Bone

BONEDR SURAJIT KUNDU

BDS. M Sc (ANATOMY)SR. LECTURER

DEPT. OF ANATOMYMAITHRI INSTITUTE OF DENTAL SCIENCES AND

RESEARCH CENTREANJORA, DURG

CHHATTISHGARH

DEFINITION

BONE CAN BE DEFINED AS A HIGHLY SPECIALISED CONNECTIVE TISSUE OF THE BODY IN WHICH THE GROUND SUBSTANCE IS IMPREGNATED WITH

CALCIUM SALTS AS A RESULT OF WHICH IT IS VERY RIGID.

GENERAL FEATURES

• UNLIKE CONNECTIVE TISSUE, BONE IS VERY RIGID, AS THE EXTRACELLULAR SUBSTANCE IS FILLED WITH CALCIUM SALTS

• BONE GIVES ATTATCHMENT TO MUSCLES

• BEARS BODY WEIGHT

• PROTECTS VITAL ORGANS- BRAIN, LUNGS, HEART

• STORES CALCIUM, PHOSPHATE AND OTHER IONS

• CONTAINS BONE MARROW- HAEMOPOETIC TISSUE

• HIGHLY VASCULAR

• COVERED BY PERIOSTEUM

• GROWS BY APPOSITIONAL METHOD

FUNCTIONS

• STORE HOUSE OF CALCIUM

• BONE MARROW IS A HAEMOPOETIC TISSUE WHICH MANUFACTURS RBC, WBC AND PLATELETS

• PROVIDE ATTATCHMENT TO MUSCLES

• HELPS IN MOVEMENT AND LOCOMOTION

• PROTECTS VITAL ORGANS- BRAIN, LUNGS, HEART

• FORMS THE SUPPORTING FRAMEWORK OF THE BODY

• TRANSMITS BODY WEIGHT

CLASSIFICATION/TYPES• (A) ACCORDING TO POSITION

AXIAL BONES (SKULL BONE, VERTEBRAE, RIBS, STERNUM), APPENDICULAR BONES (UPPER LIMB, LOWER LIMB)• (B) ACCORDING TO OSSIFICATION

MEMBRANE BONES (INTRAMEMBRANOUS OSSIFICATION),CARTILAGE BONES (ENDOCHONDRAL OSSIFICATION)MEMBRANO- CARTILAGENOUS BONES (MIXED TYPE)

• (C) ACCORDING TO SHAPELONG, SHORT, FLAT, IRREGULAR, PNEUMATIC, SESAMOID, ACCESSSORY OR

SUPERNUMERARY BONES• (D) ACCORDING TO HISTOLOGY/ MICROSCOPIC FEATURES

PRIMARY/ IMMATURE BONE AND SECONDARY/ MATURE BONE• (E) ACCORDING TO MORPHOLOGY

COMPACT/ DENSE BONE AND CANCELLOUS/ SPONGY BONE

BONE MEMBRANES

• 2 MEMBRANES- PERIOSTEUM (EXTERNAL MEMBRANE) AND ENDOSTEUM (INTERNAL

MEMBRANE)

• HAVE OSTEOGENIC POTENTIAL

• ESSENTIAL FOR BONE GROWTH AND REPAIR

PERIOSTEUM• DENSE CONNECTIVE TISSUE SHEATH COVERING

THE EXTERNAL SURFACE OF BONE EXCEPT IN ARTICULAR SURFACES,SESAMOID BONES AND AT THE POINT OF ATTATCHMENT OF TENDONS AND LIGAMENTS

• SENDS PERFORATING FIBRES CALLED SHARPEY’S FIBRES PERPENDICULAR TO THE LONG AXIS OF THE BONE TO ANCHOR ITSELF TO BONE

• HAS TWO LAYERS- OUTER FIBROUS (VASCULAR) LAYER AND INNER OSTEOGENIC (CELLULAR) LAYER

• HAS HIGH NERVE SUPPLY

• SHOULD BE PRESERVED DURING BONE SURGERY AS IT IS INVOLVED IN BONE GROWTH AND REPAIR

ENDOSTEUM

• THIN MEMBRANE OF VASCULAR LOOSE CONNECTIVE TISSUE LINING THE MEDULLARY CAVITY OF LONG BONES AND MARROW SPACES OF CANCELLOUS BONE

• LIKE PERIOSTEUM, IT ALSO HAS OSTEOGENIC POTENTIAL AND SHOULD BE PRESERVED DURING SURGERY

ENDOSTEUM

PARTS OF A BONE• EPIPHYSIS• METAPHYSIS

• EPIPHYSIAL GROWTH PLATE• DIAPHYSIS

• MEDULLARY CAVITY/ BONE MARROW

• SHAFT OF A BONE• END OF A BONE• COMPACT BONE

• SPONGY BONE/ CANCELLOUS BONE• NUTRIENT ARTERY

PARTS OF A BONE

COMPONENTS• CELLS

OSTEOPROGENITOR CELLS/MESENCHYMAL CELLS, OSTEOBLAST, OSTEOCLAST, OSTEOCYTE

• FIBRES(95%) COLLAGEN- TYPE1

• GROUND SUBSTANCE(4%)HAS BOTH ORGANIC(CHONDROITIN SULPHATE)

AND INORGANIC SALTS (CALCIUM CARBONATE(10%), CALCIUM

PHOSPHATE(85%),MAGNESIUM CARBONATE HYDROXYAPATITE CRYSTALS, FLOURIDES

CELLS

OSTEOPROGENITOR CELLSTHEY GIVE RISE TO OTHER CELLS OF THE BONE,

FOUND IN THE PERIOSTEUM

OSTEOBLASTBONE FORMING CELLS,CUBOIDAL IN SHAPE, BASOPHILLIC CYTOPLASM WITH SINGLE LARGE

NUCLEUS, LAY DOWN FIBRES AND GROUND SUBSTANCE OF THE BONE

CELLS (CONT.)

OSTEOCYTEBONE MAINTAINER, MATURE CELLS, OVAL IN SHAPE,

MANY CYTOPLASMIC PROCESSES- CANALICULI, LIE IN LACUNAE AND GETS EMBEDDED WITHIN THE

GROUND SUBSTANCE, CANALICULI OF ADJACENT CELLS COME IN CONTACT

OSTEOCLASTBONE DESTROYER, LARGE IRREGULAR GIANT CELL,

FOUND IN AREAS WHERE BONE RESORBTION IS GOING ON, HAVE RUFFLED BORDER, FOUND IN

HOWSHIP’S LACUNAE

BONE CELLS

OSTEOCLAST AND OSTEOCYTE

AXIAL SKELETON• SKELETON FORMING CENTRAL AXIS OF THE BODY

• TOTAL NUMBER OF BONES=81• THE BONES ARE AS FOLLOWS:

• SKULL=22

(FRONTAL,OCCIPITAL,TEMPORAL,PARIETAL,

SPHENOID,ETHMOID,ZYGOMATIC,LACRIMAL,NASAL,MAXILLA,PALATINE,INFERIOR NASAL CONCHA,VOMER,MANDIBLE)

• VERTEBRAE=33(CERVICAL,THORACIC,LUMBAR,SACRAL,COCCYX)

• HYOID BONE=1

• RIBS=24• STERNUM(BREST BONE)=1

AXIAL SKELETON

APPENDICULAR SKELETON• CONSIST OF 4 APPENDAGES (ARMS AND LEGS) + 2

GIRDLES (PECTORAL/CHEST GIRDLE AND PELVIC/HIP GIRDLE)

• TOTAL NUMBER OF BONES=126• THE BONES ARE AS FOLLOWS:

PECTORAL GIRDLE=4(CLAVICLE/COLLAR BONE AND SCAPULA/SHOULDER BLADE)

UPPER LIMB=60(HUMERUS,RADIUS,ULNA,CARPELS,METACARPELS,PHALANGES)

PELVIC GIRDLE=2(3 BONES FUSED TO 1:ILIUM,ISCHIUM, PUBIS)

LOWER LIMB=60(FEMUR,PATELLA,TIBIA,FIBULA,TARSELS,METATARSELS,PHALANGES)

STRUCTURE OF BONE

STUIDED UNDER 2 HEADINGS

(A)GROSS STRUCTURE(B) MICROSCOPIC STRUCTURE

GROSS STRUCTURE

BONE CUT IN LONGITUDINAL SECTION SHOWS: DENSE PORTION ON THE OUTSIDE- COMPACT BONE AND A POROUS PORTION LINING MARROW CAVITY- SPONGY/CANCELLOUS BONE

COMPACT & SPONGY BONE

MICROSCOPIC STRUCTURE

STUDIED UNDER 2 HEADINDS

(A)STRUCTURE OF COMPACT BONE (SECONDARY BONE)

(B)STRUCTURE OF SPONGY/CANCELLOUS BONE (PRIMARY/ WOVEN BONE)

STRUCTURE OF COMPACT BONE• CENTRALLY PLACED CANAL – HAVERSIAN CANAL (CONTAINING BLOOD

VESSELS, NERVE, LYMPHATICS), THE CANAL IS SURROUNDED BY 6-12 CONCENTRIC LAMELLAE OF BONE (HAVERSIAN LAMELLAE-COSTING OF COLLAGEN FIBRES AND CALCIUM SALTS)

• ON THE LAMELLAE ARE SMALL SPACES (LACUNA) CONTAINING OSTEOCYTES,CANALICULI OF ADJACENT OSTEOCYTES CONTACT WITH EACH OTHER FOR TRANSFER NUTRITION TO DISTANT OSTEOCYTES.

• HAVERSIAN CANAL AND SURROUNDING LAMELLAE TOGETHER KNOWN AS- HAVERSIAN SYSTEM/OSTEON

• HAVERSIAN CANALS CONTACT WITH ONE ANOTHER ,WITH PERIOSTEUM AND WITH MARROW CAVITY BY OBLIQUE CANALS- VOLKMANN’S CANAL

• TWO ADJACENT HAVERSIAN SYSTEM ARE SEPARATED BY INTERSTITISIAL LAMELLAE-OLDER REMNANT BONE DUE BONE REMODELLING AND REPAIR

• NEXT TO THE PERIOSTEUM LIE- OUTER CIRCUMFERENTIAL LAMELLAE• NEXT TO THE ENDOSTEUM LIE- INNER CIRCUMFERENTIAL LAMELLAE

BONE

COMPACT BONE

STRUCTURE OF CANCELLOUS/SPONGY BONE

• HAVERSIAN SYSTEM- ABSENT• CONTAIN THIN PLATES OF BONY

TRABECULAE• ADJACENT TRABECULA ENCLOSE

IRREGULAR SPACES-MARRROW SPACES CONTAINING BONE MARROW

• MARGINS OF TRABECULA CONTAIN OSTEOBLAST, OSTEOCLAST

COMPACT BONE AND SPONGY BONE

COMPACT BONE SPONGY BONE

OSTEOGENESIS

PROCESS OF DEVELOPMENT OF BONE

• HAS 2 STEPS(A)OSSIFICATION (PROCESS OF BONE

FORMATION)(B)CALCIFICATION (PROCESS OF DEPOSITION

OF CALCIUM SALTS IN A FORMED BONE SO IT BECOMES HARD)

OSSIFICATION

BONE IS FORMED BY 2 METHODS(A)INTRAMEMBRANOUS OSSIFICATION

(BONES FORMED IN THIS METHOD- MEMBRANE BONES)

(B) ENDOCHONDRAL OSSIFICATION(BONES FORMED IN THIS METHOD-

CARTILAGENOUS BONES)

INTRA MEMBRANOUS OSSIFICATION

PROCESS IN OSTEOBLAST ARE DIFFERTIATED DIRECTLY FROM MESENCHYME AND START SECRETING OSTEOID (UNCALCIFIED BONY MATRIX)

EXAMPLE-MOST FLAT BONES OF THE SKULL- FRONTAL, PARIETAL, TEMPORAL,OCCIPITAL AND MANDIBLE, MAXILLA, CLAVICLE

MEMBRANE BONES

STAGES• MESENCHYMAL CONDENSATION OCCURS IN AREAS OF BONE

FORMATION• MESENCHYMAL CELLS DIFFERTIATE INTO FIBROBLASTS • FIBROBLASTS LAY DOWN COLLAGEN FIBRES• FIBROBLASTS DIFFERTIATE INTO OSTEOBLASTS• OSTEOBLASTS START TO SECRETE BONY MATRIX • THIS UNCALCIFIED BONY MATRIX- OSTEOID• CALCIUM SALTS DEPOSITED IN THE MATRIX AS HYDROXYAPATITE

CRYSTALS• CALCIFIED BONY MATRIX FORMED• SOME OSTEOBLASTS GETS TRAPPED IN THIS CALCIFIED MATRIX AND

ARE CONVERTED INTO OSTEOCYTE, THESE OSTEOCYTE LIE IN LACUNA• THIS NEWLY FORMED BONE IS SPONGY BONE• MESENCHYME SURROUNDING THE SPONGY BONE FORMS

PERIOSTEUM EXTERNALLY & ENDOSTEUM INTERNALLY

INTRAMEMBRANOUS OSSIFICATION

INTRAMEMBRANOUS OSSIFICATION

ENOCHONDRALOSSIFICATION

:PROCESS WHERE BONE FORMATION IS PRECEEDED BY A CARTILAGENOUS MODEL WHICH IS FINALLY CONVERTED INTO BONE

:HAS 3 STAGES- (A) PRIMARY CENTRE OF OSSIFICATION AT THE DIAPHYSIS (B) SECONDARY CENTRE OF OSSIFICATION AT THE EPIPHYSIS (C) FUSION O EPIPHYSIS AND DIAPHYSIS

:EXAMPLE- LONG BONES :CARTILAGENOUS BONES

STAGES• AT THE AREA OF BONE FORMATION MESENCHYMAL CELLS FORM CARTILAGENOS MODEL• MESENCHYMAL CELLS DIFFERTIATE INTO CHONDROBLAST • THESE CHONDROBLASTS FORM PERICHONDRIUM AND LAY DOWN CARTILAGENOUS MATRIX• SOME CHONDROBLAST GETS ENTRAPPED WITHIN THE MATRIX AND ARE CONVERTED INTO

OSTEOCYTE• THESE OSTEOCYTE BECOME HYPERTROPHIED AND DUE LACK OF NOURISHMENT DIE AND

DEGENERATE, LEAVING EMPTY SPACES (AREOLAE)• A VASCULAR BUD INVADES THESE EMPTY SPACES, CARRYING WITH IT OSTEOBLAST ANS

OSTEOCLAST• OSTEOCLAST EATS UP MOST OF THE EMPTY SPACES & LARGE SECONDARY SPACES ARE NOW

FORMED• SMALL UNERODED MATRIX SERVES AS A BASE UPON WHICH OSTEOBLAST START LAYING

OSTEOID IN A MANNER SIMILAR TO MEMBRANE BONES• THUS MANY LAMELLAE OF BONE IS FORMED• THE PRIMARY CENTRE OF OSSIFICATION IS NOW ESTABLISHED• ALL THE ABOVE EVENTS TAKE PLACE AT THE DIAPHYSIS• OSTEOCLASTIC RESORBTION FORMS SPONGY BONE AT THE DIAPHYSIS WHICH FORMS THE

MARROW CAVITY• CARLAGENOUS MODEL CONTINUES TO GROW LONTUDINALLY TOWARD EPIPHYSIS

CONT.• SIMILAR EVENTS OCCUR AT THE EPIPHYSIS• THESE OCCUR LATER THAN THE PRIMARY CENTRE

EVENTS• THESE EVENTS ARE KNOWN AS SECONDARY CENTRE

OF OSSIFICATION• EPIPHYSIS IS FORMED BY SECONDARY CENTRE

EVENTS• PRIMARY & SECONDARY CENTRE OF OSSIFICATION

ARE SEPARATED BY EPIPHYSIAL GROWTH PLATE• FINALLY THE DIAPHYSIS & EPIPHYSIS UNITE AS

GROWTH IS COMPLEATED

ENDOCHONDRAL OSSIFICATION

BONE GROWTH • BY LENGTH AND THICKNESS• LENGTH- EPIPHYSIAL GROWTH PLATE- AT THE

EPIPHYSIS• THICKNESS-AT THE DIAPHYSIS- APPOSITIONAL

METHOD-BY CONTINUOUS DEPOSITION OF BONES BY OSTEOBLASTIC ACTIVITY OF TE OSTEOPROGENITOR CELLS OF THE PERIOSTEUM

• BONE REMODELLING• YOUNG AGE AND OLD AGE CHANGES• HORMONAL EFFECTS- PTH, VITAMIN D,

CALCITONIN,GH,OESTEROGENS,THYROXINE, CORTISOL

COMPARISON

APPLIED HISTOLOGY

• RICKETS & OSTEOMALACIA & SCURVY• OSTEITIS FIBROSA CYSTICA• OSTEOPETROSIS• OSTEOPOROSIS• GIGANTISM & ACROMEGALY• OSTEOSARCOMA• OSTEOMYELITIS• FRACTURE• BONE GRAFTS