Soft+Tissues

Cartilage
Cartilage is comprised of 80% water, chondrocyte and chrondoblasts. It is encased in a dense membrane called the perichondrium, which contains undifferentiated cells for potential cartilage repair. As cartilage is avascular, water transports nutrients to the tissues through diffusion and mass transport phenomena. There are three types of cartilage: Collagen type IX, XI, II exist with Type II prevailing (>90%). The GAGs are negatively charged an enable resistance to compression.
 * Hyaline: the most abundant, found at the end of long bones (articular cartilage)
 * Articular cartilage: and ECM consists of water, chondrocytes, proteins (60% - collagen, 30% - sulphated glycosominoglycans (GAGs) and 10% - other proteins (proteogylcans,hyluronic acid)).
 * Elastic: more flexible than articular cartilage due to increased number of elastin fibers. Present is ear, nose, throat (larynx and epiglottis).
 * Fibrous: fibrocartilage has bundled collagen fibers aligned along the loading direction.

The low diffusion limit of hyaline cartilage makes it difficult to self-repair. There are for zones: The hierarchical structure lends to special mechanical properties. However, aging degnerates cartilage by reduce water content due to loss of proteoglycans. Chronic osteoarthritis, rheumatoid arthritis and degenerative disc disease (DDD) are diseases that can cause significant joint pain and bone damage
 * superficial zone
 * transitional zone
 * radial zone
 * calcified zone

There are two types of injury:
 * partial-thickness: superficial legions that are hard to heal due to isolation from blood supply.
 * full-thickness: the injury penetrates the subcondral bone. healing is possible due to access to blood supply and progenitor cells.

The author refers the reader to a series of surgical procedures outlined in Chapter 11 of New Materials and Technologies for Healthcare.