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FUNCTION(S) OF THE SKELETAL SYSTEM

FUNCTION(S) OF THE SKELETAL SYSTEM. Support Protection Movement Mineral storage Formation of blood cells Hematopoiesis. CLASSIFICATION OF BONES. Types of Osseous Tissue Compact (dense) Bone Spongy (cancellous) Bone. spongy bone. compact bone. TYPES OF OSSEOUS TISSUE. Long Bones

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FUNCTION(S) OF THE SKELETAL SYSTEM

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  1. FUNCTION(S) OF THE SKELETAL SYSTEM • Support • Protection • Movement • Mineral storage • Formation of blood cells Hematopoiesis

  2. CLASSIFICATION OF BONES • Types of Osseous Tissue • Compact (dense) Bone • Spongy (cancellous) Bone spongy bone compact bone

  3. TYPES OF OSSEOUS TISSUE • Long Bones • A shaft with two widened ends • Compact and spongy bone • Examples: • Humerus • Radius & ulna • Femur • Tibia & fibula • Phalanges Femur

  4. TYPES OF OSSEOUS TISSUE • Short Bones • Cube-shaped bones • Mostly spongy bone • Examples: • Wrist and ankle bones • Sesamoid bones • Short bones embedded with a tendon • Example: Patella Tarsal Patella

  5. TYPES OF OSSEUS TISSUE • Flat Bones • Thin, flat bones • Layer of spongy bone between layers of compact bone • Examples: • Sternum • Ribs • Skull Parietal

  6. TYPES OF OSSEOUS TISSUE • Irregular Bones • Irregular shape • Mostly spongy bone • Examples: • Vertebrae • Hip bones Vertebra

  7. BONE STRUCTURE • Diaphysis • Shaft of bone • Compact bone surrounds medullary cavity • Contains yellow marrow (fat) Diaphysis medullary cavity

  8. BONE STRUCTURE proximal epiphysis • Epiphyses • Widened end of long bones • Spongy bone • May contain red marrow • Epipheseal line or plate • Bone growth during childhood • Actively mitotic plate of hyaline cartilage • Articular cartilage covers joint surface distal epiphysis

  9. BONE STRUCTURE • Bone Membranes • Periosteum • Outer C.T. membrane • Inner surface may contain osteoblasts or osteoclasts • Blood vessels and nerves periosteum

  10. BONE STRUCTURE • Bone Membranes • Endosteum • Inner C.T. membrane • Lines marrow cavities, Haversian canals and covers trabeculae • Contains osteoblasts and osteoclasts endosteum

  11. BONE MARROW • Red Bone Marrow • Found in spongy bone • Hematopoietic tissue • Found in: • Head of femur and humerus • Sternum and hip bones in adults Spongy bone spaces containing red bone marrow

  12. BONE MARROW yellow bone marrow • Yellow Bone Marrow • Composed of fat • Found in: • Medullary cavity • May convert to red marrow

  13. BONE HISTOLOGY: Compact Bone Haversian canals concentric lamella lacuna canaliculi Volkmann’s canal

  14. BONE HISTOLOGY: Compact Bone • Haversian Systems (Osteons) • Lamellae • Concentric, interstitial & circumferential • Haversian canals • Volkmann's canals • Osteocytes within lacunae • Canaliculi

  15. BONE HISTOLOGY: Osteon Haversian canal Volkmann’s canal

  16. BONE HISTOLOGY: Spongy Bone • Spongy Bone • No osteons • Scattered trabeculae for support • Called diploe in flat bones • Red marrowbetweentrabeculae diploe

  17. CHEMICAL COMPOSITION OF BONE • Organic Components • 1/3 of matrix • Includes all 3 cell types • Osteoblasts secrete osteoid = Organic bone matrix • Inorganic Components • 2/3 of matrix • Accounts for bone hardness • Hydroxyapatites [Ca10(PO4)6(OH)2] • Mineral salts of calcium phosphate

  18. BONE MARKINGS • Structures on the external surface of bone • Caused by: • Muscle or ligament attachments • Blood vessels, nerves etc. travel • Be familiar with the types of markings found on bones (see Table 6.1 in your textbook or the list in your lab notebook)

  19. OSTEOGENESIS/OSSIFICATION • Osteogenesis • Process of bone formation • Used for: • Formation of bony skeleton in embryos • Bone growth during childhood and early adulthood • Bone remodeling and repair in adults

  20. OSTEOGENESIS/OSSIFICATION • Two Types of Bone Formation • Intramembranous Ossification • Bone develops from a fibrous membrane • Endochondral Ossification • Bone develops from a hyaline cartilage model

  21. Intramembranous Ossification

  22. INTRAMEMBRANOUS OSSIFICATION • Used for formation of flat bones (skull & clavicles) • Steps • Formation of bone matrix within fibrous membrane • Initial ossification sight ( 8 wks)  A fibrous C.T. membrane • Ossification center appears in the C.T. membrane • Osteoid secreted by osteoblasts • Osteoid becomes mineralized • Formation of woven bone • Network of bony trabeculae forms = woven bone • Formation of compact bone plates • Trabeculae thicken at the edge, forming compact bone • Spongy bone remains in the center

  23. ENDOCHONDRAL OSSIFICATION hyaline cartilage perichondrium deteriorating cartilage matrix periosteum

  24. ENDOCHONDRAL OSSIFICATION • Used for formation of most bones of the skeleton (2nd month) • Steps • Formation of bone collar around hyaline cartilage model • Perichondrium around hyaline cartilage model converted to periosteum • Osteoblasts secrete osteoid onto the external shaft of the “hyaline” bone • Deterioration of cartilage matrix • Matrix within the hyaline shaft deteriorates

  25. ENDOCHONDRAL OSSIFICATION secondary ossification center articular cartilage blood vessel periosteal bud medullary cavity epiphyseal plate open spaces forming bone

  26. ENDOCHONDRAL OSSIFICATION • Steps • Formation of spongy bone by periosteal bud • Periosteal bud invades the internal cavity • Contains blood vessels and osteoblasts • Osteoblasts produce trabeculae of bone • Formation of medullary cavity • Osteoclasts break down new bone forming a medullary cavity • Ossification of epiphyses • Secondary ossification centers form in epiphyses shortly before or after birth • Spongy bone forms • Hyaline cartilage remains only at the epiphyseal plate and articular surfaces

  27. BONE GROWTH IN LONG BONES Growth in Length • Cartilage growth in epiphyseal plate • Cartilage replaced by bone • Bone remodeled • Bone resorption Growing Bone Adult Bone

  28. BONE GROWTH IN LONG BONES • Long bones lengthen by growth of the epiphyseal plates • Harden at the end of puberty • All bones grow in width or change shape by appositional growth

  29. BONE GROWTH IN LONG BONES • Growth in the Epiphyseal Plate • Hyaline plate contains dividing chondrocytes • Chondrocytes enlarge • Pushed towards diaphysis • Eventually die • Osteoblasts secrete bone matrix • Form small bone spicules

  30. BONE GROWTH IN LONG BONES • Growth in the Epiphyseal Plate (cont.) • Epiphyseal plate activity stimulated by growth hormone during childhood • Sex hormones (testosterone & estrogen) • Adolescent growth spurt • End of adolescence • Epiphyseal plate replaced by bone • Longitudinal bone growth ends

  31. BONE GROWTH IN LONG BONES • Appositional Growth • Used to widen bones for remodeling • Osteoblasts on the periosteum: • Form new Haversian systems on outer bone surface • Increase thickness of compact bone • Osteoclasts on the endosteum • Resorb bone • Enlarge medullary cavity

  32. BONE GROWTH IN LONG BONES Appositional Growth • Bone addition • Bone resorption Growing Bone Adult Bone

  33. BONE REMODELING & REPAIR • Bone Remodeling • Bone deposited and resorbed daily at the periosteal and endosteal surfaces • 5 to 7% of bone mass recycled weekly • Rate of resorption should = rate of deposit • Response to blood calcium levels • Ca2+ ions are needed for nerve impulse transmission, muscle contractions, blood coagulation • Vitamin D enhances absorption of Ca2+ from the intestine • When remodeling occurs is determined by mechanical and gravitational forces • Heavier bone usage  heavier bones • Nonuse  bone wasting

  34. BONE REMODELING & REPAIR • Bone Deposit • Osteoblasts deposit osteoid which is later mineralized into hard bone • Hormonal Control • Calcitonin • Produced by “C” cells in the thyroid glands • Secreted when blood Ca2+ levels  • Inhibits bone resorption, enhances Ca2+ deposit in bone matrix

  35. BONE REMODELING & REPAIR • Bone Resorption • Osteoclasts secrete enzymes • Digest organic matrix • Osteoclasts secrete acids • Make calcium salts more soluble • Minerals freed from bone are put into bloodstream • Hormonal Control • Parathyroid Hormone (PTH) • Produced by the parathyroid glands • Secreted in response to low blood Ca2+ levels • Stimulates bone resorption

  36. CALCIUM HOMEOSTASIS: PTH CONTROL BONE PTH promotes Ca2+ release into the blood Ca2+ removed from blood by osteoblasts BLOOD PTH promotes Ca2+ reabsorption from urine Unabsorbed Ca2+ lost in feces Ingested Ca2+ KIDNEY SMALL INTESTINE Ca2+ lost in the urine Vitamin D promotes Ca2+ absorption PTH promotes Vitamin D formation

  37. FRACTURES • Fracture • Break in the bone • Fracture Types • Simple • Compound • Comminuted • Compression • Depression • Impacted • Spiral • Greenstick

  38. TYPES OF FRACTURES comminuted fracture fissured fracture greenstick fracture transverse fracture oblique fracture spiral fracture

  39. FRACTURE REPAIR • Phases of Repair • Hematoma Formation • Blood clot forms hematoma

  40. FRACTURE REPAIR • Phases of Repair • Fibrocartilaginous Callus Formation • Fibroblasts secrete collagen • Condroblasts secrete cartilage matrix • Osteoblasts form spongy bone fibrocartilage spongy bone

  41. FRACTURE REPAIR • Phases of Repair • Bony Callus Formation • Osteoclasts and osteoblasts convert callus into a bony callus bony callus

  42. FRACTURE REPAIR • Phases of Repair • Bony Callus Remodeling • Continues for several months compact bone

  43. BONE IMBALANCES • Osteoporosis • A group of diseases in which bone resorption exceeds bone deposit = reduction in bone mass • Vertebrae and neck of femur most susceptible • Most common in postmenapausal women due to estrogen reduction

  44. BONE IMBALANCES • Osteoporosis • Risk Factors • Insufficient exercise • Poor calcium or protein intake in diet • Vitamin D or calcitonin metabolism problems • Smoking • Drinking • Immobility

  45. BONE IMBALANCES • Osteomalacia • Disorders in which bone is inadequately mineralized • Osteoid is deposited but calcium salts are not • Weight-bearing bones fracture, bend or deform • Rickets may occur in children with insufficient calcium or Vitamin D intake • Causes bowed legs and deformities of the pelvis

  46. BONE IMBALANCES • Paget’s Disease • Characterized by excessive, abnormal bone formation and resorption • Bone produced contains a high ratio of woven bone to compact bone • Bone mineralization is reduced • Bones become soft and weak

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