Bones and ossification
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The document discusses the processes of intramembranous and endochondral ossification, the classification and structure of bone, as well as the cellular components involved in bone development. It outlines the mechanics of ossification, including the primary and secondary centers of ossification, and provides insights into applied anatomy and related disorders. The conclusion emphasizes the dynamic nature of bone, highlighting the balance between bone formation and resorption in disease contexts.
Bones and ossification
- 2. INTRAMEMBRANOUS AND ENDOCHONDRAL OSSIFICATION Presented by Ashok kumar A Department of Orthodontics
- 3. SYNOPSIS • Introduction • Classification of bone • Gross structure of bone • Composition of bone • Cells of bone • Ossification • Applied anatomy
- 4. INTRODUCTION Bone is essentially a highly vascular, living, constantly changing, mineralized connective tissue. Bones protect the various organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility.
- 6. Size and shape • Long bones • Short bones • Flat bones • Irregular bones • Pneumatic bone • Sesamoid bone • Supernumerary bone
- 7. Gross structure STRUCTURE OF BONE GROSS • COMPACT (lamellar) • CANCELLOUS (spongy) • DIPLOIC BONE MICROSCOPIC • WOVEN(Immature) • LAMELLAR(Mature)
- 8. Development Membranous Bones ossify in membrane (intramembramous or mesenchymal Ossification) Eg. Bones of Vault of Skull & Facial Bones Cartilagenous Bones ossify in cartilage (intracartelagenous or endochondral Ossification) Eg.Bones of Limbs, Vertebral Column & Thoracic Cage Membrano-Cartilagenous (Bones ossify partly in membrane and partly in cartilage) Eg. Clavicle ,Mandible, Occipital, Temporal, Sphenoid
- 9. Composition of bones Bone Inorganic 67 % Organic 33 % Collagen 88-89 % Non Collagen 11-12% Calcium & phosphate (Hydroxyapatite) Glycoproteins Glycosaminoglycans water Type -I Collogen fibers –toughness & resilience Inorganic salts –rigitidy & hardness
- 10. Cells of Bone
- 11. Osteoprogenitor cells • Mesenchymal in origin • Fibroblast like cells with an Elongated nucleus & few organelles • Present in the deepest layer of periosteum and lining vascular canals of compact bone.
- 12. Osteoblast • Ovoid cells with basophilic cytoplasm & oval nucleus • Inner layer of periosteum & endosteum Function -Role in formation of bone matrix -Role in Calcification (through Alkaline phosphatase enzyme) -Synthesis of protein
- 13. Osteocyte • Maintain integrity of lacunae & Canaliculi • Play role in removal or deposition of matrix & of calcium • Skeletal maintenance
- 14. Osteoclast • Large multi-nucleated giant cells with acidophilic cytoplasm • Derived from the Hematopoietic Stem Cells • Found within the Howship’s Lacunae Ruffled membrane
- 15. CENTER OF OSSIFICATION 1. PRIMARY CENTER OF OSSIFICATION - Ossification starts at the central part of thecartilagenous model. - Portion of bone develop from this primary center of ossification is called the diaphysis. -This normally appears before birth.( 6th to 8th week foetal life) 2. SECONDARY CENTER OF OSSIFICATION -This appears at the two ends of the long bones. -Usually appear after birth. -The portion of this bone developed is called epiphysis.
- 17. LAWS OF OSSIFICATION 1.Epiphysis that ossify first fuse with diaphysis last & the epiphysis that ossify last fuses first. (Except the lower end of fibula) 2. The end of long bone where epiphysis appears first & fuses last is called growing end of the bone. 3. The direction of the nutrients artery is always away from the growing end. 4. In long bones, growing ends fuse with the shaft at about 20 yrs & opposite end at 18 yrs. 5.In bones other than long bone epiphysis fuses between 20-25 yrs
- 23. Heterotopic Ossification • The abnormal growth of bone in the non-skeletal tissue including muscle, tendons or other soft tissue. • When HO develops,new bone grows at three times the normal rate, resulting in jagged , painful joints Surgery or trauma to the hips and legs
- 26. Applied Anatomy
- 27. Synchondroses • Remains of primary cartilaginous skeleton of cranial base. Synchondroses Age of fusion Interspenoidal At birth Interoccipital 3-5 yrs Speno-occipital 20 yrs Speno-ethmoidal Exactly not known
- 32. CONCLUSION • The response of bone to inflammation includes bone formation as well as resorption. Thus bone loss in disease is not simply a destructive process, but results from the predominance of resorption over formation • Proper understanding of changes seen in the bone in growth and in variety of diseases will help in finding new therapeutic strategies.
Editor's Notes
- #7: Possess hollow space whithin which their body contain air ,it provide economical method of expansion of bone in size & make them lighter. Sesamoid means seed like ,nodules of bones develop in tendon ,has no periosteum no haversian system,ossify after birth,, eg patella Develop in additional ossification center r fail to fuse with main part during developing ,often common in foot mistaken for bone chip or fracture
- #8: 3)))In Woven bone collagen fibers -irregular and has a higher proportion of osteocytes than lamellar bone .temporary & is converted to lamellar bone; this type of bone is pathologic tissue in adults, except in a few places, such as areas near the sutures of the flat bones of the skull, tooth sockets. In lamellar bone Colagen fibers r arranged parallel to each other, the lamellae are concentrically organized around a vascular canal, termed as haversian canal
- #12: Proliferate & covert into osteoblast whenever there is need for bone formation
- #13: Normally, almost all of the bone matrix is mineralized by the osteoblasts. Before the organic matrix is mineralized, it is called the osteoid. During bone formation, consists of cuboidal cells, called active osteoblasts. When the bone-forming unit is not actively synthesizing bone, the surface osteoblasts are flattened and are called inactive osteoblasts.
- #14: These are cells of mature bone . . Osteoblasts buried in the calcified matrix are called osteocytes More in young bone ,decrese with age
- #15: Concerned with resorption of bone during growth & remodelling ,they produce acid phosphatase which dissolve inorganic constituents of bone
- #17: Diaphysis -Process of bone formation extends towards the two ends. .It is the zone of endochondral ossification in an actively growing bone or the epiphyseal scar in a fully grown bone.
- #18: Fusion of epiphysis with diaphysis occurs earlier in women then men .epiphysis also appears earlier in women.
- #19: Begins at second months in vitro. In this type of osteogenesis bone formation is preceded by formation of cartilaginous model that is subseqyently replaced by bone Base of the SkulL & bone of limbs
- #21: Thus the calcified matrix act as a support for bone formation
- #22: Occurs in utero after 8 weeks of fertilization, in this type of ossification formation of bone is not proceded by formation of cartilaginous model ,instead bone laid down directly in a fibrous membrane Eg. Bone of face ,vault of skull ,clavicle
- #23: 3.Some mesenchymal cells enlarge and acquire basophilic cytoplasm & form osteoblast ,,& it secret gelatinous matrix called osteoid around collagen fibers . They deposit Calcium salts into osteoid leading to converstion of osteoid into bone lamella ,
- #28: Cranial base is template by which face develops
- #30: Abnormal masses of bone may be formed in region of metaphysis and protrude form bone. Insufficient or disorderly formation of bone in region of epiphyseal cartilage ,this interfere with growth of long bone .dwarf Limbs are normal vertebral column remains short .
- #31: CONFINED TO MEMBRANE BONE