Connective tissue is essential for providing support within the animal body, connecting, separating, and cushioning various tissues. It consists of cells dispersed within an extracellular matrix, which is composed of proteins and a gel-like substance known as ground substance. This matrix serves as a supportive structure outside of eukaryotic cells, functioning similarly to a cell wall by offering structural support.

The most prevalent type of connective tissue in vertebrates is loose connective tissue, which plays a crucial role in holding organs in place and attaching epithelial tissue. A notable example of loose connective tissue is adipose tissue, primarily made up of adipocytes, or fat cells. This tissue is vital for energy storage and insulation.

Another category is dense connective tissue, also referred to as fibrous connective tissue, characterized by a high concentration of collagen fibers. This type of tissue is integral to the formation of tendons, which connect muscles to bones, and ligaments, which connect bones to one another, facilitating movement.

Supportive connective tissues include bone and cartilage, which provide structural integrity through a hard extracellular matrix. These tissues are essential for maintaining the shape and strength of various body structures. Fluid connective tissue, primarily blood, features a liquid extracellular matrix known as plasma, which transports nutrients and waste throughout the body.

In addition to connective tissue, nervous tissue plays a critical role in conducting electrical and chemical signals. It is divided into the central and peripheral nervous systems. Neurons are the primary cells responsible for transmitting these signals through a process called action potential, which involves the movement of ions across the cell membrane. Key components of a neuron include the axon, which transmits signals, and dendrites, which receive incoming signals and help determine the cell's response.

While neurons are often highlighted for their role in the nervous system, glial cells, or glia, are equally important. These support cells are essential for the survival and functioning of neurons, providing necessary support and even participating in signaling processes. Recent research emphasizes the significant roles glia play in the nervous system, indicating that they contribute to many functions beyond what was previously understood.