2. Intrdocution
• Bone is an extremely dense, specialized form of
connective tissue.
• It serves to store calcium and phosphate ions.
• Blood cells are formed in the bone marrow.
• The most important mineral component of bone
is apatite, a form of crystalline calcium
phosphate
(C) Natalia Dachanidze
3. Chemical composition of bone
• Bone tissue is composed of two general parts:
1. Matrix
2. Cells
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6. • The matrix proteins are characterized by their
anionic nature, being rich in phosphate
(phosphoproteins, e.g. osteonectin), sialic acid
(sialoproteins, e.g. osteopontin) or gamma-
carboxyglutamic acid (Gla proteins, e.g.
osteocalcin).
• Growth factors such as TGF-β and BMP (bone
morphogenic protein) are also stored within the
bone matrix.
(C) Natalia Dachanidze
8. Collagens
• Collagens are quantitatively the most abundant
of animal proteins, representing 25% of the
total.
• They form insoluble tensile fibers that occur as
structural elements of the extracellular matrix
and connective tissue throughout the body.
• Their name (which literally means “glue-
producers”) is derived from the gelatins that
appear as a decomposition product when
collagen is boiled.
(C) Natalia Dachanidze
9. Structure of collagens
• Nineteen different collagens are now known, and
they are distinguished using roman numerals.
• They mostly consist of a dextrorotatory triple
helix made up of three polypeptides (α-chains)
(C) Natalia Dachanidze
21. • cells are regulated by hormones, growth factors
and cytokines. In addition to the three main
regulators PTH, calcitonin and vitamin D
• Other regulatory compounds include
glucocorticoids, oestrogen, androgens,
interleukin-1 and the growth factor IGF-1.
(C) Natalia Dachanidze
