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BCT Tendons

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									The Skeletal System




Chapter 6, 7,& 8 Martini, 1st Ed.
   Anatomy and Physiology
  Liberty Senior High School
Question of the Day!

Do bones remain the same?
How do bones “know” when
  to stop growing? What
 happens when they don’t?
The Skeletal System!
 Our First System
    Cells (Osteocytes)

 Tissues (Osseous Tissue)

     Organs (Bones)

    Systems (Skeletal)
 All C.T. have Three Parts
1. Specialized Cells
2. Extracellular Protein Fibers
3. The Fibers above and a ground
 substance (usually a liquid)- make
 up the Matrix that surrounds cells.
 (most of the volume of C.T.)
         The Fibers

• Collagen Fibers- long,
  straight, unbranched, fibers
  of twisted protein; rope-like,
  very flexible, yet strong.
  (Tendons and Ligaments)
        The Matrix
• G.S. = almost no liquid;
  collagen fibers + calcium salts
  (CaPO4 and some CaCO3)
• Strong and flexible
  properties.
• Lacunae in matrix contain
  osteocytes.
   Bone (Osseous Tissue)
• Lacunae organized around a
  central canal (Haversian canal)
  which contains blood vessels.
• Diffusion cannot occur through
  calcium salts.
• Cytoplasm of osteocytes extend to
  central canal by canaliculi.
  A Basic Pattern in Bone
          Tissue
• Lacunae with osteocytes
  arranged around and connected
  to a central canal by radiating
  canaliculi- Osteon
• Many osteons in one bone.
Bone-Low Mag.
Bone-High Mag.
Osteons
Haversian or Central Canal
 Two Types of Osseous Tissue
1. Compact bone- dense bone,
 solid, more on surface of bone,
 shaft of bone.
 Function: osteons are all
 alligned;strengthen bone, the
 tissue of bone is parallel to
 stresses.
 Two Types of Osseous Tissue
2. Spongy Bone- open network
 of trabeculae which are struts
 and plates in the interior of
 bone (matrix) , light in weight;
 Function: has no osteons;
 withstand stress from a variety
 of directions, reduce the weight
 of the overall bone.
    Bone (Osseous Tissue)
• Bone surfaces covered by
  periosteum- fibrous layer of C.T.;
  attachment for tendons and
  ligaments.
• Site of appositional growth of
  bone.
• Bone is constantly remodeled-
  grow thicker with stresses.
http://www.bio.psu.edu/f
aculty/strauss/anatomy/s
kel/skeletal.htm
  Bone Development &
        Growth
Bony skeleton begins to form
6 weeks after fertilization (12 mm)
         Osteogenesis
Ossification- formation of bone is a
 dynamic process.
Osteoblasts- produce new bone
 matrix.
Osteoclasts- produce acids and
 enzymes to release the stored
 minerals in the matrix.
Osteocytes- mature bone cells that
 do not divide.
Osteoblasts
Osteoclasts
Bone Cell Interaction
   2 types of Ossification
Intramembranous - bone develops
from mesenchyme or fibrous C.T.

Endochondral – bone replaces
existing cartilage
      Intramembranous
         ossification
Occurs in the deeper layers of the
 dermis- Dermal bones
             Ex: top of skull,
 mandible, clavicle, abnormal
 stressed areas like tendons, joints,
 skeletal muscles (heterotopic bones-
 different place)
     Intramembranous
        ossification
1.Formation of bone matrix w/in
the fibrous membrane
• Mesenchymal cells make the
the matrix of calcium salts
• Mesenchymal cells turn into
osteoblasts
• Ossification occurs:
Osteoblasts  Osteocytes
    Intramembranous
       ossification
2. Formation of bone
•Bone grows outward in small
struts called: Spicules (form
trabeculae)
•Blood vessels become trapped
among spicules
    Intramembranous
       ossification
3. Formation of Compact Bone
& periosteum
•Small amount of spongy bone
is replaced with mature
compact bone
• Mesenchyme makes periosteum
Heterotopic Bone
   Formation
FOP
Endochondral Ossification
1. Hyaline chondrocytes die &
   disintegrate leaving cavities within
   cartilage.

2. Blood vessels grow at edges &
   perichondrial cells become
   osteoblasts (turns to bone on the
   edges).
 Endochondral Ossification
3. -Blood vessels penetrate the
central region
( fibroblasts osteoblasts)
  -Bone development begins at
Primary Center of Ossification
(go towards ends)
Endochondral Ossification
4. Osteoclasts- create a
 marrow cavity by dissolving
 struts
Endochondral Ossification
Increasing the Length
• Osteoblasts of the diaphysis and
  chrondrocytes of epiphysis
  continue to grow; elongate bone.
• Epiphyseal Plate is this interface
  between the two.
Endochondral Ossification
5.-Center of epiphyses begin to
calcify
 -Capillaries & osteoblasts migrate
into this area.
  -Secondary Ossification Center
Endochondral Ossification
6. Epiphysis is filled with spongy
 bone
-Articular cartilage remains at
 exposed joint cavity
-At the metaphysis, epiphyseal
 plate separates the epiphysis
 from the diaphysis
Endochondral Ossification
 •At puberty, the osteoblasts
 overcome chondrocytes; the
 plate becomes more narrow-
 epiphyseal line.
Bone Formation In An
      Embryo
Growth Plate
Endochondral Ossification
Fetal Long Bone
Developing Long Bone
 Increasing the Diameter
•Enlarges through Appositional
Growth at outer surface
•Periosteal cells  Osteoblasts 
Osteocytes
•Osteoclasts remove bone matrix at
inner surface
Achondroplasia
When bones don’t stop growing!

								
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