We chose to include the 5 types of collagen below because whether your pet is a growing puppy, an active adult, or a senior experiencing age-related issues, a diverse collagen blend provides full spectrum support of your pets lifestyle. What are the 5 collagen types and why are they important? Type I - Makes up 90% of the body's collagen. Type I is densely packed and used to provide structure to skin, bones, tendons, and ligaments. Type II - Found in elastic cartilage, which provides joint support. Type III - Found in muscles, arteries and organs. Type V - Found in the cornea of eyes, some layers of skin, hair, and tissue of the placenta. Type X - Involved in the growth, mineralization and remodeling of articular cartilage.