CartilageCartilage

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

Cells: chondrocytes

Extracellular matrixStructure fiber

ground substance

Cartilage composition

CellsChondrocytes: located within matrix; lacunae

Chondroblasts: located at periphery; secrete extracellular matrix

Fibers Collagen and elastic fibersGround substanceRich in glycosaminoglycans and proteoglycans

Cartilage composition

Perichondrium is a layer of dense irregular connective tissue.

It is essential for the growth and maintenance of cartilage.

Perichondrium

More Features of Cartilage

Avascular; Nutrients diffusion from perichondrium or syn

ovial fluid; No innervation; No lymphatic vessels; Chondrocytes have low metabolic activity

Classification:

Hyaline cartilage: most common, much type II most common, much type II collagencollagenElastic cartilage: elastic fiberselastic fibers

Fibrocatilage: dense network of type I collagendense 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 matrixfiberground substance

PerichondriumPerichondrium 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, yaline cartilage, chondrocytes are distribchondrocytes are distributed either singly or in uted either singly or in clustercluster

lacunae ：isogenous nest ： chondrocytes arranged in pair or group of four or six

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

2. Matrix

(1) Hyaline cartilage matrix is produced by chonHyaline cartilage matrix is produced by chondrocytes and contains three major classes of modrocytes and contains three major classes of molecules:lecules:

①Collagen molecules

②Proteoglycans

③Nocollagenous proteins

fiber—— mainly type collage fiber Ⅱ

ground substance

(2) Grounds substance componenGrounds substance components of hyaline cartilage matrix are ts of hyaline cartilage matrix are not distributed uniformlynot distributed uniformly

Capsusle/territorial matrix (TM) ：matrix surrounding each chondrocyte

Interterritorial matrix (IM) ：matrix between the territorial matrix

Elastic CartilageElastic Cartilage

• Auricle of ear, external auditory canal, epigAuricle of ear, external auditory canal, epiglottislottis

• Similar to HC, many elastic fibers in the mSimilar to HC, many elastic fibers in the matrixatrix

• PerichondriumPerichondrium

Elastic cartilageElastic cartilage

FibrocartilageFibrocartilage

• Found in Intervetebral disks, tendon and Found in Intervetebral disks, tendon and ligament attachment to bone, symphysiligament attachment to bone, symphysis pubiss pubis

• Combination of HC and dense regular cCombination of HC and dense regular connective tissueonnective tissue

• Chondrocytes often in rows or groupsChondrocytes often in rows or groups

• Matrix acidophilic due to high collagenMatrix acidophilic due to high collagen

• No perichondriumNo 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 tendoProvides attachment for tendons of skeletal musclesns of skeletal musclesProtection: Protects internal organsProtects internal organs

Storage: calcium ,phosphate

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]

Structure of bone

endosteum ： lined on internal surfaceperiosteum ： lined on external surface

2. Cells

osteoprogenitor, osteoblast, osteocyte and osteoclast.

-- 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

A. osteoprogenitor cell

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

epiphysis

diaphysis

Structure of long bones

Compact 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 Functional Unit is the OOsteonsteon or or Haversian SysHaversian Systemtem—concentric rings —concentric rings of lamellae around a Ceof lamellae around a Central Canal, with connentral Canal, with connecting Peripheral Canalscting Peripheral Canals

1.osteon

2.outer circumferential lamellae

3.inner circumferential lamellae

4.interstitial lamellae

Compact Bone

HistogenesisHistogenesis

Intramembranous ossification: flat boneIntramembranous ossification: flat bone

Endochondral ossification: short and long Endochondral ossification: short and long bonebone

Intramembranous Ossification

Endochondral Ossification

Endochondral Ossification

Summary

· Matrix:

organic matter, inorganic matter and a little water

· Cells ： osteoprogenitor cell, osteoblast, osteocyte and osteoclast

· Structure of long bonesperiosteum and endosteum, epiphysis, diaphysis

ossification

Questions:

1.What’s the function of cartilage?

2.Review the structure of bone.

3.Describe the two processes of ossification.