BONE+LECTURE+ONE - Bone Bone Anatomy and Physiology...

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Unformatted text preview: Bone Bone Anatomy and Physiology Function of Bone Function of Bone • Support for the body: endoskeleton vs. • • • • • exoskeleton Protection of other organs Mechanical leverage for movement Storehouse for calcium Maintains mineral homeostasis Aids in maintaining acid/base balance Types of bone Types of bone • Compact bone­ dense bone composed of the Haversion system/ osteons. These bones make up the “walls” of long bones, as well as flat bones. • Cancellous bone­trabecular bones that line the marrow cavities. This bone is composed of numerous bone spicules. Types of bone Types of bone • Woven bone­ immature formation of bone at fracture sites. Cell types of bone Cell types of bone • Osteoblasts­ bone progenitor cells that secrete collagen matrix and ground substance which ultimately becomes osteoid (cartilage­like substance which eventually mineralizes). Cell types of bone Cell types of bone • Osteocytes­ bone cells originating from oseoblasts trapped in the osteoid during formation. These cells have processes extending into the canaliculi throughout the bone. Cell types of bone Cell types of bone • Osteoclasts­ large multinuclear cells responsible for bone absorption. These cells are controlled by parathyroid hormone. Bone growth Bone growth • Intramembranous ossification­ flat bones (skull for example) grow by ossification of the membranes between them (sutures). Bone growth Bone growth • Endochondral ossification­ occurs at the physis (growth or epiphyseal plate). Cartilaginous cells divide and mineralize as they mature. Bone growth Bone growth • Heteroplastic bone growth­ results from disease processes such as cancer, certain infections, etc.. • The only “normal” heteroplastic growth is the os penis of certain species and the os cordis of the bovine heart. Fractures Fractures • Greenstick­ cortical fractures involving only one side of the bone. These fractures get their name from the appearance of a fractured green stick. The bone appears bent. Fractures Fractures • Complete fractures­ both sides of the cortex are broken. • Two types­ simple and compound Simple complete fractures Simple complete fractures • Both cortices broken, but skin is intact Compound complete fractures Compound complete fractures • Both cortices are broken, and the bone has penetrated the skin. • Very common injury at the racetrack • Very difficult to manage due to wound contamination, infection, wound care, etc.. Comminuted fractures Comminuted fractures • Complete fractures involving many pieces of bone. • May be closed or compound Epiphyseal fractures Epiphyseal fractures • Known as “Salter” fractures • Type 1­ complete fracture at the growth plate. Cells of the growth • • • • • plate remain with the epiphysis. Type 2­ complete fracture through part of the epiphysis, extending out through a region of the metaphysis. Type 3­ complete intraarticular fracture extending from the articular surface of the bone down to the physis, then along the plate to its periphery. Type 4­ complete intraarticular fracture extending from the joint surface across the physis and into the metaphysis. Type 5­crushing injury to growth plate Type 6­injury (not necessarily fracture) resulting in bridging the metaphysis and epiphysis. Resulting bone growth in young animals leads to crooked bones. Salter­Harris Bone Injuries Salter­Harris Bone Injuries Bone healing Bone healing • At the time of the fracture, blood vessels in and around • • • the bone are disrupted, leading to hemorrhage and subsequent hematoma formation. The fracture site releases osteoblasts from the endosteum and periosteum as well as from the haversian canals. These osteoblasts deposit new disorganized organic bone matrix with subsequent mineral deposition. This is called a callus. Over time the callus will remodel and become organized bone. Bone Anatomy Bone Anatomy • Periosteum­ the outer covering of bone consisting of a thin membrane. • Endosteum­ the inner lining of bone • Marrow­ the center cavity of bones which is the site of hematopoiesis and a site for fat storage. Bone Anatomy Bone Anatomy • Articular cartilage­ the smooth avascular bearing surface of the bone, generally found within a joint. • Epiphysis­ literally “upon growth”. This is the region around the physis in which endochondral ossification occurs. • Metaphysis­ the flared region of the bone • Diaphysis­ the shaft of the bone Bone Anatomy Bone Anatomy • • • • Head­ a spherical articular projection Condyle­ a cylindrical articular mass Fossa­ a large non­articulating depression Foramen­a circumscribed hole in a bone ...
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This note was uploaded on 03/09/2010 for the course MARB 1000 taught by Professor Hayes during the Spring '07 term at Texas A&M University-Galveston.

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