The Skeletal System: Bones
There are 206 bones in the skeletal system of an adult. Bones of hands and feet alone constitute 50% of the total bones in the human body. The newborn baby has 300 bones; out of which 94 bones fuse together as he/she grows. The largest bone of human body is the femur in the thigh which constitute about 27.5% of a person's stature, average length of this bone is 50 cm. The shortest bone in the human body is the stapes in the middle ear.
Composition of Bones:
- Organic Matter- 33.30%
- Phosphate of Lime- 51.04%
- Carbonate of Lime- 11.30%
- Fluoride of Calcium- 2.00%
- Phosphate of Magnesium- 1.16%
- Soda/ Chloride of Sodium- 1.00%
Muscular System:
Muscles are tissue attached to bones and composed of fibers. They are capable of contracting and relaxing to effect body movement.
Total Number of Muscles: There are about 630 important muscles in the human body. They account for about 40% of the body weight.
Largest Muscle: The bulkiest muscle in the body is gluteus maximus (buttock muscle).
Longest Muscle: Sartorius is the longest muscle in the body which originates in the upper part of the hip bone and is attached to the tibia bone of the leg.
Smallest Muscle: Stapedius muscle in the middle ear is less than 1/20 of an inch.
Muscles in the Face: It takes the interaction of 72 different muscles to produce human speech. One uses 14 muscles to smile and 43 to frown. The strongest muscle of the body is the masseter muscle, which is located in the jaw.
Respiratory System (Lungs):
A pair of spongy organs consisting of elastic tissues situated in the chest cavity. There are two lungs, the right lung is larger than the left. Together, they weigh between 1:18 and 1:19 kg in a healthy adult. Their main function is to purify blood and supply oxygen to it. The entire blood supply- 4.5 to 5 liters, washes through the lings about once a minute. If all the airways running through the lings are connected, they can go up to the length of 2,400 kilometers!
Excretory System (Kidneys):
The two kidneys are situated in the upper posterior of the abdominal cavity, one on each side of the vertebral column. Each kidney is approximately 10 cm long, 5 cm wide and 2.5 cm thick. They filter nitrogenous waste of the body from the blood and throw it out in the form of urine.
Eyes:
Each of our eyes has 120 M rods, which help us see in black and white. Each eye has 6M cones , which help us see in color. We blink our eyes about 20,000 times a day. An eyelash lives about 150 days before it falls out. Women blink twice as much as men. If one is blind in one eye, he only loses about 1/5 of vision and the sense of depth. Our eyes are always the same size from birth, but our nose and ears never stop growing.
Nose: The nose can remember 50,000 scents. When you sneeze, air rushes through your nose at the rate of 156 kmph.
Finger nail:
A finger nail takes about 6 months to grow from base to tip. The length of the finger shows how fast the fingernail grows. The nail on the middle finger grows faster. On an average, our toenails grow twice as slow as our fingernails. Hair is made of the same substance as fingernails.
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