Which six tissues have greater protein density and a higher rate of absorption?

• A. Tendon, ligament, joint capsule, fascia, muscle, and scar
• B. Skin, adipose tissue, bone, cartilage, nerve, tendon
• C. Blood, lymph, cartilage, bone, tendon, muscle
• D. Joint capsule, synovium, cartilage, tendon, bone, muscle

Answer: (A)

In ultrasound therapy, how much energy a tissue absorbs depends largely on its protein content and density; tissues with a dense, collagen-rich matrix absorb more energy and heat up more readily. Tendon, ligament, joint capsule, and fascia are all tightly bound, collagen-dense connective tissues, so they have high protein density and show greater attenuation and absorption. Muscle adds substantial protein content, contributing to higher absorption as well, and scar tissue contains increased collagen from healing, making it similarly dense and absorptive. This combination explains why these six tissues absorb ultrasound more readily.

Other tissues listed tend to have lower collagen density or different compositions that reduce absorption. Skin and adipose tissue are relatively low in dense protein networks; bone’s attenuation comes largely from mineral content rather than protein density; cartilage has substantial water and proteoglycans that affect absorption differently, and nerve tissue isn’t as collagen-rich as the fibrous tissues above.