skeletal system and bones

SKELETAL SYSTEM
THE STRUCTURES OF THE SKELETAL
SYSTEM INCLUDE:
BONES, JOINTS, AND LIGAMENTS.

SKELETAL SYSTEM
FUNCTIONS OF THE SKELETAL SYSTEM
1. SUPPORT
2. PROTECTION
3. MOVEMENT
4. MINERAL STORAGE
5. BLOOD CELL FORMATION

CLASSIFICATION OF BONES BY
POSITION
THE 206 BONES OF THE HUMAN
BODY ARE GROUPED INTO
THE AXIALAND THE
APPENDICULAR SKELETONS.

AXIAL SKELETON
THE AXIAL SKELETON
FORMS THE LONG AXIS OF THE
BODY AND INCLUDES THE
BONES OF THE SKULL, VERTEBRAL
COLUMN, AND THE RIB CAGE.

AXIAL SKELETON
GENERALLY THESE BONES ARE MOST
INVOLVED IN PROTECTING, AND
SUPPORTING.

APPENDICULAR SKELETON
THE APPENDICULAR SKELETON
CONSISTS OF THE BONES OF THE
UPPER AND LOWER LIMBS,
AND THE GIRDLES THAT
ATTACH THE LIMBS TO THE
AXIAL SKELETON.

APPENDICULAR SKELETON
THE APPENDICULAR SKELETON
CONSISTS OF 126 BONES. IT
FUNCTIONS TO HELP IN MOVEMENT.

AXIAL and APPENDICULAR
SKELETONS

CLASSIFICATION OF BONE BY
SHAPE
THE BONES OF THE HUMAN
SKELETON COME IN MANY SIZES
AND SHAPES. BONES CAN BE
CLASSIFIED BY SHAPE INTO:
LONG; SHORT; FLAT; IRREGULAR.

LONG BONES
Long bones are longer
than they are wide.
Long bones have 2
epiphyses, and a
diaphysis.
All of the bones of
the limbs, except the
patella, ankle, and
wrist, are long bones.

SHORT BONES
Short bones are
cube shaped, nearly
equal in length and
width.
The bones of the
wrist and ankle are
examples of short
bones.

SHORT BONES
A SPECIAL TYPE OF SHORT
BONE IS A SESAMOND BONE.
THIS TYPE OF BONE IS A
SHORT BONE WHICH FORMS
WITHIN A TENDON. AN EXAMPLE
IS THE PATELLA, AND THE PISIFORM.

FLAT BONES
Flat bones are thin,
flattened, and a bit
curved.
The sternum,
scapulae, ribs, and most
of the bones of the
skull are flat bones.

IRREGULAR BONES
Irregular bones have
complicated shapes
that fit none of the
preceding classes.
The vertebrae, the
bones of the hip, and
some facial bones.

GROSS ANATOMY OF A
LONG BONE
A long bone has a
shaft, the Diaphysis,
and two ends,the
epiphyses.
Covering a long bone
in all area, except the
articular surfaces, is
Periosteum.

GROSS ANATOMY OF A
LONG BONE
Covering the articular
surfaces is articular,or
hyaline, cartilage.
Deep to the periosteum
is a layer of compact bone.
this layer is thicker in the
diaphysis than the
epiphysis.

GROSS ANATOMY OF A
LONG BONE
In the diaphysis of
the long bone deep to
the compact bone is
the medullary cavity.
in an adult it is full of
yellow bone marrow.
The medullary cavity
is lined with endosteum.

GROSS ANATOMY OF A
LONG BONE
In the epiphyses deep
to the layer of compact
bone is spongy bone.
 Between the
trabecula of the spongy
bone is red bone marrow.

MICROSCOPIC STRUCTURE
OF COMPACT BONE
THE STRUCTURAL UNIT OF
COMPACT BONE IS THE OSTEON,
OR HAVERSIAN SYSTEM. EACH OSTEON
IS AN ELONGATED CYLINDER
ORIENTED PARALLEL TO THE
LONG AXIS OF THE BONE.

OF COMPACT BONE

OF COMPACT BONE
AN OSTEON IS A GROUP OF HOLLOW
TUBES OF BONE MATRIX,
ONE PLACED OUTSIDE THE NEXT
LIKE THE GROWTH RINGS OF A
TREE TRUNK. EACH OF THE MATRIX
TUBES IS A LAMELLA.

OF COMPACT BONE
THE COLLAGEN FIBERS IN A
PARTICULAR LAMELLA RUN IN
A SINGLE DIRECTION.

OF COMPACT BONE
Running through the
core of each osteon is the
central,or Haversian canal.
 The canal contains
small blood vessels and
nerve fibers that serve the
needs of the osteon’s cells.

OF COMPACT BONE
Spider shaped osteocytes
occupy small cavities called
lacunae at the junctions of
the lamellae.
Hair like canals called
canaliculi connect the
lacunae to each other.
The space between these
structures is occupied by
bony matrix.

OSSIFICATION
OSSFICATION OR OSTEOGENESIS
IS THE PROCESS OF BONE FORMATION.
THERE ARE 2 MECHANISM
WHICH FORM BONE:
1. INTRAMEMBRANOUS
2. ENDOCHONDRAL

OSSIFICATION
INTRAMEMBRANOUS OSSIFICATION
RESULTS IN THE FORMATION
OF THE CRANIAL BONES AND
THE CLAVICLES.

OSSIFICATION
ENDOCHONDRAL OSSIFICATION
RESULTS IN THE FORMATION OF THE
BONES BELOW THE
SKULL, WITH THE EXCEPTION OF
THE CLAVICLES.

OSSIFICATION
THREE TYPES OF CELLS ARE INVOLVED
IN BOTH MECHANISM OF OSSIFICATION:
1. OSTEOBLASTS
2. OSTEOCLASTS
3. OSTEOCYTES

STEPS OF INTRAMEMBRANOUS
OSSIFICATION
1. Selected
mesenchymal cells
cluster and form
osteoblasts.
2. This forms an
ossification center.

OSSIFICATION
3. Osteoblasts begin
to secrete osteoid,
which mineralized.
4. The osteoblasts are
trapped differentiate
into osteocytes.

OSSIFICATION
5. Accumulating
osteoid is laid down
between embryonic
blood vessels.
6. This forms a
network of trabulae.

OSSIFICATION
7. Vascularized
mesenchyme condenses
on the external face
of the woven bone and
becomes the periosteum.

OSSIFICATION
8. Trabeculae just deep
to the periosteum
thicken, forming a bone
collar.
9. The bony collar is
later replaced with
mature compact bone.

OSSIFICATION
10. Spongy bone,
consisting of distinct
trabeculae, are present
internally. Blood vessels
differentiate into red
bone marrow.

STEPS OF ENDOCHONDRAL
OSSIFICATION
1. The perichondrium
covering the hyaline
cartilage “bone” is
infiltrated with blood
vessels.
2. Osteoblasts secrete
osteoid against the hyaline
cartilage diaphysis,
encasing it in a bony collar.

OSSIFICATION
3. Chondrocytes
within the diaphysis
hypertrophy and signal
the surrounding
cartilage matrix to
calcify.
4. The chondrocytes,
however, die and the
matrix begins to
deteriorate.

OSSIFICATION
5. In month 3, the
forming cavities are
invaded by a collection
of elements called the
periosteal bud.
6. The entering
osteoclasts partially
erode the calcified
cartilage matrix.

OSSIFICATION

OSSIFICATION
7. Osteoblasts
secrete osteoid around
the remaining
fragments of hyaline
cartilage forming
trabeculae.

OSSIFICATION
8. As the primary
ossification center
enlarges, osteoclasts
break down the newly
formed spongy bone
and open up a medullary
cavity in the center of
the diaphysis.

OSSIFICATION
9. The epiphyses remain
formed of cartilage until
shortly before or after
birth.
10. Secondary ossification
centers form in the
epiphyses. The events of
ossification are like the
events of the diaphysis,
except, that spongy bone
mains in the internal and
no medullary cavity forms.

BONE GROWTH
THERE ARE 2 TYPES OF
BONE GROWTH:
1. LONGITUDINAL--LENGTH
2. APPOSITIONAL--DIAMETER

LONGITUDINAL BONE GROWTH
Epiphyseal
plate

APPOSITIONAL BONE GROWTH
Osteoblast

CALCIUM HOMEOSTASIS
FACTORS OF CALCIUM
HOMEOSTASIS:
1. HORMONES
2. VITAMIN D—MILK
3. CALCIUM—MILK
4. VITAMIN A—CARROTS
5. PHOSPHORUS—MEAT

HORMONAL CONTROL OF
CALCIUM HOMEOSTASIS

CALCIUM HOMEOSTASIS
OTHER FACTORS IN CALCIUM
HOMEOSTASIS:
1. VITAMIN D—AIDS IN THE ABSORPTION
OF BOTH CALCIUM AND PHOSPHORUS.
2. VITAMIN A—HELPS THE OSTEOBLASTS
PRODUCE BONY MATRIX.

CALCIUM HOMEOSTASIS
3. TESTOSTERONE AND ESTROGEN—
STIMULATES BONE DEPOSITION OF
CALCIUM STARTING AT PUBERTY.

HOMEOSTATIC IMBALANCES
OF THE SKELETAL SYSTEM
RICKETS
1. DISEASE OF CHILDREN DUE TO
LACK OF VITAMIN D.
2. CALCIUM IS NOT DEPOSITED.
3. BOWING OF THE BONES.

OSTEOMALCIA
1. RICKETS IN ADULTS
2. DUE TO A LACK OF VITAMIN D
3. CALCIUM IS NOT DEPOSITED IN
BONE.
4. MAIN SYMPTOM IS PAIN WHEN WEIGHT IS
PUT ON THE AFFECTED BONE.

OSTEOPOROSIS
1. BONE REABSORPTION IS GREATER
THAN BONE DEPOSITION.
2. CAUSES:
A. LACK OF ESTROGEN
B. LACK OF EXERCISE
C. INADEQUATE INTAKE
D. LACK OF VITAMIN D

OSTEOPOROSIS
3. SIGNS AND SYMPTOMS:
A. SPONGY BONE OF THE SPINE IS MOST
VULNERABLE.
B. OCCURS MOST OFTEN IN POSTMENOPAUSAL
WOMEN.
C. BONES BECOME SO FRAGILE THAT SNEEZING OR
STEPPING OFF A CURB CAN CAUSE FRACTURES.
4. TREATMENT
A. CALCIUM AND VITAMIN D SUPPLEMENTS.
B. HORMONE REPLACEMENT TREATMENT
C. INCREAE WEIGHT BEARING EXERCISE.

skeletal system and bones

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