
Bone cells
›
›
›
›
Osteoblasts
Osteocytes
Osteoclasts
Stem cells or osteochondral progenitor cells
Woven bone: collagen fibers randomly
oriented
 Lamellar bone: mature bone in sheets
 Cancellous bone: trabeculae
 Compact bone: dense

6-2
Bones are composed
of connective tissue,
chemicals, and fats
 Solid outer layer compact bone

› Composed of osteons

An inner layer of
spongy bone
› a honeycomb of flat,
needle-like projections
called trabeculae.
Above: Note the relationship btwn the
compact and spongy bone.
Below: Close up of spongy bone.

Haversian canals

› allow the passage of blood
vessels, lymphatic vessels,
and nerve fibers.
› Surrounded by layers of
bone called a lamella.
osteon
Volkmann’s canals
› Perpendicular to the
haversian canals.
› Connect the blood and
nerve supply in the
periosteum to those in the
haversian canals and the
medullary cavity.

Osteoblasts
› Bone building cells
› Synthesize and secrete
osteoblasts
collogen fibers and other
organic components of the
bone matrix
› Initiate calcification
› Found in the periosteum and
the endosteum
 Ossification
› Formation of bone by
Bone matrix
osteoblasts.
› Cells surround themselves by
matrix.
 Osteocytes.
› Mature bone cells.
› Osteoblasts that have
become trapped by the
secretion of matrix.
› Responsible for maintaining
the bone tissue
 Lacunae
› spaces occupied by
osteocyte cell body
 Canaliculi
› canals that allow for
nutrient filled liquid to fill
the lacunae
6-7
Osteoclasts
Cells that ecretes digestive enzymes to digest bone matrix
bone resorption
Concentrated in the endosteum.
On the side of the cell that faces the bone surface,
ruffled border.
Pumps out hydrogen ions
Create an acid environment that eats away at the matrix.
Why is there a depression underneath the osteoclast?
What advantage might a ruffled border confer?
What is the name of the third cell type shown here?
What do you think the tan material represents?
www.academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/Skeletal/
BoneTissue.ppt

Diaphysis - Shaft
› Compact bone

Epiphysis - End of the bone
› Cancellous bone

Epiphyseal plate - growth plate
› Hyaline cartilage; present until
growth stops
Epiphyseal line: bone stops growing
in length
 Medullary cavity: contains marrow
› In children medullary cavity is
red marrow,
› In adults marrow is yellow in limb
bones and skull (except for
epiphyses of long bones).
• Red marrow is found in in the
cavities of the spongy bone
of flat bones


Periosteum
›
›
›

Outer is fibrous
Inner is single layer of
bone cells including
osteoblasts, osteoclasts
and osteochondral
progenitor cells
connected to bone
matrix via Sharpey’s fibers
Endosteum.
›
›
Similar to inner layer of
periosteum.
Lines all internal spaces
•Osteocytes
•Lamellae
•Haversian
canals
•Osteon
•Volkmann’s
canals
•Lacunae
•Diaphysis
•Periosteum
•Sharpy’s fibers
•Epiphyses
•Epiphyseal
plate
•Epiphyseal line
•Yellow marrow
•Medullary
cavity
•Sharpy’s fibers

Consists of organic and inorganic
components.
› Organic component are secreted by the
osteoblasts:
 Collagen fibers
 Elastin
› Inorganic component
 Calcium phosphate
 Calcium hydroxide
 magnesium, fluoride,
& sodium.

What if the Calcium phosphate, Calcium
hydroxide and the other minerals were
removed from this bone?

What if the collagen and elastin were
removed from this bone.
Figure 5.2

Prenatal: cartilage model

Fetus: some conversion to bone

Childhood: primary and secondary
ossification sites formed

Adolescence: cartilage growth plate
elongates

Changes in shape, size, strength:
› Dependent on diet, exercise, age

Bone cells regulated by hormones:
› Parathyroid hormone (PTH): removes calcium from
bone
› Calcitonin: adds calcium to bone

Repair: hematoma and callus formation

Protection: encases most internal organs

Support: allows body positions

Permit movement: muscle attachments for
movement

Mineral reservoir: calcium, phosphorus

Classified by degree of movement:
› Fibrous joint: immovable (e.g., fontanels)
› Cartilagenous joint: slightly movable, cartilage
connection (e.g., backbone)
› Synovial joint: freely movable
Figure 5.12a

Joint capsule: synovial membrane + hyaline
cartilage

Synovial membrane secretes synovial fluid as
lubricant

Hyaline cartilage cushions

Sprains: stretched or torn ligaments

Bursitis and tendinitis: inflammations

Arthritis: inflammation of joints