the cartilage

Cartilage
Introduction : cartilage is a type of connective tissue .It exhibits tensile strength , provides frim structural support for soft tissues , allows flexibility without distortion , and is resilient to compression. Cartilage has all the common feature of connective tissue , which include ground substance ,fiber and cells called chondrocytes and chondroblasts.

Ground substance : or matrix produced and maintained by chondrocytes . matrix is solid and firm but somewhat flexible it is consist of:
a-proteoglycans : containing side chains of glycosaminoglycan s (GAGs). Diffusion from blood vessels in surrounding connective tissue
b- Glycoproteins ,including chonrdonectin and chondrocalcin (a calcium binding protein ).
c- No mineral (inorganic )component ,because cartilage is not mineralized.
d- Water (tissue fluid )- high degree of hydration (75%). E.g. joints ,
e- large amounts of hyaluronic acid gives it W B capacity especially at points of movements
Fiber
a-type I collagen is found in fibrocartilage
b- type II collagen is found in hyaline and elastic cartilage.
Cells
a- Chondrogenic cells are found in the perichondrium , where they undergo mitosis and differentiate into chondroblasts .
b- Chondroblasts arise from chondrogenic cells and many undergo mitosis and synthesize the cartilage matrix and extracellular matrix.
c- Chondrocytes reside in lacunae . They form isogenous group that are surrounded by a territorial matrix that stains basophilic due to the higher local concentration of chondroitin sulfate .Chondrocytes may undergo mitoses .
No blood or lymphatic vessels or nerves penetrate cartilage .the cell receive their nourishment from the surrounding connective tissue by diffusion through the matrix .
Injured cartilage heals slowly .

Perichondrium :
The perichondrium refers to a dense membrane of irregular connective tissue that covers cartilage in different parts of the body except the cartilage in joints most of hyaline and elastic cartilage is surrounded this layer . The perichondrium has two layers:
1-Outer fibrous layer that is chondrogenic in nature and is made of dense connective tissue .It contains fibroblasts which secrete collagen
2-Inner cellular layer is chondrogenic in nature and can proliferate and turn to form chondroblasts :It gives rise to new chondroblasts that secrets cartilage matrix .
Function
Firm support with some flexibility bear mechanical stress and protects growing and developing bones against any trauma or injury .The perichondrium is both fibrous and porous in nature .Because of this ,blood flow is easily facilitated .It helps transport oxygen from one part of the body to another and nutrients are also supplied to the different parts of the body
Properties of cartilage
- High tensile strength with stand pressure
-low metabolic rate.
-capacity of continued growth
-avascular diffusion from capillaries
Types
Cartilage is classified based on amount and types of fibers that are present in the matrix to:
Hyaline cartilage
Is the common type .In embryos, hyaline cartilage serves as a skeletal model for most bones .In individual grows, the cartilage is gradually replaced with bone through a process called endochondral ossification .in hyaline cartilage have chondrocytes in lacunae throughout matrix arranged appear either singly or in group called isogenous groups (clusters of chondrocytes derived from one cell by mitotic division).
-Extracellular matrix has type II collagen: proteoglycans chonrdonectin.
-Territorial matrix: surrounds each chondrocyte.
- Inner territorial: includes type III collagen fibers.
Found : in areas where strong support & flexibility are needed like tracheal ring , ventral ends of ribs &bone surface within joints (articular) .

Hyaline cartilage surrounds by perichondrium which consist of dense connective tissue except at articular surface
.

Elastic cartilage