10. Classification of Bones: By
Shape
• Long bones
– longer
than they
are wide
(e.g.,
humerus)
Figure 6.2a
11. Classification of Bones: By Shape
• Short bones
– Cube-
shaped
bones of the
wrist and
ankle
– Bones that
form within
tendons
Figure 6.2b
12. Classification of Bones: By Shape
• Flat bones
– thin,
flattened,
and a bit
curved
(e.g.,
sternum,
and most
skull bones)
Figure 6.2c
13. Classification of Bones: By Shape
• Irregular
bones –
bones with
complicate
d shapes
(e.g.,
vertebrae
and hip
bones)
Figure 6.2d
14. Classification of Bones: By Shape
• Sesamoid
– knee
bone (e.g.,
patella
only)
Figure 6.2d
Patella
15. Function of Bones
• Support – form the framework
• Protection – provide a protective case for
the brain, spinal cord, and vital organs
• Movement – provide levers for muscles
16. Function of Bones
• Mineral storage – reservoir for minerals,
especially calcium and phosphorus
• Blood cell formation – (hematopoiesis)
occurs within the marrow cavities of bones
17. Gross Anatomy of Bones: Bone
Textures
• Compact bone –
dense outer layer
• Spongy bone –
honeycomb of
trabeculae filled with
bone marrow
18. Spongy Bone
• Does NOT contain osteons (structural units)
• Made up of trabeculae (irregular latticework)
• Btw. spaces of trabeculae is filled with red bone
marrow
• Only site of RED bone marrow: (Forms blood cells)
• Vertebrae
• Skull
• Hips
• Ribs
• Sternum
• Ends of long bones
20. Bone Structure –
Typical Long Bone
• Diaphysis = shaft, yellow bone marrow produced here
• Epiphyses = distal & proximal ends
• Epiphyseal line = remnant of epiphyseal plate
• Periosteum = outer, fibrous, protective covering,
essential for bone growth & diameter
• Endosteum = inner lining of medullary cavity, contains
bone forming cells (osteoblasts)
• Articular cartilage = pad of hyaline cartilage on the
epiphyses where long bones articulate or join, reduces
friction, absorbs shock
• Medullary cavity= space w/in diaphysis that contains
fatty yellow marrow (produces blood cells)
25. Bone Tissue
• mineral salt makes them hard
– Magnesium salts
– Calcium salts
– Phosphorus salts
• collagen fibers gives them tensile
strength (the maximum stress the bone
can handle w/out breaking)
31. Chemical Composition of Bone:
Organic
• Osteo means bone
• Osteoblasts – bone-forming cells
• Osteocytes – mature bone cells
• Osteoclasts – large cells that resorb or
break down bone matrix
33. Microscopic Structure of Bone: Compact Bone
• Haversian system, or osteon – the structural unit
of compact bone
34. Parts of the Osteon (Haversian
System)
– Lamella – weight-bearing, column-like matrix tubes
composed mainly of collagen
35. – Haversian, or central canal – central channel
containing blood vessels and nerves
36. – Volkmann’s canals – channels lying at right
angles to the central canal, connecting blood
and nerve supply of the periosteum to that of
the Haversian canal
37.
38. Microscopic Structure of Bone: Compact Bone
• Lacuna – small cavities in bone that
contain osteocytes
39. • Canaliculi – hairlike canals that connect
lacuna to each other and the central canal
40. Hyoid Bone
• Only bone that does not articulate directly
with another bone
• Attachment point for neck muscles and
assists during swallowing and speech
41. Vertebral Column
• Formed from 26 irregular bones
• Cervical vertebrae – 7 bones of the neck
• C1=Atlas
• C2=Axis
– Thoracic vertebrae – 12 bones of the torso
– Lumbar vertebrae – 5 bones of the lower back
– Sacrum –5 fused bones
– Coccyx- 3-5 fused bones (tailbone)
46. Developmental Aspects: Fetal
Skull
• Bones are not fully connected and held
together by fontanels
• Fontanels
– Unossified membranes
– 4: anterior, posterior, mastoid, and sphenoid
48. Bone Deposition
• Occurs where bone is injured or added
strength is needed
• Requires a diet rich in
– Protein
– Vitamins C, D, and A
– Calcium
– Phosphorus
– Magnesium
– Manganese
49. Homeostasis of Bone Tissue
Nutrition
1. Vitamin D absorbs calcium
in small intestine
2. Vitamin A bone resorption
3. Vitamin C Hardens bones
Hormones
1. Growth Hormone (from
pituitary gland) stimulates
growth
2. Parathyroid Can increase
calcium levels (PTH)
3. Thyroid Can decrease
calcium levels (Calcitonin)
50. Developmental Aspects of
Bones
• By age 25, all bones are ossified
• Until age of 25 osteoblasts dominate
• Mid-old age osteoclasts dominate
51. Developmental Aspects: Old
Age
• Intervertebral discs become thin
• Loss of stature by several centimeters is
common after age 55
• All bones lose mass
52. Ossifications
• Intramembranous= forms flat bones
• Endochondral= forms all other bones
• http://health.howstuffworks.com/adam-
200125.htm
• http://commons.bcit.ca/biology/ossification/
files/ossification.html
53. Intramembranous ossification:
FLAT BONES
• Mesenchymal stem cells develop into
osteoblasts that secrete osteoids that
develop into bone tissue
• Spongy bone is formed followed by
compact bone surrounding medullary
cavity
54. Endochondral Ossification:
LONG BONES
1. Cartilage model formed
2. Primary ossification center formed in
diaphysis
3. Blood vessels, medullary cavity formed
4. Secondary ossification center formed in
epiphysis
5. Compact bone, articular cartilage, and
epiphyseal plate take shape
55. Stages of Endochondral
Ossification
Figure 6.8
Formation of
bone collar
around hyaline
cartilage model.
Hyaline
cartilage
Cavitation of
the hyaline carti-
lage within the
cartilage model.
Invasion of
internal cavities
by the periosteal
bud and spongy
bone formation.
Formation of the
medullary cavity as
ossification continues;
appearance of sec-
ondary ossification
centers in the epiphy-
ses in preparation
for stage 5.
Ossification of the
epiphyses; when
completed, hyaline
cartilage remains only
in the epiphyseal plates
and articular cartilages.
Deteriorating
cartilage
matrix
Epiphyseal
blood vessel
Spongy
bone
formation
Epiphyseal
plate
cartilage
Secondary
ossificaton
center
Blood
vessel of
periosteal
bud
Medullary
cavity
Articular
cartilage
Spongy
bone
Primary
ossification
center
Bone collar
1
2
3
4
5
56. Functional Zones in Long Bone
Growth
• Growth zone – cartilage cells undergo
mitosis, pushing the epiphysis away from
the diaphysis
“This is how you grow
Notes de l'éditeur
The atlas is just under the head and it is named for Atlas, the Greek god who supported the world on his shoulders. Because the god Atlas often adorned maps, a compilation of maps came to be known as an atlasAxis because world rotates on an axis
When a low blood calcium condition exists, the parathyroid glands respond by releasing parathyroid hormone (PTH). This hormone stimulates osteoclasts to break down bone tissue, and as a result, calcium salts are released into the blood. On the other hand, if the blood calcium level is excessively high, the thyroid gland responds by releasing a hormone called calcitonin. Its effect is opposite that of parathyroid hormone; it inhibits osteoclast activity allowing osteoblasts to form bone tissue. As a result, the excessive calcium is stored in bone matrix. The actions of these hormones are both excellent examples of some important negative feedback loops present in our bodies