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Chapter 4 Cartilage Bone. 软骨与骨. Cartilage ( 软骨 ) is a specialized form of connective tissue. Cells: chondrocytes （软骨细胞） extracellular matrix （细胞间质）. Structure （结构） :. ★ Chondrocytes synthesize and secrete extracellular matrix （细胞间质） .
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Cartilage (软骨) is a specialized form of connective tissue.
Cells: chondrocytes（软骨细胞） extracellular matrix（细胞间质） Structure（结构）: ★Chondrocytes synthesize and secrete extracellular matrix（细胞间质）. ★The chondrocytes are located in matrix cavities, called cartilage lacunae（软骨陷窝）.
Functions（功能）: ★to bear mechanical stresses without permanent disortion. ★to support soft tissue. ★to be a shocking-absorbing and sliding areas for joints and facilitate bone movements. ★to be essential for the development and growth of long bones both before and after birth.
More Features of Cartilage : ·Cartilage is avascular. ·Cartilage is nourished by the diffusion of nutrients from capillaries in adjacent connective tissue or by synovial fluid from join cavities. ·Chondrocytes exhibit low metabolic activity. ·Cartilage has no lymphatic vessels or nerves. ·Cartilage is surrounded by perichondrium in most places.
Classification: Hyaline cartilage（透明软骨）: Elastic cartilage（弹性软骨）: Fibrocatilage（纤维软骨）:
Hyaline cartilage 透明软骨 ★Fresh hyaline cartilage is bluish-white and translucent. ★In the embryo, it serves as a temporary skeleton until it is gradually replaced by bone. ★In adult mammals, hyaline cartilage is located : in the articular surfaces of the movable joins; in the walls of large respiatory passage; in the ventral ends of ribs; in the epiphyseal plate.
Hyaline cartilage 透明软骨 Chondrocytes （软骨细胞） Matrix （基质） Perichondrium （软骨膜） 结构:
①Collagen molecules (Collgenous fibril 胶原原纤维) ②Proteoghycans (蛋白多糖) ③Glycoprotein （糖蛋白）( Chondronectin ;AnchorinC2(锚蛋白C2) Hyaline cartilage 1.Cartilage Matrix（软骨基质） Hyaline cartilage matrix is produced by chondrocytes and contains three major classes of molecules:
①Collagen molecules (Collagenous Fibril 胶原原纤维) Hyaline cartilage contains primarily type II collage. Small amounts of collagen types IX, X, XI, and others are frequently present.
②Proteoghycans(蛋白多糖) chondroitin sulfate（硫酸软骨素） keratan sulfate （硫酸角质素） hyaluronic acid （透明质酸）
③Glycoprotein（糖蛋白） Chondronectin binds specifically to glycosaminoglycans and collagen type II, mediating the adherence of chondrocytes to the extracellular matrix.
2. Chondrocyte软骨细胞 (1) In hyaline cartilage, chondrocytes are distributed either singly or in cluster Chondrocyte （软骨细胞） Isogenous group （同源性细胞群）
Chondrocyte (软骨细胞) Cartilage lacuna （软骨陷窝） Cartilage capsule （软骨囊）
(2) chondrocytes are specialized cells that produce and maintain the extracellular matrix
3. Perichondrium(软骨膜) ★致密结缔组织组成. ★对软骨的生长起作用
Outer cellular layer Inner fibrous layer the perichondrium divided into two layers:
Elastic cartilage弹性软骨 ★ is distinguished by the present of elastin in the cartilage matrix.
Fibrocartilage纤维软骨 Picrosirius-hematoxylin stain
· Histology A: The mesenchyme is the precursor tissue of all types of cartilage. B: Mitotic proliferation of mesenchymal cells gives rise to a highly cellular tissue. C: Chondroblasts are separated from one another by the formation of a great amount of matrix. D: Multiplication of cartilage cells gives rise to isogenous groups, each surrounded by a condensation of territorial (capsular) matrix.
·Growth Interstitial growth（间质生长）: ‘growth from within’ • mitotic division of existing chondrocytes and production of matrix Appositional growth（外加生长）: ‘growth from the surface’ differentiation of new chondrocytes from perichondrial cells and production of matrix at surface
Summary Functions of cartilage Classification of cartilage Matrix of hyaline cartilage Chondrocyte of hyaline cartilage Histology, Growth, and Repair of Hayline cartilage
Homework: 1. What’s the function of cartilage? 2. Classification of cartilage. 3. Review the structure of cartilage.
