Loose connective tissue is found between many organs. Its main function is to absorb shock and bind tissues together. It also allows water, salts, and various nutrients to diffuse into cells that are embedded in it or present in adjacent tissues.
Adipose Tissue
Adipose tissue consists primarily of fat storage cells called adipocytes and little extracellular matrix. A large number of capillaries present within adipose tissue allow rapid mobilization of lipid molecules. White adipose tissue is the most abundant type of adipose tissue found in adults. It can appear yellow, due to the presence of carotene and related pigments derived from ingested plant food. White fat contributes mainly to lipid storage and can serve as an insulator from cold temperatures and mechanical injuries. White adipose tissue is especially involved in protecting the kidneys and cushioning the back of the eye. Brown adipose tissue is more common in infants, hence the term "baby fat." In adults, there is a reduced amount of brown fat, found mainly in the neck and clavicular regions of the body. The many mitochondria in the cytoplasm of brown adipose tissue help explain its efficiency at metabolizing stored fat. Brown adipose tissue is thermogenic, meaning that as it breaks down fats, it releases metabolic heat rather than producing adenosine triphosphate (ATP), a key molecule used in metabolism.
Areolar Tissue
Areolar tissue shows little specialization. It contains all the cell types (fibroblast, adipocytes, macrophage, mast cells, etc) and fibers (collagen, elastic fiber and reticular fiber) that are distributed in a random, web-like fashion. It fills the spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal cavity. Areolar tissue also underlies most epithelia and represents the connective tissue component of epithelial membranes.
Reticular Tissue
Reticular tissue is a mesh-like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver. Reticular cells produce the reticular fibers that form the network to which other cells attach. It derives its name from the Latin reticulus, which means "little net."
This text is adapted from Openstax, Anatomy and Physiology 2e, Section 4.3: Connective tissue supports and protects
