The Skeletal System
Functions of Bones
Support
1.


Soft tissue
Attachment of tendons
Protection
3. Assistance in movement
4. Mineral homeostasis
2.

Release minerals when
needed


99% of the body’s calcium
is stored in bone.
85% of the body’s
phosphorous is stored in
bone.
Continued
Blood cell production
(hemopoiesis)
6. Triglyceride storage
5.
Red Marrow vs Yellow Marrow
 Red marrow
 Yellow marrow
 Made (hemopoiesis) in the
 Stored in medullary cavity
spongy bone
 Consists of adipocytes,
fibroblasts and
macrophages
 Later changes to yellow
marrow
 Consists of adipocytes
which store fat
 Can be an energy reserve
Types of Bones
1. Long Bones
 Much longer than they
are wide
 Curved for strength
2. Short Bones
 Roughly cube shaped
 Equal in length and width
Carpal Bones
Continued
3.
Flat Bones
 Thin
 Large surface area for
muscle attachment
Sternum
4.
Irregular Bones
 Weirdly shaped
All Bones
 Compact Bone
 Solid outer layer
 Spongy bone
 a network of flat, needle-like
projections called trabeculae.
Structure of Long Bone
Structure of Long Bone
 Articular cartilage
 Type of hyaline cartilage
 Cushions bones and
reduces friction
 Periosteum
 Supplied with nerve fibers
and blood vessels
 Assists in growth and
repair
 Endosteum
 Contains a single layer of
bone forming cells
Structure of “other” types of Bones
 Compact (covered by
periosteum)
 Spongy bone (lined with
endosteum)
 Called the diploe
 Bone marrow made between
trabeculae
Osseous Tissue
Extracellular matrix contains:
 Water
 Collagen fibers (flexibility)
 Crystalized mineral salts
(mostly calcium
phosphorous)
 Is bone completely solid?
This bone:
a. Has been demineralized
b. Has had its organic component removed
Types of Cells in Osseous Tissue
Osteogenic cells
1.


Unspecialized stem cell
Only cell to go through
cell division
Osteoblasts
2.


Bone building
Synthesize collagen and
organic components
 http://www.youtube.com
/watch?v=78RBpWSOl08
Continued
Osteocytes
3.


Trapped osteoblasts
Maintain metabolism
Osteoclasts
4.


“Bone breaking”
Digests extracellular
matrix
•Here, we see a cartoon showing all 3 cell types. Osteoblasts and osteoclasts are indicated.
•Note the size of the osteoclast (compare it to the osteoblast), and note the ruffled border.
•Why is there a depression underneath the osteoclast?
•What is the name of the third cell type shown here?
•What do you think the greenish material represents?
Compact Bone
 Osteon
 All the “rings” of the
lamallae (dartboard)
 Central Canal
 Contain blood vessels but
do not connect layers of
bone
 Lamellae
 The “rings” of bone
 http://www.youtube.com
/watch?v=ylmanEGjRuY
Compact Bone
 Canaliculi
 Channels that connect the
rings
 Perforating Canal
 Contain blood vessels that
connect the layers of bone
Long Bone
Spongy Bone
 Is light
 Support and protect red
marrow
 Made up of trabeculae
 Have lamellae, osteocytes
(in the lacunae) and
canaliculi
 Why is spongy bone
essential to bone structure?
Bone Formation
 http://www.youtube.com/watch?v=p-3PuLXp9Wg
 Intramembranous Ossification VS Endochondral Ossification
Division of Skeletal System
 Axial skeleton
 Includes the bones of the
skull, vertebral column, and
rib cage.
 For protection and support
 Appendicular skeleton
 Bones of upper & lower
limbs, shoulder and hips
 Used for movement
Bone Structure
 Bones are organs. Thus, they’re composed of multiple
tissue types. Bones are composed of:







Bone tissue (a.k.a. osseous tissue).
Fibrous connective tissue.
Cartilage.
Vascular tissue.
Lymphatic tissue.
Adipose tissue.
Nervous tissue.