1. Shape: Contribute to our body shape
and form
2. Support: for soft tissues and organs.
a. The 2 sets of bones that function
in total body support:
1. Lower limbs support the trunk
of the body when standing
2. Rib cage supports the thoracic
wall
3. Protection: 3 key sets of bones that protect the body are:
a. skull: fused bones protect the brain
b. Vertebrae surround and protect the spinal cord
c. Rib cage: protects thoracic organs (lungs and heart)
4. Movement: skeletal muscles attach to bones via tendons. The
muscles move the bones, like levers, causing the body to move.
• Determined by:
a. The arrangement of bones
b. The design of the joints
5. Storage:
•Bone stores: fat (in adult long bones), and minerals
•Bone contains several minerals such as K, Na, Mg, P and Ca.
The two most important are: calcium and phosphate
•The bone must store these and release them into the blood
stream as ions for organs that would need them
•Example: Vitamin D stimulates the small intestine to absorb
calcium into the blood stream after foods we eat are digested.
What do you think a vitamin D deficiency does to the bones of
a human?
6. Blood Cell Formation: This
process is called hematopoiesis.
• It occurs within the cavities
and hollow spaces of certain
bones. Tissue that produces
the blood cells is
hematopoietic tissue. This
process occurs in spongy
bone, which is found in flat
bone and in the ends of the
long bone, and in the marrow
cavity of long bones in kids.
Microscopic Anatomy of Bone:
The Cells
• Osteocytes: bone cells that are trapped in the
matrix; found throughout the osteon (series of
concentric circles in the bone).
Osetocytes
Osteon
Microscopic Anatomy of Bone:
The Cells
• Canaliculae: tiny channels running through an
osteon where osteocytes receive blood.
(connect to Haversian canal)
Canaliculae
Microscopic Anatomy of Bone:
The Cells
• Osteoblasts: bone builders
– Produce collagen fibers to give bone elasticity
– Calcium phosphate crystallizes on the fibers
forming hydroxyapatite, trapping the osteoblasts
and turning them into osteocytes
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Microscopic Anatomy of Bone:
The Cells
• Osteoclasts: bone crunchers
• Large and ameba-like
– Consume bone
– Found in spongy bone and along edges of
compact bone.
– Found just under the outer membrane of the
bone
osteocyte
canaliculae
lacunae
Bone Histology
• The central structural unit of compact bone is
the osteon (Haversion system)
• Osteon: found in compact bone;
– the group of concentric circles with a canal down
the center.
– Runs longitudinally (down the length of bone)
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Microscopic Anatomy of Bone:
The Cells
• Osteocytes sit in Lacunae: depressions in
bone where osteocytes live.
Close up of
osteocytes
sitting in
lacunae
The following structures are found in an
osteon:
• Haversian canal: (central canal)- open tube in
the center of an osteon where blood vessels
and nerves are found.
• Volkman’s canal: transverse canals that
connect osteons with each other; contain
blood vessels and nerves
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3
5
The following structures are found in an
osteon:
• Sharpey’s fibers: sharp,tough fibers made of
collegen that attach the periosteum (outer
membrane of bone) to the compact bone
(dense layer that contains osteons)
osteocyte
Haversian canal
canaliculae
osteon
lacunae
Osteocyte in lacunae
Haversian canal
Volkman’s canal
osteon
Sharpey’s fibers
Blood vessels &
nerves
1. Compact, Dense, or Medullary Bone:
external layer of the bone that is
dense and looks smooth and solid
to the naked eye.
2. Cancellous or Spongy Bone: a
honeycomb of small needle-like or
flat pieces (trabeculae) and open
spaces that are filled with red or
yellow bone marrow in living bones
Diaphysis: The shaft of a long bone ; Is a tube of compact bone .
•space inside is called the medullary cavity.
•In adults, is filled with fat and is called yellow bone marrow
cavity.
•In children it is filled with red marrow (tissue that produces
blood cells) and is called hematopoietic tissue.
Fetal hand diaphysis
Epiphysis- Ends of long bone. Is usually expanded. Has a thin
layer of cartilage on the outside. Spongy bone inside contains
marrow in the spaces. It is covered with compact bone for
protection.
Articular (also called “articulating” surface)
Surface of one bone epiphysis in a skeletal joint. These surfaces
are coated with articular (hyaline) cartilage. (it forms a “cap” over
the ends of the bones that reduces friction).
Epiphyseal plate:
An area of bone growth between the diaphysis and each of the
epiphyses. Is made of hyaline cartilage and new bone is being built,
here. This is how the long bone grows in length.
Epiphyseal line:
The line or “scar” in each epiphysis that is left over when the
epiphyseal plate calcifies and bone growth stops.
Periosteum:
•Is the external surface of diaphysis and part of epiphyses of
bone.
•Is composed of dense irregular connective tissue.
•Has imbedded in it osteoclasts (“bone-crunchers”) that dissolve
bone and osteoblasts (“bone builders”) that make new bone.
•Also has many nerve fibers, lymphatic vessels and blood vessels
that enter the bone and wind around through small canals inside
the bone.
•Is held to the bone by collagen fibers called Sharpey’s fibers.
epiphysis
Spongy bone
diaphysis
Articulating surface
periosteum
Yellow/red marrow
Epiphyseal plate
trabeculae
Compact bone
Epiphyseal line
Medullary cavity
Diploe:
The spongy bone tissue inside flat bones, plus the red bone
marrow in the spaces of the red marrow cavities. This is where
most of the adult blood cells are produced.
Sharpey’s fibers
periosteum
Spongy bone
trabeculae
diploe