Respiratory System

Breathing is so vital to life that it happens automatically. Each day, you breathe about 20,000 times, and by the time you're 70 years old, you'll have taken at least 600 million breaths.

All of this breathing couldn't happen without the respiratory system, which includes the nose, throat, voice box, windpipe, and lungs.

Why Do I Yawn?

When you are sleepy or drowsy the lungs do not take enough oxygen from the air. This causes a shortage of oxygen in our bodies. The brain senses this shortage of oxygen and sends a message that causes you to take a deep long breath -a YAWN.

Why Do I Sneeze?

Sneezing is like a cough in the upper breathing passages. It is the body's way of removing an irritant from the sensitive mucous membranes of the nose. Many things can irritate the mucous membranes. Dust, pollen, pepper or even a cold blast of air are just some of the many things that may cause you to sneeze.

What Causes Hiccups?

Hiccups are the sudden movements of the diaphragm. It is involuntary - you have no control over hiccups, as you well know. There are many causes of hiccups. The diaphragm may get irritated, you may have eaten to fast, or maybe some substance in the blood could even have brought on the hiccups.

Interesting Facts about our Respiration

- We breathe 13 pints of air every minute.

- Each lung contains 300-350 million respiratory units called alveoli, making it a total of 700 million in both lungs.

- More than half a litre of water per day is lost through breathing.

- People under 30 years of age take in double the amount of oxygen in comparison to a 80 year old.

- Yawning brings more oxygen to the lungs.

- The right lung is slightly larger than the left.

- Hairs in your nose help to clean the air we breathe as well as warm it. The highest recorded "sneeze speed" is 99 miles per hour!

- The surface area of the lungs is roughly the same size as a tennis court.

- If placed end to end, capillaries would extend 960 miles.

- We lose half a litre of water every day through breathing.

- A person at rest breathes between 12-15 times a minute.

- The breathing rate is faster in children and women than it is in men.

Circulatory System

With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to all of our cells. Each day, 2,000 gallons of blood travel many times through about 60,000 miles of blood vessels that branch and cross, linking the cells of our organs and body parts.

From the hard-working heart to our thickest arteries and to capillaries so thin that they can only be seen through a microscope, the heart and circulatory system (also called the cardiovascular system) are our body's lifeline, delivering blood to the body's tissues.

Interesting Circulation Facts:

- The heart muscles will stop working only when we die.

- Every second, 15 million blood cells are destroyed in the human body.

- Platelets, which form a part of the blood cell component, are produced at the rate of 200 billion per day.

- An adult human body contains five to six litres of blood and an infant has about one litre of blood.

- Except the heart and lungs, all the other parts of the body receive their blood supply from the largest artery of the body, the aorta.

- The pulmonary vein is the only vein in the human body that carries oxygenated blood while all the other veins of the body carry deoxygenated blood.

- Human blood is colourless. It is the haemoglobin; a pigment present in the red blood cells that is responsible for the red colour of the blood.

- Heartbeat is nothing but the sound produced by the closure of valves of the heart when the blood is pushed through its chamber.

- A women's heart beat is faster than that of a man's.

- The human heart continues to beat even after it is taken out of the body or cut in to pieces.

- On an average, the human blood circulates through the whole body every 23 seconds.

- On an average, the adult's heart pumps about 4,000 gallons of blood each day.

- The left side of human heart is much thicker and stronger than the right side.

- Human blood is a make up of red blood cells carrying oxygen, white blood cells that fight disease, platelets that help the blood to clot, and a liquid called plasma.

- Every day 440 gallons of blood flow through the kidney.

- Red blood cells last only for about 4 months before they wear out.

- Red blood cells are the only cells in the body that do not have a nucleus.

- There are about 30 - 40 billion white blood cells present in our body to fight against infective and foreign organisms.

- Capillaries are so small that it would take ten of them to equal the thickness of a human hair.

- The human heart beats 30 million times a year.

Digestive System

Your digestive system started working even before you took the first bite of your pizza. And the digestive system will be busy at work on your chewed-up lunch for the next few hours or sometimes days, depending upon what you've eaten. This process, called digestion, allows your body to get the nutrients and energy it needs from the food you eat.

Interesting Facts about Structure and Physiology of the Digestive System:

- We eat about 500 kg of food per year.

- 1.7 litres of saliva is produced every day.

- The oesophagus is approximately 25 cm long. Muscles contract in waves to move the food down the oesophagus. This means that food would get to a person's stomach, even if he were standing on his head.

- An adult's stomach can hold approximately 1.5 litres of material.

- Every day 11.5 litres of digested food, liquids and digestive juices flow through the digestive system, but only 100 mis is lost in faeces.

- In the mouth, food is either cooled or warmed to a more suitable temperature.

- Hundreds of different kinds of enzymes are needed to properly digest food. Cooking destroys food enzymes, forcing the body to make its own. Over time the body may tire of this extra work, leaving room for possible indigestion.

- Stomach: secretes some enzymes and hydrochloric acid (HCL) to break down protein. Within 2-6 hours, all food is emptied into the small intestine.

- Small Intestine: over 90 percent of digestion and absorption takes place in the small intestine. The acid of the stomach is neutralized and food is mixed with enzymes, bile and pancreatic juices.

- Liver: aids in digestion and detoxification of food impurities and inspects nutrients before allowing them into the bloodstream.

- Gallbladder: stores bile used to break down dietary fat.

- Pancreas: produces digestive juices and helps control blood sugar.

- 70-year-olds may produce as little as half the enzymes they produced when they were 20.

- The liver is the largest organ in the body.

- The liver perfonns more than 500 functions.

- The small intestine is a long tube about 1 and a half to 2 inches around, and about 22 feet long.

- The large intestine is fatter than the small intestine at about 3 to 4 inches around, but shorter than the small intestine at about 5 feet long.

- The digestive tract is like a long tube, approximately 30 feet long in total, through the middle of the body. It starts at the mouth, where food and drink enter the body, and finishes at the anus, where leftover food and wastes leave the body.

- All the different varieties of food we eat are broken down by our digestive system and transported to every part of our body by our circulatory system.

Endocrine System

Although we rarely think about them, the glands of the endocrine system and the hormones they release influence almost every cell, organ, and function of our bodies. The endocrine system is instrumental in regulating mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes.

In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes, like breathing and body movement, are controlled by the nervous system. But even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly.

The endocrine system is a fascinating system, and there are many cool facts about it that one might not have been aware of. Some of these facts about the endocrine system are as follows:

- The endocrine system has no ducts. Therefore, the hormones it produces are released directly into the bloodstream. The blood then carries it to the various parts.

- The endocrine system is responsible for producing 30 distinct hormones. All these hormones have very distinct jobs to do.

- The rush of adrenaline one gets when facing adventure or fear is the result of the adrenal glands production of epinephrine hormone, or adrenaline as we otherwise know it.

- We must be thankful to the pineal gland for our sweet sleep. It secretes melatonin which regulates our sleep.

- It is responsible for the production of insulin. The failure to produce insulin will result in diabetes.

- The endocrine is the secret behind your energy levels thanks to the thyroid glands. The thyroid glands also help in metabolism.

- The hypothalamus is the one that makes you feel hunger and thirst. It also helps in body temperature.

- It aids the immune system by helping the body build resistance to disease.

- The human behaviour is also controlled by the endocrine system when it affects the nervous system.

- It is accountable for sexual characteristics and development. It is the key player in regulating menstrual cycle and ovulation in women. It even plays a role in pregnancy by stimulating contractions during delivery.

- In fact, the endocrine system has a hand in almost all functions of the human body.

Nervous System

The central nervous system consists of the brain, the spinal cord, and the body's nerve network. This complex system is based on one kind of cells -the neurons. The brain, the mass of tissue inside the head, has the greatest number of these cells, most of which are in its outer part, the cerebrum.

Interesting Facts about Structure and Physiology of the Nervous System:

- A newborn baby's brain grows almost 3 times during the course of its first year.

- The left side of the human brain controls the right side of the body and the right side of the brain controls the left side of the body.

- A newborn baby loses about half of his nerve cells before he is born.

- As we get older, the brain loses almost one gram per year.

- There are about 13, 500,00 neurons in the human spinal cord.

- The total surface area of the human brain is about 25, 000 square cm.

- The base of the spinal cord has a cluster of nerves, which are most sensitive.

- An average adult male brain weighs about 1375 grams.

- An average adult female brain is about 1275 grams.

- Only four percent of the brain's cells work while the remaining cells are kept in reserve.

- The brain utilizes 20 % of our body's energy i.e., it uses 20% of one's blood and oxygen and makes up only 2 % of our body weight.

- The human brain stops growing by 18 years of age.

- The human brain is very soft like butter.

- Sixty percent of the human body's nerves end in the forehead and the hands.

- The brain continues to send out electric wave signals until approximately 37 hours after death.

It is estimated that there are over 1, 000,000,000,000,000 connections in the human brain.

- Human brain constitutes 60 % of white matter and 40 % of grey matter.

- The average length of the human brain is about 167 mm and its average height is 93 mm.

- On an average, 100, 000 to 1000, 000 chemical reactions take place in our brain.

- The Nervous system transmits messages to the brain at the speed of 180 miles per hour.

- Reading aloud to children helps to stimulate brain development.

- The right side of the human brain is responsible for self-recognition.

- Men listen with the left side of the brain and women use both sides of the brain.

- The human brain is made up of a staggering 15 billion cells with about thousand billion connections between these cells. However, it weighs less than 3 pounds.

Senses

Our senses are the physical means by which all living things see, hear, smell, taste, and touch. Each sense collects information about the world and detects changes within the body. Both people and animals get all of their knowledge from their senses, and that is why our senses are so important. All senses depend on the working nervous system. Our sense organs start to work when something stimulates special nerve cells called receptors in a sense organ. We have five main sense organs. They are the eyes, ears, nose, tongue, and skin:

Seeing

- The part of your eye that gives it its colour is called the iris. It has lots of tiny muscles that open your pupil (the round hole in the centre) to let in more light when it's dark. The larger the pupil, the more light can enter.

- The retina has millions of two main nerve cells to catch light. Rods, which are mostly around the sides, are best at helping you to discriminate light and dark. Cones, which are near the centre, are for detecting colour. Nerve cells from the retina connect your eye to the parts of the brain that process vision, the occipital lobes, which are located in the back of your head.

- Like your fingerprints, irises and retinas are individual.

Hearing

- The three smallest bones in the body - named the hammer, the anvil and the stirrup (the smallest, at about 3 millimetres) pass sound from your eardrum to your inner ear.

- The inner ear has special nerve cells to pass sound information for processing by the brain, but a part of the inner ear helps you to keep your balance.

Smelling

- There are about 10 million smell receptors up in the space behind your nose for detecting smells. Working together with you brain, this group of nerve cells is able to detect about 10,000 different odours.

- Children can distinguish between the smell of their siblings and other children of the same age.

- Babies recognise their own mothers' smell and mothers recognise their own babies' smell.

Taste

- You are born with about 10,000 taste buds, but this drops over time to about 5000 by the time you are old.

- Taste buds detect sweet, sour, salty and bitter. Tasting is about 80% smell, and your sense of smell increases when you are hungry.

Touch

- The skin is the largest organ in the body, weighing at about 6 - 10 lb. Your skin detects touch via receptors for pain, pressure and movement, cold and heat.

- Most touch receptors are for pain. Skin is least sensitive in the middle of your back, and most sensitive in hands, fingertips, and lips.

Urinary System

Excretion can be defined as the removal of toxic waste products of metabolism from the body. These wastes can be either solid, liquid or in the gaseous state. The liquid wastes are ammonia and urea, which exist in the blood along with the nutrients and other useful substances. So there is a need of complex organ that may separate or filter out the dissolved excretory wastes from blood while retaining the nutrients in the latter. Two kidneys in human beings are the organs that perform this task. There is a distinct advantage of the two kidneys in our body. If one kidney fails, the other can still deal with functions of excretion and regulation.

The kidneys are solid, bean-shaped, reddish brown-paired structures, which lie in the abdominal cavity one on either side of the vertebral column. The kidneys collect the excretory products and eliminate them in the form of urine, which then passes down the two tubular ureters into the collapsible urinary bladder, which is a muscular reservoir of urine. The urine is released periodically to the outside via the urethra.

Interesting Urine Facts:

- Adults pass about a quart and a half of urine each day, depending on the fluids and foods consumed.

- The volume of urine formed at night is about half of that formed in the daytime.

- Normal urine is sterile. It contains fluids, salts and waste products, but it is free of bacteria, viruses and fungi.

- The tissues of the bladder are isolated from urine and toxic substances by a coating that discourages bacteria from attaching and growing on the bladder wall.

- The human bladder can stretch to hold about 400 ml of urine.

- All the blood in our body passes 400 times through each kidney every day.

- Urine therapy uses urine by applying it to the skin or drinking it; this is common practice in traditional medicine in India.

- Since urine contains large amounts of urea, it is an excellent source of nitrogen for plants and a good accelerator for compost; it is thousands of times less toxic than ammonia. Gardeners often recommend a dilution of 10-15 parts water to one of urine for application to pot plants and flower beds during the growing season.

- The ancient Romans used urine as a bleaching agent for cleaning clothes.

- People adrift at sea or lost in the desert for long periods often resort to drinking their urine when no rainwater is available. However, this won't prevent you from dying of dehydration, especially if it causes vomiting.

- Urine has historically been used as an antiseptic. In times of war, when other antiseptics were unavailable, urine, the darker the better, was utilized on open wounds to kill bacteria.

- The yellow colour of urine was once thought to come from gold. Alchemists in the middle ages spent much time trying to extract gold from urine. Of course, they were unsuccessful, but along the way made other discoveries, including white phosphorus and urea.

Reproductive System

The human reproductive system is a complex process, both male and female, that must work together flawlessly to produce a new living baby. This is a process where the generation of a living organism brings into being the next generation. It is full of details, facts and complexities that make it one of the most difficult processes to reproduce outside the natural production.

Interesting fact about the reproductive system in the human body is that it isn't essential to the preservation of any individual and yet it is essential to the preservation of the species. Most men would disagree that the act of sexual intercourse is essential to the individual; and at some point in their lives many women feel that reproduction is essential to the individual; but science underscores the point that the preservation of the species doesn't hinge on one reproductive couple.

There are some Interesting Facts about the Reproductive System:

- Male sperm is significantly smaller than the female egg. While the sperm measures 2.5 to 3.5 microns across the head, the fully mature egg is 100-125 microns in diameter.

- The largest cell in the female body is the egg.

- A woman never runs out of eggs. At birth she has between 1 and 2 million potential eggs (follicles) and by puberty has 300,000 to 400,000 viable eggs (follicles) that can be fertilized.

- About 500 million sperm mature every day in a healthy male.

- The male scrotum hangs outside the body since the internal body temperature is too high and will kill the sperm.

- The average lifespan of an egg once it is released from the ovary is 12-24 hours, after which it either disintegrates or is flushed out of the body with the menstrual flow. The average life span of the sperm is 2-3 days.

- The male reproductive system consists of penis, testicles, scrotum, ducts and accessory glands. The system produces millions of sperm to transmit them to the female body to fertilize one egg.

- Once the sperm has penetrated the egg, the outer shell becomes impenetrable to other sperm.

- In the uterus, prior to birth, the baby's body is covered by a thin layer of hair. As soon as the baby is born, that hair soon disappears. The hair is called lanugo.

- When a baby is bom, both male and female, the mammary glands are sometimes so stimulated by the mothers' hormones that they give tiny drops of milk for about a week.

- Female babies can actually bleed vaginally for several days after birth in response to the removal of the mothers' hormones during pregnancy.

- The female human body is capable of giving birth to 35 children in one lifetime.