In vivo refers to biological processes, experiments, or treatments that occur within a living organism, as opposed to in vitro, which refers to studies conducted outside of the organism, usually in a controlled laboratory environment such as a cell culture or test tube.
Tissues in vivo are the functional groups of cells and extracellular matrix that make up the different organs and structures within a living organism. Tissues are classified into four main types, each with distinct functions and characteristics:
- Epithelial tissue: This tissue forms the outer layer of the skin, as well as the lining of internal organs and body cavities. Epithelial tissue functions in protection, secretion, absorption, and filtration.
- Connective tissue: As the name suggests, connective tissue provides support and connects various structures within the body. It includes diverse structures such as bone, cartilage, tendons, ligaments, adipose tissue (fat), and blood.
- Muscle tissue: This tissue is responsible for producing force and motion. There are three types of muscle tissue: skeletal (which attaches to bones and allows for voluntary movement), smooth (found in the walls of internal organs and blood vessels, enabling involuntary movement), and cardiac (found only in the heart, responsible for pumping blood).
- Nervous tissue: This tissue is specialized for transmitting electrical signals and processing information. It is composed of neurons (nerve cells) and glial cells (support cells). Nervous tissue is the main component of the central nervous system (brain and spinal cord) and the peripheral nervous system.
Studying tissues in vivo is essential for understanding the physiological functions and interactions of different cell types and tissue structures within a living organism, as well as for evaluating the efficacy and safety of new treatments and therapies. In vivo studies often involve the use of animal models, such as mice or zebrafish, which can closely mimic human physiology and disease processes.