Mennonite College of Nursing
At
Illinois State University
Pathophysiologic Bases of Health Deviation 437
Musculoskeletal Content
A & P Review
Bones
Functions
·
Mechanical
o
Protection for
the brain, spinal cord, and chest organs
o
Rigid internal
support for the limbs
·
Mineral storage
o
Principal
reservoir for calcium
o
Also stores
other ions, such as phosphate, sodium, and magnesium
·
Hemopoietic
o
Serves as a
host for the hemopoietic bone marrow
Anatomy
·
Cortical
bone = dense, compact bone whose
outer shell defines the shape of the bone
·
Coarse cancellous bone
(also referred to as spongy, trabecular, or marrow
bone) = generally found at the ends of long bones within the medullary canal
·
Sections of the
bone
o
Epiphysis =
area of the bone that extends from the subarticular
bone plate to the base of the epiphyseal cartilage
plate (“growth plate”)
o
Metaphysis = the region from the side of the epiphyseal cartilage plate facing away from the joint to
the area where the bone develops its funnel shape; contain coarse cancellous bone
o
Diaphysis = the body or shaft of the bone; the zone between the
two metaphyses in a long tubular bone.
·
Cells of bone
tissue
o
Osteoblast =
protein-synthesizing cells that make bone tissue; arranged in a line along the
bone surface
o
Osteocyte = osteoblasts that are completely embedded in bone matrix
o
Osteoclast =
multinucleated cells that resorb bone; found on the
surface of bones in a shell depression termed a Howship
lacuna.
Muscles
Functional Classification of Muscle
·
Skeletal muscle
o
Muscle fibers
are striated, under voluntary control
o
Bundles of
multinucleated cells
o
Cells function
independently
§ Muscle force = sum of force of individual cells
o
Normally in
relaxed state
§ Skeleton supports most of gravity load
§ Recruited to generate force and movement
·
Smooth muscle
o
Continue sheet
of muscle in walls of hollow organs
o
Involuntary
control
o
Interdependent
§ Function simultaneously; must contract uniformly
§ Pressures transmitted to all cells; all bear same
stress
o
Functions
§ Maintain organ dimension against load
§ Generate force and movement
Pathophysiological Conditions
Disorder of the growth plate
·
Achondroplasia = an autosomal dominant trait that represents the most common
inherited form of dwarfism, in which the zone of proliferative cartilage is
either absent or attenuated.
Delayed maturation
·
Osteogenesis Imperfecta
o
“brittle bone disease”
o
a group of inherited disorders in which a generalized
abnormality of the connective tissue is expressed principally as fragility of
bone
o
basic defect is synthesis of abnormal type I collagen
Fracture
·
defined as a discontinuity of the bone
·
most common bone lesion
·
healing of a fracture divided into 3 phases
o
inflammatory phase
·
rupture of blood vessels in periosteum
and adjacent soft tissue à extensive hemorrhage
·
extensive necrosis of bone at the fracture site
·
neovascularization begins to occur peripheral to the blood clot
·
granulation tissue containing bone cartilage (callus) forms as early as 7 days
o
reparative phase
·
phase extends for months
·
involves both fibroblasts and osteoblasts
·
blood clot is resorbed, and the
callus bridges the fracture site
o
remodeling phase
·
several weeks after the fracture, the ingrowth
of callus has sealed the bone ends…remodeling then begins
·
the original cortex is restored, but remodeling may
proceed for years.
Osteonecrosis
(avascular necrosis, aseptic necrosis)
·
refers to the ischemic death of bone and marrow in the
absence of infection
·
causes
o
trauma (fracture, surgery)
o
emboli (producing focal bone infarction)
o
systemic diseases (polycythemia,
SLE, sickle cell disease, gout)
o
radiation
o
corticosteroids administration
o
specific focal bone necrosis at various sites (such as in
the head of the femur in Legg-Calve-Perthes disease)
o
oesteochondritis dissecans (condition of unknown
cause in which a piece of articular cartilage and subchondral bone breaks off into a joint)
o
idiopathic factors (high incidence of osteonecrosis
of the head and the femur among chronic alcoholics)
Osteomyelitis
·
an inflammation of bone caused by an infectious
organism
·
most common pathogens are Staphylococcus sp.
·
Organisms
introduced by:
o
Direct
penetration (wounds, fractures, surgery)
o
Hematogenous osteomyelitis (infectious organisms may reach the bone from
a focus elsewhere in the body through the bloodstream)
·
Examples of
foci: skin pustule, infected teeth and
gums
·
Most common
sites affected: ends of the long bones,
such as the knee, ankle, and hip
Osteoporosis
·
A metabolic
bone disease that is characterized by diffuse skeletal lesions in which normally
mineralized bone is decreased in mass so that it no longer provides adequate
mechanical support
·
Single most
common bone disorder encountered in practice
·
Reflects
enhanced bone resorption relative to formation
·
Types
o
Primary – most
common variety, uncertain causes, occurs principally in postmenopausal women
and elderly persons of both sexes
§ Risk factors:
genetic factors, estrogens, aging, calcium intake, exercise,
environmental factors (smoking)
o
Secondary –
associated with a defined cause, including a number of endocrine and genetic
abnormalities (corticosteroids administration, hematologic malignancies, malabsorption, alcoholism)
Paget Disease of Bone
·
Chronic
condition caused by disordered bone remodeling, in which excessive bone resorption initially results in lytic
lesions that are followed by disorganized and excessive bone formation
·
Unknown cause
·
Lesions may be
solitary or may occur at multiple sites
·
Lesions tend to
localize to the bones of the axial skeleton, including the spine, skull, and
pelvis
Neoplasms
of Bone
·
A primary bone
tumor may arise from any of the cellular elements of bone.
·
Most occur near
the metaphyseal area
·
More than 80%
of primary tumors occur in either the distal femur or the proximal tibia
·
Benign
tumors
o
Nonossifying fibroma = a
benign and usually solitary, fibromatous lesion of
childhood that occurs in the metaphysis of along
bone, most commonly in the tibia or femur
§ May be present in as many as 25% of all children
between 4 and 10 years of age, after which time it characteristically regresses
§ Most patients are asymptomatic, although pain or
fracture through the thin cortex overlying the lesion occasionally may call
attention to the condition.
o
Osteoid osteoma
o
Solitary chondroma (Enchondroma)
·
Malignant
tumors
o
Osteosarcoma (Osteogenic sarcoma)
§ Highly malignant bone tumor that is characterized by
the formation of neoplastic bone tissue
§ Most common primary malignant bone tumor, accounting
for 1/5 of all bone cancers
§ Most frequent in adolescents between 10 and 20 years
of age
§ Male:female ratio 2:1
§ Often arises in the vicinity of the knee or proximal
humerus
§ Pathogenesis:
> 2/3 cases exhibit mutations in the retinoblastoma (Rb) gene; in older persons, it is almost always as a
complication of Paget disease or radiation exposure (example: radium watch-dial painters who wetted their
brushes with saliva developed osteosarcoma many years
later because of the deposition of radium in their bones
o
Chondrosarcoma
§ A malignant tumor that originates from cartilage
cells and maintains its cartilaginous nature throughout its evolution
§ Male:female ratio 2:1
§ Most frequently seen during the 4th to 6th
decades of life (average age = 45 years)
o
Giant cell
tumor
§ Locally aggressive, potentially malignant neoplasm
that is characterized by the presence of multinucleated giant cells
§ Usually occurs during the 3rd and 4th
decades of life
§ Slightly more common in women
§ More common in Asia than in Western countries
o
Ewing
Sarcoma
§ An uncommon, malignant bone tumor that is composed
of small, uniform, round cells, which belong to a family of primitive neuroectodermal tumors of children
§ Represents only 4-5% of all bone tumors
§ Found in both children and adolescents, with 2/3 of
cases occurring in patients younger than 20 years of age
§ Male:female ratio 2:1
§ Primarily a tumor of the long bones, especially the humerus, tibia, and femur, where it occurs as a midshaft or metaphyseal lesion
§ Patient initially presents with pain, which becomes
more intense and is followed by swelling of the affected area
o
Metastatic
tumors
§ The most common malignant tumor of bone is
metastatic cancer
§ Usually from tumors of the breast, prostate, lung,
thyroid, and kidney
§ Tumor cells usually arrive in the bone via the
bloodstream
§ Skeletal metastases are found in at least 85% of the
cases of cancer that have run their full clinical course.
§ The vertebral column is by far the most commonly
affected bony structure (tumor cells transported through the vertebral veins).
Osteoarthritis
·
Slowly
progressive degeneration of the articular cartilage
that manifests in the weight-bearing joints and fingers of older persons or in
the joints of younger persons subjected to trauma
·
Single most
common form of joint disease
·
Progressive
degradation of articular cartilage leads to joint
narrowing
·
The bone’s
attempt to grow a new articular surface results in
large peripheral growths of bone and cartilage, called osteophytes.
·
Primary
osteoarthritis = a disease of
unknown cause in which destruction of the joints is believed to result from an
intrinsic defect of the joint cartilage
o
Prevalence and
severity increases with age
o
Also known as
“wear-and-tear” arthritis and “degenerative joint disease”
·
Secondary
osteoarthritis = has a known
underlying cause, including congenital or acquired incongruity of joints,
trauma, crystal deposits, infection, metabolic diseases, endocrinopathies,
inflammatory diseases, osteonecrosis, and hemarthrosis
Rheumatoid Arthritis (RA)
·
A systemic,
chronic inflammatory disease in which chronic polyarthritis
involves diarthrodial joints bilaterally
·
Most commonly
affected joints: proximal interphalangeal and metacarpophalangeal
joints, elbows, knees, ankles, and spin
·
Onset usually
occurs during the 3rd or 4th decade of life, but
prevalence increases with age until 70 years
·
Female:male ratio 3:1
·
Course of the
disease is variable and includes remissions and exacerbations
·
Factors
implicated as causes of RA include genetic factors, humoral
immunity, cellular immunity, and infectious agents
Gout
·
Represents a
heterogeneous group of diseases in which the common denominator is an increased
serum level of uric acid and the deposition of urate
crystals in the joints and kidneys
·
Primary gout = hyperuricemia in the
absence of any other disease
·
Secondary
gout = occurs in association with
another illness that results in hyperuricemia