BONE

CAPT DR POONAM SINGH

BONE

1. INTRODUCTION2. FUNCTIONS3. CLASSIFICATIONS4. PARTS OF GROWING

LONG BONE5. BLOOD SUPPLY OF A

LONG BONE6. HISTOLOGY7. DEVELOPMENT8. APPLIED

INTRODUCTION

• Specialized CT with a solid matrix which is mineralized & adapted for giving strength, support & helping in wt transmission.

• Inorganic material ( calcium phosphate, traces of other salts..) provides hardness & rigidity to the bone radiopaque in XR.

FUNCTION1. Shape & support

( forms framework)2. Protection3. Movement4. Storage5. Blood cell formation6. PNS:- Resonance to

voice

REGIONAL CLASSIFICATION

Axial skeleton (80) Skull & facial bones Vertebral column Thoracic cage

Appendicular skeleton (126) Upper limb: Girdle & free bones Lower limb: Girdle & free bones

206 number is not exact; varies

DEVELOPMENTAL CLASSIFICATION

1) Membranous bones• Ossify in membrane • Derived from mesenchymal condensation

Bones of skull vault & facial bones

2) Cartilaginous bones• Ossify from cartilage• Derived from preformed cartilage models

Bones of limbs & vertebral column

3) Membrano-cartilaginous bones• Dev by both

STRUCTURAL CLASSIFICATION (MACROSCOPICALLY)

1. COMPACT BONE:- - Hard & dense , resembles ivory - No visible spaces.

• Consists of :- - Lamellae of collagenous sheets - Haversian system / Osteons

COMPACT BONE

Lamellae :- 3 types1. Concentric: surrounds Haversian canal

2. Interstitial: lie between osteons

3. Circumferential: flat plates extend around the bone

STRUCTURAL CLASSIFICATION (MACROSCOPICALLY)

2. CANCELLOUS BONE:-- Sponge work of trabeculae,

trabeculae are oriented along lines of stress.

- Large spaces filled with red bone marrow.

- Osteoblasts +nt on their surfaces.

STRUCTURAL CLASSIFICATION(MICROSCOPICALLY)

1). Woven bone- Warp & weft of a woven fabric.- Eg.. Young fetal bones Callus at # sites

2). Lamellar bone- mineralized matrix arrange in thin layers.- 2 diff patterns a) concentric cylindrical units. Eg. Compact bone b) branching & anastomosing curved plates. Eg. Spongy

bone

MORPHOLOGICAL CLASSIFICATION

1. Long bones2. Short bones3. Flat bones4. Irregular bones5. Pneumatic bones6. Sesamoid bones7. Accessory bones

LONG BONES

- Length exceeds the breadth & thickness. - confined to limbs - one elongated shaft & 2 expanded ends - Shaft has medullary cavity, typically has 3

borders & 3 surfaces - Ossify in cartilage: 1 primary and 2

secondary ossification centre - Are weight bearing

- May be– Typical- Humerus– Miniature- One epiphysis

(Metatarsals)– Modified- No medullary cavity

(Clavicle)

SHORT BONES

• Cubical or modified cubes

• Have generally 6 surfaces; 4/ less are articular, & 2/ more for attachments of ligaments & for blood vessels to enter

• Develop in cartilage

• Begin to ossify after birth

– Eg..Carpals & tarsals

Flat bones

• Resemble sandwiches

• Consists of two layers of compact bone & marrow spread between them

• Form boundaries of certain bony cavities

– Eg..Bones of skull vault, Scapula

IRREGULAR BONE

• Irregular or mixed shape

• Composed of spongy bone & marrow in compact covering bone

– Eg..Vertebrae, Hip bone

PNEUMATIC BONE• Irregular bones which contain

air spaces lined with mucous membrane

• Typically in skull bones

• Make the skull light

• Impart resonance to voice

• Act as conditioning chambers for inspired air– Eg..Maxilla, Ethmoid

SESAMOID BONES -Develop in some tendons -Periosteum absent -Rubbing surface is covered with articular cartilage-Appear after birth usually by multiple centers-Lacks haversian systems.

Functions1) Minimize friction2) Alter direction of pull of muscle3) Act as pulleys for muscle contraction

Eg….Patella, Pisiform

ACCESSORY BONES

• Generally not +nt in our body

• s/t clinicians confuse with fractures

• Formed due to non fusion of epiphysis

• Appearance of extra ossification centers in skull

GENERAL STRUCTURE

1. Outer surface: Periosteum ( dense fibrous CT)

-Tendons & ligaments attach to bone & become

continuous with fibers of periosteum. - Sharpy’s fibers: some collagen fibers of

tendons or ligaments penetrate the periosteum and into the bone. Strengthen attachment of tendon or ligaments to bone.

2. Bony cavities: Endosteum (thin CT) Bone marrow ( red & yellow) More cellular

PARTS OF GROWING LONG BONE

• 2 ends & a shaft.

• Before ossification:- 1). Epiphysis - types 2). Epiphyseal plate 3). Metaphysis 4). Diaphysis

BLOOD SUPPLY OF LONG BONE1. Nutrient / Medullary Artery

• Main artery of shaft

• Enters at nutrient foramen; runs obliquely thru cortex

• Divides into ascending & descending branches in medullary cavity

• Each subdivides into small parallel channels terminating in metaphysis

• Supplies: Medullary cavity, Inner 2/3 cortex & Metaphysis

3

1 2

4

BLOOD SUPPLY OF LONG BONE2. Periosteal arteries:• Enter at many points , numerous, ramify

beneath the Periosteum• Enter the bone thru Volkmann's canal• Supply: Outer 1/3rd cortex

3. Epiphyseal arteries: From periarticular vascular arcade

4. Metaphyseal arteries: derived from neighboring arteries & enter the

metaphysis directly along the attachment of jt capsule

MICROSCOPIC STRUCTURE OF BONE

• Cells + Matrix ( ground substance + fibers)

Fibers:- Type I collagen fibers -mechanical strength & elasticityGround substance:- 1) 1/3 Organic:- Proteoglycans, glycoprotein,.. 2) 2/3 inorganic:- Hydroxyapatite CaPO4 crystals

IN MATURE BONE10-20%= Water60-70%= Inorganic mineral salts30% = CollagenRemainder= Non-collagenous protein & carbohydrates

BONE CELLS

• CELLS:- 5 Types1. Osteoprogenitor

cells2. Osteoblasts3. Osteocytes4. Bone lining cells5. Osteoclasts

OSTEOPROGENITOR CELLS

• Derived from mesenchymal stem cells.

• Osteoblasts precursor cells.

• Flattened , elongated ovoid nuclei.

• Transcription factor CBFA1 ( RUNTX2)

• Location:- Periosteum, endosteum, stromal component of BM.

OSTEOBLAST

• Differentiated bone- forming cell that secretes bone matrix.

• Shape:- Cuboidal / polygonal.• Nucleus:- eccentric

• fxns: 1.Synthesize & secrete osteoid 2. Mineralization of matrix

OSTEOCYTES

• Mature bone cell enclosed by bone matrix.

• Oval, 25µ in long axis• Prominent nucleus• Cell lacunae

Processes Canaliculi

• Fxn:- 1)Maintains bone tissue. 2)Mechanotransduction.

3)Calcium homeostasis

BONE LINING CELLS

• Inactive Osteoblasts.• Flattened

• 2 types:--Periosteal cells

-Endosteal cells

OSTEOCLASTS• Large , multinucleated

cells found at sites where bone is being removed.

• Cells lie in pit:- Resorption bay (Howship’s lacunae).

• Helps in resorption of bone and remodeling.

OSTEON

Bone Ground Section T.S

Bone Ground Section L.S

Compact Bone TS (H&E)

Spongy Bone/ Trabecular Bone

Bone Development

• All the bones develop from a mesenchyme.• Two types of ossification:-1) Intramembranous -Takes place in connective tissue membrane.

2) Intracartilaginous/ Endochondral -Takes place in cartilage.

INTRAMEMBRANOUS OSSIFICATION• Takes place in CT membrane formed from embryonic

mesenchyme

• Skull bones, Part of mandible, Diaphyses of clavicles

• Centers of ossification: appear in membrane where ossification begins (centers of ossification expand outwards to form a bone by gradually ossifying the membrane)

• Fontanels: large membrane-covered spaces between developing skull bones; unossified (bones eventually grow together

& all fontanels have closed by 2 years of age)

INTRACARTILAGINOUS OSSIFICATION• Cartilage formation begins at end of 4th wk of

development.

• Some ossification begins at about 8th wk; some does not begin until 18-20 years of age.

• Bones of the base of the skull, Part of the mandible, Epiphyses of the clavicles, Remaining bones of skeletal system.

INTRACARTILAGINOUS OSSIFICATION

Zones of the Epiphyseal Plate

Growth in Bone Length

FRACTURE OF BONE

1. Simple / closed #2. Compound / open #

T/t :- realigning the broken ends & then immobilizing them until # is healed.

REPAIR OF FRACTURE

RICKETS• Softening of bones in immature

mammals• Frequent chilhood disease in many

developing countries• Cause:-1). deficiency or impaired metabolism

of vitD, phosphorous or Ca++ fractures and deformity.

2). severe diarrhea and vomiting may be the cause of the deficiency

3). severe malnutrition

OSTEOMALACIA

• softening of the bones caused by defective bone mineralization.

• Cause:- - inadequate amounts of available phosphorus and calcium - overactive resorption of calcium from the bone as a result

of hyperparathyroidism. - vitamin D deficiency

• Signs:- diffuse body pains muscle weakness fragility of the bones

OSTEOMYELITIS• infection and inflammation of the bone or

bone marrow.OSTEOPOROSIS• Bone mineral density(BMD) is reduced• bone micro architecture deteriorates• the amount and variety of proteins in bone are

altered. • Fractures are the most dangerous aspect of

osteoporosis.

OSTEOPHYTE (bone spur)

-commonly referred to as bone spurs or parrot beak-bony projections that form along joint margins

Sites:- 1) Back of the spine.2) Feet either along toes or heel.3) Hands.

Osteophytes on the fingers & toes :- Heberden’s node,if +nt on the distal interphalangeal joint & Bouchard’s node, if +nt on the proximal IP jt.

POSHITIS• Poshitis is a concept conceived in 2013

describing a Girl that Carry a heavy handbag and get sick of it.

• The name is derived from Victoria Beckham's use of heavy handbag's.

THANK YOU