Cartilage and Bone Tissue软骨组织和骨组织

Department of Histology and Embryology Medical college in Three Gorges University

Cartilage is composed of cartilage tissue( 软骨组织） and the perichondrium （软骨膜） .

Cartilage 软骨

Cell

Cartilage

tissueExtracellular

matrix

fibers

Ground substances

Chondrocytes 软骨细胞

• Within the ground substance are embedded

varying proportions of collagen and elastic

fibres giving rise to three main type of

cartilage: hyaline, fibrocartilage and elastic

cartilage.

Cartilage cells 软骨细胞 :

The cells of cartilage are called

chondrocytes. They lie in spaces or lacunae

present in the matrix. At first the cells are

small and show the features of metabolically

active cells. This cell is also called as

chondroblasts or embryonic cartilage

producing cells.As the cells mature, they

enlarge and be in group.

• Ground substance:

The ground substance of cartilage is made

up of complex molecules containing

proteins and carbohydrates （碳水化合物）

(proteoglycans 蛋白多糖 ) these molecules

form a meshwork which is filled by water

and dissolved salts.

Fibres of cartilage:

1.Collagen fibers:

type II collagen: hyaline cartilage

type I collagen: the normal collagen fiber

fibrocartilage, and the perichondrium,

2.Elastic fibers are in the Elastic cartilage

• Hyaline cartilage 透明软骨

• HC is the most common type of cartilage

found in the nasal septum, larynx ,tracheal

rings, most articular surfaces and the sternal

ends of the ribs etc.

perichondrium

Evident: an inner, strongly basophilic zonea narrow, pale stained peripheral zone

Isogenous cell group

• The cells are small present in single in

the Periphery.

• Towards the center of a mass of HC, the

chondrocytes are large and are usually

present in groups (of two or more ),these

cells are called cell-nests (or isogenous cell

groups).

•Chondrocytes: lacuna area housing the cell

What is the structure between the chondrocytes

• The deep staining matrix around cell or

cell nests is newly formed and is called

the territorial matrix or lacunar capsule.

an amorphous matrix of ground substance reinforced by collagen fibres

Their tiny matrix enclosed compartments are

termed lacunae. (occupy space)

FCh

chondrocytes

Extracellular matrix

• The matrix of HC appears fairly

amorphous since the ground substance

and collagen have similar refractive

properties.or its intercellular substance

appears to be homogeneous. We cannot

identified the fiber in the light microscope

with common method stained preparation

of the cartilage.

• Fibrocartilage

Fibrocartilage, unlike hyaline and elastic

cartilage, does not possess a perichondrium

and its matrix possesses type I collagen.

•Distribution:the intervertebral discs( 椎间盘） ,

some Articular cartilage 关节软骨 ,

the pubic symphysis 耻骨联合 ,etc.

•Elastic cartilage

• The histological structure of EC is similar to

that of hyaline cartilage, its elasticity,

however, being derived from the presence of

numerous bundles of branching elastic fibres.

•Distribution: (1)in the external ear and external

auditory canal 外耳道 (2)the epiglottis 会厌 ,

parts of the laryngeal cartilage 喉软骨

Bone Tissue

• It is composed of cells and a predominantly

collagenous extracellular matrix (type I collagen )

called osteoid 类 骨 质 which becomes

mineralized by the deposition of calcium

hydroxyapatite 羟 磷 灰 石 , which produce an

extremely hard tissue capable of support and

protecting (rigidity and strength).

• Bone are an organ,and bone tissue is the structural

component of bones.

• Bone consist of bone tissue and other connective

tissue ,including hemopoietic 造血的 tissue, fat

tissue, blood vessels, and nerves.

• Bone is classified as either compact (dense ) or

spongy (cancellous).

•Bone and bone tissue 骨和骨组织 :

To 49

Cells

Elements

of bone

tissue Extracellular

matrix

Fibers-collagen fibers

Ground substances:

the mineral

Calcium phosphate

Osteoblast 成骨细胞Osteocyte 骨细胞Osteoclast 破骨细胞

osteoprogenitor cell 骨原细胞

• The cells of bone:

• Osteoblast 成骨细胞 – which synthesize osteoid

and mediate its mineralisation; they are found

lined up along bone surface.

• Osteocytes 骨 细 胞 -which represent largely

inactive osteoblasts trapped within formed

bone; they may assist in nutrition of bone.

lacuna

canaliculi

• Bone lacuna 骨陷窝 : cell body of the osteocyte.

• The canaliculi 骨小管 are occupied by delicate

cytoplasmic processes of osteocytes, Spreading out

from the lacuna.

• (filled in tissue fluid).

• Osteoclasts 破 骨 细 胞 -phagocytic cells

which are capable of eroding bone and

which are important, along with osteoblasts,

in the constant turnover and refashioning of

bone. Osteoclasts are multinucleate

phagocytic cells derived from the

macrophage-monocyte cell line

• Osteoprogenitor cell 骨祖细胞：

The osteoprogenitor cell is a resting cell that

can transform into an osteoblast and secrete

bone matrix. It is found on the external and

internal surfaces of bones. They resemble

fibroblast in appearance.

• Extracellular matrix :

The feature that distinguishes bone from

other connective tissue is the mineralisation

of its matrix,which produce an extremely

hard tissue capable of support and

protecting.The mineral is calcium

phosphate in the form of hydroxyapatite

crystals 羟磷灰石 .

• fiber:collagen fiber (I)

Ground substance Composition

Chemical constituents

Organic constituent

Glycosaminoglycans

Proteoglycans

Fibers and matrix

Inorganic constituent

Calcium

phosphorous

other ions

• According to the arrangement of the matrix

in the bone tissue:

There are several kind of lamellae:

concentric lamellae 同心圆排列的骨板

circumferential lamellae 环状骨板

interstitial lamellae 间骨板

• Lamellar bone: 板层骨 or 骨板： When

we examine the structure of any bone of an

adult, we find that it is, made up of layers

or lamellae. this kind of bone is called

lamellar bone. Each lamellus is a thin plate

of bone consisting of collagen fibers and

mineral salts that are deposited in a

gelatinous ground substance.

•between adjoining lamellae we see small flattened spaces or lacunae which contain osteocytes.

Spongy bone and compact bone

Epiphysis 骨骺 Diaphysis 骨干

Structure of cancellous bone:(spongy 松质骨 )

The bone plates or rods that form the meshwork of

cancellous bone are called trabeculae. Each

trabeculus is made up of a number of lamellae

between which there are lacunae containing

osteocytes. Canaliculi containing the processes of

osteocytes, radiate from the lacunae.

• The trabeculae enclose wide spaces which

are filed in by bone marrow. They receive

nutrition from blood vessels in the bone

marrow.

• Spongy bone is distributed mainly in

epiphysis of long bone.

Structure of compact bone 密质骨 :(dense)

When we examine a section of compact

bone we find that this type of bone is also

made up of lamellae.It is constitute the

main parts of diaphysis.

According to the arrangment of lamellae,

there are several kind of lamellae:

circumferential lamellae 环骨板

concentric lamellae 同心圆骨板

interstitial lamellae 间骨板

• ( 1 ) circumferential lamellae 环骨板 :

The outer circumferential lamellae are

just deep to the periosteum, forming the

outermost region of the diaphysis and

contain Sharpey’s fibres anchoring the

periosteum to the bone.

• The inner circumferential lamellae

completely encircle the marrow cavity.

Trabeculae of spongy bone extend from the

inner circumferential lamellae into the

marrow cavity, interrupting the endosteal

lining of the inner circumferential lamellae.

• ( 2 ) Haversian system 哈弗斯系统 :

Most of the lamellae are arranged in the

form of concentric rings that surround a

narrow Haversian canal present at the

center of each ring. The Haversian canal is

occupied by blood vessels, nerve fibers

and some cells. One Haversian canal and

the lamellae around it constitute a

Haversian system.or named osteon.

• ( 3 )Interstitial lamellae 间骨板 : It is

located between adjoining osteons.These

lamellae are remnants of osteons, the

greater parts of which have been destroyed.

• Formation of bone

• Histogenesis of Bone 骨发生• Two types:Intramembranous

Endochondral

• Intramembranous ossification 膜 内成骨

• Intramembranous bone formation occurs

within mesenchymal tissue.

• Most flat bones are formed by

intramembranous bone formation.

• (1) occurs in a richly vascularized

mesenchymal tissue, whose cells make

contact with each other via long processes.

• (2)Mesenchymal cells differentiate into

osteoblasts that secrete bone matrix,in which

fibers is embedded. This mass of swollen

fibers and matrix, no calcium, is called

osteoid.

• (3) Calcium salts is deposited in osteoid, this

process is named calcification and osteoblasts

trapped in their matrices become osteocytes.

As soon as this happens the layer of osteoid

can be said to have become one lamellus of

bone. This region of initial osteogenesis is

known as the primary ossification center.

• (4)In this way a number of lamellae are laid

down one over another,and these lamellae

together form a trabeculaus of bone

•Moreover, the spongy bone deep to the

periosteum and the periosteal layer of the

dura mater of flat bones are transformed

into compact bone, forming the inner and

outer tables with the intervening diploë.

• Endochondral Bone Formation 软骨内成骨

• Most of the long and short bones of the

body develop by endochondral bone

formation. This type of bone formation

occurs in two steps: (1)a miniature hyaline

cartilage model is formed, and (2) the

cartilage model continues to grow and

serves as a structural scaffold for bone

development, is resorbed, and is replaced

by bone.

• 1. In the region where bone is to grow

within the embryo, a hyaline cartilage

model of that bone is developed.

• 2.Concurrently, the perichondrium at

the midriff of the diaphysis of

cartilage becomes vascularized .

When this happens, chondrogenic cells

become osteoprogenitor cells forming

osteoblasts, and the overlying

perichondrium becomes a periosteum.

• 3.The newly formed osteoblasts

secrete bone matrix, forming the

subperiosteal bone collar on the

surface of the cartilage template by

intramembranous bone formation.

• 4.The bone collar prevents the diffusion of

nutrients to the hypertrophied chondrocytes

within the core of the cartilage model, causing

them to die. This process is responsible for the

presence of empty, confluent lacunae forming

large concavities—the future marrow cavity in

the center of the cartilage model.

• 5. Holes etched in the bone collar by

osteoclasts permit a periosteal bud

(osteogenic bud), composed of

osteoprogenitor cells, hemopoietic cells,

and blood vessels, to enter the

concavities within the cartilage model .

• 6..Osteoprogenitor cells divide to form

osteoblasts. These newly formed cells

elaborate bone matrix on the surface of

the calcified cartilage. The bone matrix

becomes calcified to form a calcified

cartilage/calcified bone complex.

• This complex can be appreciated in

routinely stained histological sections

because calcified cartilage stains

basophilic, whereas calcified bone

stains acidophilic.

This is a first place for calsification,

primary center of ossification.

• 7. As the subperiosteal bone becomes

thicker and grows in each direction

from the midriff of the diaphysis

toward the epiphyses, osteoclasts

begin resorbing the calcified

cartilage/calcified bone complex,

enlarging the marrow cavity.

• .

• As this process continues, the cartilage of

the diaphysis is replaced by bone except for

the epiphyseal plates, which are responsible

for the continued growth of the bone for 18

to 20 years.

•  

hyaline cartilage model of that bone is developed.

• Bone growth in length

• The continued lengthening of bone depends

on the epiphyseal plate.

• Histologically, the epiphyseal plate is

divided into five recognizable zones.

• ■Zone of reserve cartilage 软骨储备区 : Chondrocytes randomly distributed throughout the matrix are mitotically active.

• ■Zone of proliferation 软 骨 增 生 区 : Chondrocytes, rapidly proliferating, form rows of isogenous cells that parallel the direction of bone growth.

• ■Zone of maturation and hypertrophy:

软骨成熟区或软骨肥大区 Chondrocytes mature, hypertrophy, and

accumulate glycogen in their cytoplasm. The

matrix between their lacunae narrows with a

corresponding growth of lacunae.

• ■Zone of calcification 软 骨 钙 化 区 : Lacunae

become confluent, hypertrophied chondrocytes

die, and cartilage matrix becomes calcified.

• ■Zone of ossification 成骨区 :

Osteoprogenitor cells invade the area and

differentiate into osteoblasts, which

elaborate matrix that becomes calcified

on the surface of calcified cartilage. This

is followed by resorption of the calcified

cartilage/calcified bone complex.

• As long as the rate of mitotic activity in the

zone of proliferation equals the rate of

resorption in the zone of ossification, the

epiphyseal plate remains the same width

and the bone continues to grow longer.