Bone (basic)
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The document provides a detailed overview of bone structure, function, classification, and growth, highlighting the composition of bones, including organic and inorganic components. It specifies various types of bones based on shape, development, and classification criteria, as well as the roles of bone marrow and vascular supply. Additionally, it describes the process of bone growth, including length and thickness, along with the mechanisms of remodeling.
Bone (basic)
- 2. Definition • 1/3 connective tissue • 2/3 impregnated with calcium • Highly vascular • Greater regenerative power • Characteristic pattern of growth • Mould itself according to change in stress and strain • Constant turnover of its Ca content • Absence of Ca salt due to acid the bone becomes flexible (tied as a ‘knot’) • Absence of collagen due to burning the bone crumples into pieces
- 3. • It has two components: Organic component Inorganic component a) Consists of connective tissue (collagen fibers) a) Consists of Ca salts (Ca phosphate, partly Ca carbonate) b) Tough and resilient (flexible) b) Hard and rigid c) Resistant to tensile forces c) Resistant to compressive forces of WB and impact forces of jumping d) salt: Calcium hydroxyapatite
- 4. Function • Gives shape and support to the body • Resistant to any form of stress • Provide surface for the attachment of muscles, tendons, ligaments • Serve as levers for muscular action • Bone marrow manufactures blood cells • Store 97% of the body Ca and P • Bone marrow contains reticuloendothelial cells which are phagocytic in nature and take part in immune response of the body
- 5. Classification A) According to shape: 1. Long bones: • Has an elongated shaft (diaphysis) • 2 expanded ends (epiphysis) • Smooth and articular • Has 3 surfaces, 3 borders, central medullary cavity, nutrient foramen a) Typical long bones: humerus, ulna, radius, femur, tibia and fibula b) Short long bones: MC, MT, Phalanges c) Modified long bones (no medullary cavity): clavicle
- 7. 2) Short bones: a) Shape is usually cuboid (cube) or scaphoid (boat) b) Pierced by blood vessels c) Tarsals and carpals
- 8. 3) Flat bones: a) Resemble shallow plates b) Form boundaries of certain body cavities c) Cranium, sternum, ribs and scapula
- 9. 4) Irregular bones: hip bone, first and second cervical vertebra, sphenoid 5) Pneumatic bones: a) Large air spaces lined by epithelium b) Maxilla, sphenoid, ethmoid c) They: i) make the skull light in weight ii) help in resonance of voice iii) act as air conditioning chambers iv) improves timbre of the voice
- 12. 6) Sesamoid bones: • Bony nodules • Found embedded in the tendon or joint capsules • No periosteum • Ossify after birth • Related to an articular and non- articular bony surface • Surfaces of contact are covered with hyaline cartilage • Lubricated by bursa or synovial membrane • Function: a) To resist pressure b) To minimise friction c) Alter the direction of pull of muscle d) Maintain local circulation, protect the vessels and nerves e) E.g: patella, pisiform
- 14. 7) Accessory bones: • Not always present • May occur as ununited epiphysis developed from extra centres of ossification • Cervical rib, sutural bones of the skull • Often bilateral • Smooth surfaces without any callus
- 15. B) Developmental classification 1 a) Membrane (dermal) bones: • Ossify in membrane • Intramembranous or mesenchymal ossification • Frontal, parietal and maxilla b) Cartilaginous bones: • Ossify in cartilage • Intracartilaginous or endochondral ossification • Humerus, femur, vertebraes and thoracic cage c) Membrano- cartilaginous bones: • Ossify partly in membrane and partly in cartilage • Clavicle, mandible, occipital, temporal, sphenoid.
- 16. 2 a) Somatic bones: • Most of the bones are somatic b) Visceral bones: • Develop from pharyngeal arches • Hyoid bone, part of mandible and ear ossicles
- 17. C) Regional classification: 1) Axial skeleton: skull, vertebra and thoracic cage 2) Appendicular skeleton: bones of the limbs
- 18. D) Structural classification: I. Macroscopically: a) Compact: • Dense in texture • Extremely porous • Best developed in the cortex of long bones • Adaptation to bending and twisting forces b) Cancellous: • Open in texture • Made up of meshwork of trabeculae (rods and plates) • Between which are marrow containing spaces • Types of meshwork: i) meshwork of rods ii) Meshwork of rods and plates iii) meshwork of plates • Adaptation to compressive forces
- 20. Compact Cancellous Location Diaphysis Epiphysis Lamellae Arranged to form Haversain system Arranged in a meshwork Bone marrow Yellow which stores fat after puberty. Red before puberty Red, produce RBC’s, granular series of WBC and platelets
- 21. II Microscopically: a) Lamellae bone (including compact and cancellous): • Composed of thin plates of bone tissue (lamellae) • Arranged as branching curved plates in cancellous • Arranged as concentric cylinders in compact b) Woven bone: • Seen in fetal bones, fracture repair and cancer of bone • Bone crystals and collagen fibres are arranged randomly c) Fibrous bone: • Found in young fetal bones • Common in reptiles and amphibia d) Dentine and e) cement occur in teeth
- 23. Gross structure A Shaft: composed of: • Periosteum • Cortex • Medullary cavity a) Periosteum: thick fibrous membrane Covering the external surface of bone Made up of: i) outer fibrous layer ii) inner cellular layer (osteogenic in nature) United to the underlying bone by Sharpey’s fibres At articular margin continuous with the capsule of joint Rich nerve supply Absent in sesamoid bone Function: i) osteogenic ii) bone growth iii) bone repair iv) protection
- 25. b) Cortex: • Made up of compact bone • Gives it the desired strength to withstand all strain c) Medullary cavity: • Lined by endosteum • Osteoblasts help in bone repair and remodelling • Filled with red or yellow bone marrow • Red marrow persists in the cancellous ends of long bones • Sternum, iliac crest, vertebra, ribs B. 2 Ends: • Made up of cancellous bone • Covered with hyaline cartilage
- 27. Parts A Epiphysis: • Ends and tips of a bone • Ossify from secondary centres I. According to number of epiphysis: a) Simple: • ends develop from many epiphyses • Fuse independently with shaft • Femur b) Compound: • Ends develop from many centres which unite to from a single epiphysis • Single epiphysis fuse with the shaft • Humerus
- 28. II. Based on function: a) Pressure epiphysis: • Articular • Takes part in the weight transmission • E.g: head of humerus, head of radius b) Traction epiphysis: • Non articular • Does not take part in the weight transmission • Provides attachment to one or more tendon which exert traction • Ossify later than the pressure epiphysis • E.g: trochanter of femur, tubercles of humerus
- 29. c) Ativastic epiphysis: • An independent bone • Fused to another bone • E.g: coracoid process, lateral tubercle of posterior process of talus d) Aberrant epiphysis: • Not always present • E.g: epiphysis at the head of Ist MC, bases of other MC bones
- 31. B Diaphysis: • Elongated shaft • Ossifies from a primary centre • Receives blood supply from nutrient artery
- 32. C Metaphysis: • Epiphyseal ends of a diaphysis • Zone of active growth • Richly supplied with blood through end artery forming ‘hair-pin’ ends (before epiphyseal fusion) • Common site of osteomyelitis (because the bacteria or emboli are easily trapped in the ‘hair-pin’ ends) • After epiphyseal fusion there is vascular communication between metaphysial and epiphyseal artery, hence no more end artery because of which no chances of osteomyelitis • Maybe of two types: i) Intracapsular: both ends of humerus ii) Extracapsular: upper and lower ends of radius and ulna
- 34. D Epiphyseal plate of cartilage: • Separates epiphysis from metaphysis • Proliferation of cells in this plate is responsible for lengthwise growth of a long bone • After epiphyseal fusion, no longer grow in length • Nourished by both the epiphyseal and metaphyseal artery
- 35. Blood supply AArterial supply: 1) Young long bones: a) Nutrient artery: • Enters the shaft through the nutrient foramen • Runs through the cortex • Divides into ascending and descending branches • Turn down to form hairpin bends • Each branch divides into a number of small parallel channels • Terminate in the adult metaphysis by anastomosing with the epiphyseal, metaphyseal and periosteal artery • Supplies medullary cavity, inner 2/3 of cortex and, metaphysis • E.g: upper end of humerus, lower end of radius and ulna, lower end of femur and upper end of tibia • Nutrient foramen is directed away from the growing ends of bone
- 36. b) Periosteal artery: • Numerous beneath the muscular and ligamentous attachments • Ramify beneath the periosteum • Enter the Volkmann’s canals to supply the outer 1/3 of the cortex c) Epiphyseal artery: • Derived from vascular arcades (circulus vasculosus) • Found on the non articular bony surface d) Metaphyseal artery: • Derived from the neighbouring systemic vessels • Pass directly into the metaphysis • Reinforce the metaphyseal branches from the primary nutrient artery
- 38. 2) Long short bones: • Nutrient artery enters the middle of shaft • Divides to form plexus • Infection begins in the middle of shaft • Periosteal artery supplies major part of bone • May replace the nutrient artery 3) Short bones: • Supplied by numerous periosteal vessels which enter their non articular surfaces
- 39. 4) Vertebra: • Supplied by anterior and posterior vessels (body) • Vertebral arch by large vessels entering the base of transverse process • Red marrow is drained by 2 large basivertebral veins 5) Rib: • Nutrient artery which enters it just beyond the tubercle • Periosteal artery
- 40. B) Venous drainage: • Numerous and large in cancellous bone • Accompany artery in the Volkmann’s canals (compact bone) C) Lymphatic drainage: • Some do accompany the periosteal blood vessels • Drain to the regional lymph nodes
- 41. Growth of long bone • Length: multiplication of cells in the epiphyseal plate of cartilage • Thickness: multiplication of cells in the deeper layers of periosteum • Grow by deposition of new bone on the surface and at the ends (appositional growth) • Remodelling: unwanted bone is removed by osteoclasts