The various tissues of the human body , with their diverse functions and characteristics, are all composed of the same basic, microscopic unit of life: the cell . For example:neurons, adipocytes, macrophages.
Depending on their specific role within the structural complexity of the body and, therefore, their morphology, cells can be of very different types. It is estimated that there are around 200 types among the 37 trillion cells that make up our body.
In terms of their nature, our cells are not so different from those of most mammals . Our animal cells differ from those of plants and fungi in that they lack a rigid cell wall and also lack chlorophyll and cellulose.
A typical human cell is composed of:
- A permeable cell membranethat allows osmosis and the expulsion of material.
- A nucleusthat contains genetic information and occupies 10% of the cell mass.
- A nucleoluswithin the nucleus, where ribosome production takes place.
- Cytoplasm, a gelatinous substance that makes up the “inside” of the cell and where all its organelles are found.
- Various organelles: the mitochondria, responsible for cellular respiration and energy production; the vacuole, responsible for transporting substances within the cell; the ribosome, responsible for protein synthesis ; the lysosome, responsible for producing enzymes ; as well as a network of membranes, tubes, and sacs called the endoplasmic reticulum (smooth and rough).
- You may be interested in: Organs of the human body
Examples of human cells
- Epithelial cells. They constitute cellular networks of epithelial tissue that cover all the body’s free surfaces: ducts, mucous membranes, hollow organs, glands , and the inner lining of cavities. The different layers of the skin are primarily formed by them.
- Neurons. A type of cell whose plasma membrane is electrically excitable, serving as a conductor and receiver of stimuli from the nervous system. They do not typically reproduce once they reach maturity and are vital for body control.
- Fibroblasts. The most common and least specialized cells in the body, they are part of the connective tissue that keeps the body’s structure integrated and sustained.
- Adipocytes. Cells responsible for managing the body’s energy reserves: fats . Through enzymes, they activate lipogenesis and lipolysis, the processes of fat creation and burning, respectively, and respond primarily to hormonal regulation .
- Osteoblasts. The primary cells of bone , they are responsible for forming and organizing the bone matrix, which is later mineralized to achieve its strength. They are cuboidal cells that receive calcium.
- Glial cells, or neuroglia. They support the neuronal network and are important in the body’s information processing. They are responsible for ionic and neurotransmitter control , serving as a kind of glue for nervous tissue itself. They are much more abundant (1:10 to 50) than neurons.
- Macrophages. Cells belonging to the body’s immune system, they deal with pathogens or contaminants , as well as dead cells in renewing tissues, by phagocytosing these harmful elements. In doing so, they generate a cellular information system that triggers the immune response.
- White blood cells, or leukocytes. They are a diverse group of defensive cells originating in the bone marrow and lymphatic tissue, which act to combat the presence of pathogens in the body. There are five highly specialized types, designed to hunt down different antigens : neutrophils, eosinophils, basophils, lymphocytes, and monocytes.
- Red blood cells, or erythrocytes. They are the most numerous cells in the blood, the only ones that contain hemoglobin to transport oxygen. Unlike the rest, red blood cells are so specialized in their function that they lack a nucleus or mitochondria, so they obtain their energy through lactic acid fermentation rather than cellular respiration.
- Gametes. Destined exclusively for reproduction, they carry only half of an individual’s entire genome. In men, they are motile and smaller, called sperm; in women, they are larger and less motile, called eggs.
- Rods. Located in the retina of the eye, they are extremely light-sensitive, so they are responsible for vision in low-light environments. They are not color-sensitive.
- Cones. Unlike rods, cones are eye cells in the retina, specialized in perceiving different wavelengths of light, thus capturing different colors from green, red, and blue.
- Hepatocytes. Part of the liver, these are cells rich in organelles, glycogen, and fat. They are responsible for secreting bile.
- Basal cells. Located in the outermost part of the skin, they produce the scaly layers of tissue that form the body’s boundary with the outside world.
- Odontoblasts. They constitute the pulp of the teeth and are responsible for producing dentin, the substance to which tooth enamel is attached.
- Peptide cells. Found in the stomach, their function is to secrete the hydrochloric acid needed to form pepsin and break down ingested food.
- Goblet cells. Responsible for the production of mucus, which keeps the epithelium of the respiratory tract and digestive system moist and protected. Their name comes from their inverted goblet shape.
- Pneumocytes. Lung cells that line the alveolar cavity, allowing gas exchange with the blood and initiating the respiratory circuit. There are type I and II pneumocytes, each with distinct morphologies and functions.
- Myocytes. They make up the muscular tissue mass that supports the skeleton and allows for strength and mobility. They possess a complex network of proteins that allows them to expand and contract without losing their original shape.
- Endothelial cells. Flattened cells that line the interior of blood vessels and the heart, constituting their outermost cellular layer, in constant contact with the blood. They also perform several important homeopathic functions.