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SKELETAL SYSTEM

SKELETAL SYSTEM. Osteology – study of bones Bone is a vascular, innervated connective tissue cartilage is a nonvascular, non-innervated connective tissue Skeletal system is derived from mesoderm. Bone functions. 1. support 2. protection 3. movement

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SKELETAL SYSTEM

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  1. SKELETAL SYSTEM • Osteology– study of bones • Bone is a vascular, innervated connective tissue • cartilage is a nonvascular, non-innervated connective tissue • Skeletal system is derived from mesoderm

  2. Bone functions 1. support 2. protection 3. movement 4. mineral storage – calcium, phosphorous , magnesium 5. hemopoiesis – blood cell formation 6. triglyceride storage

  3. Long bone anatomyhumerus, femur, etc (typically appendicular) 1. diaphysis – shaft 2. epiphysis (es) – bulbous ends 3. metaphysis (es) – between 1&2 *contains epiphyseal plate in youth*

  4. 4. articular cartilage (hyaline) friction reduction at joints 5. periosteum (dense irregular) wraps outer bone surface 6. endosteum lines inner cavities 7. medullary cavity - in diaphysis contains yellow marrow 8. yellow marrow triglycerides (fat) 9. compact bone – “compact” “surface” bone 10. spongy bone – porous normally in epiphyses in adult long bones

  5. red marrow – hemopoietic tissue found in spaces of spongy bone *compare long bones to flat bones which have two layers of compact bone and one layer of spongy bone *analogous to a sandwich : compact =slices of bread spongy = filler

  6. Bone matrix *nonliving, cellular products- composes most of bone 1. mineral salts (50%)– calcium phosphate(hydroxyapatite), calcium carbonate, magnesium hydroxide, fluoride, sulfates - results in the hardness of bone -minerals arrive via blood 2. collagen(25%) - results in tensile strength of bone - secreted by osteoblasts (bone cells)

  7. Bone cells 1. Osteogenic - mitotic, one daughter differentiates, other maintained as osteogenic (like stem cells) Located beneath periosteum and endosteum. 2. Osteoblast – formed directly from osteogenic cells - bone “builder” – produces/secretes collagen 3. Osteocyte – retired osteoblast - most mature, true bone cell - resides in matrix (lacuna) until death ________________________________________________ 4. Osteoclast - * not related to previous cells - made of fused monocytes (wbc’s) - bone destoyer -secretes enzymes to dissolve matrix

  8. Compact Bone *compact bone is the outer bone type of all bones *consists of Haversian Systems (Osteons) 1. Haversian Canal – penetrating blood vessel 2. Canaliculus (i) – liquid (H2O) filled canals connecting Haversian canals to lacunae 3. Lacuna (ae) – space containing an osteocyte (cave) 4. Lamellae – surrounding rings of matrix

  9. Spongy Bone spongy bone is deep to compact bone *porous * no true Haversian system, has only 1. canaliculi 2. lacunae 3. lamellae *spongy bone is arranged into thin strands called trabeculae

  10. Bone Formation – osteogenesis or ossification A- Intramembranous Ossification *bone forming from soft tissue – no cartilage* *forms cranial skull bones and possibly the clavicles a) mesenchymalosteogenic  osteoblasts  bone

  11. B- Endochondral Ossification *future bone composed of hyaline cartilage, then converted to bone *most bones of the body form by endochondral ossification a) mesenchymal chondroblastshyaline cartilage osteogenicosteoblastsbone

  12. Steps of endochondral ossification • primary ossification center -located in the middle of the future bone -dying cartilage cells trigger the penetration of cartilage by a blood vessel -ossification proceeds superficial to deep

  13. 2) secondary ossification centers -located inside of epiphyses -ossification proceeds deep to superficial *overall resultsgrowth plate in metaphysis & articular cartilage on epiphyses WHY?

  14. Nutrients for healthy bones • VITAMINS 1) vitamin C - collagen synthesis -osteoblastosteocyte differentiation 2) vitamin B12 – collagen synthesis 3) vitamin K - collagen synthesis 4) vitamin A - increased osteoblast activity 5) vitamin D- calcification (rickets) and calcium absorption

  15. B) MINERALS Calcium, phosphorous, magnesium, fluoride, iron,manganese

  16. Fractures / Repair / Healing A) Fracture types – see handout *a fracture is any break or crack in a bone 1. simple(closed) fracture does not break skin 2. compound (open) fracture breaks skin as well as bone 3. greenstick fracture one side breaks, other side bends common in youth

  17. 4. comminuted fracture fragments at break site, usually requires surgery 5. impacted fracture(compression) two ends of bone driven into each other 6. stress fracture tiny, often microscopic cracks in a bone painful, overuse injury

  18. Spiral fracture - ragged break due to twisting force • Epiphyseal fracture - break at growth plate (epiphyseal plate) • Depressed fracture - broken bone pressed inward (skull)

  19. 7. Colle’s Fracture common sports injury (falling while running) radius breaks near wrist distal portion of radius(near hand) moves posterior to rest of radius 8. Pott’s Fracture common ankle injury sole of foot moves laterally fracture to tibia (medially) as well as fibula

  20. 5 stages of healing 1. Fracture hematoma stage blood clots at break site – can take several hours. Why? 2. Procallus stage- broken area becomes vascular

  21. 3. Fibrocartilaginous stage fibrocartilage holds broken ends together (approx 3 weeks) 4. Bony callus stage ( 3-4 mo.) fibrocartilage replaced by spongy bone 5. Remodeling stage spongy bone slowly converted to compact bone (months)

  22. Reduction -realigning broken ends of bone 1) open reduction – surgical 2) closed reduction - nonsurgical

  23. Bone growth A) length epiphyseal plate is ossified on side of diaphysis cartilage cells proliferate on side of epiphysis B) thickness matrix forms around blood vessel on surface of bone vessel becomes a Haversian canal

  24. Hormones affecting bones . 1. PTH (parathyroid hormone) - increases blood calcium levels -”pulls” calcium from bones by stimulating osteoclast activity 2. CT (calcitonin) - lowers blood calcium levels -increases bone calcium levels -may slow osteoclast activity -most effective in youth

  25. Cartilage 1. *matrix is similar to bone ----- collagen and water * but different ----- chondroitin sulfate and hyaluronic acid (GAG’s) rather than mineral salts

  26. 2. Collagen for sheer strength Water (tissue fluid) for resilience

  27. 3. a)hyaline - shiny, glassy, most common in human body Locations: trachea, nose, bone joints, growth plates, larynx, rib cage Functions: Support, cushion, glide

  28. 4. a)chondrocyte– mature cartilage cell found in lacuna b)chondroblasts– secrete collagen to initiate cartilage formation - analogous to osteoblast c) Perichondrium – analogous to periosteum

  29. 5. ELASTIC Cartilage: most elastin* Locations: Epiglottis, External ear Functions: structure , flexibility

  30. 6. c)fibrocartilage – thicker collagen, no perichondrium Functions: resists compression , structure Locations: meniscus, vertebral disks, bone repair

  31. 7. Fibrocartilage

  32. 8. Fibrocartilage

  33. 9. cartilage is an avascularconnective tissue *lacks a direct nerve supply

  34. 10. Avascular (no direct blood supply)

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