skeletal system

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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

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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 - PowerPoint PPT Presentation

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Page 1: 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

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Bone functions

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

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Long bone anatomy humerus, femur, etc (typically appendicular)

1. diaphysis – shaft 2. epiphysis (es) – bulbous ends 3. metaphysis (es) – between 1&2 *contains epiphyseal plate in youth*

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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

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11. 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

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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)

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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

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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

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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

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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

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B- Endochondral Ossification

*future bone composed of hyaline cartilage, then converted to bone

*most bones of the body form by endochondral ossification

a) mesenchymal chondroblastshyaline cartilage osteogenicosteoblastsbone

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Steps of endochondral ossification

1) 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

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2) secondary ossification centers

-located inside of epiphyses -ossification proceeds deep to

superficial *overall resultsgrowth plate in metaphysis &

articular cartilage on epiphyses WHY?

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Nutrients for healthy bones

A) 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

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• B) MINERALSCalcium, phosphorous, magnesium, fluoride,

iron,manganese

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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

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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

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7. Spiral fracture - ragged break due to twisting force

8. Epiphyseal fracture - break at growth plate (epiphyseal plate)

9. Depressed fracture - broken bone pressed inward (skull)

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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

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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

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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)

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Reduction

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

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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

Page 24: SKELETAL  SYSTEM

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

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Cartilage

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

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2. Collagen for sheer strength

Water (tissue fluid) for resilience

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3. a)hyaline - shiny, glassy, most common in human body

Locations: trachea, nose, bone joints, growth plates, larynx, rib cage

Functions: Support, cushion, glide

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4.

a)chondrocyte – mature cartilage cell found in lacuna b)chondroblasts – secrete collagen to initiate cartilage formation - analogous to osteoblastc) Perichondrium – analogous to periosteum

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5.

ELASTIC Cartilage: most elastin*

Locations: Epiglottis, External ear

Functions: structure , flexibility

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6.

c)fibrocartilage – thicker collagen, no perichondrium

Functions: resists compression , structure

Locations: meniscus, vertebral disks, bone repair

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7.

Fibrocartilage

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8.

Fibrocartilage

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9.

cartilage is an avascular connective tissue *lacks a direct nerve supply

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10.

Avascular (no direct blood supply)