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This 4 page Class Notes was uploaded by Ally Merrill on Thursday September 22, 2016. The Class Notes belongs to ANA 109 at University of Kentucky taught by Dr. Platt in Fall 2016. Since its upload, it has received 15 views.
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Date Created: 09/22/16
ANA109 Week 6—Unit 2 material (Bones/Muscles) 9/27/16 UNIT 2 What is bone? What is it made of? Are there components other than bone that make up the skeletal system? Bones are composed of several different tissues working together o Osseous tissue o Cartilage o Dense connective o Epithelium o Adipose tissue o Nervous tissue All of the bones and their cartilages, along with ligament and tendons, constitute the skeletal system What are the functions of the skeletal system? Supports soft tissues and provides attachment points for tendons of skeletal muscles Protects the most important internal organs Assists in movement by acting as levers for skeletal muscles Osseous tissue stores and releases minerals, particularly calcium and phosphorus Red marrow within bones produce blood cells Yellow marrow within bones stores triglycerides, a source of potential energy How do anatomists classify bones? Long bones o Greater length than width Short bones o Nearly equal length and width Flat bones o Thin Sternum Irregular bones o Complex shapes Sesamoid bones o Shaped like sesame seed Patella Describe the anatomy of a long bone Regions of a long bone o Diaphysis (the shaft) o Medullary cavity (inside shaft) o 2 epiphyses (proximal and distal) o 2 metaphyses (joins diaphysis and epiphysis with epiphyseal plate, or line once growth stops) Surface tissues o Endosteum—inside o Periosteum—outside Perforating (sharpey) fibers—fibers that penetrate into the bone matrix o Articular cartilage What is bone marrow? Are there different types? What is the function? Bone marrow—generic term for soft tissue that occupies the marrow cavity or a long bone and small spaces amid the trabeculae of spongy bone Red marrow (myeloid tissue) o In nearly every bone in a child o Hemopoietic tissue—produced blood cells and is composed of multiple tissues in a delicate, but intricate arrangement that is an organ to itself o In adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur Yellow marrow found in adults o Most red marrow turns into fatty yellow marrow o No longer produces blood What are the cells that make up bone (osseous tissue)? Four principal types of cells o Osteogenic—undifferentiated, give rise to osteoblasts by cell division o Osteoblasts—bone building by calcification o Osteocytes—maintain daily tissue activities o Osteoclasts—bone destroying by resorption Extracellular matrix of connective tissue o Water o Collagen fibers—gives property of flexibility and tensile strength o Crystallized mineral salts of hydroxyapatites—gives property of hardness Bone is a composite—combination of two basic structural materials, a ceramic and a polymer o Ceramic portion allows the bone to support the body weight, and protein portion gives bone some degree of flexibility What is the matrix? Matrix of osseous tissue is about 15% water, 30% collagen fibers, and 55% crystallized minerals Fibers—synthesized by osteoblasts—the “polymer” (ex: collagen) Crystallized minerals—the “ceramic” o 85% hydroxyapatite—crystallized calcium phosphate salt o 10% calcium carbonate (ex: egg shell, snail shell) o other minerals (fluoride, sodium, potassium, magnesium) Clinical reasoning: bone matrix disorders Rickets—soft bones due to deficiency of calcium salts o “ceramic” o vitamin D-assists in absorption of dietary calcium Osteogenesis imperfects or brittle bone disease—excessively brittle bones due to lack of protein, collagen What are the bone forming cells called? What is the function of each? Osteogenic (osteoprogenitor) cell—develops into an osteoblast, stem cells that arise from undifferentiated precursors. They are found in endosteum, periosteum and in central canals Osteoblast—forms bone extracellular matrix, bone forming cells o Line up under endosteum and periosteum o Synthesize soft organic matter of matrix which then hardens by mineral deposition o Stress and fractures stimulate osteogenic cells to multiply more rapidly and increase number of osteocytes to reinforce or rebuild bone Osteocyte—maintains bone tissue, former osteoblasts that have become trapped in the matrix they have deposited, when stressed, produce biochemical signals that regulate bone remodeling o Lacunae—tiny cavities where osteocytes reside o Canaliculi—little channels that connect lacunae Osteoclast—functions in resorption, the breakdown of bone extracellular matrix How is new bone created and old bone destroyed? Remodeling—results from combined action of the bone-dissolving osteoclasts and the bone-depositing osteoblasts In general, most of your skeleton is completely different from your skeleton 5-10 years ago The distal femur is replaced every 4 months Osteoclasts—bone dissolving cells found on the bone surface o Osteoclasts develop from the same bone marrow stem cells that give rise to blood cells, thus have a different origin than other bone tissue o Unusual, large cells formed from the fusion of several stem cells Typically have 3 to 4 nuclei, may have up to 50 o Ruffled border—side facing bone surface Several deep infoldings of the plasma membrane which increases surface area and resorption efficiency Two major types of osseous tissue Compact bone o Forms external layer of all bones and comprises most of the diaphysis of long bones Spongy bone (or trabecular bone) o Forms interior of short, flat, irregular, and sesamoid bones, most of epiphysis of long bones, and narrow rim around medullary cavity of long bones
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