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Skeletal System

Skeletal System. Function of the Skeletal System. Support - framework that supports body and cradles its soft organs Protection - for delicate organs, heart, lungs, brain Movement - bones act as levers for muscles Mineral storage - calcium & phosphate Blood cell formation - hematopoiesis.

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Skeletal System

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  1. Skeletal System

  2. Function of the Skeletal System • Support- framework that supports body and cradles its soft organs • Protection- for delicate organs, heart, lungs, brain • Movement- bones act as levers for muscles • Mineral storage- calcium & phosphate • Blood cell formation- hematopoiesis

  3. The Skeletal System Parts of the skeletal system·Bones (skeleton)·Joints·Cartilages·Ligaments (bone to bone)(tendon=bone tomuscle) Divided into two divisions·Axial skeleton·Appendicular skeleton – limbs and girdle

  4. Axial Skeleton

  5. Appendicular Skeleton

  6. Bones of the Human Body The skeleton of an adult has 206 bones·Two basic types of bone tissue·Compact bone·Homogeneous·Spongy bone·Small needle-likepieces of bone·Many open spaces

  7. 275 bones12 weeks (6-9 inches long) Fetal Skeleton

  8. Bone Classification

  9. Types of Bones • Long Bones- metacarples, metatarsals, phalanges, humerus, ulna, radius, tibia, fibula • Short Bones- carpals, tarsals • Flat Bones- rib, scapula, skull, sternum • Irregular Bones- vertebrae, some facial bones • Sesamoid- patella

  10. Classification of Bones Long bones·Typically longer than wide·Have a shaft with heads at both ends·Contain mostly compact bone•Examples: Femur, humerus

  11. Classification of Bones Short bones·Generally cube-shape·Contain mostly spongy bone·Examples: Carpals, tarsals

  12. Classification of Bones Flat bones·Thin and flattened·Usually curved·Thin layers of compact bone around a layerof spongy bone·Examples: Skull, ribs, sternum

  13. Classification of Bones Irregular bones·Irregular shape·Do not fit into other bone classificationcategories·Example: Vertebrae and hip

  14. Sesamoid bones • Embedded within tendonwhere its passes over a joint • Free surface covered with cartilage; the other part embedded within tendon; no periosteum • Patella (withinthe tendon of m.quadriceps femoris)

  15. Additional bones • Mainly in the skull: ossa interfrontalis, coronalis, sagittalis, lambdoidalis, etc. • Known also asossa suturarum

  16. Anatomy of a Long Bone spongy bone Proximal epiphysis compact bone Endosteum diaphysis epiphyseal line yellow marrow Sharpey’s fibers Distal epiphysis periosteum hyaline cartilage

  17. Structures of a Long Bone Periosteum·Outside covering ofthe diaphysis·Fibrous connectivetissue membrane Sharpey’s fibers·Secure periosteum tounderlying bone Arteries·Supply bone cellswith nutrients

  18. Structures of a Long Bone Articular cartilage·Covers theexternal surface ofthe epiphyses·Made of hyalinecartilage·Decreases frictionat joint surfaces

  19. Structures of a Long Bone Medullary cavity·Cavity of the shaft·Contains yellowmarrow (mostly fat)in adults·Contains red marrow(for blood cellformation) in infants

  20. Components of Bone • Cortical bone – Structural • Trabecular bone – Structural • Bone Marrow – Structural and RBC • Vessels – Nutritional and Innervation

  21. Cortical Bone • Osteon (Harvesian Canals) • Cylindrical tubes made of concentric lamellae • Central opening • Blood vessels • Neural tissue • Lymphatic • Periosteum • Fibrous tissue covering • Enables attachment of muscles and tendons

  22. Cortical bone • Lamellae • Concentric layers of mineralized bone • Crisscross pattern at 90 • Torsion and bending strength • Osteoclasts • Bone resorbing • Osteoblasts • Bone forming

  23. Trabecular Bone • Cancellous or Spongy • Lattice structure • Pores filled with marrow • 20% Bone Mass • 80% Bone Surface

  24. Trabecular Structure • Plate and rod structure • Low loads - rod • Higher loads - plate • Light yet spongy • Oriented in direction of loads • “Wolff’s Law”

  25. Bone Marrow Consists of stroma, myeloid tissue, fat, lympatic tissues Red marrow Involved with the production of RBC Consists of haemopoetic tissue Highly vascularized Yellow marrow Not as vascularized as red marrow Large amount of fat cells Percentage increases wrt red marrow with age (up to20yrs)

  26. Mechanisms of bone formation • Membranousossification how: directdifferentiationofcellswithinmesenchymalcondensationsintoboneformingcells (osteoblasts) flatbonesoftheskull,clavicle,periosteum • Endrochondralossification how: replacementof a cartilagenoustemplatebybone endochondralbones:axialandappendicularskeleton,somebonesintheskull

  27. Membranous bone formation

  28. Endochondral Ossification

  29. Fetus: 1st 2 months Endochondral Ossification 2o ossification center bone cartilage calcified cartilage Just before birth epiphyseal line epiphyseal plate Childhood Adult

  30. Types of bone cellsinvolved in bone homeostasis

  31. How do cells look?

  32. Origin of bone cells

  33. Repair of Fractures hematoma callus bony callus bone remodeling

  34. Diseases of the Skeletal System: • Osteoporosis- bone reabsorption outpaces bone deposit; bones become lighter and fracture easier • Factors: • age, gender (more in women) • estrogen and testosterone decrease • insufficient exercise (or too much) • diet poor in Ca++ and protein • abnormal vitamin D receptors • smoking

  35. 29 40 84 92 Osteoporosis

  36. Diseases of the Skeletal System Rickets- vitamin D deficiency Osteomalacia- soft bones, inadequate mineralization in bones, lack of vitamin D Pagets Disease- spotty weakening in the bones, excessive and abnormal bone remodeling Rheumatoid arthritis- autoimmune reaction

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