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
fiber
Extracellular matrix
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
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
--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:
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:
1.What’s the function of cartilage?
2.Review the structure of bone.
3.Describe the two processes of ossification.