First Aid Understanding Cells, Tissues, and Organs By Rod Brouhard, EMT-P Rod Brouhard, EMT-P Facebook LinkedIn Twitter Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients. Learn about our editorial process Updated on October 31, 2021 Medically reviewed Verywell Health articles are reviewed by board-certified physicians and healthcare professionals. These medical reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Michael Menna, DO Medically reviewed by Michael Menna, DO Michael Menna, DO, is board-certified in emergency medicine. He is an attending emergency medicine physician at White Plains Hospital in White Plains, New York and also works at an urgent care center and a telemedicine company that provides care to patients across the country. Learn about our Medical Expert Board Fact checked Verywell Health content is rigorously reviewed by a team of qualified and experienced fact checkers. Fact checkers review articles for factual accuracy, relevance, and timeliness. We rely on the most current and reputable sources, which are cited in the text and listed at the bottom of each article. Content is fact checked after it has been edited and before publication. Learn more. by Heather Mercer Fact checked by Heather Mercer Heather Mercer is native to Northwest Ohio (go Walleye!) and graduated from Loma Linda University with two doctorate degrees (psychology and public health). She is currently a professor at Owens Community College, as well as a fact-checker for Verywell Health. She has gained experience in a variety of settings, ranging from corporate wellness and preventive medicine, to mental health, chronic disease, and end-of-life care. Learn about our editorial process Print Medical and first aid articles regularly use terms that don't always make sense out of context or if you're just not familiar with them. If they don't make sense in the piece, it could completely change how much you understand. Here to help you with the most basic of all anatomical terms are the foundational building materials of the body: cells, tissues, and organs. These are the basis for the entire body. Once you have these down, we can move on to organ systems or get more specific, like the nervous system. Maskot / Getty Images Cells Cells are the smallest unit of life. To understand what a cell looks like, picture a chicken egg. It has an outer membrane (in the case of an egg, it's a hard shell, but most cells aren't like that); it's filled with nutrient-rich fluid (whites of the egg versus cytoplasm in a cell) and has a nucleus (egg yolk). Not all cells look alike. Nerve cells are long, thin and covered in myelin, natural insulation. Nerve cells conduct impulses, which are used to communicate. They're basically the telephone wires of the body, and they look the part. Muscle cells are thick and elongated, like live rubber bands. Red blood cells are flat and discoid-shaped. The shapes of the cells help them with their individual functions. Each cell serves a specialized purpose in the body. Muscle cells contract and nerve cells transmit impulses. Red blood cells bind to oxygen, while white blood cells fight infection. Tissues When cells of a certain type are grouped together, the resulting structure is called tissue. There is muscle tissue, which is made of strands of muscle cells. Adipose tissue is one layer of skin made of fat cells. Connective tissue is a term used for various types of tough, fibrous matter like tendons or ligaments. Most of the time in first aid, we refer to tissues more than cells. Cells are typically microscopic, while tissues can be seen and manipulated. When you look at a laceration to determine if it needs stitches, you are looking for adipose tissue in the wound. Indeed, stitches hold together the tissue, not the individual cells. Organs When different types of tissues are organized together to perform a complex function, it's called an organ. The heart is an organ. It has muscle tissue, connective tissue, and nerve tissue all working together to pump blood. Organs can do more than one function and each function can be pretty complicated. The eyes sense color, movement, and light. They move and focus. The biggest organ in (or on) the human body is the skin. It's a great example of layers of tissue working together to do several functions: Holds in fluidsRegulates temperatureSenses heat, itch, pressure, painProduces hormones The organization of the anatomy starts with these three building blocks. Whether you're talking about delicate tissue of the brain or the hardness of bone, it's still made of cells banded together into tissue and organized into organs. 1 Source Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Skin laceration repair with sutures. UpToDate. Editorial Process Medical Expert Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit