Anatomy and physiology Set 3 of 13
Anatomy and physiology Set 3 of 13 A103
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This 12 page Class Notes was uploaded by Tarn Notetaker on Friday November 13, 2015. The Class Notes belongs to A103 at Republic Polytechnic taught by Felicia Liew in Fall 2015. Since its upload, it has received 43 views. For similar materials see Anatomy and Physiology in Natural Sciences and Mathematics at Republic Polytechnic.
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Date Created: 11/13/15
Bones: Bones are organs Strength of bones Ground substance Hydroxyapatite crystals (inorganic substance) → resistant to compression Collagen fibers (organic substances) → resistant to stretch They are composed of multiple tissues Osseous tissue (cells and extracellular matrix) Vascular tissue Lymphatic tissue Adipose tissue Nervous tissue All bones store Inorganic salts: Ca 3PO4; Ca(OH) 2CaCO 3 2+ + 2 Ions: Mg ; F; K ; SO4 Types of bone tissues: Cortical/ compact bone Forms the harder outer layer Covered with a thin periosteum Basic structural unit Osteon Concentric lamellae Haversian canal Lacunae (contains osteocytes) Trabecular/ Spongy/ Cancellous bone Forms the inner layer Less compact than cortical bone Contains bone marrow (red or yellow) highly vascular Basic unit Trabeculae, containing the bone cells Bone cells: Osteocytes Mature osteoblasts Regulate the activity of osteoblasts and osteoclasts Does the bone building Mature bone cells that maintain the bone matrix Osteoblasts Immature bone cells that secrete matrix compounds (bone formation/ growth) Can be found in the periosteum (tissue around bones: the sheath of connective tissue that surrounds all bones except those at joint) and endosteum (lining of bones: a layer of vascular tissue lining the inside of some bones) Builds new bone Synthesize and secrete collagen fibers and other components needed to build the extracellular matrix of bone tissue Initiate calcification Osteoclasts Perform osteolysis (breaking down of bone via chemical reactions) Important in bone remodelling, as well as in releasing the stored calcium in bones into the blood stream Giant, multinucleated cells, dissolve bone matrix and released stored minerals (osteolysis) Does the bone recycling Osteogenic cells Unspecialized cells Only bone cells undergo cell division Resulting cells develop into osteoblasts Note: Bone building and bone recycling must be balanced. The bone cells are derived from stem cells that produce macrophages Types of bones: Flat bone Thin curvy bone with the outer layer being the compact bones. The inner layer being spongy bones Short bone Cube shaped bone with a thin layer of compact bone covering the spongy interior Sesamoid bone Bones embedded in tendons which increase leverage of the muscles Irregular bone Non uniform shape consisting of thin layers of compact bones Surrounds a spongy interior Long bone Characterised by a shaft, diaphysis and epiphysis (a round head at each end) Functions of bones: Support Large, heavy leg bones support the body against pull of gravity The mandible (jawbone) supports the teeth Other bones support various organs and tissues Protection Skeletons protect organs: skull (brain), vertebral column (spinal cord), and rib cage (heart and lungs) Ribs and sternum (breastbone) protect the lungs and heart Vertebrae protect the spinal cord Movement Hands and foot bones permit flexible body movement (jointsto provide flexibility) Skeletal muscles use the bones as levers to move the body Acts as reservoir for minerals All bones store inorganic calcium and phosphorous salts 99% of the body’s calcium is stored in bone 85% of the body’s phosphorus is stored in bone Adipose tissue is found in the marrow of certain bones Hematopoiesis (blood formation) Flat bones of skull, ribs, and breastbone contain red bone marrow, which manufactures blood cells Blood cell formation All blood cells are made in the marrow of certain bones Vinegar akes bones: Spongy Can be cut easily Hollow on the inside Bleach makes bones: Brittle Can be broken by hand Hyaline Cartilage: Contains no nerves and blood vessels Joint capsule is attached to the whole circumference of the articular end of each bone Types of fractures: Greenstick fracture Incomplete fracture Bone is bent Occurs most often in children Transverse fracture Broken piece of bone is right angle to the bone’s axis Comminuted fracture Bone breaks into several pieces Oblique fracture When a break has a curved or a sloped pattern Buckle fracture Ends are driven into each other Pathological fracture Caused by a disease that weakens the bones Stress fracture Hairline crack Phases: 1. Reactive When a bone fracture, causes bleeding Blood vessels constrict, stopping any further bleeding Blood cells form a blood clot, called hematoma Cells within the blood clot degenerate and die Phagocytic cells clean the dead cells away Fibroblast migrates into site and begins proliferation 2. Reparative Days after fracture, cells of the periosteum duplicate and transform Cell proximal (closest) to the fracture gap develop into chondroblasts which form hyaline cartilage Cells distal (further from) the fracture gap develop into osteoblasts which form woven bone Fibroblasts within the granulation tissue develop into chondroblasts which also form hyaline cartilage Two new tissues grow in size until they unite with their counterparts from other parts of the fracture until the gap is bridged (by the hyaline cartilage and woven bone), restoring some of its original strength Next is replacement of the hyaline cartilage + woven bone with lamellar bone → known as endochondral ossification. Periosteum is a membrane that covers the outer surface of all bones other than the joints of the long bones Endosteum lines the inner surface of all bones 3. Remodeling Maturation of wound healing Unnecessary vessels are formed in the granulation tissue Removed by apoptosis Type 3 collagen replaced by Type 1 collagen Phase last from 3 weeks to 12 months Granulation Tissue: New connective tissue and tiny blood vessels that forms on the surfaces of a would during the healing process Grows from the base of a wound and is able to fill wounds of almost any size Endochondral Ossification: One of two essential processes of fetal development Development of mammalian skeletal system Bone tissue replaces hyaline cartilage, forming all bones below the skull except for the clavicles (collar bone) Before birth, the primary center of ossification happens At the time of birth, the secondary center of ossification happens Cartilage between the primary and secondary ossification centers is called epiphyseal Continues to form a new cartilage, which is replaced by bone. This increases the length of the bone Steps 1. As the cartilage enlarges through appositional and interstitial growth, chondrocyte near the center of the shaft increase greatly in size The matrix is reduced to a series of small structs that soon begin to calcify The enlarged chondrocytes then die and disintegrate, leaving cavities within the cartilage 2. Blood vessels grow around the edges of the cartilage and the cells of the perichondrium convert to osteoblasts The shaft of the cartilage then becomes ensheathed in a superficial layer of bone 3. Blood vessels penetrate the cartilage and invade the central region Fibroblasts migrating with the blood vessels differentiate into osteoblasts and begin producing spongy bone at a primary ossification center Bone formation then spreads along the shaft toward both ends 4. Remodeling occurs as growth continues creating a marrow cavity The bone of the shaft becomes thicker and the cartilage near each epiphysis is replaced by shafts of bone Further growth involves increases in both length and diameter 5. Formation of articular cartilage Formation of epiphyseal plate Both structure consist of hyaline cartilage Capillaries and osteoblasts migrate into the epiphyses to crease secondary ossification centers Each epiphysis is filled with spongy bone Over time the articular cartilage will reduce to a thin superficial layer Bone healing: There are three stages 1. Inflammation Soon after a fracture occurs, a hematoma forms at the injury site Macrophages and inflammatory leukocytes move into the damaged area to scavenge debris and begin producing the proinflammatory agents that initiate healing 2. Soft Callus Inflammation triggers cell division and the growth of new blood vessels Among the new cells, chondrocytes secrete collagen and proteoglycans, creating fibrocartilage that forms the soft callus 3. Hard Callus Through endochondral ossification and direct bone formation, woven bone replaces the soft callus Creating a hard callus around the broken fragments of bone 4. Remodeling Over time, mechanically strong, highly organized cortical bone replaces the weaker, disorganized woven bone Because it is continually remodeled, bone is the only tissue to heal without a scar Other terms: Woven bone (primary bone tissue): Temporary and is eventually converted to lamellar bone
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