The human body is made up of 37 trillion cells , which are the unit of life.
It is not surprising that we find a great diversification among them to be able to carry out different functions, allowing them to complement each other and cover the vital needs of an organism, such as the maintenance of the body structure, nutrition and breathing. It is estimated that there are about 200 types of cells that we can distinguish in the organism, some more studied than others.
Throughout this article we will talk about the main categories that group cell types according to their characteristics.
Why do these microscopic bodies matter?
Although our mental processes seem to arise from some remote point in our head where the connection between soul and body is established, as the philosopher Descartes believed, the truth is that they are basically explained through the relationship between the human organism and the environment in which it lives. That is why knowing the types of cells we are composed of helps us to understand how we are and how we experience things.
As you can imagine, we will not talk about each of them, but we will make some general brushstrokes about some of them to know our body better.
Classifying the classes of cells
Before we start, it would be ideal to group the cell types to better organize the topic. There are several criteria to distinguish the different cell types .
For the case at hand (human cells) we can classify them depending on the group of cells they belong to, that is, in which type of tissue they can be found.
The human body is made up of four different types of tissue, thanks to which we are able to maintain relatively isolated from each other the different environments that our body needs to function properly . These categories of tissue are as follows:
- Epithelial tissue : configures the superficial layers of the organism. In turn, it can be divided into lining and glandular.
- Connective tissue : acts as a connection between tissues and forms the structure of the body. Bone, cartilage and blood are the most specialized tissues of the conjunctive.
- Muscle tissue : as its name indicates, it is made up of the grouping of cells that form the muscles.
- Nervous tissue : formed by all the elements that form the nervous system.
1. Epithelial tissue cells
In this group we find the cells that are part of the most superficial layers of the organism. It is subdivided into two types which we will see below with their fundamental characteristics.
1.1. Covering fabric
These are the actual layers that cover the organism.
Epidermal or keratin cells : cells that make up the skin. They are placed in a compact way and are kept tightly together, so as not to allow the entry of external agents. They are rich in keratin fiber, which kills them as they rise to the most superficial part of the skin, so that when they reach the outside they are hard, dry and strongly compacted.
- Pigmented cells : this type of cells is the one that gives the color to the skin thanks to the production of melanin, which serves as a protector against solar radiation. Problems in these cells can cause many skin and vision problems, for example, as occurs in certain types of albinism.
- Merkel cells : these cells are in charge of providing us with the sense of touch. They are interconnected with the nervous system to transmit this information in the direction of the brain.
- Pneumocytes : located in the alveoli of the lungs, they act as a bridge between the air collected in the lungs and the blood, to exchange oxygen (O2) for carbon dioxide (CO2). In this way, they are at the beginning of the sequence of functions responsible for bringing oxygen to all parts of the body.
- Papilla cells : cells found in the tongue. They are the ones that allow us to have the sense of taste, thanks to the capacity to receive chemical substances and transform this information into nerve signals, which constitute taste.
- Enterocytes : cells of the smooth intestine, which are responsible for absorbing digested nutrients and transmitting them to the blood for transport. Their function is therefore to make the wall permeable to certain nutrients and impenetrable to other substances.
- Endothelial cells : are those that configure and structure the blood capillaries, allowing the correct circulation of the blood. Failures in these cells can produce cell damage in very important organs, which would stop working properly and, in some cases, this can lead to death.
- Gametes : are the cells that participate in the fertilization and formation of the embryo. In the woman it is the egg and in the man it is the sperm. They are the only cells that contain only half of our genetic code.
1.2. Glandular tissue
Groups of cells that share the function of generating and releasing substances
- Sweat gland cells : types of cells that produce and expel sweat to the outside, mainly as a measure to reduce body temperature.
- Tear gland cells : are responsible for generating the tear, but do not store it. Their main function is to lubricate the eyelid and make it slide correctly over the eyeball.
- Cells of the salivary glands : in charge of producing saliva, which facilitates the digestion of food and, at the same time, are a good germicidal agent.
- Hepatocytes : belonging to the liver, they perform several functions, including the production of bile and the energy reserve of glycogen.
- Calciform cells : cells found in various parts of the body, such as in the digestive or respiratory system, which are responsible for generating “mucus”, a substance that serves as a protective barrier.
- Palietal cells : located in the stomach, this class of cells is responsible for producing hydrochloric acid (HCl), which is responsible for proper digestion.
2. Connective tissue cells
In this category we will find the types of cells that are part of the connecting and structural tissue of the body.
- Fibroblasts : are large cells that are responsible for maintaining the entire body structure through the production of collagen.
- Macrophages : types of cells found on the periphery of connective tissue, especially in areas at high risk of invasion, such as at the entrances to the body, with the function of phagocytising foreign bodies and presenting antigens.
- Lymphocytes : commonly grouped in leukocytes or white blood cells, these cells interact with antigens signalled by macrophages and are responsible for generating a defence response against them. They are the ones that generate the antibodies. They are divided into T and B types.
- Monocytes : they are the initial form of macrophages but, unlike them, they circulate in the blood and are not settled in a specific place.
- Eosinophils : are a class of leukocytes that generate and reserve different substances that are used to defend against a parasitic invasion by a multicellular organism.
- Basophils : white blood cells that synthesize and store substances that support the inflammation process, such as histamine and heparin. They are responsible for the formation of edemas.
- Mast cells : class of cells that produce and store a large amount of substances (including histamine and heparin) that are released as a defensive response, helping the other cells of the immune system.
- Adipocytes : cells that are found throughout the body and have the ability to capture fat as an energy reserve, mainly.
- Chondroblasts and chondrocytes : are responsible for forming the tissue we know as cartilage. The chondroblasts produce the chondrocytes, which have the function of producing the necessary components to form the cartilage.
- Osteoblasts and Osteocytes : cells in charge of forming the bones, generating the process of calcification and therefore conditioning the process of growth and maturation of people. The difference between the two is that the osteoblast is the initial phase of an osteocyte.
- Red blood cells : also known as erythrocytes, this type of cell is the main cell in the blood, carrying O2 to the cells and extracting CO2 to the lungs. They give the blood its distinctive color by containing the protein hemoglobin.
- Platelets or thrombocytes : small cells that are activated when a blood vessel has been damaged and needs to be repaired to prevent blood loss.
3. Muscle tissue cells
In this group we find only one type of cell that structures the muscles, which are responsible for the mobility of the organism.
- Of the muscle fibers or myocytes : the main cell that configures the muscles. They are elongated and have the capacity to contract. The muscle fibres can be differentiated between skeletal striated, which allows us to control the body voluntarily; cardiac striated, which is non-voluntary and keeps the heart moving; and smooth, which is involuntary and controls the activity of other internal organs, such as the stomach.
4. Nerve tissue cells
Finally, in this category are the cells that are part of the nervous system.
Neurons : this class of cell is the main cell of the nervous system, which has the function of receiving, conducting and transmitting nerve impulses.
- For more on this topic, you can read the article “Neuron Types: Characteristics and Functions”.
- Neuroglia : set of cells with the function of giving support to neurons, as protection, isolation or means through which they move, mainly.
- Cones : cells found in the retina, which capture high-intensity light, providing the sense of daytime vision. They also allow us to differentiate colours.
- Sticks : cells that work together with the previous ones in the retina, but capture low intensity light. They are responsible for night vision.