Amazing Facts about the Human Body

The Nervous System

A human adult brain weighs about three pounds and can be referredto as a “three pound gem”
The brain and spinal cord are surrounded and protected bycerebrospinal fluid.
There are about 100 billion neurons in the adult human brain
The brain looks like a giant, wrinkled walnut.

The largest bone is the pelvis, or hip bone. In fact it is made ofsix bones joined firmly together.
The longest bone is the femur, in the thigh. It makes up almostone-quarter of the body’s total height.
The smallest bone is the stirrup, deep in the ear. It is hardlylarger than a grain of rice.
The ears and end of the nose do not have bones inside them. Theirinner supports are cartilage or gristle, which is lighter and moreflexible than bone. This is why the nose and ears can be bent.
After death, cartilage rots faster than bone. This is why theskulls of skeletons have no nose or ears.

There are about 60 muscles in the face. Smiling is easier thanfrowning. It takes 20 muscles to smile and more than 40 to frown.
The longest muscle in the body is the sartorius, from the outsideof the hip, down and across to the inside of the knee. It rotates thethigh outward and bends the knee.
The smallest muscle in the body is the stapedius, deep in the ear.It is only 5 mm long and thinner than cotton thread. It is involved inhearing.
The biggest muscle in the body is the gluteus maximus, in thebuttock. It pulls the leg backward powerfully for walking, running andclimbing steps.

The heart beats around 3 billion times in the average person’slife.
About 2 million blood cells die in the human body every second,and the same number are born each second.
Within a tiny droplet of blood, there are some 5 million red bloodcells, 300,000 platelets and 10,000 white cells.
It takes about 1 minute for a red blood cell to circle the wholebody.
Red blood cells make approximately 250,000 round trips of the bodybefore returning to the bone marrow, where they were born, to die.
Red blood cells may live for about four months circulatingthroughout the body, feeding the 60 trillion other body cells.

The skin secretes antibacterial substances. These substancesexplain why you don’t wake up in the morning with a layer of mold growingon your skin, because most bacteria and spores that land on the skin diequickly.
Tears and mucus contain an enzyme (lysozyme) that breaks down thecell wall of many bacteria.
Lymph nodes contain filtering tissue and a large number of lymphcells. When fighting certain bacterial infections, the lymph nodes swellwith bacteria and the cells fighting the bacteria, to the point where youcan actually feel them. Swollen lymph nodes may therefore be a goodindication that you have an infection of some sort.

Adults eat about 1,100 pounds of food per year.
About 3 pints of saliva are produced each day.
The esophagus is approximately 10 inches long.
Muscles contract in waves to move the food down the esophagus.This means that food would get to a person’s stomach, even if they werestanding on their head.
An adult’s stomach can hold approximately 3 pints ofmaterial.
Every day 3 gallons of digested food, liquids and digestive juicesflow through the digestive system, but only a small amount of fluid islost in feces.
In the mouth, food is either cooled or warmed to a more suitabletemperature.
We get two sets of teeth. Our 20 “baby teeth” are replacedstarting at around six to seven years of age with our 32 “adult teeth.”

At rest, the adult body takes in and breathes out about one-fourthof a cubic foot of air each minute.
The right lung is slightly larger than the left.
Hairs in the nose help to clean the air we breathe as well aswarming it.
The highest recorded “sneeze speed” is 103 miles per hour.
The surface area of the lungs is roughly the same size as a tenniscourt.
The capillaries in the lungs would extend nearly 1,000 miles ifplaced end to end.
We lose half a liter of water a day through breathing. This is thewater vapor we see when we breathe onto glass.
A person at rest usually breathes between 12 and 15 times a minute.
The breathing rate is faster in children and women than in men.