Bone i

BONE-I DR. SADAF AZIZLECTURER, NORTHWEST COLLEGE OF PHYSICAL THERAPY

TODAY’S LECTURE

Bone Classification of bone Parts of developing long bone Gross structure of bone Development of bone

WHAT IS BONE?

One-third organic connective tissue. Makes it tough & resilient. Afford resistance to tensile forces.

Two-third inorganic calcium salts. Makes it hard & rigid. Afford resistance to compressive forces of weight- bearing and impact forces of jumping.

Living tissue & highly vascular. Greater regenerative power. Mould itself to changes in stress. Shows disuse atrophy & overuse hypertrophy

GROSS STRUCTURE OF AN ADULT LONG BONE

SHAFT Perisoteum Cortex Medullary cavity

THE TWO ENDS Cancellous bone covered with hyaline cartilage

PARTS OF A YOUNG BONE

Primary center & secondary center1. Epiphysis2. Diaphysis3. Metaphysis4. Epiphysial plate of cartilage

1. EPIPHYSIS

The ends & tips of bone which ossify from secondary centres Pressure epiphysis Traction epiphysis Atavistic epiphysis Aberrant epiphysis

2. DIAPHYSIS

Elongated shaft of bone which ossify from a primary center

3. METAPHYSIS

The epiphyseal end of a diaphysis Zone of active growth, hair-pin bends Common site of osteomyelitis in children after the epiphyseal fusion vascular communications establish

between metaphysical and epiphyseal arteries.

4. EPIPHYSEAL PLATE OF CARTILAGE

Separates epiphysis from metaphysis Lengthwise growth of a long bone After epiphyseal fusion, the bone can no longer grow in length

DEVELOPMENT & OSSIFICATION OF BONES

Bones first laid down as mesodermal (connective tissue) condensations Conversion of mesoderm into bone is Intramembranous/ mesenchymal

ossification. The bones are called Membrane (dermal) bones Conversion of cartilaginous model into bone is called Intracartilaginous /

endochondral ossification. The bones are called Cartilaginous bones Ossification takes place by centers of ossification Primary centers forms diaphysis Secondary centers form epiphysis Fusion of epiphysis with diaphysis starts at puberty and complete by age of

25 years Law of ossification Growing end of bone

GROWTH OF BONE

CLASSIFICATION OF BONES

A. According to shapeB. Developmental classificationC. Regional classificationD. Structural classification

A. ACCORDING TO SHAPE

1. LONG BONES

Diaphysis & epiphysis. Shaft separated by 3 borders. Nutrient foramen

EXAMPLES: Typical long bone, humerus, radius , ulna Miniature long bone, metacarpals, metatarsals, phalanges Modified long bone, clavicle

2. SHORT BONES

Shape is cuboid, cuneiform, trapezoid , scaphoid.

EXAMPLE: Tarsal & carpal bones

3. FLAT BONES Resemble shallow plates and form boundaries of body cavities

EXAMPLE: Bones in the vault of skull, ribs, sternum and scapula

4. IRREGULAR BONE

Vertebrae, hip bone, bone in the base of skull

5. PNEUMATIC BONES

Irregular bones containing large air spaces lined by epithelium

EXAMPLES: Maxilla, sphenoid, ethmoid

6. SESAMOID BONES

Bony nodules found embedded in tendons or joint capsules. No periosteum, ossify after birth. Surface of contact are covered with hyaline cartilage and

lubricated by bursa or synovial membrane

EXAMPLES: Patella, pisiform, fabella etc

7. ACCESSORY BONES

Not always present . May occur as un-united epiphysis developed from extra centres

of ossification

EXAMPLES: Sutural, lateral tubercle, tuberosity of 5th metatarsal

8. HETEROTROPIC BONES

Bones sometimes develop in soft tissues Rider’s horse

B. DEVELOPMENTAL CLASSIFICATION

1. MEMBRANE BONES

Ossify in membrane Intramembranous or mesenchymal ossification Derived from mesenchymal condensations

EXAMPLES: bones of vault of skull and facial bones

2. CARTILAGINOUS BONES

Ossify in cartilage Intra-cartilaginous or endochondral ossification Derived from preformed cartilaginous models

EXAMPLES Bones of limbs, vertebral column, thoracic age

3. MEMBRANO-CARTILAGINOUS BONES

Ossify partly in bones and partly in cartilage

EXAMPLE Clavicle, mandible, occipital, temporal , sphenoid

4. SOMATIC BONES

Most of the bones are somatic

5. VISCERAL BONES

Develop from pharyngeal arches

EXAMPLES Hyoid bones, part of mandible, ear ossicles

C. REGIONAL CLASSIFICATION

Axial skeleton Appendicular skeleton

D. STRUCTURAL CLASSIFICATION

Macroscopically Compact bone Cancellous/ spongy bone

Wolf’s Law Pressure Lamellae Tension lamellae

WOLFF’S LAW

PRESSURE & TENSION LAMELLAE

Microscopically; Lamellar bone Woven bone Fibrous bone Dentine Cement

LAMELLAR BONE

WOVEN BONE

DENTINE & CEMENT

BLOOD SUPPLY OF BONE

SELF STUDY….

Functions of bone Growth of a long bone

THE END…!!