Download Chapter 6 BoneTissue

Bone Tissue
Chapter 6
Bone Classifications
Skeleton-divisions
A. Axial- skull, thorax, vertebral column
B. Appendicular- shoulder girdle and
arm; pelvic (hip) girdle and leg
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Bone Types
Long bones-length bigger than width
 Short bones-roughly cube shaped
 Flat bones-thin, flat, usually curved
 Irregular bones-bones whose shape
doesn’t fit the 3 previous categories eg.
Hip bones, vertebrae

Function of bone
Support-framework for body
 Protection
 Movement-helped by skeletal muscle via
attachment with tendons
 Mineral storage-calcium, phosphate
 Blood Cell formation-completed in marrow

Bone Markings
p. 179 Table 6.1
 Fossa  depression
 Foramen  hole
 Tuberosity  Larger round projection,
rough (muscle)
 Condyle  rounded projection (joint)
 Spine  slender

Long Bone Structure
Diaphysis-shaft or long axis of bone
 Medullary cavity-hollow space inside;
contains fat; also called marrow
 Epiphysis-rounded ends of bone; covered
in hyaline cartilage
 Epiphyseal plate-disc of hyaline cartilage;
growth plate in children

Quiz Picture
p. 180 Fig.
6.3 a, c
Short, Irregular, Flat bone structure

Thin external covering of compact bone

Internally contain spongy bone (called
diploe in these bones)
Bone Coverings
External Coverings
Periosteum-double layer membrane
Outer = dense irregular CT
Inner = thin ET
osteoblast cells (forming)
osteoclasts cells (destroying)
Internal Coverings
Endosteum-thin, CT membrane, both cells
Microscopic Anatomy of Bone
Compact bone (Lamellar bone)
 Haversian System- structural unit of
compact bone; also called osteon
 Cylinders of concentric lamellae 
collagen fibers run opposite each other
 Center of Osteon - Haversian canalcontains blood vessels, nerve fibers
 Osteocytes- bone cells that live in
lacunae surrounding the lamellae
Lamella(e)
Growth circles, like a tree
 Opposite twisting collagen fibers
 Resist torque forces

Two special ones
 Interstitial  fill in spaces between osteons
 Circumferential  around all the osteons
Quiz Picture
p. 183 Fig
6.6a
Quiz Picture
p. 183 Fig
6.6 b
Microscopic Anatomy of Bone
Spongy Bone- no osteons present;
lamellae are irregularly arranged
Two types
 Trabeculae  middle of long bones
 Dipolë  middle of short/irregular bones
*same thing in different spots*
Chemical Composition of Bone
Organic portion (1/3)- cells  osteoblasts,
osteoclasts, osteocytes &
osteoid  ground substance proteoglycans
& glycoproteins, collagen fibers
Inorganic portion- 2/3 hydroxyapatite
(mineral salts); calcium phosphate packed
tightly around collagen fibers
67%
33%
Bone Formation

Intramembranous Bone Formation- results in
formation of cranial bones of skull and clavicles
(Flat and Irregular Bones)
1. Mesenchyme cells invade membrane;
become osteoblasts
2. Osteoblasts secrete matrix; calcifies
3. Spongy bone forms; develops periosteum
4. Grows outward to develop external compact
bone; internal bone becomes mature diploe;
develops red marrow
Bone Formation

Endochondral Ossification (Long bones)
Growth of Long Bones
Growth Zone- epiphyseal plate cartilage
cells reproduce and grow away from the
diaphysis
 Transformation Zone- chondrocytes die
as the cartilage matrix calcifies
 Osteogenic Zone- osteoblasts invade the
area and form spongy bone

Transformation
Wolff’s Law
•Bone resists
mechanical stress
•Trabeculae form
scaffolding along stress
lines
•Thicker compact bone
(markings) where
tendons and ligaments
attach
Bone Remodeling
Bone deposit- addition of bone; occurs
with injury or need for added strength;
deposit osteoid which calcifies; alkaline
phosphatase necessary; osteoblasts
 Bone resorption- removal of bone;
osteoclasts; about the bone and release
enzymes from lysosomes and HCl
 Occurs at periosteal and endosteal
surfaces

Hormonal
Control
Of
Bone
Formation
Osteoporosis
Bone resorption out paces bone deposit, bone
is porous and light
 Many causes:
Lack of exercise, poor diet
Post menopausal women  lack of estrogen
leaves osteoclasts unchecked
 Exercise, vitamins and hormone therapy are
most common treatments
 Main key is calcium during childhood
(Prevention)

Normal Bone
Osteoporosis
Homeostatic Imbalances
Paget Disease
• Improper bone formation
• To much spongy bone
Osteomalacia/Rickets
• Osteoid improperly calcified
• Growth plates in children
• Extra long and wide bones
• No calcium or sunlight
Bone Repair