Transcript SKELETAL SYSTEM

SKELETAL SYSTEM
rev 12-12
• Bone or Osseous Tissue
– consists primarily of nonliving extracellular
crystals of calcium minerals which make the
bone hard
– contains several types of living bone cells,
nerves, and blood vessels
– Is classified as a connective tissue
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Bones perform 5 important functions:
• support-provides a hard framework that supports
the body, attaches the skeletal muscles and cradles
the body’s organs
• movement-supports muscles to allow us to move
• protection-because they are hard and surround
our internal organs, they protect our organs
• formation of blood cells within the marrow cavity
• mineral storage-bones store minerals that are important
to body metabolism and function
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Bones can be classified into 4 categories based on
shape
• Long--bones of the limbs and fingers
– are longer than they are wide
– consist of a hollow, cylindrical shaft called the
diaphysis and
– an enlarged knob at each end called the
epiphysis
– An internal marrow space or cavity
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• Short--bones of the wrists
– are approximately as wide as they are long
• Flat--including the cranial bones, sternum and ribs
– are thin, flattened and sometimes curved, with a small
amount of spongy bone between 2 layers of compact
bone
• Irregular--hip bones and vertebrae
• include a variety of shapes that don’t fit into the
other categories
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• All bones contain 2 types of osseous tissue
– a solid, compact tissue which forms the
external layer of bone
– a spongy tissue with trabeculae
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• Periosteum covers the outer surface of all bones
• is a tough connective tissue consisting of 2 layers
• the outermost layer is dense irregular connective
tissue
– is richly supplied with nerve fibers, lymphatic
vessels and blood vessels which enter the bone
through openings called nutrient foramen
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– provides insertion or anchoring points for the
tendons and ligaments
– contains specialized bone forming cells
– if the end of a long bone forms a movable joint,
the joint surface is covered by a thin layer of
articular or hyaline cartilage that reduces
friction, cushions the bone ends during joint
movement, and absorbs mechanical stress
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• The internal part of the bone surface is covered by
endosteum (a delicate connective tissue
membrane)
– this covers the trabeculae in the marrow
cavities of the spongy bone
– lines the canals that pass through compact bone
– contains osteoblasts (bone forming cells),
osteoclasts (bone resorption cells), and
osteocytes (bone cells)
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Long bones
• Compact bone forms the external layer
• central cavity of the shaft of long bones is called
the medullary cavity
– this cavity is filled with red marrow in children
(for RBC production), and with yellow bone
marrow in adults
• yellow marrow is primarily fat which can be
utilized for energy
• Compact bone consists of calcium phosphate laid
in a pattern around the central cavity
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• Structural Unit of Compact bone is the
– Osteon (or Haversian system) this forms a
pattern of hollow tubes like the growth rings of
a tree trunk
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• Parts of the Haversian system:
– each ring of bone tissue in the hollow tube is
called a lamellae
– Haversian or Central canal: middle cavity in
a Haversian system. Contains the blood
vessels and nerve fibers
– lacunae: found at the junctions of the lamellae
and is filled with bone cells called osteocytes
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• canaliculi: thin canals in bone tissue which
connect the lacunae to each other and to the
central canal
– provide a path for nutrients to travel to the osteocytes
and for wastes to be removed
• Volkmann’s canals lie at right angles to the long
axis of the bone and connect the blood and nerve
supply of the periosteum to those in the central
canals and the medullary cavity
– this allows all osteocytes to get nutrients even
though they aren’t near a blood vessel
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Spongy bone
– Is found inside the epiphysis
• spongy bone is less dense than compact bone
allowing the bones to be light but strong
– this helps the bone to withstand mechanical stress
• spongy bone is a honeycomb of hard, strong pieces
called trabeculae
– helps the bone to resist mechanical stress
– the open spaces of the trabeculae are filled with red or
yellow bone marrow
• blood cell formation (hemopoiesis) takes place in
the spongy bone
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– Contains the epiphyseal plate: line of cartilage where
bone lengthening takes place in childhood
• When bone length growth is completed, the
epiphyseal plate becomes ossified (hardened) and
leaves an epiphyseal line
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SKELETAL SYSTEM
• Skeleton
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provides support
protects internal organs
produces blood cells
stores minerals (calcium and phosphorus)
stores energy
Permits movement via muscle attachments
Provides levers to make movement easier
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Skeletal system contains 3 types of
connective tissue
• bone--hard elements of the skeleton
• ligaments--dense fibrous connective tissue
that binds the bones to each other
• cartilage--specialized connective tissue
consisting primarily of fibers of collagen
and elastic in a gel-like fluid called ground
substance
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Knuckle Cracking
The snapping sound is made by the rush of synovial fluid
from one area of the joint to another as the joint is
forcefully pulled apart. Research shows that:
• this should not cause an increase in osteoarthritis,
• that people who crack their knuckles eventually have
decreased grip and hand function.
• Joint damage may be caused by long term chronic
ligament inflammation with subsequent pain
Related research found that knuckle crackers are also
more likely to bite their fingernails, smoke, and drink
alcohol
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The Skeleton is organized into the
• Axial skeleton and the Appendicular skeleton
• Axial skeleton
– forms the long axis of the body which supports the
head, neck and trunk
– consists of the
– skull,
**bones of the ear
– vertebral column,
**hyoid bone (in the throat)
– ribs and
**these bones are
– sternum
also parts of the axial
skeleton
Appendicular skeleton
• bones which help get us from place to place
(locomotion) and enable us to manipulate our
environment
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• The Skull includes the bones of the face, the
cranial bones and the jaws
• Frontal bone (forehead)
• Parietal bones (behind the frontal bone, on the top
rear part of the skull)
• Occipital bone (forms the back of the skull)
near the base of this bone is an opening called
the foramen magnum. This is where the
vertebral column connects to the skull and the
spinal cord enters the skull to communicate with
the brain
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• Occipital condyles--2 rounded bumps at the base of
the skull which pivot on the 1st vertebrae (as in
nodding the head to say “yes”)
• Temporal bones (on the lateral [left and right side]
of the skull under the parietal bone)
– each temporal bone has an opening into the ear canal
which allows sound to travel to the eardrum
• Sphenoid bone which forms the back of the eye
sockets
• Ethmoid bone which helps support the nose and
part of the eye socket
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• Facial bones and jaws-comprise the front of
the skull
– zygomatic bones form the cheeks and the outer
part of the eye sockets
– nasal bones (including the ethmoid) underlie
only the upper bridge of the nose (the rest of the
nose is made up of cartilage and other
connective tissue)
– lacrimal bones are the inner part of the eye
sockets
» each is pierced by a tiny opening through
which the tear ducts drain
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– maxillary bones form part of the eye sockets,
anchors the upper row of teeth, and forms
part of the upper palate
» upper, immovable, jaw bone is called the
maxilla
– Mandible or lower jaw anchors the lower
teeth
• Hyoid bone: not really part of the skull; lies
inferiorly to the mandible in the anterior neck
– is the only bone in the body which doesn’t
articulate with another bone
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• Ear bones
– present in the middle ear and move when air
vibrations bend the eardrum inward
» called the malleus (hammer), incus (anvil)
and stapes (stirrup)
• Several of the cranial and facial bones contain air
spaces which form the sinuses and make the skull
lighter
• Vertebral column or spine
– supports the head, protects the spinal cord and serves as
the attachment for each of our arms and legs and the
body’s muscles
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– Is a column of 33 vertebrae (irregular bones)
which extends from the skull to the pelvis
– is classified into 5 anatomical regions
• cervical (neck)-7 vertebrae
• thoracic (chest or thorax)- 12 vertebrae
• lumbar (lower back)-5 vertebrae
• sacral (sacrum/upper pelvic region)- 5
vertebrae which have fused
• coccygeal (coccyx or tailbone)- 4 fused
vertebrae
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– The first cervical vertebrae is called the Atlas
• it articulates with the occipital condyles
– The second cervical vertebrae is called the Axis
• you need to know these names
– vertebrae share 2 points of contact called
articulations
• The spinal cord passes through a canal between the
articulations
– vertebral bodies are separated from each other
by intervertebral disks which serve as shock
absorbers and permit a limited amount of
movement and flexibility
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• Ribs and sternum (breastbone)
– Sternum is actually 3 fused bones
– protect the chest cavity
– we have 12 pairs of ribs
• the upper 7 pairs, called “true” ribs,
• “False ribs:
– pairs 8-10 are joined to the 7th rib by
cartilage and are thus indirectly attached
to the sternum
• Floating ribs: pairs 11 and 12: don’t attach
to the sternum at all.
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Appendicular skeleton
• bones which help get us from place to place (locomotion)
and enable us to manipulate our environment
– includes the:
– Pectoral or Shoulder Girdle is a supportive
frame for the upper limbs
• consists of the clavicles and scapulas
– Arms (the humerus, ulna, radius, carpals [wrist
bones], the palm [metacarpal bones], and the
fingers [the phalanges])
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– The Pelvic or Hip Girdle consists of the 2
pelvic (hip) bones and the sacrum and coccyx
of the vertebral column
• they meet in front at the pubic symphysis where
cartilage joins the 2 bones
• primary purpose is to support the weight of the
upper body against the force of gravity
• in adult women, the pelvic girdle is
– broader and shallower than in men and
– the pelvic opening is wider/rounder--to allow for
childbirth
– the sacrum is flatter
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– The leg bones:
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Femur (thigh)
Patella (knee cap)
Tibia (lower leg)
Fibula (lower leg)
Tarsals (ankle joint)
Metatarsals (foot)
Phalanges (toes)
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Mature Bone Remodeling and Repair
• Changes in shape, size, strength:
– Dependent on diet, exercise, age
• Bone cells regulated by hormones:
– Parathyroid hormone (PTH): removes calcium
from bone
– The thyroid hormone Calcitonin adds calcium to
bone
• Repair: hematoma and callus formation
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• Joints or Articulations
– are sites where 2 or more bones meet
– give our skeleton mobility
– hold the skeleton together
– are the weakest parts of the skeleton
• Ligaments (connective tissues) and tendons
(muscular tissue) stabilize each joint
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• Joint types
– freely movable or synovial --bones are separated by a
thin fluid filled synovial cavity which secretes synovial
fluid as a lubricant
• Synovial membrane lines the interior surfaces of the
joint.
• Hyaline cartilage lines the articulating surfaces of
the bones
Types of synovial joints:
• Ball and socket--the ball end of one bone fits into
the socket of another bone: shoulder and hip joints
• Hinge joint —allows movement in one plane
– Knee and elbow joints
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• Slightly Movable or Cartilaginous --has no
synovial cavity and permit only slight movement
(this type joint is mainly found in the axial skeleton)
– has a pad of fibrocartilage between 2 bones
• Pubic Symphysis (is only moveable during
childbirth)
• intervertebral discs
• sacroiliac
• joint connecting the lower ribs to the sternum
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• Immovable or Fibrous Joints
– flat bones in a baby’s skull
• at birth these bones are separated by space filled
with fibrous connective tissue. These “soft spots”
are called fontanels
– allow the baby’s head to squeeze through the birth canal
– allow for brain growth and development
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Diseases and Disorders of the Skeletal System
• Sprains: stretched or torn ligaments or muscular
injury
– Partially torn ligaments will repair themselves but take
a long time due to poor vascularization
– Completely torn ligaments require surgery to repair
• Cartilage injuries usually due to overuse
– Require surgery to remove damaged cartilage
• Bone dislocation: occurs when bones are forced
out of alignment
– Subluxation is a partial dislocation
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• Bursitis: inflammation of the part of the joint
which contains the synovial fluid
– Falling on your knees, repeated leaning on your elbows
• Inject with anti-inflammatory drugs
• Remove some excess fluid by needle aspiration to
relieve pressure in the joint
• Tendinitis: inflammation of the tendon sheath
– Typically caused by overuse
• Arthritis: inflammation of joints
– Rheumatoid Arthritis
– Osteoarthritis= Degenerative Joint Disease (DJD)
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Rheumatoid Arthritis
• Thought to be an autoimmune disease that causes chronic
joint inflammation as well as inflammation of tissue
around the joints
– Inflammation in other body organs
• ? Genetic cause, environmental, viral, bacterial
• Exacerbations and remissions
• Chronic inflammation leads to destruction of cartilage,
bone and ligamentsjoint deformity
• Symptoms: fatigue, energy loss, decreased appetite, lowgrade fever, muscle and joint aches and stiffness (worse in
mornings)
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Treatment: ---REST
– reduce joint inflammation and pain
– Patient education to maximize joint function
– Prevent joint destruction and deformity
• Medications:
– Aspirin and corticosteroids, NSAIDs (non-steroidal
anti-inflammatory drugs), to decrease pain and
inflammation
• No known cure
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Osteoarthritis
Most common form of arthritis
• Characterized by the breakdown of cartilage
and can also damage ligaments and muscles
• Causes changes in joint structure and joint
capsule thickening that leads to stiffness,
aching and pain
• Causes: obesity, joint injury, repetitive
stress to a joint
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Homeostatic Imbalances
• Rickets
– Bones of children are inadequately mineralized
causing softened, weakened bones
– Bowed legs and deformities of the pelvis, skull,
and rib cage are common
– Caused by insufficient calcium in the diet, or by
vitamin D deficiency
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Homeostatic Imbalances
• Osteomalacia (in adults)
– Bones are inadequately mineralized causing
softened, weakened bones
– Main symptom is pain when weight is put on
the affected bone
– Caused by insufficient calcium in the diet, or by
vitamin D deficiency
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Homeostatic Imbalances
• Osteoporosis
– Group of diseases in which bone reabsorption
outpaces bone deposit
• Excessive loss of calcium and also collagen
fibers from bone
– Spongy bone of the spine is most vulnerable
– Occurs most often in postmenopausal women
– Bones become so fragile that sneezing or
stepping off a curb can cause fractures
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Osteoporosis: Treatment
• Calcium and vitamin D supplements
• Increased weight-bearing exercise
• Hormone (estrogen) replacement therapy (HRT)
slows bone loss
• Natural progesterone cream prompts new bone
growth
• Statins increase bone mineral density
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Paget’s Disease
• Characterized by excessive bone breakdown with
new bone formation
– Initially have excessive bone resorption (osteoclastic
phase) followed by a reactive phase of excessive,
abnormal bone formation (osteoblastic phase)
• Pagetic bone is chaotic, fragile and weak and
tends to have reduced mineralization
• Usually localized in the skull, spine, pelvis, femur,
• Unknown cause (possibly viral)
• Treatment includes the drugs Didronate and
Fosamax
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Bone Fractures (Breaks)
• Bone fractures are classified by:
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The position of the bone ends after fracture
The completeness of the break
The orientation of the bone to the long axis
Whether or not the bones ends penetrate the
skin
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Types of Bone Fractures
• Nondisplaced – bone ends retain their normal
position
• Displaced – bone ends are out of normal
alignment
• Complete – bone is broken all the way through
• Incomplete – bone is not broken all the way
through
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Types of Bone Fractures
• Compound (open) – bone ends penetrate the skin
• Simple (closed) – bone ends do not penetrate the
skin
• Comminuted – bone breaks into three or more
pieces; common in the elderly
• Oblique - a fracture which goes at an angle to the
axis
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Common Types of Fractures
• Epiphyseal – epiphysis separates from diaphysis
along epiphyseal plate; occurs where cartilage
cells are dying
• Greenstick – incomplete fracture where one side
of the bone breaks and the other side bends;
common in children
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Spine Curvature Disorders
• Lordosis. Also called “swayback”, the spine
curves significantly inward at the lower back.
• Kyphosis. characterized by an abnormally
rounded upper back, also called “humpback or
hunchback”
• Scoliosis. sideways curve to the spine. The
curve is often S-shaped or C-shaped.
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Causes
• Osteoporosis
• Obesity
• Inflammation of the disc space between the bones of the
spine most often caused by infection
• Abnormal vertebrae development in utero (congenital
kyphosis)
• Poor posture or slouching (postural kyphosis)
• Arthritis
• Osteoporosis
• Spina bifida: the spinal column of the fetus does not close
completely
• Spine infections
• Spine tumors
• Genetic
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• Idiopathic (80%).
• Neuromuscular conditions (15%) include cerebral palsy, spina
bifida and poliomyelitis.
• Metabolic problems
• Crush fracture from trauma, osteoporosis, tuberculosis or
malignancy.
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Symptoms: vary depending on the type and
severity of curvature
• Appearing swayback
• Having a large gap between the lower back and
the floor when lying on your back on a hard
surface that doesn’t change when you bend
forward
• Back pain and discomfort
• Problems moving certain ways
• head appears to bend forward
• Hump or curve to the upper back
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• Fatigue in back or legs
• Uneven shoulder blades with one being higher
than the other
• An uneven waist or hip
• Leaning toward one side
• clothing seems longer on one side than on the
other.
• when looking in a mirror the height of the hips
and shoulders appears uneven.
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Treatment
• determined based on the severity and type of spinal
curvature disorder
• Medication to relieve pain and swelling
• Exercise to increase muscle strength and flexibility
• Wearing a back brace
• Weight loss
• Surgery
• Observation. If there is a slight curve your doctor may
choose to check your back every four to six months to
see if the curve gets worse.
• Bracing. A back brace is often prescribed for kids and
adolescents who are still growing to prevent the curve
from getting worse.
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Types of surgery
• Spinal instrumentation. Instruments such as
hooks, rods, and wire are attached to the spine
to realign the bones of the spine and keep them
secure following spinal fusion.
• Artificial disc replacement. Degenerated discs
in the spine are replaced with artificial ones.
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Complications
• Distortion of the spinal column may cause restriction
of the chest with impairment of lung function
• Compression of abdominal contents can occur
• Severe deformity may impinge on the spinal cord and
cause paraplegia
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