Anatomy & Organs

Cell – Structure, Function & Diseases


The cell (Latin cellula ) is the smallest unit of life. Humans are made up of many different types of cells that vary in appearance and function.

What is a cell

Some organisms, such as bacteria , consist of only a single cell and are therefore referred to as protozoa. Higher organisms are made up of a large number of cells and are called multicellular organisms. Humans are made up of around ten trillion cells that specialize in different tasks and differ in size and shape depending on the type of cell.

For example, there are long, thin nerve cells , spherical red blood cells and round fat cells. At 110 to 140 micrometres, the egg cell is the largest human cell. What all cells have in common is that they contain all of the genetic information in the form of DNA (deoxyribonucleic acid), can generate and use energy and are able to multiply through cell division. Cells can assemble into tissue structures. Four main tissue groups are composed of over 200 different types of human cells : epithelial tissue , muscle tissue, connective tissue and nerve tissue .

Anatomy & Structure

Human cells are surrounded on the outside by the cell membrane . Unlike plant cells, they do not have a cell wall. The size of the cells is not related to the size of an organism. Larger organisms are just made up of more cells. Inside the cell membrane is the cytoplasm .

Various so-called organelles are located in the cytoplasm. These include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes and peroxisomes. The organelles are specialized for different tasks. The cell nucleus contains the genetic information in the form of DNA and in humans is separated from the cytoplasm by a nuclear envelope.

Part of the DNA is also found in the mitochondria. The endoplasmic reticulum (ER) is divided into rough and smooth ER. The rough ER has ribosomes that are absent on the smooth ER. Other cell components include the cytoskeleton, RNA (ribonucleic acid) and centrioles. The extracellular matrix is ​​located between the individual cells outside of the cell membrane.

Function & Tasks

The cell membrane serves to separate the cell from its surroundings and to protect it. They control which substances get into the cell and which get out. It can communicate with neighboring cells via proteins contained in the cell membrane . The cytoskeleton is responsible for the elasticity and stability of the cell. It allows both active movement of the cell and movement within the cell. The ribosomes are the place in the cell where proteins are synthesized using specific RNA.

The Golgi apparatus forms various secretions and is involved in the metabolism of the cell. The lysosomes represent the cell’s digestive system. They contain numerous enzymes with which they can break down foreign and cell-specific substances. The peroxisomes are used for detoxification. They can utilize oxygen, bind free radicals and break down various metabolic products.

The centrioles are required for cell division and thus for cell proliferation. Since each cell can gain and use energy and multiply, each cell is capable of surviving on its own. However, some specialized cells have lost this ability. Depending on their specialization, the cells have different tasks. The specialized cells originally originate from so-called stem cells .

Stem cells are general cells of the body that can both multiply by dividing into new stem cells and develop into specific cell types. When a cell specializes, certain genes are inactivated while others are activated. This leads to the formation of the proteins that are specifically required in a certain cell type. As a result, a liver cell, for example, has a different chemical and structural structure to a nerve cell, although both carry the same genetic information.

Diseases & Ailments

A common disease of cells is cancer . In the case of cancer, the balance between cell division and cell death (so-called apoptosis), which is regulated by the genes, is disrupted. This leads to uncontrolled growth of cells and tumors . In various neurodegenerative diseases, nerve cells in the brain die off. This can depend on age, such as dementia or Parkinson’s disease.

However, the age-related loss of cells and their functions is normal to a certain extent and is usually well tolerated by the body. Only when an above-average number of cells die does it lead to clinical pictures. Other neurodegenerative diseases occur regardless of age, such as amyotrophic lateral sclerosis (ALS), Huntington ‘s disease or Creutzfeldt-Jakob disease .

In allergic reactions, specialized cells in the immune system overreact. In the event of an allergy , these fight a substance that is harmless to the body, which leads to the allergic symptoms. A very rare cell disease is the hereditary I cell disease , also known as mucolipidosis II. It is a lysosomal storage disease in which one of the enzymes normally found in the lysosome cannot be transported here because of a genetic defect.

In the case of mastocytosis or what is known as Czernin’s disease, there is a greatly increased proliferation of mast cells. The skin or internal organs can be affected. Symptoms are triggered by substances released by the mast cells, primarily histamine .

Lisa Newlon
 | Website

Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.