SKELETAL SYSTEM
SKELETAL SYSTEM
FUNCTIONS
Support (Primary function)
Movement (Passive)
Protection of Vital Organs
Mineral Storage
Blood Cell Formation (Hematopoiesis or
Hemopoiesis)
OSSEOUS C.T.
 Compact (dense) Bone
- Hard & heavy
- Forms surface & diaphysis
- Osteons = building blocks
 Cancellous (spongy) Bone
- Lightweight
- Fills epiphyses, Contains red marrow
- Trabeculae = building blocks
 Matrix
- Mineral Salts (hardness)
- Collagen (strong & flexible)
Two Types of Bone
Compact Bone
Spongy Bone
Bone Cells
Osteoblasts – Secrete to form bone
Osteocytes
* Mature bone cells
* Maintain matrix
* “Trapped” osteoblasts
 Osteoclasts – destroy bone
* Enzymes digest protein
* Acids dissolve minerals
* Forms Marrow Cavity; Involved in
Remodeling
Osteoblasts & Osteocytes
SEM Osteocyte
Osteoclast
SEM Osteoclast
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SKELETAL DIVISIONS
 Axial
 Appendicular
Classification: Shape & Location
 Long
 Short
 Flat
 Irregular
 Sesamoid (develop in
tendons; patella)
 Sutural (between
cranial bones)
Torus Bones
LONG BONE ANATOMY
 Diaphysis = shaft made of
compact bone
 Epiphyses = ends filled
with spongy bone
containing red marrow
 Articular cartilage covers
epiphyses
 Epiphyseal line indicates
earlier location of
epiphyseal (growth) plate
LONG BONE ANATOMY
 Periosteum is C.T.
covering bone
 Endosteum is C.T.
lining medullary cavity
 Medullary cavity
contains yellow marrow
 Nutrient Foramina –
holes allowing for
penetration of arteries
BONE DEVELOPMENT
 Ossification = replacement of other
connective tissue with bone
 Begins during the 2nd month of gestation
 Size increases until late teens (females) to
mid-twenties (males)
 Two different ossification processes:
- Intramembranous bone formation
- Endochondral bone formation
INTRAMEMBRANOUS
OSSIFICATION
 Occurs in flat bones of skull,
clavicles, mandible
 Begins with fibrous C.T.
membrane
 Membrane calcifies & ossifies
into bone
 Fontanels
- “Soft spot”, not yet ossified
- Allows for birth & brain
growth
Process of Intramembranous
Ossification
 Embryonic cells
form osteoblasts
 Osteoblasts produce
matrix = ossification
center
 Matrix calcifies
 Matrix traps
osteoblasts,
Osteocytes form
Process of Intramembranous
Ossification
 Trabeculae form
 Surface trabeculae form
compact bone
ENDOCHONDRAL
OSSIFICATION
Occurs in remainder of skeleton
Begins with hyaline cartilage model
Cartilage is replaced by bony tissue
Steps include:
-
Bone collar forms
Cartilage in shaft calcifies
Primary Ossification center forms in shaft
Secondary Ossification centers in epiphyses
Formation of Bone Collar &
Primary Ossification Center
Formation of Secondary
Ossification Centers
Epiphyseal Plates & Articular
Cartilage
APPOSITIONAL GROWTH
 Bone Widens
 Osteoclasts enlarge medullary cavity
 Osteoblasts add bone to surface of diaphysis
BONE REMODELING
Replacement of old bone with new bone
Involves resorption (osteoclasts) &
deposition (osteoblasts)
Alters bone shape in response to stress
Benefits:
- Allows for growth
- Removes injured bone
- New bone is more resistant to fracture
FRACTURES AND THEIR
REPAIR
Definition: Any break in a bone
Repair may take months
Requires:
-
Adequate minerals
Vitamins
Hormones
Weight-bearing exercise
STEPS IN FRACTURE REPAIR
Broken blood vessels form a hematoma
(blood clot)
C.T. and Capillaries invade site; C.T. cells
form fibrocartilage callus
Bony callus of spongy bone replaces
fibrocartilage callus
Bony callus is remodeled
Types of Fractures
Open (Compound) –
Broken bone ends
protrude through the
skin
Closed (Simple) –
Bone does not
penetrate the skin
Types of Fractures
Comminuted – splintered,
crushed; small pieces between
broken ends. Elderly. Most
difficult to treat.
Greenstick – Partial fracture;
one side breaks, other side
bends. Children.
Types of Fractures
Impacted – One end of
fractured bone
forcefully driven into
other end
Spiral – fracture spirals around
long bone axis from twisting
force
Types of Fractures
Pott’s – distal end of
fibula, tibia or both
Colles’ – distal end of
radius
Types of Fractures
Stress Fracture
- Fracture without visible break
- Microscopic fissures
- No apparent damage to surrounding
tissues
- Results from repeated, strenuous
activities
- Can result from reduced calcium
deposition in disease
- 25% involve tibia
Osteoarthritis of the Knee
BONES AS LEVERS
 Lever (bone): A rigid rod that moves about a
fixed point
 Fulcrum (joint): The fixed point around which a
lever moves
 Forces: Applied to levers at two points
- Resistance: Force to be overcome
- Effort or Work: Force required to overcome
resistance; supplied by skeletal muscles
CLASSES OF LEVERS
First Class: The fulcrum is between the
effort/force and the resistance
- Seesaw
- Tilting head backward
FIRST CLASS LEVER
R
F
E
CLASSES OF LEVERS
CONTINUED
Second Class: Resistance is between the
fulcrum and the effort/force
- Wheelbarrow
- Rising up on
one’s toes
SECOND CLASS LEVER
E
R
F
CLASSES OF LEVERS
CONTINUED
Third Class: The effort/force is between
the fulcrum and the resistance
- Most common type in the human body
- Flexing the elbow
THIRD CLASS LEVER
E
R
F
CLASSIFICATION OF JOINTS
Structural
- Based on what tissues or structures are found
between the bones
- Fibrous, Cartilagenous, Synovial
Functional
- Based on amount of movement (& amount of
movement is determined by structures found
between bones)
- Freely movable, Slightly movable, Immovable
ARTICULATIONS:
CLASSIFICATION BY
STRUCTURE
CLASSIFICATIO N
STR U CTU R E
Fibrous joint
Sutures of skull
Cartilagenous joint
Pubic symphysis
Synovial joint
Knee
ARTICULATIONS:
CLASSIFICATION BY
FUNCTION
CLASSIFICATIO N
FU N CTIO N
Synarthrosis
Immovable
joints
Slightly movable
joints
Freely movable
joints
Amphiarthrosis
D iarthrosis
ARTICULATIONS: EXAMPLES
Sutures
Functional: Synarthrosis
Structural: Fibrous
Pubic symphysis
Functional: Amphiarthrosis
Structural: Cartilagenous
Knee
Functional: Diarthrosis
Structural: Synovial
STRUCTURE OF A
SYNOVIAL JOINT
 Articular cartilage – covers bone ends
 Synovial membrane – lines joint capsule
 Synovial fluid – lubricates & nourishes
cartilage
 Synovial cavity – space between the bones
 Joint capsule – fibrous C.T.
 Ligaments – reinforce joint
 Bursae – synovial sacs at other sites of
friction
TYPES OF SYNOVIAL
JOINTS
Classified based on shape of articular
surfaces
Gliding (plane)
Hinge
Pivot
Ellipsoidal (condyloid)
Saddle
Ball-and-socket