Human Body

We are complex and composite system made up of trillions of individual cells/microbes.
Number of cells in the human body is around 30-40 trillion.
Microbes - 300-400 trillion
Gastrointestinal tract alone comprise at least 10 trillion organisms of more than 1,000 species

Elements in the Human Body

Six elements account for 99% of the mass of the human body.
  1. Oxygen: 65%
  2. Carbon: 18%
  3. Hydrogen: 10%
  4. Nitrogen: 3%
  5. Calcium: 1.5%
  6. Phosphorus: 1.2%
  7. Potassium: 0.2%
  8. Sulfur: 0.2%
  9. Chlorine: 0.2%
  10. Sodium: 0.1%
  11. Magnesium: 0.05%
Traces of Iron, Cobalt, Copper, Zinc, Iodine, Selenium and Fluorine. Tiny amounts of elements include germanium, antimony, silver, niobium, lanthanum, tellurium, bismuth, thallium, gold, and even radioactive elements like thorium, uranium, and radium. However, not all elements on the periodic table are found in the body.

Every atom in our body is billions of years old. Hydrogen, the most common element in the universe and a major feature of your body, was produced in the big bang 13.7 billion years ago. Heavier atoms such as carbon and oxygen were forged in stars between 7bn and 12bn years ago, and blasted across space when the stars exploded. We are stardust.

Major Compounds in the Human Body

  1. Water is the most abundant chemical compound in living human cells, accounting for 60% by mass.
  2. Fat account for 16 percent by mass.
  3. Protein is another 16 percent by mass. Muscles, including the heart, Skin, Hair and fingernails are protein. Minerals account for about 6 percent of the body.
  4. Sugar and other carbohydrates only account for about 1% of body mass.

Major organs

Major organs in the body include: skin, liver, brain, lungs, heart, kidney, spleen, pancreas, thyroid, Skeletan and sense organs.

Skin is the largest external organ ( 2 square metters) of the human body. It is a vital organ and provides outer covering, which protects from external elements. It also functions by protecting our internal organs from the invading pathogens, regulates our body temperature and pH, prevents dehydration and also functions as the main sense organ.

The liver weighs between 1.3 to 1.5 kg. It is triangular, bilobed in structure and performs more than 500 functions, including blood clotting, protecting from the invading pathogens, synthesis of hormones and proteins and secretes various enzymes and chemicals. Liver is the only organ that can completely regenerate itself. If someone donated his or her liver to someone else, their liver would grow back to its original size again in a few weeks.

Brain is surrounded by a strong bony structure, called the skull and is suspended in a layer of fluid called the cerebrospinal fluid, which functions by protecting the brain from minor mechanical shocks and jolts. The brain, along with the spinal cord, composes the central nervous system. It is responsible for thoughts, interpretation, regulation and control of body movements. At birth, there are 14 billion cells in the human brain. This number does not increase throughout a person's lifetime. After 25 years, the number of cells falls by 100,000 every day. After 40 years, the decline of the brain accelerates sharply, and after 50 years neurons (that is, nerve cells) shrink and the brain gets smaller. The human brain has a memory capacity which is the equivalent of more than four terabytes on a hard drive.

Heart keeps on beating until the death of an individual. On average, our heartbeats seventy times per minute, and pumps about 10,000 litres of blood every day. Located in the thoracic cavity medial to the lungs, slightly towards the left and behind the breastbone. The human heart is approximately equal in size to that of a person's fist. An adult’s heart weights 220-260 grams.

Lungs, (a pair) facilitates exchange of gases. They are lined by a thin membrane, presence of bronchioles – the smaller tubes, alveoli – a balloon-like structure and the group of blood capillaries, which expands the surface area for exchange of gases.

Pancreas is a vital part of the human digestive system and is responsible for regulating blood sugar levels. It is an abdominal organ located behind the stomach and surrounded by spleen, liver and small intestine. It is also involved in producing hormones, such as glucagon, insulin, somatostatin and pancreatic polypeptide and secreting digestive enzymes such as proteases, amylase and lipase into the duodenum.

Kidneys are bean-shaped structures located on either side of the backbone and are protected by the ribs and muscles of the back. It functions by filtering excess water and removing harmful toxins from the blood. Along with excretion, kidneys also produce a hormone called Renin, which regulates blood pressure.

Small intestine is the longest part of the alimentary canal and a part of the digestive system that runs between the stomach and large intestine. It is narrower than the large intestine and is responsible for the absorption of nutrients from the digested food, secretion of intestinal juice, receives bile juice from the liver and pancreatic juice from the pancreas.

Thyroid is a large ductless gland in the neck which secretes hormones regulating growth and development through the rate of metabolism.

Skeletal system has a complex architecture that includes 206 named bones connected by cartilage, tendons, ligaments, and three types of joints: synarthroses (immovable) amphiarthroses (slightly movable)

The sense organs are the eyes (for seeing), nose (for smelling), ears (for hearing), tongue (for tasting), and skin (for touching or feeling). Some add Vestibular sense, which gives us information about where our head and body are in space and Proprioception (Body awareness), which tells us where our body parts are relative to each other.

Eye helps us to perceive the world around us. They are the visual sensory organs in our body, which are sensitive to light images. It is enclosed within the eye sockets in the skull and is anchored down by muscles within the sockets. The retinas inside the eye cover about 650 square mm and contain 137 million light-sensitive cells: 130 million are for black and white vision and 7 million are for helping you see in colour.

An adult is made up of around 7 octillion (7*10^27) atoms.

Cells Microbes human

Number of cells in the human body is around 30-40 trillion.
Microbes - 300-400 trillion
Gastrointestinal tract alone comprise at least 10 trillion organisms of more than 1,000 species
Humans produce a new generation every 20 years
Bacteria do it every 20 to 30 minutes, and
Viruses even faster every 20 to 30 seconds.

The human body is occupied by large collections of microorganisms, commonly referred to as our microbiome, that have evolved with us since the early days of man. Scientists have only recently begun to quantify the microbiome, and discovered it is inhabited by at least 38 trillion bacteria and over 380 trillion viruses inhabiting us, a community collectively known as the human virome. Many of these viruses infect the bacteria that live inside you and are known as bacteriophages, or phages for short. The study of the human virome lags so far behind the study of bacteria.

Cells - DNA

The human genome contains billions of pieces of information. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. An international research effort called the Human Genome Project, which worked to determine the sequence of the human genome and identify the genes that it contains, estimated that humans have between 20,000 and 25,000 genes (about 1 to 1.5 percent of our genome*). *People have been working hard at this for more than 20 years, and we still don’t have correct count of genes.

A normal human cell has 23 pairs of chromosomes in its nucleus, each a single, very long, molecule of DNA. Humans have 23 pairs of chromosomes--22 pairs of numbered chromosomes, called autosomes, and one pair of sex chromosomes, X and Y. Each parent contributes one chromosome to each pair so that offspring get half of their chromosomes from their mother and half from their father.
*except sperm cells and egg cells in the ovaries which are "haploid" and have 23 chromosomes (with the 23rd being an X in the eggs, and either an X or a Y in the sperm)

The term ‘chromosome’ itself comes from the Greek for colour (chroma) and body (soma). An individual chromosome, is made up of a single molecule of double-stranded DNA (deoxyribonucleic acid) and protein. These long molecules of DNA are ‘coiled’ up around proteins called histones. Uncoiled and placed end to end, the DNA molecules from just one cell would be as long as 2 meters. In 2003 scientists around the world announced the results of an immense collaborative scientific effort, the final sequencing of the entire human genome – a sequence of around 3 billion base pairs.

The DNA molecule is formed in the shape of a double helix, similar in shape to a spiralling twisted ladder. In DNA there are four nucleotide bases – adenine, thymine, cytosine and guanine, abbreviated to A, T, C and G respectively. These bases help form the double helix when two base pairs link together, with A only linking to T and C only linking to G. This complementary linking of bases is particularly important during cell division (a process called mitosis).

Each gene has the coding information for a protein or polypeptide, or a sequence of another type of nucleic acid called RNA (ribonucleic acid). Thus, the human genome codes for all the proteins in the body. This was a scientific breakthrough of immense importance.

Our DNA includes the genes from at least eight retroviruses. These are a kind of virus that makes use of the cell's mechanisms for coding DNA to take over a cell. At some point in human history, these genes became incorporated into human DNA. These viral genes in DNA now perform important functions in human reproduction, yet they are entirely alien to our genetic ancestry.

Genes are only around 3% of our DNA. The other 97% was thought may also have influence on our development.

Studying the genetic sequence of different individuals allows scientists to work out which genes are responsible for how our cells work or which genes are associated with particular human features – such as some medical conditions and how people might respond to medicines.

Eight percent of our DNA consists of remnants of ancient viruses, and another 40 percent is made up of repetitive strings of genetic letters that is also thought to have a viral origin. The viral part of our DNA as dark matter within the genome.

RNA also contains four different bases. Three of these are the same as in DNA: adenine, guanine, and cytosine. RNA contains uracil (U) instead of thymine (T).
Cytosine (C) C4H5N3O
Adenine (A) C5H5N5
Thymine (T) C5H6N2O2
Guanine (G) C5H5N5O
Uracil (U) C4H4N2O2
thymine Mass: 126.1133 g/mol
Cytosine mass: 151.13 g/mol
6.02214076×10²³ = 602*10^21
There will be around 2*(10^21) base pairs in gm
The human genome contains approximately 3 billion base pairs

Some Facts About The Human Body!

The smallest cells are sperm cells.
Every second, body produces 25 million new cells.
There are about 40,000 bacteria in the human mouth.
The total weight of the bacteria in the human body is 2 kg.
There are more than 100 different viruses which cause a cold.

Blood makes up about eight percent of your body weight.
Around 120,000 Kms of blood vessels in the human body. 
The human heart pumps 182 million litres of blood during the average lifetime.
The human embryo acquires fingerprints within three months of conception.
Women's hearts beat faster than men's.

Exhaled air consists of 78% nitrogen, 16% oxygen, 4% carbon dioxide and 2% others.
The average adult inhales and exhales something like 7 or 8 liters of air per minute.
At 1.2929 gram per litre, we breathe out 10 grams per minute.
Breath has often been considered in terms of the concept of life force.
The terms spirit, prana, the Polynesian mana, and the psyche are related to the concept of breath.
The word "spirit" comes from the Latin spiritus, meaning breath. 

Accounting for 2% of our body mass, the brain uses 20% of our oxygen and blood supply.
Nerve impulses in the human body move at about 90 m/s.
100,000 chemical reactions occur in the human brain every second.
One can recall, on average, around 150 trillion pieces of information.
Information zooms along nerves at about 400kmph!

The human eye can distinguish 10 million different colours.
One percent of people can see infra-red light and 1% can see ultra violet radiation.
Cornea of the eye has no blood supply and receives oxygen directly from the air.

Ear is self-cleaning because of ear wax. It keeps  ears clean and protects from bacteria.

The tongue is the strongest muscle with around 2,000 taste buds.
Sense of smell is closely linked with your memories. 
Certain smells can trigger very strong emotions and memories.
Women have a stronger sense of smell than men.
A cough is an explosive charge of air which moves at speeds up to 90 Kmph.
The nose can recognise a trillion different scents!

Bones are about 5 times stronger than steel.
The largest bone in the human body is the femur or thigh bone.
The smallest bone is the stirrup bone, which is located inside your ear drum.
Skull is made up of 29 different bones.
Babies are born with 300 bones – adults have only 206.
Human teeth are just as strong as shark teeth.

The acid in stomach is so strong that it could dissolve metal.

In whole lifetime, the length of someone's hair would be about 725 kilometres.
Human skin is completely replaced about 1,000 times during a person's lifetime.
We loose 200 million skin cells every hour.

In the morning, a person is about 8 millimetres taller than in the evening.

The music you listen to can cause physiological changes in your blood pressure, heart rate and respiration. 

we have about the same number of hairs on our bodies as a chimpanzee, it's just that our hairs are useless, so fine they are almost invisible. Goosepimples occur when tiny muscles around the base of each hair tense, pulling the hair more erect. Humans used to have a similar defensive fluffing up of their body hairs.

Gastrointestinal system (commonly called your gut), is often referred to as the "second brain." Gut has its own independent nervous system, which transmit information to nerve cells, muscles and gland cells throughout your body. We have an immense number of bacteria in our gut that can impact neural development, brain chemistry, emotional behaviors, pain perception and stress. Your gut is sterile when born. Over time, your GI tract will develop a diverse colony of bacterial species.

Egg Sperm

A human sperm cell consists of a flat, disc shaped head 5.1 µm by 3.1 µm and a tail 50 µm long. The tail propels the sperm cell at about 1–3 mm/minute in by whipping.

Normal semen contains 40 million to 300 million sperm per milliliter. Twenty million sperm per milliliter may be adequate for pregnancy if the sperm are healthy. In contrast, women are born with an average 2 million egg follicles, the reproductive structures that give rise to eggs.

Egg are larger than any other cell in the human body, at about 100 microns (or millionths of a meter) in diameter, about the same as a strand of hair. Those 1–2 million egg cells are actually created in utero, at just nine weeks after conception. That means that the egg that created you was inside your mother, when she was inside your grandmother. A persons real age from view point of egg, will be 0.5 years plus the number of years after the birth of person's mother.

Humans - sturdy animals

While humans may not be the strongest. fastest or toughest around, they are actually pretty sturdy as animals. Our endurance is literally the best in the mammal world, known to outrun horses and wolves long distance. Humans have higher survival rates for severe injuries like missing limbs or muscles wounds above an inch deep, compared to lions and bulls.

Our biology has given us a lot of advantages over animals. Many large animals like horses have very fragile bones for their size, so when they fracture they shatter. Meanwhile humans have proportionally much stronger bones than needed for our muscle mass, leading to fractures that normally can be fixed. We can survive higher lactic buildup in our muscles, subsist on a far more varied diet and lose more water and survive than almost every other mammal and even most fish and bird species.

Humans are the best at long distance running. In fact, early humans used to hunt their prey by chasing it for long periods of time until the animals literally died from exhaustion, a technique known as persistence hunting.

Humans did not evolve from apes/chimpanzees. But there is a common ancestor. Dinosaurs did not look like crocodiles, they had feathers.


Most of our organs are not necessary for life. Many can be removed without significant ill effects. Uterus, ovaries,testicles, prostate, bladder, spleen, eyes, ears, etc. Some would require supplemental replacement of their function; thyroid, kidneys, stomach, etc. Others could be substituted for short periods by artificial means such as heart and lungs but then you are just keeping the body technically alive.

A new generation of medical devices that keeps those organs functioning outside the body could change that. The system has doctors place donor lungs in a sterile chamber warmed to body temperature. The lungs are then connected to a ventilator, which pumps oxygen into the lungs, and a centrifugal pump, which acts as an artificial heart to pump a combination of red blood cells and STEEN solution through the lungs. STEEN solution consists of human serum albumin, a protein that keeps blood volume (and pressure) constant; dextran to coat and protect lung tissue from forming clots; and an electrolyte that prevents free radical formation that can lead to vascular spasms.

The STEEN solution takes the place of blood. Functioning lungs inhale oxygen and transfer it to the circulating fluid, exchanging it with carbon dioxide that they then exhale, just as they would naturally in a body. After the fluid leaves the lungs, it passes through a gas exchange membrane to deoxygenate it and replenish it with carbon dioxide before it reenters the lungs. Doctors can assess lung function by testing the amount of oxygen in the fluid leaving the lungs and knowing the amount introduced through ventilation.

This system can keep lungs alive outside of the body for 12 hours. A transplanted heart was kept 'alive' for five hours outside the body.

Death - Not much Known

Every one fears death. It is hard-wired into our systems to avoid death. Ideal situation is everything should be eternal, so no birth or death. Because there is a birth, it is a grace that we die. No one knows for certain what is and after death. Many cultures believe in an afterlife.

After death, body is just a bag of chemicals/basic elements. Bacteria which was part of us, will start eating the flesh/meat.

During cremation, a corpse is burned at around 1,000 degrees for two hours. The final remnants are known as ashes or cremains will weigh around 3.5% of the person’s original weight.

Alkaline hydrolysis reduces human remains to bone fragments, or hydrolyzed remains, through a water-based dissolution process which uses alkaline chemicals (a mixture of water and lye), heat, agitation, and pressure to accelerate natural decomposition. Body is effectively broken down into its chemical components in three hours.

Water cremation or aquamation, is dissolving a body in water.