Cartilage

Functions: ◘ Support soft tissues (nose, ear, trachea). ◘ Shock-absorbing and sliding areas for joints, facilitate bone movements. ◘ Essential for the development and growth of long bones.

Structure Structure Cells: chondrocytes Extracellular matrix fiber ground substance

Cartilage composition Cells Chondrocytes: located within matrix; lacunae Chondroblasts: located at periphery; secrete extracellular matrix Fibers Collagen and elastic fibers Ground substance Rich in glycosaminoglycans and proteoglycans

Cartilage composition Perichondrium Perichondrium is a layer of dense irregular connective tissue. It is essential for the growth and maintenance of cartilage.

More Features of Cartilage Avascular; Nutrients diffusion from perichondrium or synovial fluid; No innervation; No lymphatic vessels; Chondrocytes have low metabolic activity

Classification: Hyaline cartilage: most common, much type II collagen Elastic cartilage: elastic fibers Fibrocatilage: dense network of type I collagen Properties of extracellular matrix

Hyaline Cartilage Blue-white and translucent distribution： Joint surfaces, nose, larynx, trachea, bronchi, ends of ribs adjacent to sternum

Structure Cells: chondrocytes Extracellular matrix fiber ground substance Perichondrium Perichondrium is a layer of dense irregular connective tissue. It is essential for the growth and maintenance of cartilage. Found around all HC except joint HC Rich in fibroblasts, chondroblasts, blood vessels, and nerves.

1. Chondrocyte (1) In hyaline cartilage, chondrocytes are distributed either singly or in cluster lacunae： isogenous nest：chondrocytes arranged in pair or group of four or six

(2) chondrocytes are specialized cells that produce and maintain the extracellular matrix

2. Matrix (1) Hyaline cartilage matrix is produced by chondrocytes and contains three major classes of molecules: ①Collagen molecules ②Proteoglycans ③Nocollagenous proteins fiber—— mainly type Ⅱ collage fiber ground substance

(2) Grounds substance components of hyaline cartilage matrix are not distributed uniformly Capsusle/territorial matrix (TM)： matrix surrounding each chondrocyte Interterritorial matrix (IM)： matrix between the territorial matrix

Elastic Cartilage Auricle of ear, external auditory canal, epiglottis Similar to HC, many elastic fibers in the matrix Perichondrium

Elastic cartilage

Fibrocartilage Found in Intervetebral disks, tendon and ligament attachment to bone, symphysis pubis Combination of HC and dense regular connective tissue Chondrocytes often in rows or groups Matrix acidophilic due to high collagen No perichondrium

Fibrocartilage

summary Cartilage is a semi-rigid form of connective tissue 3 types of cartilage structure of hyaline cartilage

Chapter 5. Bone

Overview of bone · Bone is a specialized form of connective tissue. Cells Extracellular matrix: mineralization · Functions of bone: Support: Provides attachment for tendons of skeletal muscles Protection: Protects internal organs Storage: calcium ,phosphate

Structure of bone 1. Matrix · Organic matter endosteum：lined on internal surface periosteum：lined on external surface 1. Matrix · Organic matter type I Collagen: 90% Ground substance: 10% · Inorganic matter（bone mineral） The inorganic matter is calcium phosphate in the form of hydroxyapatite crystle [Ca10(PO4)6(OH)2]

2. Cells osteoprogenitor, osteoblast, osteocyte and osteoclast.

A. osteoprogenitor cell -- Resting cell that can transform into osteoblast. -- Found on the external and internal surfaces of bones. -- Only bone cells that undergoes cell division, daughter cells becomes osteoblasts

B. osteoblast -- secretes organic compounds for bone matrix. -- located at the surfaces of bone.

C. osteocyte -- mature cell and is enclosed by bone matrix -- osteocytes are found in matrix. Lacuna Canaliculi

D. osteoclast -- responsible for bone resorption. -- rest directly on bone where resorption is taking place.

3.Types of bone epiphysis diaphysis epiphysis Structure of long bones

Compact bone Spongy bone --has no cavities. --forms the outside of the bone. Spongy bone --has numerous interconnecting cavities. --forms the interior of the bone.

Compact Bone Functional Unit is the Osteon or Haversian System—concentric rings of lamellae around a Central Canal, with connecting Peripheral Canals

Compact Bone 1.osteon 2.outer circumferential lamellae 3.inner circumferential lamellae 4.interstitial lamellae

Histogenesis Intramembranous ossification: flat bone Endochondral ossification: short and long bone

Intramembranous Ossification

Endochondral Ossification

Endochondral Ossification

Summary · Matrix: · Cells： · Structure of long bones organic matter, inorganic matter and a little water · Cells： osteoprogenitor cell, osteoblast, osteocyte and osteoclast · Structure of long bones periosteum and endosteum, epiphysis, diaphysis ossification

Questions: What’s the function of cartilage? Review the structure of bone. Describe the two processes of ossification.