In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. A chemical mechanism describes in detail exactly what takes place at each stage of an overall chemical reaction (transformation). It also describes each reactive intermediate, activated complex, and transition state, and which bonds are broken (and in what order), and which bonds are formed (and in what order).
Grade IV capsular contracture in the right breast of a 29 y.o. woman, seven years after subglandular placement of 560cc silicone gel-filled breast implants. Capsular contracture is a response of the immune system to foreign materials in the human body. Medically, it occurs mostly in context of the complications from breast implants and artificial joint prosthetics.
Nondisplaced Tear. Fig. 2. Subcortical cysts and posterior capsular stripping in a 16-year-old male who had right shoulder pain when throwing for 3 months. (A) Subcortical cysts (arrow) in the greater tuberosity at the insertion of the supraspinatus tendon are seen as high signal intensity on a fat-suppressed T2-weighted image. (B) Axial gradient echo T2-weighted image shows a nondisplaced tear of the posterior labrum and capsular stripping (arrow). Fig. 3. Posterosuperior labral tear and impaction of the greater tuberosity in a 17-year-old female pitcher who had right shoulder pain and impingement for 5 years.