Skeletal system

1
Skeletal system
2
functions

• Framework / support
• Protection
• Movement by Levers actuated by muscles
• Storehouse for calcium and phosphorus
• Produce blood cells hemopoiesis
• Triglyceride storage Yellow bone marrow
  (adipose cells)

3
Bone classification

• BONES CLASSIFIED BY SHAPE
• Flat bones rib, skull, sternum, scapulae
• Short / Cube bones wrist, ankle
• Irregular bones vertebrae
• Long bones (typical) arms / legs

4
Long bone anatomy

• Compact bone Hard and dense, main shaft of long
  bone (diaphysis), outer layers of others.
  Osteocytes are located in the rings of bones
  around a central canal (Haversian system)
• Spongy bone meshwork of small boney plates
  (trabeculae) filled with red marrow and found at
  ends of long bones (epiphysis), center of others

5
Long bone cont

• Medullary cavity (marrow) Red makes blood
  cells, Yellow- largely fat, adults
• Membranes Periosteum (dense irregular) covers
  on outside inner layer has osteoblasts.
  Endosteum lines marrow cavity inside, single
  layer, bone forming cells
• Metaphyses end of bones, diaphysis joins
  epiphyses (epiphyseal plate) , when harden in
  early 20s. A line forms on Xray and growth
  stops.

6
Long bone
7
Ossification formation

• Bones are organs that as we are babies they start
  out as cartilage. During the 2/3rd month the
  osteoblasts become active. First the
  intercellular material has collagen and Calcium
  (Ca) deposited the material. It hardens. Now the
  cells are called osteocytes. When bone is
  damaged, osteoclasts reabsorb the bone fragments.

8
Haversian system

• Compact bone consists of closely packed osteons
  or haversian systems. The osteon consists of a
  central canal called the osteonic (haversian)
  canal, which is surrounded by concentric rings
  (lamellae) of matrix. Between the rings of
  matrix, the bone cells (osteocytes) are located
  in spaces called lacunae. Small channels
  (canaliculi) radiate from the lacunae to the
  osteonic (haversian) canal to provide passageways
  through the hard matrix. Blood vessels penetrate
  through transverse Volkmanns canals.

9
Haversian system
10
Haversian system
11
Bone formation

• 1) the initial formation in embryo / fetus
• 2) growth during infancy, childhood, adolescence
• 3) remodeling of bone
• 4) repair of fractures

12
Initial bone formation

• Embryonic skeleton first composed of mesenchyme
  (gelatin / reticular tissue -shaped like bones)
  which provides the template for ossification.
• Intramembranous bone forms directly within
  mesenchyme arranged in sheetlike layers that
  resemble membranes
• Endochondrial bone forms within hyaline
  cartilage that develops from mesenchyme

13
Intramembranous

1. Ossification center
2. Calcifcation
3. Formation of trabeculae
4. Periosteum

14
Endochondrial

1. Development of the cartilage model
2. Growth of the cartilage model
3. Development of the primary ossification center
4. Cavity formation
5. Development of secondary ossification center
6. Formation of articular cartilage and epiphyseal
   plate

15
Bone growth

• Appositional growth increase the width of new
  bone onto old bone
• Endochondrial growth Chondrocytes (epiphyseal
  plate) divide to align in columns. Expansion
  causes the bone to elongate. Old cartilage
  replaced by bone.
• Remodeling Removal of existing bone by
  osteoclast and deposition of new by osteroblast.
  Outside is deposited, medullary cavity is
  removed. Calcium levels maintained this way by
  hormonal control

16
Bone fractures

• Open (compound) bone protrudes through the skin
• Closed (simple) skin intact
• Complete bones separate
• Greenstick incomplete break on convex side of
  bone curve
• Communited more than 2 fragments
• Callus zone of tissue repair between two
  fragments

17
Lifestyle and bone development

• Diet - Daily intake of Calcium (Ca) form dairy
  products (milk, yogurt, and cheese),phosphorus,
  magnesium vitamin A, C, D
• Exercise (weight bearing), needed for proper
  remodeling
• Hormones Human growth hormone, Insulin Growth
  factors, Thyroid hormones, Estrogen female,
  Androgens males growth spurts in teenagers

18
Calcium homeostasis

• Bone stores 99 of Calcium. Small changes in
  blood calcium level can be deadly too high stops
  heart, too low breathing stops.
• Parathyroid hormones blood Ca drops, parathyroid
  produces cyclic Amp causing PTH synthesis to
  increase, increases osteoclasts to release Ca
  from bone and decrease loss form urine
• Calcitonin thyroid, decreases blood Ca

19
Bone features

• Head enlarged rounded end
• Crest prominent ridge
• Process projection
• Tubercle lump, knob
• Trochanter Large knob found only on the
  proximal femur
• Foramen hole in bone, nerve / blood vessel pass
  through

20
Bone features cont

• Fossa depression in bone
• Condyle smooth round articular surface, like on
  humerous, femur
• Shaft main body of bone

21
Abnormal curvatures

• Kyphosis hunchback abnormal posterial
  curvature of spine, upper thoracic.
• Lordosis abnormal anterior curvature in spine,
  lumbar region
• Scoliosis abnormal lateral curvature of spine,
  C or S

22
Disorders

• Osteoporosis- loss of bone mass, fractures
• Herniated disk rupture of fibrocartilage
• Spina bifida laminae not unite at midline
• Rickettes vitamin D deficiency
• Dwarfism inadequate ossification at long bone,
  shortness
• Gigantism abnormal ossification of growth plate
• Pagets disease older, irregular thickening and
  softening of bone.