Category Human Body

Each type of cell has a shape and size related to its own vital task in the body.

Red blood cells

Red blood cells are doughnut shaped, and this lets them pick up and carry oxygen easily. Hemoglobin is the protein inside red blood cells. It carries oxygen. Red blood cells also remove carbon dioxide from your body, transporting it to the lungs for you to exhale.

Red blood cells are made in the bone marrow. They typically live for about 120 days, and then they die.

Nerve cells

Nerve cells are long, thin, and carry electrical signals over long distances. Essentially, nerve cells, also known as a neurons, are the active component of the nervous system. Neurons communicate with each other as well as with other cells through electric signals (nerve impulses), which in turn allows effector organs to respond to the appropriate stimuli.

Muscle cells

Muscle cells can contract (shorten) and relax to produce movement. Muscle cells, commonly known as myocytes, are the cells that make up muscle tissue. There are 3 types of muscle cells in the human body; cardiac, skeletal, and smooth. 

Epidermal cells

Epidermal cells in the skin fit tightly together to form a protective layer. Epidermal cells include several types of cells that make up the epidermis of plants. Although they serve a number of important functions, their primary role is to protect from a variety of harmful factors (environmental stressors) including microbes, chemical compounds as well as ultraviolet light among others.

Fat cells

Fat cells are filled with droplets of liquid fat as an energy store. Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through adipogenesis.

Cone cells

Cone cells in the eye detect light, enabling us to see. They respond differently to light of different wavelengths, and are thus responsible for color vision, and function best in relatively bright light, as opposed to rod cells, which work better in dim light.

Cell lifespans

Different types of body cell have different lifespans. Some, such as kin cells, are worn away. Other cells wear out and self-destruct. They are replaced with more of their kind by special cells called stem cells.

White blood cells fighting infection: Less than 1 day

Skin cells: 30 days

Liver cells: 12-18 months

Muscle cells: 15 years

Some nerve cells in the brain: A whole lifetime

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Tissues are groups of connected cells. Many tissues are made entirely from one type of cell. The four main types of tissue in the human body are connective, epithelial, muscular, and nervous.

Nerve tissue

Large groups of nerve cells create nervous tissue. This forms the brain, spinal cord, and masses of nerves that wok together in the nervous system, the body’s high-speed communications network.

Epithelial tissue

Made up of three main shapes of cell, epithelial tissue lines and covers surfaces inside and outside the body. It forms skin and the linings of body cavities such as the gut and lungs.

Muscle tissue

Built from long, thin cells, muscle tissue can relax and contract to allow muscles to move bones. It also helps sustain blood pressure and carry blood through the digestive system.

Connective tissue

This dense tissue is the body’s “glue”, filling the space between other tissues and organs, and binding them together. Examples include adipose tissue (fat), bone, and blood.

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Everything in the body id made up of atoms, the tiniest building blocks of matter. Atoms combine to form molecules. Millions of molecules form every cell in the body. There are more than 200 types of cell, with similar cells working in teams called tissues. The body’s many organs and systems are made up of different tissues.

Atoms and molecules

The smallest parts in the body are atoms. These tiny building blocks form the elements in the body, such as carbon. Atoms can also join together in groups called molecules – for example, water is a molecule, made from a combination of hydrogen and oxygen atoms.

Cell

Molecules build up to create body cells. There are about 37 trillion cells in the average human, with different types of cells carrying out a variety of body functions, from transporting oxygen to sensing light and colour in the eye.

Tissue

Cells performing the same function are grouped together to form body tissues, such as skin, fat, or heart muscle. Blood is also a tissue, in liquid form.

Organ

Different kinds of tissue combine to make larger structures called organs. Each organ works like a machine, performing its own role. An example of an organ is the stomach, which plays a part in the process of digesting food.

Body system

Organs are at the centre of 12 internal body systems. Each system has a specific job to keep the body in working order. The stomach is one of the main organs of the digestive system.

Complete human

When this common combination of integrated systems, organs, and tissues works together, the human body is complete. Each individual component plays its part in maintaining a fully functioning body.

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The human body is made from substances containing the element carbon. Called organic compounds, these often contain hydrogen and oxygen, too. Although organic compounds are based on only a few elements, they produce more than 10 million different compounds. Four main types of carbon compound exist inside the human body.

Nucleic acids

The molecules DNA and RNA carry all the instructions for making the proteins that our bodies are made of. They also carry code that controls how cells work and reproduce.

Proteins

Proteins are vital body molecules. Organs such as the brain are made o protein, as well as muscles, connective tissues, hormones that send chemical messages, and antibodies that fight infection.

Fats

Fats are made from carbon and hydrogen atoms. They form the outer barrier of cells. The layer of fat beneath the skin stores energy and helps the body to keep out the cold.

Carbohydrates

Carbohydrates are made of carbon, oxygen, and hydrogen, and are the body’s main source of energy, carbohydrates circulate in the blood as sugars, or are stored in the liver and muscles.

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More than 93 per cent of the human body consists of three chemical elements – oxygen (65%), carbon (18.5%) and hydrogen (10%). Nitrogen (3%), calcium (1.5%), and phosphorous (1%) are also present in significant amounts. At least 54 chemical elements feature in total, but most of these are tiny traces.

Oxygen 65%

About two-thirds of the body is oxygen. Most of the oxygen is bonded with hydrogen to form H2O – the chemical formula for water.

Carbon 18.5%

Nearly one-fifth of the body is carbon, the same element that coal, diamond, and the lead of pencils are made from.

Hydrogen 10%

The most common element in the universe, hydrogen has the tiniest atoms, and is mostly bonded with carbon or oxygen in the body.

Others in Human Body- 6.5%

Other elements less than 1.0%

Iron 0.006%

Sodium 0.2%

Potassium 0.4%

Phosphorus 0.4%

Calcium 1.5%

Nitrogen 3.2%

Precious elements

The human body contains a tiny amount of gold – less than the weight of a grain of sand. Most of the body’s gold is in the blood.

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The human body is made from the same components as every other living thing. It is the way that they are put together that makes our bodies uniquely human. The basic materials are simple chemicals such as water, carbon, and oxygen, but they join to create more complex compounds. Trillions of microscopic cells become the building blocks of life, grouping together to form skin, bone, blood, and organs, until the body becomes complete.

Body composition may be analyzed in various ways. This can be done in terms of the chemical elements present, or by molecular type e.g., water, protein, fats (or lipids), hydroxylapatite (in bones), carbohydrates (such as glycogen and glucose) and DNA. In terms of tissue type, the body may be analyzed into water, fat, connective tissue, muscle, bone, etc. In terms of cell type, the body contains hundreds of different types of cells, but notably, the largest number of cells contained in a human body (though not the largest mass of cells) are not human cells, but bacteria residing in the normal human gastrointestinal tract.

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