How Many Cells Are In The Human Body?


The human body is composed of some million numbers of cells. Unfortunately, the Census cannot take the count of your cells to get the actual figures. Rather it is not quite simple or practically possible to count the cells looking under a microscope. Some cells are not easy to be found under the microscope as well. While others are obscure and tangled. Be careful do not chop your body cells to an experiment of counting. Let us explore how many cells are in the human body? Read further to know about cells that are the building blocks of the human body.

How Many Cells Are In The Human Body?

how many cells are in the human body

The count of the human cells runs into several million. A team of scientists from various countries claims that they are hardly the first ones to crack this. When looked back into some of the scientific journals and research figures, you can see some estimates. Usually, the estimates range between 5 billion and 200 million trillion cells. The range of the numbers is pretty sprawling. Additionally, no scientist has a satisfactory justification for the estimate. This clearly indicates it is pointing for an advanced research.

So, can scientist count the cells? No, it is practically not possible. Then what are the means they adopt to get the accurate or approximate numbers? A cell on an average weighs 1 nanogram. Consequently, an adult man weighing 70 kilograms by applying simple arithmetic logic has 70 trillion cells. On the other hand, you can also know the number of cells based on the volume of the cells. The average volume of a human cell is 4 billionths of a cubic centimeter. On the basis of the volume, you can conclude that the human body has 15 trillion cells.

Unfortunately, the results based on volume and weight does not remain the same. Both estimates vary drastically. To make the calculation tough, our body is made of different type of cell and is not uniform resembling a jar of jellybeans. Cells are of different size, different shape, and different origin. When you are considering blood, you can find red blood cells packed intact. In case, if the density of the blood cells is considered to get an estimate of the total number of cells, the figures you may arrive at are staggering as it may be 724 trillion cells. Whereas, if you consider skin cells they are sparse resulting in a negligible estimate of 35 billion cells.

To get the right estimates it is pretty hard and there are a lot of advanced studies taking place in this regard. Also, there are few microbes that dwell in the human body and if taken that into account the numbers may vary. The scientific literature went into the detailed study of the density and volume of cells present in knee joints, bone marrow, gall bladder, intestines, and other tissue. Further, estimates of each type of cells were given. For instance, the estimates are 2 billion heart muscle cells and 50 billion fat cells. On adding all these numbers, it results in 37.2 trillion cells.

So, arrived at final numbers but these are not the actual figures. The number of cells in people varies depending on the size of the people. The scientists declare these estimates are wrong and the right numbers are yet to be discovered. However, now with these numbers scientist got an opportunity to go further to attain the real numbers.

The actual numbers unleashed just do not satisfy the curiosity but also have some scientific and medical benefits. The sophisticated computer models resembling hearts, lungs, and other organs are built by the scientists to study the functioning of these organs. If these built organs have cells ten times that off the real then the results also varies on a large scale.

Moreover, the number of cells has an impact on the healthy state. A healthy and fit liver has about 240 billion cells whereas; the one affected with cirrhosis results in 172 billion.It is quite interesting to study the tale of 34 trillion cells cooperating through the decades to result in a human body. The evolution took off from the basic level of the cell from unicellular to multicellular. But, most of the prior investigations have gone away beyond anatomy to discover the cell traverse. As you further proceed into deep studies, you are likely to know the reality.


Apart from the number of cells, you must have some insight into cytology to garner some interesting facts about our own self. Cytology is the branch of biology studying function and structure of the cells. Human cells have variable sizes. The ovum or egg has 300 μm diameters. This cell can be seen by the naked eyes. However, the remaining body cells are about a fraction of these cells. The cells lining the stomach are comparatively large. Similar to skin cells, these cells shed.

Myofibrils or muscle fibers in their first glance may appear to be the largest ones and their size varies between 1 mm to 3 cm in length. A single cell membrane binds all these fibers together. Though all have one cell membrane, these are not termed as a single cell due to multiple nuclei present. Red blood corpuscles are the smaller among all the cells. Most of the internal features are not present in these cells owing to their smaller size.

Cell Structure

All cells are similar and contain gelatinous substance. The substance is made of protein, water, acids, minerals, and fats. Let us see the components of the cell.

Cell Membrane

It is the protective outer layer of the cell and acts as a barrier to inflow and outflow of substances.


The structure of the cell is controlled by the nucleus. Cell reproduction and other functions of the cell is directed by the nucleus.


Chromosomes are rod-like structures. All cells of the human body except the sex cells have 23 pairs of chromosomes and sex cells have 23 single chromosomes. The sex cells of male and female unite to form an embryo and it has 46 chromosomes or 23 pairs.

Genes are the area present in the chromosomes. Each chromosome has thousands of number of genes present in an orderly sequence. Deoxyribonucleic acid or DNA forms the chromosome. DNA is crucial in regulating all the activities of the cell to take place in a consequential order. A series of codes are present on DNA. Manufacturing of proteins and cellular reproduction are some of the activities controlled by the DNA.

Karyotype is a process through which the size, arrangement, and number of chromosomes can be analyzed. Additionally, the procedure also determines whether the chromosome is normal in all aspects. Doctors perform this by piercing the sac surrounding the fetus during pregnancy through the process of amniocentesis. Trisomy-21 syndrome and Down syndrome or Mongolism are some of the disorders taking place due to the abnormal count of chromosomes.


It is the powerhouse of the cell. These organelles produce the required energy by burning the food and appear small with sausage shape. The process of breaking complex food into simple food particles to release energy is called catabolism.

Stages Of Organization

The body of a living creature is made of variable substances in variable stages. Beginning with the basic the levels of the organization get complicated with advanced levels.

  1. Atoms and molecules constitute any substance and these form the building block.
  2. The smallest living unit of the body is a cell.
  3. A group of cells with similar function and structure forms a tissue.
  4. Tissues together form organs.
  5. Various organs when work together forms a system. Say, for instance, the digestive system.
  6. On the whole, the body is the result of operation and coordination at different levels.

Few trillion numbers of cells combine together and function at various levels and have different size and shape. The organs formed with aligning of tissues form a separate structure in the body for a specific function.

Different Cell Types

Different type of cells is assigned with different functions. Five types of cells are present in the body. They are:

1. Muscle Cell

It is made up of fibers and is slender. The fibers help to contract and release the muscle actions. The three type of muscles in the body are:

  • Striated muscle
  • Cardiac muscle and
  • Smooth muscle

2. Nerve Cell

Nerve cells are also known as neurons. These cells are electrically excitable and transmit information. The brain and spinal cord have neurons as basic components in vertebrates. In case of invertebrates, you can find ventral nerve cord and peripheral nerves.

3. Fat Cell

These are large empty cells designed for storage of material. It is also called adipocyte. These cells are mainly made of fat. Fat storing is the primary function of these cells. Two types of adipose tissue are brown and white. Also, known as brown fat and white fat.

4. Skin Cell Or Epithelial Cell

Epithelial cells are flat and square. These cells form a protective layer. There are two types of skin cells: dermis outer layer of the body and epidermis inner layer of the body.

5. Sex Cell

Sperm is the male sex cell and the egg is the female sex cell. Both sex cells irrespective of male or female it contains 23 single chromosomes and all other cells of the body contain 23 sets of chromosomes.


  • Cells organize themselves in layers. And these cells may be of the same type or the different ones. Cells of a particular tissue are devoted to a specific function.
  • Cells forming a thin layer of tissue is the epithelium and you can find this in the lining of the mouth.
  • Cells arranged to form a small tube (tubule) are present in kidney tubule.
  • In muscle tissue, cells are arranged in a sheet as it appears in the arterial blood vessels.


Different type of tissues grouped together to form organs. The organs include heart, skin, kidneys, and liver. Human skin have certain different layers, they are:

  • Protective layer made of dead cells that prevent drying out and infection
  • Some cells that form the hair follicles, the epidermal cells
  • A layer present in the basement separating dermis from the epidermis
  • The dermis layer provides the integrity and strength of the skin. Additionally, this layer has blood vessels, muscle fibers, and sensory nerve endings.