Which sequence correctly lists tissues from lowest to highest speed of sound?

Which sequence correctly lists tissues from lowest to highest speed of sound?

• A. Lung, Fat, Soft tissue, Liver, Blood, Muscle, Tendon, Bone
• B. Bone, Tendon, Muscle, Blood, Liver, Soft tissue, Fat, Lung
• C. Lung, Soft tissue, Fat, Liver, Blood, Tendon, Muscle, Bone
• D. Fat, Lung, Soft tissue, Liver, Blood, Muscle, Tendon, Bone

Answer: (A)

Sound travels fastest in stiffer, denser materials and slows down in things that contain air or are more compressible. In tissues, air in the lungs makes that region the slowest for wave propagation. Fat is less stiff than water-like soft tissues, so it comes next. Among soft tissues, speeds are in a narrow range but tend to increase as the tissue becomes a bit stiffer: liver and blood are slightly faster than fat, followed by muscle. Tendon is even stiffer due to its dense collagen, so it carries the wave faster than muscle. Bone is much stiffer than all the others, so it has the highest speed. So the sequence from lowest to highest speed is lung, fat, soft tissue, liver, blood, muscle, tendon, bone.

Sound travels fastest in stiffer, denser materials and slows down in things that contain air or are more compressible. In tissues, air in the lungs makes that region the slowest for wave propagation. Fat is less stiff than water-like soft tissues, so it comes next. Among soft tissues, speeds are in a narrow range but tend to increase as the tissue becomes a bit stiffer: liver and blood are slightly faster than fat, followed by muscle. Tendon is even stiffer due to its dense collagen, so it carries the wave faster than muscle. Bone is much stiffer than all the others, so it has the highest speed.

So the sequence from lowest to highest speed is lung, fat, soft tissue, liver, blood, muscle, tendon, bone.