Cartilage
· The cartilage is a specialized connective tissue.
· It is formed of cells separated by extracellular matrix.
· Its cells are called chondrocytes and they occupy cavities called lacunae.
· The chondrocytes secrete the extracellular matrix.
· The extracellular matrix:
· The cartilage is avascular and does not have nerve supply or lymph vessels. Nutrients come by diffusion from the perichondrium or synovial fluid.
· It is flexible and smooth.
· Perichondrium:
o It is covered by a connective tissue sheath,
· The cartilage can be classified into three types according to their fiber type.
o Hyaline cartilage.
o Elastic cartilage.
o Fibrocartilage.
Hyaline cartilage (fig. 34)
· It is the most common cartilage.
· It is bluish-grey,
· It contains type II collagen, basophilic matrix
· Location:
o Nose, larynx, thyroid, cricoid cartilage, tracheal ring and bronchi.
o Epiphyseal plates of growing bones.
· Function:
o It help to absorb shock
Histogenesis and growth of hyaline cartilage
· Chondrification center:
· The mesenchymal cells differentiate into chondroblasts.
· Chondroblasts secrete the extracellular matrix and become chondrocytes.
· Isogenous groups:
· Interstitial growth:
· Appositional growth:
Cartilage cells
Chondrogenic cells
· They are spindle shaped cells
· They can differentiate into chondroblasts and osteoprogenitor cells.
Chondroblasts
· They are flat basophilic cells with flat oval nuclei.
Chondrocytes
· They are situated in lacuna (space in the matrix).
The matrix
· It is homogenous mass, which contains type II collagen.
· Territorial matrix:
· Interterritorial matrix:
· Pericellular capsule:
Elastic cartilage (fig. 35)
· In is yellow
· The elastic cartilage is similar to the hyaline cartilage.
· The matrix contains abundant elastic fibers and type II collagen.
· The chondrocytes are larger and more abundant than those of hyaline cartilage.
· Location:
o Pinna of the ear, external and internal auditory tubes.
o Epiglottis.
· Function:
o It gives the flexibility.
Fibrocartilage (fig. 36)
· It does not have perichondrium.
· It gives strength.
· The matrix contains type I collagen, which stains acidophilic.
· Chondrocytes are present in alternating parallel rows
· Location:
o Intervertebral disks.
o Articular disks.
· The intervertebral disk:
Clinical notes:
Rupture disk
Slipped disk
Athletic foot
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