Skeletal System
Week 1
Introduction
Bones and organs of the Skeletal System
Support and protect softer tissues
Provide points of attachment for muscles
House blood-producing cells
Store inorganic salts
There are 206 Bones in the human body!!!
Bones Classification
Bones are classified according to their shapes.
Bone Classification
Long bones – have long longitudinal axes and
expanded ends.
Short bones – are somewhat cubelike, with
roughly equal lengths and widths.
Flat bones – are platelike structures with broad
surfaces.
Irregular bones – have a variety of shapes and
most are connected to several other bones.
Parts of a
Long Bone
Parts of a Long Bone
Epiphysis – the ends of a long bone.
Proximal – nearest to the trunk.
Distal – furthest from the trunk.
Articular cartilage - covers the external surface
of the epiphyses.
 Made of hyaline cartilage
 Decreases friction at joint surfaces
Diaphysis – the shaft of the bone, between the
epiphysis.
Parts of a Long Bone
Periosteum – outside covering of the
diaphysis.
Medullary cavity – cavity of the shaft
Contains yellow marrow (mostly fat) in
adults
Endosteum – a thin layer of cells that
lines the medullary cavity.
Types of Bone Tissue
Compact bone –
tightly packed tissue
with no gaps.
Spongy bone – small
needle-like
pieces of bone
(trabeculae)
Many open spaces
Microscopic Structure
Microscopic Structure
Osteocytes – bone cells
Lacunae – cavities containing bone cells
(osteocytes).
Lamellae – rings around the central canal.
Canaliculi – tiny canals used to transport
substances from central canal to lacunae.
Microscopic Structure
Central (Haversian) canal – opening in the
center of an osteon.
Carries blood vessels and nerves.
Perforating (Volkmann's) canal – canal
perpendicular to the central canal.
Carries blood vessels and nerves.
Osteon – a unit of bone.
Check Your Understanding
1.Explain how bones are classified.
2.List the major parts of a long bone.
3.How do compact and spongy bone differ
in structure?
4.Describe the microscopic structure of
compact bone.
Bone Development and Growth
Intramembranous bones – the flat bones
of the skull.
Formed by unspecialized connective
tissue appearing at future bone sites.
Osteoblasts – bone forming cells.
Ossification – the formation of bone.
Bone Development and Growth
Endochondral bones – most of the bones of the
skeleton.
developed in the fetus from masses of hyaline
cartilage.
Primary Ossification Center – first region where
bone begins to form. (center of diaphysis)
Secondary Ossification Center – second region
where bone forms. (epiphysis)
Epiphyseal Plate – a band of cartilage between
the diaphysis and the epiphysis.
Bone Development and Growth
Epiphyseal plate includes layers of young
cells that are producing new cells.
Bone will continue to grow as long as
this is active.
Osteoclasts – bone destroying cells.
Break down bone matrix for remodeling
Bone Development and Growth
Check for Understanding
1. Describe the development of an intramembranous
bone.
2. Explain how an endochondral bone develops.
3. Explain the function of osteoclasts and osteoblasts and
how they help remodel the bone.
4. What factors do you think affect bone development
and growth.
5. What do you think would happen if there was damage
to the epiphyseal plate?
Bone Function
Shape, support, and protect body
structures
Aid in body movement
House tissue that produces blood cells
Store inorganic salts (calcium)
Week 2
Skeletal Organization
Axial skeleton – consists of the parts that
support and protect the organs of the
head, neck, and trunk.
Appendicular skeleton – consists of the
bones of the upper and lower limbs and
the bones that anchor the limbs to the
axial skeleton.
Skull
Skull
Skull
Vertebral Column
Thoracic Cage
Skeleton
Bones of the Hand