Connective Tissue Flashcards
1
Q
Collagen
A
- The extracellular matrix is a network of interstitial proteins that maintain normal tissue architecture
- Collagen is a major component of connective tissue and consists of 3 polypeptide α chains held together by hydrogen bonds to form a ropelike triple helix structure (tropocollagen).
- Lysyl oxidase then forms covalent bonds between individual tropocollagen molecules, generating mature collagen fibers.
- The variation in amino acid sequences in the collagen α chains gives rise to collagen diversity in different tissues.
- Collagen types I, II, III, and V provide tensile strength in skin, bones, cartilage, tendons, and blood vessels.
- After post-translational hydroxylation and glycosylation of procollagen molecules, disulfide bond formation between the C-terminal propeptide regions of 3 α-chains brings the chains into a favorable alignment for triple helix assembly.
2
Q
Elastin
A
- fibrous protein in the connective tissue, is named for the elastic properties it imparts to skin, blood vessels, and lung alveoli.
- Elastin fibers can be stretched to several times their original length but will recoil when the stretching forces are withdrawn
- synthesized from the polypeptide precursor tropoelastin.
- fibrous connective tissue protein that provides elasticity to the skin, blood vessels, and pulmonary alveoli.
- Elastin assembly is closely related to that of collagen. Similar to collagen, elastin is synthesized as a large polypeptide precursor (tropoelastin) composed of about 700, mostly nonpolar, amino acids (eg, glycine, alanine, valine)
- Elastin also contains proline and lysine residues; however, in contrast to those found in collagen, few of these amino acids are hydroxylated
- After tropoelastin is formed, it is secreted into the extracellular space where it interacts with microfibrils (fibrillin) that function as a scaffold
- lysyl oxidase (requires copper) oxidatively deaminates some of the lysine residues of tropoelastin, facilitating the formation of desmosine cross-links between neighboring polypeptides
These cross-links account for the rubber-like properties of elastin.
3
Q
Fibrillin-1
A
- major component of the microfibrils that form a sheath around elastin
- Microfibrils are abundantly present in blood vessels and in the suspensory ligaments of the lens.
- Defects in the fibrillin-1 gene cause classic autosomal dominant Marfan syndrome.
4
Q
Hyaluronic acid
A
another major component of the soft tissue’s extracellular matrix, including synovial fluid and skin.
- Exogenous injection can be used to restore viscoelasticity to the synovial fluid in osteoarthritis
- soft-tissue fillers can also be used in patients concerned about age-related volume loss (eg, nasolabial folds).
5
Q
Laminins
A
- heterotrimeric glycoproteins that bind to type IV collagen underlying epithelial cells
- contribute to the organization and function of the basal lamina (basement membrane)
6
Q
Proteoglycans composed of glycosaminoglycans (GAGs), which provide compressibility to tissues
A
- composed of glycosaminoglycans (GAGs), which provide compressibility to tissues
- Patients with deficiencies in lysosomal enzymes cannot break down GAGs, resulting in mucopolysaccharidoses (eg, Hurler syndrome, Hunter syndrome) characterized by soft tissue and skeletal disease.
