bone tissue. support provides attachment for tendons of skeletal muscles provides attachment for...

Bone TissueBone Tissue

SupportSupport

Provides attachment for tendons of Provides attachment for tendons of skeletal musclesskeletal muscles

ProtectionProtection

Protects internal organsProtects internal organs

Example: Skull (brain), vertebrae Example: Skull (brain), vertebrae (spinal cord), and rib cage ( heart (spinal cord), and rib cage ( heart and lungs)and lungs)

Assistance in movementAssistance in movement

Contraction of muscles results in Contraction of muscles results in pulling of bone due to tendonspulling of bone due to tendons

Mineral HomeostasisMineral Homeostasis

Stores calcium and phosphorousStores calcium and phosphorous

Blood Cell ProductionBlood Cell Production

Red bone marrow produces red Red bone marrow produces red blood cells, white blood cells and blood cells, white blood cells and plateletsplatelets

Triglyceride StorageTriglyceride Storage

Yellow bone marrow stores Yellow bone marrow stores triglyceridestriglycerides

NewbornsNewborns

Have only red bone marrowHave only red bone marrow

NewbornsNewborns

Red bone marrow changes into Red bone marrow changes into yellow bone marrow with increasing yellow bone marrow with increasing ageage

Structure of BoneStructure of Bone

DiaphysisDiaphysis EpiphysisEpiphysis MetaphysesMetaphyses Articular cartilageArticular cartilage PeriosteumPeriosteum Medullary cavityMedullary cavity EndosteumEndosteum

DiaphysisDiaphysis

Bone’s body or shaftBone’s body or shaft

EpiphysisEpiphysis

The distal and proximal ends of the The distal and proximal ends of the bonebone

MetaphysisMetaphysis

The region where the diaphysis joins The region where the diaphysis joins the epiphysisthe epiphysis


When the bone is growing the When the bone is growing the metaphysis consists of an epiphyseal metaphysis consists of an epiphyseal plate. This is a layer of hyaline plate. This is a layer of hyaline cartilage that allows the bone to cartilage that allows the bone to grow in length.grow in length.


When the bone stops growing the When the bone stops growing the cartilage is replaced by bone and cartilage is replaced by bone and becomes the epiphyseal line. becomes the epiphyseal line.

Articular CartilageArticular Cartilage

Hyaline cartilage that covers the Hyaline cartilage that covers the epiphyses in order to reduce frictionepiphyses in order to reduce friction

PeriosteumPeriosteum

Dense irregular tissue that Dense irregular tissue that surrounds the bone. surrounds the bone.

PeriosteumPeriosteum

Contains osteoblasts responsible for Contains osteoblasts responsible for bone growth in thickness.bone growth in thickness.

Medullary CavityMedullary Cavity

The space in the diaphysis that The space in the diaphysis that contains yellow bone marrow.contains yellow bone marrow.

EndosteumEndosteum

A thin membrane that lines the A thin membrane that lines the medullary cavitymedullary cavity

Bone HistologyBone Histology

25% water25% water 25% collagen fibers25% collagen fibers 50% mineral salts50% mineral salts

Bone HistologyBone Histology

Most mineral salts are calcium Most mineral salts are calcium phosphate and calcium carbonatephosphate and calcium carbonate

Bone Histology Bone Histology ContinuedContinued

These minerals crystallize only in the These minerals crystallize only in the presence of collagen fibers presence of collagen fibers

Bone Histology Bone Histology ContinuedContinued

Crystallized inorganic mineral salts Crystallized inorganic mineral salts responsible for hardnessresponsible for hardness

Bone CellsBone Cells

1.1. Osteogenic Cells Osteogenic Cells Only bone cells that undergoes cell Only bone cells that undergoes cell

divisiondivision Daughter cells becomes osteoblastsDaughter cells becomes osteoblasts


OsteoblastsOsteoblasts Secretes collagen fibers and organic Secretes collagen fibers and organic

compounds for matrixcompounds for matrix When mature they become When mature they become

osteocytesosteocytes


OsteocytesOsteocytes Mature bone cellsMature bone cells Exchange nutrients and waste with Exchange nutrients and waste with

bloodblood


OsteoclastsOsteoclasts Breaks down bone matrix or Breaks down bone matrix or

resorptionresorption Derived from the fusion of 50 Derived from the fusion of 50

monocytes (wbc)monocytes (wbc)

Compact Bone TissueCompact Bone Tissue

Forms the external layer of all bones Forms the external layer of all bones and most of the diaphysis in long and most of the diaphysis in long bonesbones


Provides protection and supportProvides protection and support


Compact bone thickest in areas Compact bone thickest in areas where stress is applied in few where stress is applied in few directionsdirections


1.1. Osteons – units in boneOsteons – units in bone


2. Volkmann’s canals – Tranverse 2. Volkmann’s canals – Tranverse canals in which blood vessels, canals in which blood vessels, lymphatic vessels, and nerves lymphatic vessels, and nerves residereside


3. Haversian canals – longitudinal 3. Haversian canals – longitudinal canalscanals


4. Concentric lamellae – rings of 4. Concentric lamellae – rings of calcified matrixcalcified matrix


5. Lacunae – contain osteocytes5. Lacunae – contain osteocytes


6.6. Canaliculi – tiny channels filled Canaliculi – tiny channels filled with extracellular fluid that contain with extracellular fluid that contain the fingerlike processes of the fingerlike processes of osteocytes.osteocytes.

CanaliculiCanaliculi

Connect lacunae with one anotherConnect lacunae with one another


Connect lacuane with Haversian Connect lacuane with Haversian CanalsCanals


Allow osteocytes to communicate Allow osteocytes to communicate with each other via gap junctionwith each other via gap junction


Allow exchange of nutrients and Allow exchange of nutrients and wastes with bloodwastes with blood


7. Interstitial lamellae – fragments of 7. Interstitial lamellae – fragments of older osteonsolder osteons

Spongy Bone TissueSpongy Bone Tissue

Lacks osteonsLacks osteons


Contains trabeculae which are an Contains trabeculae which are an irregular latticework of thin columns irregular latticework of thin columns of boneof bone


Contains red bone marrow between Contains red bone marrow between spaces of trabeculaespaces of trabeculae


Make up most of the bone tissue in Make up most of the bone tissue in short, flat, irregularly shaped bones, short, flat, irregularly shaped bones, and epiphysis of long bones and the and epiphysis of long bones and the narrow rim around the medullary narrow rim around the medullary cavity of the diaphysis of long bonecavity of the diaphysis of long bone


Red Bone marrow is found in spongy Red Bone marrow is found in spongy bone tissue of hip bones, ribs, bone tissue of hip bones, ribs, breastbone, back bones, and ends of breastbone, back bones, and ends of long boneslong bones


Spongy Bone tissue found where Spongy Bone tissue found where stresses are applied from several stresses are applied from several directionsdirections

Bone FormationBone Formation

1. Intramembranous ossification1. Intramembranous ossification

2. Endochondral ossification2. Endochondral ossification

Intramembranous Intramembranous OssificationOssification

Skull bones and mandible form this Skull bones and mandible form this wayway

Fetal soft spots harden via this Fetal soft spots harden via this processprocess

IntramembranousIntramembranous

1.1. Development of the center of Development of the center of ossificationossification

Development of the center Development of the center of ossificationof ossification

The site where mesenchymal cells The site where mesenchymal cells cluster togethercluster together


The mesenchymal cells become The mesenchymal cells become osteogenic cellsosteogenic cells


These osteogenic cells become These osteogenic cells become osteoblastsosteoblasts


2.2. CalcificationCalcification

CalcificationCalcification

Secretion of matrix stopsSecretion of matrix stops


Osteoblasts now called osteocytes Osteoblasts now called osteocytes and lie within lacunaeand lie within lacunae


Calcium and other mineral salt are Calcium and other mineral salt are deposited and the matrix hardens or deposited and the matrix hardens or calcifiescalcifies


3.3. Formation of trabeculaeFormation of trabeculae

Formation of trabeculaeFormation of trabeculae

Bone matrix develops into Bone matrix develops into trabeculae to form spongy bonetrabeculae to form spongy bone

Formation of trabeculaeFormation of trabeculae

Connective tissue associated with Connective tissue associated with blood vessels in trabeculae become blood vessels in trabeculae become red bone marrowred bone marrow


4.4. Development of the periosteumDevelopment of the periosteum

Development of the Development of the periosteumperiosteum

Mesenchyme condenses around the Mesenchyme condenses around the periphery and becomes the periphery and becomes the periosteumperiosteum


Compact bone replaces spongy bone Compact bone replaces spongy bone at the surfaceat the surface


Spongy bone remains in the centerSpongy bone remains in the center

Endochondral Endochondral OssificationOssification

Replacement of cartilage by boneReplacement of cartilage by bone Most bones are formed this wayMost bones are formed this way

EndochondralEndochondral

1.1. Development of the cartilage modelDevelopment of the cartilage model

Development of the Development of the cartilage modelcartilage model

Mesenchymal cells cluster together Mesenchymal cells cluster together in the shape of the future bone and in the shape of the future bone and differentiate into chondroblastsdifferentiate into chondroblasts


Chondroblasts secrete a cartilage Chondroblasts secrete a cartilage matrix, producing a hyaline cartilage matrix, producing a hyaline cartilage modelmodel


A perichondrium develops around A perichondrium develops around the cartilage modelthe cartilage model


2.2. Growth of the cartilage modelGrowth of the cartilage model

Growth of the cartilage Growth of the cartilage modelmodel

Once chondroblasts are surrounded Once chondroblasts are surrounded by matrix called chondrocytesby matrix called chondrocytes


Grows in length because Grows in length because chondrocytes continue to divide and chondrocytes continue to divide and secretion of cartilage matrixsecretion of cartilage matrix


Grows in width occurs due to Grows in width occurs due to addition of more matrix by new addition of more matrix by new chondroblasts that develop from the chondroblasts that develop from the perichondriumperichondrium


Cartilage model calcifiesCartilage model calcifies


3.3. Development of the primary Development of the primary ossification centerossification center

Development of the primary Development of the primary ossification centerossification center

A nutrient artery penetrates the A nutrient artery penetrates the perichondrium and calcified perichondrium and calcified cartilage via a nutrient foramencartilage via a nutrient foramen


Osteogenic cells in perichondrium Osteogenic cells in perichondrium become osteoblastsbecome osteoblasts


Osteoblasts secretes a periosteal Osteoblasts secretes a periosteal bone collar made up of compact bone collar made up of compact bonebone


Perichondrium becomes periosteumPerichondrium becomes periosteum


Capillaries that penetrate the Capillaries that penetrate the calcified cartilage induce growth of calcified cartilage induce growth of the primary ossification centerthe primary ossification center


Osteoblasts deposit bone matrix over Osteoblasts deposit bone matrix over calcified cartilage forming spongy calcified cartilage forming spongy bone trabeculaebone trabeculae


As the ossification center grows As the ossification center grows length wise it begins to destroy the length wise it begins to destroy the trabeculae which becomes the trabeculae which becomes the medullary cavitymedullary cavity


4.4. Development of the secondary Development of the secondary ossification centerossification center

Development of the Development of the secondary ossification secondary ossification

centercenter Epiphyseal artery penetrates Epiphyseal artery penetrates

epiphyses and a secondary epiphyses and a secondary ossification center developsossification center develops

Development of the Development of the secondary ossification secondary ossification

centercenter Bone formation is similar to that of Bone formation is similar to that of

diaphysis except spongy bone diaphysis except spongy bone trabeculae is not destroyedtrabeculae is not destroyed


5.5. Formation of articular cartilage Formation of articular cartilage and the epiphyseal plateand the epiphyseal plate

Formation of articular Formation of articular cartilage and the cartilage and the epiphyseal plateepiphyseal plate

Hyaline cartilage that surrounds Hyaline cartilage that surrounds epiphyses becomes the articular epiphyses becomes the articular cartilagecartilage

Formation of articular Formation of articular cartilage and the cartilage and the epiphyseal plateepiphyseal plate

There is a layer of cartilage between There is a layer of cartilage between the epiphyses and the diaphysis the epiphyses and the diaphysis called the epiphyseal platecalled the epiphyseal plate

Bone GrowthBone Growth

Growth in lengthGrowth in length Growth in thicknessGrowth in thickness

Growth in LengthGrowth in Length

Growth in length occurs due to the Growth in length occurs due to the epiphyseal plate epiphyseal plate

Growth in LengthGrowth in Length

The epiphyseal plate is made up of a The epiphyseal plate is made up of a layer of cartilage with four zoneslayer of cartilage with four zones

Four ZonesFour Zones

1.1. Zone of resting cartilageZone of resting cartilage Made up of chondrocytesMade up of chondrocytes

Zone of resting cartilageZone of resting cartilage

Does not contribute to bone growthDoes not contribute to bone growth

Zone of resting cartilageZone of resting cartilage

Anchors epiphyses to the epiphyseal Anchors epiphyses to the epiphyseal plateplate


2.2. Zone of proliferating cartilageZone of proliferating cartilage Chondrocytes largerChondrocytes larger

Zone of proliferating Zone of proliferating cartilagecartilage

Chondrocytes divide in order to Chondrocytes divide in order to replace dying chondrocytes on the replace dying chondrocytes on the diaphyseal side of the epiphyseal diaphyseal side of the epiphyseal plateplate

Zone of proliferating Zone of proliferating cartilagecartilage

Responsible for lengtheningResponsible for lengthening


3.3. Zone of hypertrophic cartilageZone of hypertrophic cartilage Chondrocytes largerChondrocytes larger

Zone of hypertrophic Zone of hypertrophic cartilagecartilage

Lacunae grows and the matrix Lacunae grows and the matrix between lacunae narrowbetween lacunae narrow

Zone of hypertrophic Zone of hypertrophic cartilagecartilage

Responsible for lengtheningResponsible for lengthening


4.4. Zone of calcified cartilageZone of calcified cartilage Matrix is calcifiedMatrix is calcified

Zone of calcified cartilageZone of calcified cartilage

Chondrocytes are deadChondrocytes are dead


Osteoclasts dissolve the calcified Osteoclasts dissolve the calcified cartilagecartilage


Osteoblasts from diaphysis invade Osteoblasts from diaphysis invade the area and lay down bone matrixthe area and lay down bone matrix

Epiphyseal LineEpiphyseal Line

Epiphyseal plate becomes a bony Epiphyseal plate becomes a bony structure called an epiphyseal line structure called an epiphyseal line between the age of 18 and 25between the age of 18 and 25

Epiphyseal LineEpiphyseal Line

Bone replaces all the cartilage and Bone replaces all the cartilage and the bone can no longer grow in the bone can no longer grow in lengthlength

Growth in ThicknessGrowth in Thickness

Bone can only grow in thickness by Bone can only grow in thickness by appositional growthappositional growth

Growth in Growth in Thickness/Step 1Thickness/Step 1

Osteoblasts secrete collagen fibers Osteoblasts secrete collagen fibers and organic molecuesand organic molecues


Bone ridges form on either side of a Bone ridges form on either side of a periosteal blood vesselperiosteal blood vessel


A groove forms for the blood vesselA groove forms for the blood vessel


The ridges fold and fuse enclosing The ridges fold and fuse enclosing the blood vesselthe blood vessel


The periosteum is now becomes the The periosteum is now becomes the endosteum surrounding the blood endosteum surrounding the blood vesselvessel


Osteoblasts in the endosteum lay Osteoblasts in the endosteum lay down bone matrix forming new down bone matrix forming new concenteric lamellaeconcenteric lamellae


The concenteric lamellae is added The concenteric lamellae is added toward the center of tunneltoward the center of tunnel


The periosteum lays down new The periosteum lays down new outer concenteric lamellaeouter concenteric lamellae

Step 1-4 repeatsStep 1-4 repeats

Calcium HomeostasisCalcium Homeostasis

When blood calcium levels are below When blood calcium levels are below normal, parathyroid hormone is normal, parathyroid hormone is released by the parathyroid glands. released by the parathyroid glands.


Parathyroid hormone increases bone Parathyroid hormone increases bone resorption. In other words it resorption. In other words it increases the activity of osteoclasts, increases the activity of osteoclasts, thereby breaking down bone and thereby breaking down bone and releasing more calcium into the releasing more calcium into the blood stream.blood stream.


Parathyroid hormone also act on the Parathyroid hormone also act on the kidneys to decrease loss of calcium kidneys to decrease loss of calcium in urinein urine


When blood calcium levels are high, When blood calcium levels are high, calcitonin is released by the thyroid calcitonin is released by the thyroid gland in order to increase calcium gland in order to increase calcium uptake and stimulate bone uptake and stimulate bone formation.formation.

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