Vascular means that it has a blood supply, because it needs oxygen to operate normally. Avascularity is the complete absence of any blood vessels;simply because that part of the body does not require them.
Why Are Cartilage And Tendons Avascular?
Most cartilage is located inside of the joint capsule, surrounded by the synovium. The joint capsule receives ample blood supply while the contents of the joint rely on the synovial fluid. There are no arteries and veins because these would compromise the biomechanical properties (creep and stress-relaxation) of the cartilagenous tissue. Cartilage must be required to absorb loads, reduce friction, and allow mobility. For this reason, they are also aneural (no innervation).
Tendons are vascularized if they are not surrounded by synovial sheath, but surrounded by paratenon. These tendons receive blood supply from the longitudinal capillaries that run within the epitenon and endotenon. The portion of tendon at the bone junction receives blood supply from the periosteum. These portions of the tendon are used for load transmission from muscle to insertion. These portions are innervated with receptors such as Golgi tendon organs, pressure receptors, pain receptors, and other proprioceptors to provide feedback of muscle tension, mechanical stimuli, pain, and joint location in space. Changes in length are detected by muscle spindles causing muscle contraction (stretch-reflex).
Tendons located in synovial sheaths are avascular and rely on the diffusional nutrition from the synovial fluid. These portions of tendons have limited healing abilities. (ex: Long head of biceps tendon located within the glenohumeral joint). These portions of tendons are usually for support, anchoring the muscle to the origin.
Tendons are vascularized if they are not surrounded by synovial sheath, but surrounded by paratenon. These tendons receive blood supply from the longitudinal capillaries that run within the epitenon and endotenon. The portion of tendon at the bone junction receives blood supply from the periosteum. These portions of the tendon are used for load transmission from muscle to insertion. These portions are innervated with receptors such as Golgi tendon organs, pressure receptors, pain receptors, and other proprioceptors to provide feedback of muscle tension, mechanical stimuli, pain, and joint location in space. Changes in length are detected by muscle spindles causing muscle contraction (stretch-reflex).
Tendons located in synovial sheaths are avascular and rely on the diffusional nutrition from the synovial fluid. These portions of tendons have limited healing abilities. (ex: Long head of biceps tendon located within the glenohumeral joint). These portions of tendons are usually for support, anchoring the muscle to the origin.