Human Anatomy

A:

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.

See Full Answer
Filed Under:
  • How many muscles are there in a human body?

    Q: How many muscles are there in a human body?

    A: According to the Library of Congress, the human body has at least 650 skeletal muscles and as many as 840 depending on what counts as a muscle. Some sources count complex muscles as a single muscle, while others count complex muscles' individual parts as separate muscles, which leads to dissent.
    See Full Answer
    Filed Under:
  • How long can the human intestine stretch?

    Q: How long can the human intestine stretch?

    A: The combined length of the small and large intestines averages 25 feet long. Individually, the uncoiled small intestine has an average length of 20 feet, while the large intestine has an average length of 5 feet. The length of the intestines allows for enough time for nutrients to be absorbed before waste is expelled from the body.
    See Full Answer
    Filed Under:
  • What part of the brain does music affect?

    Q: What part of the brain does music affect?

    A: Initially, a person's temporal and frontal lobes begin processing the sounds of music when a song begins to play, with brain cells deciphering melody, rhythm and pitch. Many researchers believe most activity concerning music happens in the brain's right hemisphere, while other researchers say it happens on both sides.
    See Full Answer
    Filed Under:
  • What is the area behind the knee called?

    Q: What is the area behind the knee called?

    A: The area behind the knee is called the posterior cruciate ligament (PCL), and it connects the femur, or thigh bone, to the tibia, or shin bone. The ligament prevents the tibia from moving backward to a point that can cause injury, according to the American Academy of Orthopaedic Surgeons.
    See Full Answer
    Filed Under:
  • What is the largest vein in the human body?

    Q: What is the largest vein in the human body?

    A: The two largest veins in the human body are the superior and inferior vena cavae. These veins, which are roughly the same size, are the final conduits for deoxygenated blood before it is returned to the heart.
    See Full Answer
    Filed Under:
  • What causes a body to jerk during sleep?

    Q: What causes a body to jerk during sleep?

    A: According to the National Institute of Neurological Disorders and Stroke (NINDS), the sudden, involuntary jerking of a muscle or group of muscles while drifting off to sleep is called myoclonus. It is caused by sudden muscle contractions, also known as positive myoclonus, or muscle relaxation, which is referred to as negative myoclonus. Myoclonic jerks may occur alone or in sequence, in a pattern or without pattern.
    See Full Answer
    Filed Under:
  • 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.
    See Full Answer
    Filed Under:
  • How do you put someone to sleep fast using pressure points?

    Q: How do you put someone to sleep fast using pressure points?

    A: An acupressure practitioner can send someone to sleep quickly by applying pressure on one or several of his pressure points. For example, applying pressure on the middle of the inner side of the wrist, between the eyebrows or on the center of the breastbone can help induce quick sleep.
    See Full Answer
    Filed Under:
  • How does a sheep brain and a human brain compare?

    Q: How does a sheep brain and a human brain compare?

    A: There are significant differences between the human brain and the brains of sheep; for instance, the human brain is larger in size and heavier when compared to a sheep’s brain. An adult human brain weighs 1,300 to 1,400 grams, while the brain of a sheep weighs in at around 140 grams. Sheep brains have less ridges and contours in comparison to human brains.
    See Full Answer
    Filed Under:
  • How long does it take to grow a mustache?

    Q: How long does it take to grow a mustache?

    A: The time it takes to grow a mustache depends on how fast the hair grows and the type of mustache desired. On average, hair on the body, including the face, grows at a rate of 1/2-inch per month.
    See Full Answer
    Filed Under:
  • Does everybody have a birthmark?

    Q: Does everybody have a birthmark?

    A: Everybody is not born with a birthmark. More than 10 babies out of 100 have a birthmark when they are born or develop one shortly after birth.
    See Full Answer
    Filed Under:
  • What do the different types of chins mean?

    Q: What do the different types of chins mean?

    A: In the Chinese face reading practice, a round chin belongs to a person who is supportive, generous, sympathetic, kind and family-minded, whereas a square chin alludes to a more stubborn individual. A pointed or narrow chin characterizes a hot-tempered, stubborn, fiery, sensitive, fun-loving and sociable person who also loves to gossip.
    See Full Answer
    Filed Under:
  • Why do optical illusions work?

    Q: Why do optical illusions work?

    A: Optical illusions work because humans have binocular vision, which allows people to see different objects with each eye and sometimes the images do not merge properly. The brain must also interpret the signals correctly. Persistence of vision can also make optical illusions work.
    See Full Answer
    Filed Under:
  • What causes yawning?

    Q: What causes yawning?

    A: The theories regarding why people yawn range from boredom to cooling the brain to helping the brain to stay more alert. Regardless of what causes yawning, it is widely accepted that yawning is contagious.
    See Full Answer
    Filed Under:
  • What causes flushed cheeks?

    Q: What causes flushed cheeks?

    A: According to the National Health Service of the U.K., flushed cheeks, or "blushing," is a result of the involuntary nervous system responding to stress or embarrassment. Your face muscles relax, which allows your face's blood vessels to expand and take in more blood, causing the reddish hue of blushing.
    See Full Answer
    Filed Under:
  • 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.
    See Full Answer
    Filed Under:
  • What is the torso area of the body?

    Q: What is the torso area of the body?

    A: The torso is the main part of the body to which the neck and limbs attach, and it is a common feature of all vertebrates. The torso holds the body’s major internal organs except for the brain. Often, scientists refer to either the lower torso or the upper torso for better clarity.
    See Full Answer
    Filed Under:
  • What is the capacity of a human stomach?

    Q: What is the capacity of a human stomach?

    A: According to the National Center for Biotechnology Information (NCBI), the human stomach is an elastic organ that can expand to hold from 0.25 to 1.7 L of contents without causing any discomfort. The average human stomach has a capacity of roughly 1 L, or a little more than a quart.
    See Full Answer
    Filed Under:
  • Does the time of day affect your body temperature?

    Q: Does the time of day affect your body temperature?

    A: According to the National Institute of General Medical Sciences, the time of day affects the body temperature through a physiological phenomenon called circadian rhythm. The UCLA Sleep Disorders Center explains this cycle is controlled by small nuclei in the brain, called the suprachiasmatic nuclei, along with other circadian rhythms.
    See Full Answer
    Filed Under:
  • 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.
    See Full Answer
    Filed Under:
  • How long does it take for water to get to the bladder?

    Q: How long does it take for water to get to the bladder?

    A: On average, it takes the human body approximately two to three hours to excrete a liter of water through the bladder. This is dependent on several factors, including the absorption of water, the components in the water, if dehydration is present, the time of day and the general health of the person.
    See Full Answer
    Filed Under: