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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
MetaphysisMetaphysis
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.
MetaphysisMetaphysis
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
Bone CellsBone Cells
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
Bone CellsBone Cells
OsteocytesOsteocytes Mature bone cellsMature bone cells Exchange nutrients and waste with Exchange nutrients and waste with
bloodblood
Bone CellsBone Cells
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
Compact Bone TissueCompact Bone Tissue
Provides protection and supportProvides protection and support
Compact Bone TissueCompact Bone Tissue
Compact bone thickest in areas Compact bone thickest in areas where stress is applied in few where stress is applied in few directionsdirections
Compact Bone TissueCompact Bone Tissue
1.1. Osteons – units in boneOsteons – units in bone
Compact Bone TissueCompact Bone Tissue
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
Compact Bone TissueCompact Bone Tissue
3. Haversian canals – longitudinal 3. Haversian canals – longitudinal canalscanals
Compact Bone TissueCompact Bone Tissue
4. Concentric lamellae – rings of 4. Concentric lamellae – rings of calcified matrixcalcified matrix
Compact Bone TissueCompact Bone Tissue
5. Lacunae – contain osteocytes5. Lacunae – contain osteocytes
Compact Bone TissueCompact Bone Tissue
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
CanaliculiCanaliculi
Connect lacuane with Haversian Connect lacuane with Haversian CanalsCanals
CanaliculiCanaliculi
Allow osteocytes to communicate Allow osteocytes to communicate with each other via gap junctionwith each other via gap junction
CanaliculiCanaliculi
Allow exchange of nutrients and Allow exchange of nutrients and wastes with bloodwastes with blood
Compact Bone TissueCompact Bone Tissue
7. Interstitial lamellae – fragments of 7. Interstitial lamellae – fragments of older osteonsolder osteons
Spongy Bone TissueSpongy Bone Tissue
Lacks osteonsLacks osteons
Spongy Bone TissueSpongy Bone Tissue
Contains trabeculae which are an Contains trabeculae which are an irregular latticework of thin columns irregular latticework of thin columns of boneof bone
Spongy Bone TissueSpongy Bone Tissue
Contains red bone marrow between Contains red bone marrow between spaces of trabeculaespaces of trabeculae
Spongy Bone TissueSpongy Bone Tissue
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
Spongy Bone TissueSpongy Bone Tissue
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 TissueSpongy Bone Tissue
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
Development of the center Development of the center of ossificationof ossification
The mesenchymal cells become The mesenchymal cells become osteogenic cellsosteogenic cells
Development of the center Development of the center of ossificationof ossification
These osteogenic cells become These osteogenic cells become osteoblastsosteoblasts
IntramembranousIntramembranous
2.2. CalcificationCalcification
CalcificationCalcification
Secretion of matrix stopsSecretion of matrix stops
CalcificationCalcification
Osteoblasts now called osteocytes Osteoblasts now called osteocytes and lie within lacunaeand lie within lacunae
CalcificationCalcification
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
IntramembranousIntramembranous
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
IntramembranousIntramembranous
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
Development of the Development of the periosteumperiosteum
Compact bone replaces spongy bone Compact bone replaces spongy bone at the surfaceat the surface
Development of the Development of the periosteumperiosteum
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
Development of the Development of the cartilage modelcartilage model
Chondroblasts secrete a cartilage Chondroblasts secrete a cartilage matrix, producing a hyaline cartilage matrix, producing a hyaline cartilage modelmodel
Development of the Development of the cartilage modelcartilage model
A perichondrium develops around A perichondrium develops around the cartilage modelthe cartilage model
EndochondralEndochondral
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
Growth of the cartilage Growth of the cartilage modelmodel
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
Growth of the cartilage Growth of the cartilage modelmodel
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
Growth of the cartilage Growth of the cartilage modelmodel
Cartilage model calcifiesCartilage model calcifies
EndochondralEndochondral
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
Development of the primary Development of the primary ossification centerossification center
Osteogenic cells in perichondrium Osteogenic cells in perichondrium become osteoblastsbecome osteoblasts
Development of the primary Development of the primary ossification centerossification center
Osteoblasts secretes a periosteal Osteoblasts secretes a periosteal bone collar made up of compact bone collar made up of compact bonebone
Development of the primary Development of the primary ossification centerossification center
Perichondrium becomes periosteumPerichondrium becomes periosteum
Development of the primary Development of the primary ossification centerossification center
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
Development of the primary Development of the primary ossification centerossification center
Osteoblasts deposit bone matrix over Osteoblasts deposit bone matrix over calcified cartilage forming spongy calcified cartilage forming spongy bone trabeculaebone trabeculae
Development of the primary Development of the primary ossification centerossification center
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
EndochondralEndochondral
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
EndochondralEndochondral
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
Four ZonesFour Zones
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
Four ZonesFour Zones
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
Four ZonesFour Zones
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
Zone of calcified cartilageZone of calcified cartilage
Osteoclasts dissolve the calcified Osteoclasts dissolve the calcified cartilagecartilage
Zone of calcified cartilageZone of calcified cartilage
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
Growth in Growth in Thickness/Step 1Thickness/Step 1
Bone ridges form on either side of a Bone ridges form on either side of a periosteal blood vesselperiosteal blood vessel
Growth in Growth in Thickness/Step 1Thickness/Step 1
A groove forms for the blood vesselA groove forms for the blood vessel
Growth in Growth in Thickness/Step 2Thickness/Step 2
The ridges fold and fuse enclosing The ridges fold and fuse enclosing the blood vesselthe blood vessel
Growth in Growth in Thickness/Step 2Thickness/Step 2
The periosteum is now becomes the The periosteum is now becomes the endosteum surrounding the blood endosteum surrounding the blood vesselvessel
Growth in Growth in Thickness/Step 3Thickness/Step 3
Osteoblasts in the endosteum lay Osteoblasts in the endosteum lay down bone matrix forming new down bone matrix forming new concenteric lamellaeconcenteric lamellae
Growth in Growth in Thickness/Step 3Thickness/Step 3
The concenteric lamellae is added The concenteric lamellae is added toward the center of tunneltoward the center of tunnel
Growth in Growth in Thickness/Step 4Thickness/Step 4
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.
Calcium HomeostasisCalcium Homeostasis
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.
Calcium HomeostasisCalcium Homeostasis
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
Calcium HomeostasisCalcium Homeostasis
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.