Cells are the basic units of life. They’re so small that trillions of them are in your body, and they do everything from fighting disease to helping you digest food. But what are cells? How do they work? And what are all the different types of cells?
This article is about the types of cells that make up your body. We’ll talk about each kind, how they work, and where they live—so you can understand exactly how they help keep you healthy!
Go Deep Inside Your Cells
Each of the tiny dots that make up the cell are called organelles. These organelles work together to keep your cells alive and functioning: they produce energy, help with immunity, and even control your metabolism. The key to maintaining these healthy organelles is ensuring they have what they need to do their jobs properly.
The human body is made up of over 37 trillion cells. Each cell has its DNA and environment, which affects how it behaves. For example, some have more mitochondria than others, some have more receptors for specific hormones and neurotransmitters, some have more myelin than others—and each has a function in the overall operation of your body.
The cell membrane is a semi-permeable lipid bilayer that separates the inside and outside of a cell. It’s composed of two layers, with the outer layer being made up of phospholipids and cholesterol. The inner layer contains integral proteins embedded in the lipid bilayer.
The cell membrane is made up of lipids, which are fatty molecules that can dissolve in water but not in oil. This means that they are amphiphilic: they have both hydrophobic and hydrophilic regions, meaning they are attracted to each other and repel each other simultaneously. This allows them to form a bilayer (two layers) with an interior space between them for carrying out biological functions within cells, like transporting nutrients or secreting hormones.
Mitochondria are the cell’s powerhouses, converting energy from food into a form that cells can use. As a result, they are often referred to as the “cellular powerhouse” and are responsible for generating most of the energy found in our bodies.
Mitochondria contain their DNA and reproduce independently of the rest of the cell. They were once considered bacteria that invaded eukaryotic cells (cells with a nucleus), but now they are recognized as true organelles.
Mitochondria are bounded by two membranes: an inner membrane and an outer membrane. The inner membrane contains many pores through which molecules can pass into or out of the mitochondrion.
Ribosomes are large, complex protein machines that are responsible for synthesizing proteins. Ribosomes have two subunits, each composed of ribosomal RNA (rRNA) and many different proteins. The rRNA contains the genetic code and is copied into a growing polypeptide chain as the ribosome moves along the mRNA strand.
The nucleus is the cell’s “brain.” It’s where all of the genetic information for the cell is stored, and it has a lot of control over what the cell does. The nucleus contains two types of DNA: nuclear DNA (or simply “nDNA”), which includes the instructions for all of the proteins that make up our bodies, and mitochondrial DNA (or “mtDNA”), which contains instructions for some things like how cells work together to break down food into energy.
The nucleus also contains ribosomes, like factories within your body that produce proteins. These ribosomes are responsible for making sure you have enough energy to live!
Cell Types Explained
There are several different types of cells in the human body, each with its function. Understanding these different cell types is important because they all interact with one another to keep your body healthy.
But instead of wasting your time talking about the minutia of each type, here are the basics about some of the most common varieties of cells in your body.
Skin and Epithelial Cells
Skin is the largest organ in the human body and is also one of the most important. It serves as a protective barrier between us and the outside world and helps regulate our body temperature. The skin comprises three layers: the epidermis, dermis, and subcutaneous tissue.
When you look at the cells, you can most easily see that you’re looking at your epithelium. This skin layer covers your entire body, and it’s made up of special skin cells called epithelial cells. These are the same type of cells that line your digestive tract, blood vessels, and hollow organs.
- Skin and epithelial cells are the most abundant cells in your body. They come together to create tissues that can secrete mucus, sweat, and oil.
- The cells that line agoradesign.it your body’s internal organs and cavities harden into a tough material called keratin to protect you from invading pathogens and injuries.
- Melanin is the protein in your skin cells that determines your skin color and whether or not
you have freckles.
- Skin also helps maintain hydration levels. This is because the outermost skin cells, which protect your more sensitive inner layers, are good at absorbing water.
- The mucus secreted by epithelial cells lines the inside of your body’s cavities, including your esophagus, nasal passages, and intestines.
Blood cells are essential for carrying oxygen around the body. They are also important for fighting infections and removing garbage from our bodies. They are made in the bone marrow, soft, spongy tissue inside bones.
There are different blood cells: red blood cells, white blood cells, and platelets. Red blood cells carry oxygen around the body. White blood cells help fight infections. Platelets help with clotting.
Red blood cells, or erythrocytes, are responsible for oxygen transportation. They can be found in the blood and carry oxygen from the lungs to the rest of the body. They also help to remove carbon dioxide from tissues and transport it back to the lungs.
White blood cells, or leukocytes, are produced by the bone marrow and are involved in fighting infections. They protect us from bacteria, viruses, and fungi by destroying or marking them so other parts of our immune system can later destroy them.
Platelets are tiny fragments of cytoplasm that stick together when released into your blood. They form clots around damaged areas to stop bleeding until new tissue can form there.
Blood cells are a vital part of your body’s immune system. There are two main classes of WBCs—granulocytes and mononuclear leukocytes:
- Granulocytes include neutrophils, eosinophils, and basophils. These are short-lived cells that fight infections. They’re particularly important in fighting bacteria. Neutrophils are the most common granulocyte type, accounting for about half of all WBCs in your blood.
- Mononuclear leukocytes include lymphocytes (B and T cells), natural killer cells, and monocytes. Lymphocytes help the body fight viruses and tumors; natural killer cells can destroy cancer cells; monocytes help the body fight bacterial infections by engulfing foreign particles—including bacteria—and then digesting them in macrophages (another type of white blood cell).
Nerve and Brain Cells
Nerve cells are a type of cell that is responsible for the transmission of signals within our bodies. They perform this function by transmitting electrical signals through their axons, or extensions, which carry information from one body part to another.
These cells are found throughout the body and are responsible for many functions, including our ability to move, feel pain, and see the light.
Nerve cells can be divided into two categories: neurons and glial cells. Neurons are responsible for sending messages from one place to another, while glial cells help maintain homeostasis by providing support for neurons and other cells in the body.
The heart, hamstrings, and all other muscles in the body are composed of muscle cells. Each muscle cell is composed of smaller strands of protein known as muscle fibers. These fibers wrap tightly around each other like bundles of strong, stretchy cords to create your muscles.
Muscle fibers are filamentous proteins that allow them to lengthen and contract. Actin, myosin, and titin are three of these proteins; they each have different functions in the contraction-relaxation cycle of a muscle fiber.
Your muscles move when nerve cells in your central and peripheral nervous systems signal muscle fibers. Voluntary muscle movements, such as waving hello, happen when you decide to make them happen. Involuntary muscle contractions, such as constricting your pupils in bright light, happen without conscious effort.
Muscle fibers and muscle tissue come in three main types, and each type is used differently by the body:
- Skeletal muscles are attached to bones via tendons and are controlled by conscious thought. Skeletal muscle cells are long, cylindrical tubes with more than one nucleus.
- Smooth muscle tissue is composed of smooth muscle fiber, which may be found in the organs of your body. These smooth muscle fibers are responsible for involuntary actions or movements, such as those that occur in your eyes, stomach, bladder, intestines, and blood vessels.
- Cardiac muscle cells, which can only be found in the heart, are unique in their structure and function. Cardiac muscle fibers have a distinct appearance that sets them apart from other types of muscle tissue and allows them to contract more efficiently than skeletal or smooth muscle cells.
The storage of fat is a sometimes taboo topic. But adipocytes—the cells that house fats—are an essential part of your body. Adipose tissue is a group of cells composed entirely of adipocytes.
Rather than considering fat a bad thing, try to regard it as a necessary substance. Your body stores fat just like a bank stores money: it can use this fat to provide energy when needed. Adipocytes are cells that contain fat and release it when your body needs more energy.
Brown adipocytes are sometimes called “baby fat” because they are most abundant in infants. Brown fat cells contain more mitochondria than white adipocytes, and the primary role of these cells is to generate heat through thermogenesis. This helps infants maintain body temperature, which is especially important for newborns that have not yet developed shivering capabilities or other means of keeping warm.
As you grow, the quantity of brown fat in your body—the cells that burn calories to generate heat—diminish. Mitochondria—the power plants within each cell that enable aerobic respiration and energy production—disappear from brown fat cells, causing them to resemble fat white cells. Brown fat is important for newborns because it helps them to maintain their body temperature.
White fat cells store energy, which can be released when a person is not consuming enough calories from food. Glucose is the preferred energy source for most cells in our bodies; however, the brain and red blood cells can use ketone bodies (a type of molecule made during fat breakdown) as an alternative energy source. This process is called gluconeogenesis, which occurs when we are fasting or starving.
Cellular Health Comes First
If you want to feel better and live longer, your first step should be ensuring your cells are healthy.
When it comes to your overall health, it’s all about the cells. Your body consists of trillions of them—your bones, blood, brain, skin, organs… all are tiny little cells. And if those cells are sick or damaged, you’ll experience health problems.
When it comes to food, choose quality over quantity. Avoid processed foods that are low in nutrients and packed with preservatives, and instead opt for whole foods like lean proteins, plant-based fats, fiber, vegetables, and fruit.
When you prioritize the health of your cells, it is reflected in your overall wellness. For example, a diet rich in essential vitamins and minerals can optimize the health and well-being of the cells that make you. When you give your body the nutrients it needs, you feel great.