My Science School

People are born with 5 million hair follicles, 100,000 of which are located on your scalp, according to the American Academy of Dermatology. Male hair grows faster than female hair.

The number of hairs that someone has on their head can vary by individual. However, the average person has about 100,000 hairs on their head at one time.

The hair on our bodies serves many functions. It helps to protect us from the elements, to regulate our body temperature, and to perceive sensations.

The amount of hair on a person’s head can vary by individual. The average human head has about 100,000 hairs with a similar number of hair follicles.

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The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger and every process that regulates our body. Together, the brain and spinal cord that extends from it make up the central nervous system, or CNS.

Weighing about 3 pounds in the average adult, the brain is about 60% fat. The remaining 40% is a combination of water, protein, carbohydrates and salts. The brain itself is a not a muscle. It contains blood vessels and nerves, including neurons and glial cells.

The brain sends and receives chemical and electrical signals throughout the body. Different signals control different processes, and your brain interprets each. Some make you feel tired, for example, while others make you feel pain.

Some messages are kept within the brain, while others are relayed through the spine and across the body’s vast network of nerves to distant extremities. To do this, the central nervous system relies on billions of neurons (nerve cells).

The cerebrum (front of brain) comprises gray matter (the cerebral cortex) and white matter at its center. The largest part of the brain, the cerebrum initiates and coordinates movement and regulates temperature. Other areas of the cerebrum enable speech, judgment, thinking and reasoning, problem-solving, emotions and learning. Other functions relate to vision, hearing, touch and other senses.

Credit : Johns Hopkins 

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The brain is the fattiest organ in our body it is composed of nearly 60% fat. The largest part of the central nervous system, the brain controls our thoughts, speech, movements and memory. It is composed of billions of neurons, or nerve cells, and glial cells.

Each day humans must consume a certain amount of water to survive. Of course, this varies according to age and gender, and also by where someone lives. Generally, an adult male needs about 3 liters (3.2 quarts) per day while an adult female needs about 2.2 liters (2.3 quarts) per day. All of the water a person needs does not have to come from drinking liquids, as some of this water is contained in the food we eat.

According to Dr. Jeffrey Utz, Neuroscience, pediatrics, Allegheny University, different people have different percentages of their bodies made up of water. Babies have the most, being born at about 78%. By one year of age, that amount drops to about 65%. In adult men, about 60% of their bodies are water. However, fat tissue does not have as much water as lean tissue. In adult women, fat makes up more of the body than men, so they have about 55% of their bodies made of water. 

Credit : USGS

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The glabella is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. The word 'glabella' translates to 'smooth' from the original Latin glabellus. This is because this area tends to be hairless.

Glabella lines and frown lines are often used interchangeably to describe the lines above the nose and around the forehead, with some even using the term “glabella frown lines.” While the two terms refer to similar lines in the same area of the face, they do not mean exactly the same thing.

Glabellar lines are found above the eyebrows on the forehead. These lines run horizontally from one of the eyebrows to the other. Frown lines, however, can be found between the eyes, adjacent to the eyebrows. These creases are deep, vertical lines that stretch from above the side of the nose to right above the eyebrows in most people.

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The skin is the soft outer cover/organ that forms the outer surface of the body. There are over 4 million pores in the skin. In 1 square inch of skin there lies 4 yards of nerve fibers, 1300 nerve cells, 100 sweat glands, 3 million cells, and 3 yards of blood vessels. Every square inch of the human body has an average of 32 million bacteria on it. Humans shed about 600,000 particles of skin every hour - about 1.5 pounds a year. Most dust particles in your house are made from dead skin. By 70 years of age, an average person will have lost 105 pounds of skin.

Skin shields the body against infection, dehydration, injuries, parasites, and temperature changes. It provides sensory information about the environment, manufactures vitamin D; and excretes salts and small amounts of urea. Skin provides a relatively dry and semi-impermeable barrier to fluid loss. The skin acts as a water resistant barrier so essential nutrients aren't washed out of the body.

Like a big bag of grain that takes shape on what is inside it. The largest human organ is the skin, with a surface area of about 25 square feet.

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The elbow is a complex joint formed by the articulation of three bones –the humerus, radius and ulna. The elbow joint helps in bending or straightening of the arm to 180 degrees and assists in lifting or moving objects.

The elbow can move in three ways based on slight variations in the positions of the heads of the three bones. The first is the large hinge action that is used in most movements of the arms, such as holding bags of groceries or doing bicep curls. The other movements are so small that the untrained eye rarely notices the changes in position, but they are important for motor function of the hand and wrist. Inside and outside the elbow joint, there are points where tendons attach. These tendons allow for wrist and hand movements. For example, they allow the hand to rotate.  The elbow bones are held together primarily by fibrous tissue known as ligaments. The ulnar collateral ligament, or UCL, on the inner side of the joint closest to the body is the primary stabilizer. This thick triangle-shaped band connects the head of the humerus to the heads of the ulna and radius.

The UCL can be torn or completely ruptured, which would cause severe pain on the inside of the elbow, a popping noise, swelling, and bruising. Injuries to the UCL are common among baseball pitchers, football quarterbacks, ice hockey players, and racquet sport players due to the type of motion these sports involve.

The other ligament in the elbow is the radial collateral ligament. Located on the outside of the elbow, it prevents excessive extension of the elbow.

Credit :  Healthline 

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The more times a person has been bitten by mosquitoes, the more likely it is that they’ll become desensitized over time. That means adults typically have less serious reactions to mosquito bites than children do.

Common symptoms of mosquito bites include soft bumps on the skin that may become pink, red, and itchy. In most cases, redness and puffiness appears minutes after the mosquito punctures the skin. A firm, dark red bump often appears the next day, although these symptoms may occur up to 48 hours after the initial bite. According to the American Academy of Allergy, Asthma, & Immunology (AAAAI), contact with a mosquito must be six seconds or longer to produce a reaction.

As your mosquito bite heals, the itching sensation will fade, and skin will gradually take on a less red or pink hue until it returns to its normal color. This usually takes about three to four days. Swelling will also go down after about a week.

A typical mosquito bite is less than a ½-inch across.

Credit : Healthline

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Micronutrients are one of the major groups of nutrients your body needs. They include vitamins and minerals.

Vitamins are necessary for energy production, immune function, blood clotting and other functions. Meanwhile, minerals play an important role in growth, bone health, fluid balance and several other processes.

Humans must obtain micronutrients from food since your body cannot produce vitamins and minerals — for the most part. That’s why they’re also referred to as essential nutrients.

Vitamins are organic compounds made by plants and animals which can be broken down by heat, acid or air. On the other hand, minerals are inorganic, exist in soil or water and cannot be broken down.

When you eat, you consume the vitamins that plants and animals created or the minerals they absorbed.

The micronutrient content of each food is different, so it’s best to eat a variety of foods to get enough vitamins and minerals.

Credit : Healthline

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Malnutrition refers to deficiencies or excesses in nutrient intake, imbalance of essential nutrients or impaired nutrient utilization. The double burden of malnutrition consists of both undernutrition and overweight and obesity, as well as diet-related noncommunicable diseases. Undernutrition manifests in four broad forms: wasting, stunting, underweight, and micronutrient deficiencies.

Wasting is defined as low weight-for-height. It often indicates recent and severe weight loss, although it can also persist for a long time. It usually occurs when a person has not had food of adequate quality and quantity and/or they have had frequent or prolonged illnesses. Wasting in children is associated with a higher risk of death if not treated properly. Stunting is defined as low height-for-age. It is the result of chronic or recurrent undernutrition, usually associated with poverty, poor maternal health and nutrition, frequent illness and/or inappropriate feeding and care in early life. Stunting prevents children from reaching their physical and cognitive potential. Underweight is defined as low weight-for-age. A child who is underweight may be stunted, wasted or both.

Micronutrient deficiencies are a lack of vitamins and minerals that are essential for body functions such as producing enzymes, hormones and other substances needed for growth and development.

Credit : WHO

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If you've ever seen a real skeleton or fossil in a museum, you might think that all bones are dead. Although bones in museums are dry, hard, or crumbly, the bones in your body are different. The bones that make up your skeleton are all very much alive, growing and changing all the time like other parts of your body.

A baby's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults have. Some of a baby's bones are made entirely of a special material called cartilage (say: KAR-tel-ij). Other bones in a baby are partly made of cartilage. This cartilage is soft and flexible. During childhood, as you are growing, the cartilage grows and is slowly replaced by bone, with help from calcium.

By the time you are about 25, this process will be complete. After this happens, there can be no more growth — the bones are as big as they will ever be. All of these bones make up a skeleton that is both very strong and very light.

Credit : Kids Health

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There are 206 bones in an adult human's body. We have 26 bones in each foot. So our feet consist of 52 bones, which amount to more than 25%. Not surprisingly, our feet support our entire body's weight and allow us to jump, run, and climb. Those bones and joints also enable our feet to absorb and release energy efficiently.

The skeletal structure of the foot is similar to that of the hand but, because the foot bears more weight, it is stronger but less movable.

The bones of the foot are organized into the tarsal bones, metatarsal bones, and phalanges.

The foot begins at the lower end of the tibia and fibula, the two bones of the lower leg. At the base of those, a grouping of bones form the tarsals, which make up the ankle and upper portion of the foot.

There are five metatarsal bones in each foot. Similar to the bones of the hand, these nearly parallel bones create the body of the foot. Numbered one through five, the bone that sits behind the big toe is number one, and the one behind the little toe is number five.

Credit : Health line

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If you see green or yellow phlegm, it’s usually a sign that your body is fighting an infection. The color comes from white blood cells. At first, you may notice yellow phlegm that then progresses into green phlegm. The change occurs with the severity and length of the potential sickness.

If you've ever stopped to look at the contents of the tissue after you've blown your nose, you may have noticed that your mucus isn't always perfectly clear. It may be yellow, green, or have a reddish or brownish tinge to it. What do those colors mean?

You might have heard that yellow or green mucus is a clear sign that you have an infection, but despite that common misperception, the yellow or green hue isn't due to bacteria.

When you have a cold, your immune system sends white blood cells called neutrophils rushing to the area. These cells contain a greenish-colored enzyme, and in large numbers they can turn the mucus the same color.

Mucus can also contain tinges of reddish or brownish blood, especially if your nose gets dried out or irritated from too much rubbing, blowing, or picking. Most of the blood comes from the area right inside the nostril, which is where most of the blood vessels in the nose are located. A small amount of blood in your mucus isn't anything to worry about, but if you're seeing large volumes of it, call your doctor.

Credit : WebMD

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Bronchitis is when the tubes that carry air to your lungs, called the bronchial tubes, get inflamed and swollen. You end up with a nagging cough and mucus.

Most often, the same viruses that give you a cold or the flu cause acute bronchitis. But sometimes, bacteria bring it on.

In both cases, as your body fights the germs, your bronchial tubes swell and make more mucus. That means you have smaller openings for air to flow through, which can make it harder to breathe.

Your doctor usually can tell whether you have bronchitis based on a physical exam and your symptoms. They’ll ask about your cough, such as how long you’ve had it and what kind of mucus comes up with it. They’ll also listen to your lungs to see whether anything sounds wrong, like wheezing.

Your doctor may need to do some tests, depending on whether they think you have acute or chronic bronchitis.

Credit : WebMD

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The bronchi are the airways that lead from the trachea into the lungs and then branch off into progressively smaller structures until they reach the alveoli, the tiny sacs that allow for the exchange of oxygen and carbon dioxide in the lungs.

Primary bronchi are located in the upper portion of the lungs, with secondary bronchi near the center of the lungs. Tertiary bronchi are located near the bottom of these organs, just above the bronchioles. No gas exchanges occur in any of the bronchi. When the bronchi become swollen due to irritants or infection, bronchitis results and makes breathing more difficult. Bronchitis sufferers also tend to have much more mucus and phlegm than someone without inflamed bronchi.

The secondary bronchi continue to branch off to form the tertiary bronchi, which are further divided into terminal bronchioles.

There are as many as 30,000 tiny bronchioles in each lung. They lead to the alveoli (tiny air sacs where the exchange of carbon dioxide and oxygen occurs) by way of alveolar ducts.

Together, the trachea and the two primary bronchi are referred to as the bronchial tree. At the end of the bronchial tree lie the alveolar ducts, the alveolar sacs, and finally the alveoli.

The tubes that make up the bronchial tree perform the same function as the trachea. They distribute air to the lungs.

The alveoli are primarily responsible for exchanging carbon dioxide and oxygen, which occurs in the lungs.

Credit : Health Line

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In terrestrial vertebrates, including humans, the receptors are located on olfactory receptor cells, which are present in very large numbers (millions) and are clustered within a small area in the back of the nasal cavity, forming an olfactory epithelium. 

There are about 1,000 genes in the olfactory gene family, the largest known family of genes. (Although humans possess all 1,000 olfactory receptor genes, making up roughly 3 percent of the entire human genome, only about 350 of these genes encode working olfactory receptors.) Since each gene produces a different odour receptor protein, this contributes to the ability of animals to smell many different compounds. Animals not only can smell many compounds but can also distinguish between them. This requires that different compounds stimulate different receptor cells. Consistent with this, evidence indicates that only one olfactory gene is active in any one olfactory receptor cell. As a consequence, each receptor cell possesses only one type of receptor protein, though it has many thousands of the particular type on the membrane of the exposed cilia of the cell. Since each cell expresses only one type of receptor protein, there must be large numbers of cells expressing each type of receptor protein to increase the likelihood that a particular odour molecule will reach a cell with the appropriate receptor protein. Once the molecule reaches the matching receptor, the cell can respond.

Credit : Britannica

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