans, including eyes, mouths, ears, noses, bones, tongues, teeth and skin.
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  • What Is the Name of the Gland That Excretes Water and Salt Through the Skin?

    Q: What Is the Name of the Gland That Excretes Water and Salt Through the Skin?

    A: The glands that excrete water and salt through the skin are named the sudoriferous glands. These are also known as sweat glands and are divided into eccrine sweat glands and apocrine sweat glands.
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  • Can the Veins in Your Body Reach Around the World?

    Q: Can the Veins in Your Body Reach Around the World?

    A: When laid out back-to-back in a single line, the blood vessels of one human being are long enough to wrap around the world more than two times, according to The Franklin Institute. This equals a length of 60,000 to 100,000 miles long, depending on the individual.
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  • What Causes Lack of Oxygen?

    Q: What Causes Lack of Oxygen?

    A: Lack of oxygen, or hypoxia, can be caused by a wide range of medical and environmental factors. Externally, lack of oxygen is usually the result of exposure to low-oxygen environments, such as those at high altitudes. This is why the FAA recommends that pilots use supplemental oxygen for altitudes over 10,000 feet in the day and 6,000 feet at night, according to About.com.
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  • Why Do People Snort When They Laugh?

    Q: Why Do People Snort When They Laugh?

    A: People snort when they laugh because they are also exhaling through the nose. The snorting sound, similar to snoring, is caused by an obstruction in the airway as the breath is exhaled.
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  • What Is the Length of an Average Walking Stride?

    Q: What Is the Length of an Average Walking Stride?

    A: The length of an average walking stride is 62 inches. People frequently mistake stride for step length, or wrongly assume they are one in the same. Step length is defined as the distance between the heel strike of one foot and the heel strike of the opposite foot. On the other hand, stride refers to the consecutive heel strikes of the same foot.
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  • Why Do Fingernails Bend?

    Q: Why Do Fingernails Bend?

    A: Fingernails bend easily if they are weakened by environmental damage, poor nutrition or illnesses. Healthy fingernails are supposed to be strong and firm and should not bend or break easily. A person with weak fingernails has a number of factors to consider in order to determine the exact cause.
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  • How Much Do Humans Sleep in a Lifetime?

    Q: How Much Do Humans Sleep in a Lifetime?

    A: According to the National Institutes of Health, an average human spends about one third of his life sleeping. Assuming an average human life span of 78 years, that equates to about 26 years each person spends sleeping in his lifetime.
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  • What Is an Average Wrist Size?

    Q: What Is an Average Wrist Size?

    A: According to Watch Cases, the average wrist size for adults is 7.17 inches. This measurement varies according to the height, build and age of a person.
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  • What Are the Advantages of Jointed Appendages?

    Q: What Are the Advantages of Jointed Appendages?

    A: Jointed appendages are an advantage because they allow for any activity that requires movement, including walking, swimming, feeding, and defense. Jointed appendages act the same as a system of levers or like the joints on the human body.
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  • At What Age Does a Girl Stop Growing?

    Q: At What Age Does a Girl Stop Growing?

    A: On average, girls reach their final adult height and stop growing by age 14 or 15, though this figure skews either younger or older depending on when puberty begins. Most girls experience a growth spurt between ages 10 to14, and a female's rate of growth peaks around two years after puberty begins, which is usually around age 12.
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  • Where Is the Brachial Pulse?

    Q: Where Is the Brachial Pulse?

    A: The pulse of the brachial artery, located in the upper arm, can be felt on the elbow's ventral aspect. This artery is the major blood vessel that supplies the upper arm with blood.
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  • What Is a Nasal Passage?

    Q: What Is a Nasal Passage?

    A: The nasal passage is a channel wherein air flows through the nose. Respiratory mucous membranes with many hair-like cells line the walls of this passage.
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  • What Is the Fastest Healing Part of the Body?

    Q: What Is the Fastest Healing Part of the Body?

    A: The fastest healing part of the body is the tongue. This is due to the rich supply of blood the tongue receives, making it able to heal twice as fast as any other part of the body. This includes taste buds, which is why someone can burn taste buds eating hot food and later be able to taste perfectly fine because the taste buds have quickly healed.
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  • On Average, How Many Hairs Are on a Human Head?

    Q: On Average, How Many Hairs Are on a Human Head?

    A: On average, there are 100,000 hairs on a human head. Everyone is born with a set amount of hair follicles. Hair grows from follicles that enclose the hair root in the person's scalp. The reason children's hair looks thicker is because their heads are smaller.
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  • What Is the Function of the Alveoli?

    Q: What Is the Function of the Alveoli?

    A: The function of the alveoli is to assist in oxygen exchange through the membranes of the small balloon-like structures. The alveoli are found on the branches of the bronchial passages.
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  • What Are Six Substances Transported by Blood?

    Q: What Are Six Substances Transported by Blood?

    A: The blood transports oxygen, carbon dioxide, nutrients, water, hormones, waste substances and heat. The waste substances are moved to the liver and kidneys, which remove toxins from the blood. Urea is moved from the liver to the kidneys.
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  • What Body Part Doesn't Grow?

    Q: What Body Part Doesn't Grow?

    A: The only human body part that does not grow after birth is the ossicular chain, which is composed of three small bones and is located in the middle ear. These bones are also the smallest lightest bones in the human body. Each bone is smaller than a grain of rice. The stapes is the smallest and is only 2.8 millimeters or 0.11 inch long.
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  • How Do You Get Pregnant With Quintuplets?

    Q: How Do You Get Pregnant With Quintuplets?

    A: According to the American Pregnancy Association, there are two ways that a woman can become pregnant with more than one child at a time, either multiple eggs are fertilized at the same time, or one fertilized egg divides into multiple embryos. The chances of becoming pregnant with more than baby is low however. In particular quintuplets are very rare, accounting for less than 41 births in 2011 out of almost four million total births, as noted by Multiples of America.
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  • What Causes Severe Hunger Pains?

    Q: What Causes Severe Hunger Pains?

    A: Better Medicine states that hunger is the result of a complicated group of interactions controlled by the body's endocrine, digestive and neurological systems. These systems send chemicals to the brain to indicate both hunger and fullness. When a person consistently experiences excessive hunger, it can be a sign of illness.
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