hyaluronic acid A glycosaminoglycan that is part of the ground substance of connective tissue. Hyaluronic acid binds cells together and helps to lubricate joints. It may play a role in the migration of cells at wounds; this activity ceases when hyaluronidase breaks down hyaluronic acid.

hyaluronic acid A highly viscous acid mucopolysaccharide, composed of D-glucuronic acid and N-acetyl-D-glucosamine. It is widely distributed throughout the connective tissues of animals. It is thought to have various functions, including maintaining the level of hydration in tissues, acting as a molecular sieve in restricting the movement of large molecules in tissues, and preventing the spread of pathogens and toxic substances.