Final answer:
Blood is the tissue least abundant in collagen, as it is a fluid tissue with a liquid matrix and lacks supporting fibers, unlike bone, cartilage, and tendon which are rich in collagen.
Step-by-step explanation:
Collagen is a protein that is most abundant in connective tissues throughout the body, including bone, cartilage, and tendon. However, when comparing these tissues, blood is the least abundant in collagen fibers. Bone has a rigid extracellular matrix that is mostly composed of collagen fibers embedded in a mineralized ground substance. Cartilage contains a variable amount of fibers including collagen and has cells called chondrocytes that are lodged within spaces known as lacunae. Tendons are made up of dense connective tissue with collagen fibers aligned in parallel, providing high tensile strength. On the contrary, blood is characterized as a fluid tissue with a liquid matrix and does not contain supporting fibers such as collagen.