Cartilage and bone

2 1. Cartilage: organ=Cartilage tissue+perichondrium

3 ① chondrocyte: ---Structure: LM embedded in cartilage lacuna peripheral cells: --small and immature --single and flattened central cell: --large and mature, --round and appearing in group of 2-8 cells --small and round nucleus --basophilic cytoplasm

4 Chondrocytes in Lacunae EM: rich in RER and Golgi complex

5 ② Cartilage matrix ---ground substance: proteoglycan: --same to loose CT --there are more chondroitin sulfate distributed at the periphery of cartilage lacuna---called as cartilage capsule (basophilic) chondronectin water ---fiber: type and number of fiber depends on the type of cartilage

6 Classification: according to the Characteristics of the matrix,3 types of cartilage can be distinguished: a.Hyaline cartilage: b. Elastic Cartilage c. Fibrocartilage

7 Hyaline Cartilage Found at ends of bones, articular surface, rib cartilage nose, trachea, larynx bronchi (fresh)Bluish-white color,translucent. Strong, rubbery, flexible tissue.

8 Hyaline Cartilage less collagenous fibril←type II collagen

9 Elastic Cartilage Similar to hyaline cartilage but has elastic fibers running in all directions in addition to collagen. Found in auricle of ear, walls of external auditory canals, eustachian tubes, epiglottis, larynx Maintains shape, deforms but returns to shape; flexibility of organ; strengths and supports structures.

10 Fibrocartilage typically found in relation to joints (forming intra- articular lips, disks and menisci), is the main component of the intervertebral disks, symphysis pubis.

11 Appositional Growth Differentiation of innermost perichondrial cells  chondroblasts Synthesis of matrix Increase in girth

12 Perichondrium of cartilage Dense CT that covers cartilage (except articular cartilage of joints.) Contains blood, nerve supply, lymphatics. Contains collagen fibers, fibroblasts

13 2. Bone

14 Support Storage of minerals and lipids Blood cell production Protection Leverage Functions of bone

15 1.Osteocytes : mature bone cells –Cell body lies in lacunae –Cell processes connected by canaliculi 2.Osteoblasts : synthesize new matrix –Osteogenesis 3.Osteoclasts: dissolve bone matrix –Osteolysis 4.Osteoprogenitor cells ： differentiate into osteoblasts Cells in Osseous tissue :

16 b. osteoblast : ---structure: LM: single layer of cuboidal or low columnar cell round nucleus basophilic cytoplasm located on the surface of bone tissue

17 EM: fine processes rich in RER, Golgi complex osteoblast

18 c.osteocyte ---structure: flattened cell with multiple long thin processes located in bone lacuna and bone canaliculus basophilic cytoplasm adjacent cells connect in bone canaliculus by gap junctions ---function: Maintain bone matrix regulate the balance of calcium and phosphonium

19 d. osteoclast ---structure: LM: multinuclear large cell, um 5-50 nuclei acidophilic cytoplasm located at peripheral part of bone

20 Basic unit of compact bone is an osteon –Osteocytes arranged around a central canal –Perforating canals extend between adjacent osteons osteon

21 a. circumferential lamella: /outer concentrically-arranged /inner around inner surface of bone

22 c. interstitial lamella: /irregular lamella /remnant of Haversian or circumferential lamella *perforating canal: /transverse canal /connect with Haversian canal

23 Ossification = converting other tissue to bone –Intramembranous Ossification –Endochondral Ossification Calcification = depositing calcium salts within tissues Bone development and growth

24 Cartilage model gradually replaced by bone at metaphysis –Increasing bone length Appositional growth increases bone diameter Endochondral ossification

25 You should now be familiar with: Identify cell types in bone and list their functions. Compare spongy and compact bone. Compare intramembranous and endochondral ossification. Osteons; types of cartilage; isogenous groups