Download Skeletal System

Chapter 6
Bones and Skeletal System
Classification of Bones
• Axial skeleton –
bones of the skull,
vertebral column, and
rib cage
• Appendicular skeleton
– bones of the upper
and lower limbs,
shoulder, and hip
Function of Bones
• Support – form the framework that
supports the body and cradles soft organs
• Protection – provide a protective case for
the brain, spinal cord, and vital organs
• Movement – provide levers for muscles
• Mineral storage – reservoir for minerals,
especially calcium and phosphorus
• Blood cell formation – hematopoiesis
occurs within the marrow cavities of bones
Classification of Bones:
By Shape
• Long bones – longer than they
are wide
(e.g., humerus)
• Short bones
• Cube-shaped bones of the
wrist and ankle
• Bones that form within tendons
(e.g., patella)
• Flat bones – thin, flattened,
and a bit curved (e.g., sternum,
and most skull bones)
* Irregular bones – bones with
complicated shapes (e.g.,
vertebrae and hip bones)
General Facts
a. The skull is made of 22 bones: 8 cranial, 13
facial, mandible
b.There are 206 individual bones in an adult.
Some are hinged and others are fused to one
another
c. The upper jaw (maxillae) is fused to the cranium.
The lower jaw (mandible) is moveable.
d.The infant skull is incompletely developed and
features fontanels or soft spots to aid passage
thru the birth canal
General Facts continued. . .
e. The vertebrate is made of:
i. 7 cervical vertebrae
ii. 12 thoracic vertebrae
iii. 5 massive lumbar vertebrae
iv. Sacrum, which is a triangular bone made of 5
fused bones at the end of the vertebral column.
v. Coccyx, which is made up of 4 fused bones at
the end of the sacrum (tailbone). It is immovable
in humans, but flexible in cats, dogs, and monkeys
General Facts continued. . .
f. There are 12 pairs of ribs which attach to the
sternum thru the thoracic vertebrae.
-the first 7 pairs of ribs are true (or
vertebrosternal) ribs that join the sternum directly
by their costal cartilages.
-the remaining 5 ribs are false ribs: the first 3
pairs are vertebrochondral ribs and the last 2 pairs
are floating ribs.
g.Bones grow from the growth
plates in the epiphyseal disks
Parts of the Long Bone
• Periosteum – double-layered protective
membrane
– Outer fibrous layer is dense regular connective tissue
– Inner osteogenic layer is composed of osteoblasts
and osteoclasts
– Richly supplied with nerve fibers, blood, and
lymphatic vessels, which enter the bone via nutrient
foramina
– Secured to underlying bone by Sharpey’s fibers
• Endosteum – delicate membrane covering
internal surfaces of bone
Parts of the Long Bone (cont.)
• Marrow:
i. Yellow: Located in the center of the
diaphysis in the medullary canal. Made
mostly of fat cells, contains many blood
vessels, some leukocytes (WBC).
Functions as a fat storage center.
ii. Red: Located at the ends of the long
bones. Where some erythrocytes (RBC)
and WBCs are made.
Gross Anatomy of Bones: Bone
Textures
• Compact bone – dense outer layer. Makes up the walls of the
diaphysis.
• Spongy bone – honeycomb of trabeculae filled with yellow bone
marrow. Fills the epiphyses to reduce the weight of the skeleton.
Bone Markings
Structure of Long Bone
• Long bones consist of
a diaphysis and an
epiphysis
– Diaphysis
• Tubular shaft that forms
the axis of long bones
• Composed of compact
bone that surrounds the
medullary cavity
• Yellow bone marrow
(fat) is contained in the
medullary cavity
Structure of Long Bone (cont.)
• Epiphyses
– Expanded ends of long bones
– Exterior is compact bone, and the interior is
spongy bone
– Joint surface is covered with articular
(hyaline) cartilage
– Epiphyseal line separates the diaphysis from
the epiphyses
Microscopic Structure of Bone:
Compact Bone
• Osteocytes – mature bone cells
• Lacunae – small cavities in bone that
contain osteocytes
• Canaliculi – hairlike canals that connect
lacunae to each other and the central
canal
Microscopic Structure of Bone:
Compact Bone
• Haversian system, or
osteon – the structural unit
of compact bone
• Lamella – weight-bearing,
column-like matrix tubes
composed mainly of
collagen
• Haversian, or central canal
– central channel containing
blood vessels and nerves
• 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
Formation of the Bony Skeleton
• Begins at week 8 of embryo development
• Bones form by replacing connective tissue
in the fetus. This process is called
ossification
Bone Development (cont.)
There are 2 types of bones:
i. Intramembraneous bones1. Osteopblasts deposti bondy tissue
around themselves and they become
oseteocytes.
2. The membrane layer on the outside of
the developing bone become the
periosteum.
Bone Development (cont.)
There are 2 types of bones:
ii. Endochondral bones1. Classification of most bones in the
body.
2. Starts as hyaline cartilage and are
replaced by bones.
3. Cartilage is invaded by blood vessels
and oseoblasts that first form the
spongy bone.
10 Types of Fractures
1. Compression Fracture: bone crushed; common
in the vertebral column
2. Comminuted fracture: most commonly seen in
the brittle bones of the elderly
3. Compound fracture: fracture in which the bone
ends penetrate the skin
4. Closed reduction: non-surgical realignment of
broken bone ends and splinting of the bone.
5. Depressed fracture: common fracture of the skull
in which the bones become concave
10 Types of Fractures (cont.)
6. Simple fracture: bone is cleanly broken and does
not penetrate the skin; commonly called a closed
fracture
7. Impacted fracture: fracture in which the broken
ends are pushed into each other
8. Open fracture: fracture that required surgical
realignment of the broken bone ends
9. Greenstick fracture: common in children; bone
splinters but doesn’t break completely;
sometimes referred to as a “hairline” fracture
10.Spiral fracture: bone breaks due to twisting
forces: common in sports injuries
Closed reduction
Open reduction
compound
Impacted
Impacted
Bone Videos
• X-rays
• http://video.about.com/orthopedics/HowDoes-an-X-Ray-Work--.htm
• Hip Replacements
• http://video.about.com/orthopedics/HipReplacement.htm
• Knee Replacement
• http://video.about.com/orthopedics/KneeReplacement.htm