Anatomy of Bone PDF

APOLLO COLLEGE OF VETERINARY MEDICINE DEPARTMENT OF VETERINARY ANATOMY & HISTOLOGY ANATOMY OF BONE Prepared By:- Dr. GAJENDRA SINGH  Bone ❖ Bones are mineralized connective living tissue...

APOLLO COLLEGE OF VETERINARY MEDICINE DEPARTMENT OF VETERINARY ANATOMY & HISTOLOGY ANATOMY OF BONE Prepared By:- Dr. GAJENDRA SINGH  Bone ❖ Bones are mineralized connective living tissue, its not a static material. ❖ It has its growth and death. ❖ It has blood vessels (Artery & Veins) and nerves supply. ❖ Composed of Compact and Spongy tissue. Characters Forming the basis of skeleton and is a mass of osseous cells. Dens and hard structure. External dens and smooth layer is Compact tissue Internal loose and spongy layer is Cancellated tissue / Spongy tissue. In middle of long bone a hollow space known as Medullary cavity.  Associate Structures 1. Periosteum:- Thick outer membranous layer, but absent over articular ends. Differentiate into Two type membrane- ✓ External fibrous layer- Give attachment to muscle, tendon, ligaments and ramification of blood vessels. ✓ Internal osteogenic layer- Function as bone forming layer and helps to retain the partially fractured fragments. 2. Endosteum:- It lines the medullary cavity of long bones also known as Medullary membrane. It is highly vascularised and nerve supply. 3. Marrow:- It is soft fatty substance, which fill the medullary cavity and space of cancellated tissue of long bones. Two types- Red Marrow- Reddish in colour, Present in young ones Yellow Merrow- Yellowish in colour due to group of fat cells, present in adult animals.  Structure of Bone A. Diaphysis B. Epiphysis C. Metaphysis D. Epiphysial Cartilage Middle part of long bone ❖ Generally forms the ends, 3 ❖ End of diaphysis Plate of Hyaline & form shaft, ossified types----- part towards cartilage, placed from primary ossification ❖ Pressure epiphysis-transmits epiphysis. between diaphysis and center. body weight. E.g. Head & epiphysis in growing Condyles of femur. long bones. ❖ Traction epiphysis- formed by In adult animals it is pull of muscles. E.g. replaced by bone. Trochanter of femur. ❖ Atavistic epiphysis- when one bone is attached on another host bone for nutrition. E.g. Coracoid process of Scapula.  1. Compact tissue A. Haversian system/Osteons:- arrangement of bony tissue in a definite pattern. Contents of Haversian system:- ❖ Haversian canal:- very narrow hollow space pass through the compact substance along the length. It carry blood vessels and nerves. ❖ Haversian lamellae:- Haversian canal surrounded by concentric layer of osseous deposition. It is 2-6 in numbers. ❖ Lacunae:- Between the concentric layer of bone, minute space are present k/as Lacunae, which accommodate bone producing cells-the Osteocytes. ❖ Canaliculi:- Radiate of lacunae. ❖ Haversian cylinder- each unit. ❖ Interstitial lamellae- Triangular space between Haversian system, devoid of Haversian canal and filled up of irregular bony deposit. ❖ Volkmann’s canal/Perforating canal- Small horizontal canals in the bone which transmit blood vessels from periosteum to bone and communicate with Haversian canal. 2. Cancellated tissue:- Consist of thin boney plates in divergent directions, which enclosed space filled with red marrow. Haversian system is absent. In shaft it is small in quantity, but larger at extremities. It is main mass in short and irregular bones.  Bone Cells A. Osteoblast B. Osteoclast C. Osteocytes ❖ Derived from mesenchymal cells. ❖ Multinucleated cells. ❖ Derived from Osteoblast cells. ❖ Produce Ca ions, alkaline ❖ Cytoplasmic process absent, brush ❖ Found in tiny space- Lacunae. phosphatase, which help in border present. ❖ numerous cytoplasmic precipitation of Ca po4 in matrix. So ❖ Form by fusion of Osteoblast cells. processes with centrally placed known Bone forming cells. ❖ Help in Resorption of bone. nucleus. ❖ Nucleus is eccentric, numerous cytoplasmic processes.  Composition of Bones A. Organic Matter B. Inorganic Matter About 30-40% ❖ About 60-70%. Present in the form of Membrane, Cartilage, ❖ Disposed in the form of salt during ossification. Marrow, Vessels, Nerves an Fluids. ❖ The strength and hardness of bone is due to The growth and development of the bone inorganic matter. is possible due to organic matter. ❖ Proportion:- ✓ Calcium Phosphate- 86.00% ✓ Calcium Carbonate- 5.80% ✓ Mg Phosphate- 3.00% ✓ Na Carbonate & Fluoride- 5.20% NOTE- ❖ Proportion of organic and inorganic matter is 1:2, but it may varies with the bone situated on different parts of body. ❖ In growing animals, organic matter is more, which is slowly replaced by inorganic matter.  OSSIFICATION ❖ It is a process of bone formation. ❖ The Calcification is an event in the process of Ossification. 1. Intra-membranous / 2. Intra-cartilaginous / Mesenchymal Ossification Endochondral Ossification E.g. – Bones of Skull E.g. – Most of the Bones of Body. Mesenchymal cells are a small spindle-shaped cells with large nuclei. It is a type of multipotent stem cells that differentiate into various types of connective tissue cells such as fibroblasts, osteoblasts, chondroblasts.  1. INTRAMEMBRANOUS OSSIFICATION Mesenchymal Cells ❖ Periosteum developed by Differentiation at the condensation of mesenchyme. centre of ossification Osteoblast ❖ Osteoblast surrounding bony spicules ✓ Osteoblast produce Collagen fiber meshwork and deposit more calcium to free ends between cells and it become vascularised. and sides. ✓ Osteoblast also produced organic intercellular ❖ Now Calcification spread all over the substance. surface and bone become compact. ✓ Non-calcified matrix known as Osteoid. ❖ Few osteoblast entrapped between matrix and form osteocytes. Trabeculae join together and ❖ Remaining osteoblast divided and form cancellous bone. Matrix is Calcified by arrange in radiating manner from centre Osteoblast and form trabeculae between cells.  2. INTRACARTILAGINOUS OSSIFICATION It is a Three stage ossification Process Mesenchymal tissue Condensation Stage-I At the same time, the osteoblast cells appear at inner layer of perichondrium and form sub-periosteal collar bone around primary ossification center. Now perichondrium is called as periosteum. ❖ Formation of Hyaline Cartilaginous model ❖ Perichondrium appears around cartilage Calcium salt cause death of surrounding cartilage cells and form space between cells known as primary areolae. This zone is primary Ossification center ❖ Chondroblast cell come in mid-section and proliferate by mitosis. ❖ Arranged in radiating manner. Hypertrophic cells produce ❖ Chondroblast became mature and get Precipitation of calcium salt at alkaline phosphatase Matrix – Is known as Calcification hypertrophied.  Peri-osteal Bud contain Stage-II osteoclast, osteoblast, and blood vessels. (Then they enter into Osteoclast absorb irregular calcified mass and form secondary large areolae and form Sub-periosteum collar bone primary ossification center.) marrow cavity. which become filled up by eroded by activity of sub- bone marrow. periosteal Osteoclast. Stage-III Osteoblast appear and laying down Longitudinal groove (True bone formation) lamellated bone appear on outer surface Lining osteoblast of tunnel convert Ridge of each groove Whole process repeat again and it into Haversian system by proliferate and lodge of again and ossification extends proliferation and differentiation blood vessels and longitudinally. into osteocytes. convert into tunnels  Secondary Ossification Centres ❖ Appears at the ends- Epiphysis and ossification occurs in similar way. ❖ At the end of long bone a layer of cartilage does not ossify and remain as articular cartilage throughout the life. ❖ In the growth phase a portion of the cartilaginous model remains as epiphysial cartilage between epiphysis and diaphysis, which helps in longitudinal growth of bone. ❖ This epiphysial cartilage totally replaced by bone, when growth is complete. ❖ Therefore the length of the bone increase with growth of epiphysial cartilage. ❖ The growing part of diaphysis adjacent to epiphysis cartilage known as Metaphysis.  Type of Bones On the basis of gross appearance with regards to their shape, size and structure. 1. Long Bones- ❖ These are long, hollow, cylindrical bones found in limbs. ❖ Weight bearing ❖ Long bones have a shaft and two expended ends. ❖ Shaft contain medullary cavity, which is filled up by bone merrow. ❖ Large muscles of locomotion is attached. ❖ E.g. Femur, Humerus Modified long bones:- The long bones which do not possess medullary cavity. E.g. Clavicle in dog, rabbit, fowl, Ribs. Miniature long bones:- Certain long bones varying in growth they are small long bones. E.g. Small metacarpal 2. Short bones:- ❖ Small piece like bones with smooth surface. ❖ Found in joints. ❖ Help in mobility ❖ Having six surface ❖ Composed of spongy bone with thin outer layer ❖ They increase the mobility of joints by distributing pressure. ❖ E.g. Carpals 3. Flat bones:- ❖ Flat irregular boney plate like. ❖ Enclose body cavity. ❖ Wide and extensive muscles attached ❖ Composed of two plates of compact bone with intervening spongy tissue. ❖ Diploe:- Spongy tissue of cranial vault. ❖ E.g. Scapula, Bones of skull. 4. Irregular bones:- ❖ These are unpaired and irregular shaped bones. ❖ Found in skeleton of vertebral column. ❖ They have many projections and help in the attachment of various muscles ❖ Composed of spongy bones which is covered by compact bones. ❖ E.g. Vertebrae 5. Pneumatic bones:- ❖ Some long bones have cavities inside their bodies which accommodate air cavity through pneumatic foramen. ❖ E.g. Humerus of birds, frontal, maxilla and ethmoid bone of skull in mammals. 6. Sesamoid bones:- ❖ Small seed like structure bone. ❖ Develop within tendon and ossify after birth. ❖ No haversian system and periosteum. ❖ Work as pully to avoid frictions ❖ E.g. Patella, Proximal sesamoid bones. 7. Visceral Bones:- ❖ Found in the viscera of animals and birds. ❖ E.g. Os- optic= Eyes of Birds Os- cordis= Heart of Ox Os- penis= Penis of dog Os- rostrale= Snout of pig Os- phrenic= Diaphragm of camel