117.The answer is c.(Kumar, pp 1274–1275.)Type I collagen is respon-
sible for the three-dimensional fiber structure of the matrix. It is synthe-
sized by osteoblasts and accounts for 85–90% of total bone protein. The
noncollagenous bone proteins are primarily synthesized by osteoblasts and
constitute 10–15% of bone protein. Some plasma proteins are preferen-
tially absorbed by the bone matrix. The noncollagenous proteins include
cytokines and growth factors, which are synthesized endogenously and
become trapped in the matrix. Also included in the category of noncol-
lagenous proteins are the cell attachment proteins (fibronectin and osteo-
pontin); proteoglycans (e.g., chondroitin 4-sulfate and chondroitin
6-sulfate), which appear to play a role in collagen fibrillogenesis; and the
GLA proteins, such as osteocalcin (containing γ-carboxyglutamic acid),
which binds Ca^2 +and mineral components to the matrix.
118.The answer is c.(Young, pp 189–191. Kumar, pp 1304–1309. Ross and
Pawlina, pp 189, 205.)The structure labeled Cis the articular cartilage that
is the site of wear-and-tear damage, which is the hallmark of osteoarthritis.
The joint shown in the diagram is a freely movable joint known as a
diarthrosis. Other joints allow limited or no movement (synarthroses) and
may be classified by the uniting connective tissue: hyaline cartilage (syn-
chondroses), bone (synostoses), or dense connective tissue (syndesmoses).
The joint cavity (A) is lined by an epithelium (B), which is surrounded by
an external fibrous layer (E). The synovial fluid is formed from the synovial
capillary ultrafiltrate as well as mucins, hyaluronic acid, and glycoproteins
produced by fibroblast-like cells in the synovial epithelium (B) that lines the
fluid-filled joint cavity (A). Macrophage-like cells in the epithelium perform a
phagocytic function. The ends of the bone (D) are covered by hyaline cartilage
that lacks a perichondrium. Synovial fluid, which differs from blood serum in
its reduced protein content, acts as a lubricant and becomes more viscous
with age. It may be used to diagnose joint disorders such as arthritis. Rheuma-
toid arthritis is an autoimmune disease in which infiltration of cells from the
immune system leads to the destruction of the synovial capsule and the artic-
ular cartilages. Inflammation of the synovium leads to the formation of a pan-
nus and eventually to changes in the articular cartilage converting it into a
fibrocollagenous structure.
119.The answer is d.(Favus, pp 58–59, 150–152, 277–282. Kierszenbaum,
pp 126–128. Reszka, pp 45–52. High-Yield Facts, p 21.)The woman in the
Specialized Connective Tissues: Bone and Cartilage Answers 213