Skeletal Systemfigure 6.2

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Skeletal System figure 6.2

• _____________ cells- unspecialized stem cells
• only bone cells to undergo cell division
• daughter cells become osteoblasts
• __________________- bone building cells
• synthesize secrete collagen fibers other
  organic components to build matrix
• Initiate calcification
• Become osteocytes mature bone cells
• ____________- huge cells, fusion of monocytes
• digest protein and mineral of underlying bone
• Resorption- normal develop, growth, maintanance
  repair

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Skeletal system figure 6.1

• Supports soft tissues attachment for muscle
• Protects internal organs
• Provides movement
• Stores releases minerals
• Contains
• ___________________ - produce blood cells
• ____________________- stores fat, few blood cells

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Bone defined

• ________- matrix is abundant w/ inorganic mineral
  salts (50), 25 water, 25 collagen
• Hydroxyappatite- main mineral salt
• calcium phosphate and calcium carbonate
• __________________ - crystallization or hardening
  of the matrix
• Is a connective tissue
• AKA osseous tissue

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Types of bones figure 7.2

• ________bones- greater length than width
• Shaft and extremities, curved for strength
• Femur, tibia, fibula, humerus, radius, ulna
• _______ bones- somewhat cube shaped
• length and width
• Carpals, tarsals
• _____ bones- thin, composed of 2 parallel plates
  of compact bone (spongy inside)
• Sternum, ribs, scapula

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Types of bones figure 7.2

• _____________ bones- complex shapes
• Cannot be grouped into previous categories
• Varying amt of spongy and compact
• Vertebrae, some facial bones
• ________ bones- shape like sesame seed
• Develop in certain tendons where ? friction,
  tension, physical stress
• Palms, soles (usually few mm, except patella)

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Haversian System fig 6.3

• Haversian system __________ units of
  _____________________
• Haversian or central canal longitudinal thru
  center of osteon
• contains b.v., lymphatic vessels nerves
• _______ concentric rings of calcified matrix
• ___________ small, hollow space in which
  osteocytes lie
• ________ small canals connecting lacunae

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Haversian system osteon

• Osteocyte mature cell, maintains daily activity
• _____________ membrane lining marrow cavity
• consists of osteogenic cells scattered
  osteoclasts
• Perforating or Volkmanns canal small
  passageway by which b.v. nerves from periosteum
  penetrate into compact bone
• ________ membrane covering bone, consists of
  CT, osteoprogenitor cells osteoblasts
• essential for growth, repair, nutrition

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Compact bone tissue

• Contains few spaces, arranged in osteons
• ____________________________
• Bulk of diaphyses of long bones
• Provides protection and support
• Resists stresses produced by weight and movement
• Osteons __________________ (such as long axis of
  a bone) to resist bend or fracture

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Spongy bone figure 6.3

• Spongy bone does NOT contain osteons
• _____________ of thin columns _________
• microscopic spaces between filled w/ RB marrow
• Within each trabecula osteocytes lie in lacunae
• Canaliculi radiate from lacunae

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Spongy bone (2)

• Osteocytes receive nourishment directly from
  blood vessels in the medullary (marrow) cavity
• Trabeculae are oriented along stress lines
• _____________________________
• Spongy tends NOT to be located in heavily
  stressed areas

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Long bone parts Figure 6.1

• 1. Diaphysis- bone shaft long, cylinderal
• 2. Epiphyses- distal proximal ends
• 3. Metaphyses- region of mature bone where 1 and
  2 meet
• in growing bone contains epiphyseal plate-
  layer of hyaline cartilage allowing the diaphysis
  to grow in length, not width

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• 4. ______________- thin layer of hyaline
  cartilage covers epiphysis,reduce friction, shock
  absorbtion.
• 5. _____________- tough sheath of dense irregular
  CT surrounding bone surface where not covered by
  articular cartilage, grows in thickness not
  length protects nourishes repairs attach
  ligaments tendons.
• 6. Medullary cavity marrow cavity, space in
  diaphysis containing YBM
• 7. ______________- lines medullary cavity,
  osteogenic cells osteoclasts

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Bone marrow functions

• Red bone marrow
• Produces RBC, WBC, platelets________________
• Consists of blood cells, adipocytes, fibroblasts,
  macrophages
• Developing bones of fetus pelvis, ribs, sternum,
  vertebrae, skull, ends of some long
• Yellow bone marrow
• ________________ storage in fat cells
• Few blood cells
• With ?? age much red turns to yellow

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Types of ossification

• Endochondral ossification- bone forms from
  cartilage
• Intramembranous ossification- bone forms directly
  on or within CT, does not form from cartilage

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Intramembranous ossification, 6.5
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Intramembranous Ossification

• Formation of bone directly on or within fibrous
  CT
• form directly from mesenchyme without going thru
  cartilage stage
• fewer steps than endochondral
• 1. Mesenchymal cells condense differentiate
  osteogenic cells ? __________________
• -center of ossification
• -Osteoblasts secrete organic matrix of bone until
  completely surrounded by it

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• 2. Matrix secretion stops. Osteoblasts become
  ________________. Calcium mineral salts
  deposited, matrix hardens
• 3. Matrix develops into trabeculae, which fuse
  form spongy bone
• -BV grow into spaces between trabeculae
  mesenchyme along surface
• -CT assoc w/ b.v. in trabeculae differentiates
  into RB marrow

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• 4. On outside, mesenchyme condenses develops
  into _______________
• -most layers of superficial spongy bone replaced
  by compact bone
• -remains spongy at center
• -much of this bone remodeled (destroyed
  reformed) ? transform into adult size shape

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Endochondral ossification

• _________________________ by bone
• most bones are formed this way
• 1. Development of cartilage
• -mesenchymal cells crowd together in the shape of
  future bone differentiate into chondroblasts
• -Chondroblasts produce a hyaline cartilage
  matrix,
• - Perichondrium is around outside cartilage

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• 2. Growth of cartilage
• -chondroblasts buried in matrix become
  chondrocytes
• -cartilage grows in _________ by cell division
  secretion of matrix ______ growth from
  within
• -Growth in __________by addition of matrix on
  periphery by chondroblasts in perichondrium
  ___________ growth
• -Chondrocytes increase in size, may burst ?
  release contents ? ? pH
• Change in pH causes calcification, other
  chondrocytes will die essential materials cannot
  diffuse thru new matrix

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• 3. Nutrient artery penetrates perichondrium
  calcifying cartilage, stimulating osteogenic
  cells to differentiate into osteoblasts
• -Under perichondrium- thin shell of compact bone
  secreted periosteal bone collar
• -periochondrium is developing bone periosteum
• __________ ossification center region where
  bone will replace most cartilage _________ from
  external surface
• -Osteoblast secrete bone matrix
• -Trabeculae form
• -Osteoclast breakdown trabeculae leaving
  medullary cavity

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• 4. _____________ oss center forms - b.v. enter
  epiphyses, _at_ birth. Spongy bone remains at
  center of epiphyses- no medullary cavities
  ossif proceeds _________
• 5. Hyaline cartilage covering epiphyses becomes
  ________________
• -Prior to adulthood hyaline cartilage between
  epiphysis diaphysis epiphyseal plate-
  responsible for lengthwise growth

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Endochondral ossification
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Lengthening of bone fig 6.7

• Epiphyseal plate is a layer of hyaline in the
  metaphysis of growing bone 4 zones
• 1. _________cartilage -layer nearest epiphysis,
  small scattered chondocytes
• -no function in bone growth, anchor epiphyseal
  plate to bone of epiphysis

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• 2. ____________ cartilage - slightly larger
  chondrocytes
• -zone arranged like stack of coins, chondrocytes
  divide, replacing dying ones at diaphyseal side
• 3. ____________ cartilage - chondrocytes larger
  remain arranged in columns
• -lengthening of diaphysis result of cell
  division and maturation here

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• 4. __________ cartilage- final zone, few cells,
  thick
• -mostly dead chondrocytes calcified matrix
• -Calcified cartilage dissolved by osteoclasts
  invaded by osteoblasts capillaries
• -Osteoblasts lay down bone matrix, diaphyseal
  border of epiphyseal plate firmly cemented to
  diaphysis
• between the ages of 18-25 the epiphyseal plates
  close, plate fades, leaving a line

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Zones- lengthening
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Thickness (appositional) fig 6.8

• At surface periosteal cells differentiate into
  osteoblasts- secrete collagen fibers other
  molecules to form matrix
• Surrounded with matrix they become osteocytes
• Bone ridges form on sides of periosteal b.v. and
  enlarge to leave groove for b.v.
• Ridges fuse, form tunnel
• Periosteum now endosteum in tunnel

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Thickness (appositional) fig 6.8

• Osteoblasts in endosteum deposit matrix forming
  new lamellae
• Proceeds inward toward b.v. filling in tunnel
• Osteon is formed
• Osteoblasts deposited a new lamellae? ?? thick

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Appositional growth, fig 6.8
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Remodeling of bone

• Bone is continually renewed
• Osteoclasts carve out tunnels in old bone
• Osteoblasts rebuild new
• In different parts of skeleton full cycle 2-3
  months or much longer
• Remodeling purposes
• Renew ________________
• Redistribute matrix along lines of mechanical
  stress
• Remodeling is the way injured bone heals.

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Remodeling of bone

• Bone reabsorption breakdown of matrix by
  osteoclasts
• Attach to endosteum or periosteum
• Form leak proof seal (ruffled border)
• Release protein digestion lysosomal enzymes
  (digest collagen) and acids (dissolve minerals)
  into pocket
• Proteins and minerals mainly Ca2 and P are
  endocytosed, then exocytosis from other side
• Vesicle of proteins and minerals absorbed into
  blood
• Osteoblasts move in
• Bone building must bone reabsorption

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Nutrients for bone

• Calcium and phosphorus while growing
• And lesser amt of fluoride, magnesium, iron
  manganese
• Vitamin C for collagen synthesis
  differentiation of osteoblasts?osteocytes
• Vitamin K and B12 for protein synthesis
• Vitamin A stimulates osteoblast activity

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Sex hormones and bone

• At puberty estrogens and androgens cause an ?
  osteoblast activity matrix synthesis
• Cause growth spurt
• ___________________? widening of pelvis
• Shut down epiphyseal growth plate in both sexes
• Females close earlier because ? estrogen levels
  than men
• Those lacking estrogen or its receptor grow
  taller before closure
• During adulthood sex hormones- slow reabsorption
  of old deposition of new
• Estrogens promote osteoclast apoptosis
• BUT, post-menopause, no estrogen, osteoblasts not
  stimulated ? osteoporosis

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Growth hormone and bone

• _____ insulin like growth factor most imp in
  stimulation bone growth as children
• Produced by bone tissue and liver
• Promote cell division at epiphyseal plate
  periosteum
• Enhance protein synthesis need for new bone
• Production stim. by human growth hormone (hGH)
• Oversecretion of hGH in childhood __________
• Undersecretion of hGH _____________

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Parathyroid hormone (PTH)

• Most imp hormone in regulation Ca2 exchange
  between ____________________
• From parathyroid glands
• Secretion via negative feedback
• If Ca2 in blood ?, parathyroid receptors detect
  cause ?? cAMP, detected? ? PTH
• ? PTH cause ? osteoclast activity
• Ca2 reabsorbed into blood
• PTH works on kidneys to ? loss of Ca2 to urine
• Stimulates calcitrol to ? Ca2 absorbtion from GI
  tract

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Calcitonin (CT)

• Secreted by parafollicular cells of parathyroid
  when __________________
• Inhibits activity of osteoclasts
• ? uptake of blood Ca2 by bone
• Accelerates Ca2 deposition in bone
• Promotes bone formation ? blood Ca2
• Harvested from salmon for osteoporosis

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Bone fracture types fig 6.9

• Open (compound) broken ends protrude thru skin
• Closed (simple) do not break skin
• Comminuted together crumbled bone splinters
  at site of impact
• Fragments between 2 larger pieces
• Greenstick partial fracture, one side of bone
  is broken other side bends
• Only in children- not fully ossified

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• Impacted one end of fractured bone forcibly
  driven into interior of another
• Potts fracture at distal end of fibula with
  serious injury at distal tibial articulation
• Colles fracture of distal end of radius
  distal fragment displaced posteriorly

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Bone fracture repair fig 6.10

• 1. Formation of __________________
• -B.V. crossing the fracture are broken
• -Clot forms in 6-8 hrs
• -circulation in that areas stops?osteocytes die
• ?swelling and inflammation
• -capillaries grow into clot, macrophages
  osteoclasts remove dead damaged tissue
• -may take several weeks

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• 2. _________________ _________ forms
• -new capillaries organize growing CT procallus
• -fibroblasts osteogenic cells invade procallus
• ?produce collagen to connect broken ends
• osteogenic cells ?chondroblasts secrete
  fibrocartilage
• -phagocytes removing debris
• -this stage 3 weeks

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• 3. __________________ formation- in well
  vascularized areas closer to healthy bone tissue.
• osteogenic cells ? osteoblasts produce
  trabeculae
• Fibrocartilage?spongy bone
• - this stage 3-4 months
• 4. ____________________- dead portions of old
  fragments reabsorbed by osteoclasts
• -Compact bone replaces spongy
• healed area may now be thicker, stronger

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Diseases

• ____________- condition of porous bones
• Bone reabsorption outpaces bone deposition,
  largely due to depletion of calcium in the body
  (lost in urine, feces, and sweat rather than
  absorbed from the diet).
• Bone mass becomes so depleted that bones often
  fracture
• causes shrinkage of vertebrae?height loss
• hunched back and bone pain

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• Rickets and Osteomalacia- bones fail to calcify,
  organic matrix is produced but calcium salts are
  not deposited
• bones soft, rubbery and easily deformed
• ___________- in children- forming bone
• _______________- in adults- new bone formed
  during remodeling fails to calcify.
• Pain, tenderness, possible fracture from minor
  trauma.

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• ________________- infection of bone
• Characterized by high fever, sweating, chills,
  pain, and nausea
• Pus formation, edema, and warmth over affected
  bone and overlying muscle
• Bacteria reach bone thru
• Open fracture
• penetrating wounds
• orthopedic procedures
• Other sites of infection

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Medical terms/disorders

• Kyphosis- lump condition
• Exaggeration of the thoracic curve of vertebral
  column
• In elderly can be caused by degeneration of
  intervertebral discs
• Other causes ricket, poor posture, female
  advanced osteoporosis, tuberculosis of the spine
• Lordosis bent backwards AKA swayback
• Exaggeration of lumbar curve
• Causes ? wgt of abdomen pregnancy or obesity,
  poor posture, rickets, tuberculosis of the spine

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Medical terms/disorders

• Scoliosis- crooked, lateral bending of
  vertebral column (usually thoracic)
• Causes congenitally malformed vertebrae, chronic
  sciatica, paralysis of muscles on one side of
  vertebral column, poor posture, one leg shorter
  than other.
• Herniated (slipped) disc- ligaments holding
  intervertebral disc are injured or weakened
  causing the nucleus pulposus (inner portion) to
  herniate (protrude).
• Usually in lumbar region- wgt bearing
• Slip towards spinal cord or spinal nerves ?pain

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• _________skeleton- bones arranged along axis of
  the skeleton
• 80 bones
• Skull, hyoid, auditory ossicles, vertebral
  column, thorax
• ______________ skeleton- bones of upper lower
  limbs, girdles connecting the limbs to the
  axial.
• 126 bones
• Pelvic girdle- connect legs to axial skeleton
• Pectoral girdle- connect arms to axial