Musculoskeletal System Disorders 2 Flashcards
The four basic functions of skeletal muscle
Facilitate body movement by muscle contraction
Maintain body position by continuing muscle tone
Stabilize the joints and prevent excessive movement
Maintain body temperature by producing heat through muscle contraction
What are the connective tissue coverings of skeletal muscles?
Epimysium - surrounds whole muscle
Perimysium - surrounds the fascicles
Endomysium - surrounds individual muscle fibers
Motor unit
The motor neuron of the spinal cord and all the muscle fibers it stimulates
Neuromuscular Junction
The synapse between the end of the motor nerve and the receptor site in the muscle fiber where acetylcholine is released
Explain the mechanism for muscle contraction
Action potential from motor neuron arrives at the presynaptic terminal
Arrival of the action potential results in depolarization of presynaptic terminal
Depolarization causes calcium influx into presynaptic terminal
Calcium influx causes exocytosis of Ach into synaptic cleft
Diffusion of neurotransmittor to postsynaptic receptor results in muscle action potential
Muscle action potential travel down the t-tubules to cause second messenger activation
Calcium is released from sarcoplasmic reticulum and causes the power stroke
Calcium is transported back into the sarcoplasmic reticulum
Both muscle contraction and relaxation require ATP
What is myoglobin?
Binds oxygen in muscle fibers, similar structure to hemoglobin
What is the function of glycogen?
Stores glucose, present in muscle fibers
When does anaerobic respiration begin?
If the supply of oxygen does not meet demand, glucose is used as a primary energy source
What is an oxygen debt?
The amount of oxygen required to restore the muscle cell to its normal resting state, including converting lactic acid to pyruvic acid, glucose or glycogen and replenishing ATP
Tendon
The connective tissue covering the muscle extends to form a cordlike structure or tendon
Ligaments
Form a direct attachment between two bones
Muscle antagonists
One muscle opposes the action of another
What effect does cardio (aerobic or endurance) have on muscle cells?
Increases the capillaries and blood flow in a muscle as well as the mitochondria and myoglobin content - efficiency and endurance
What effect does anaerobic or resistance exercise (weight lifting) have on the muscle?
Increases muscle strength by increasing muscle mass
Side effects of anabolic steroids
Liver damage, cardiovascular disease, personality changes, emotional lability and sterility
Reasons a muscle may atrophy
Disuse, Nutritional deficiency (protein), disorders like anorexia and Crohn’s, degenerative changes involving accumulations of fatty or fibrous tissue.
What happens to muscle with age?
A decrease in the number of cells and a decrease in the size of the fibers.
What is muscle twitch?
Tetany, increased irritability of the motor nerves supplying the muscle.
Synarthroses
Type of joint movement, immovable, ex. sutures in skull
Amphiarthrosis
Slightly moveable - joints where bones are connected by fibrocartilage or hyaline cartilage. Ex. Symphysis pubis
Diarthroses or synovial
Freely movable joints
Articular capusle
Composed of the synovial membrane and its outer covering, the fibrous capsule. Tough, protective, extends into the periosteum.
Menisci
Moon-shaped fibrocartilage pads
Bursae
Fluid-filled sacs composed of synovial membrane and located between structures like tendons and ligaments.
Electromyogram (EMG)
Measure electrical charge associated with muscle contraction, helpful in differentiating muscle disorders from neurologic disease.
Arthroscopy
Used to visualize joints - insertion of lens into joint
A complete fracture
Bone is broken in two
Incomplete fracture
Bone is partially broken
Open or compound fracture
Skin is broken, more damage to soft tissue including blood vessels and nerves
Closed fracture
Skin is not broken at fracture site
SImple fracture
A single break, the bone ends maintain alignment and position
Comminuted fracture
Multiple fracture lines and bone fragments
Compression fracture
Bone is crushed or collapses into small pieces
Impacted fracture
One end of the bone is forced or telescoped into the adjacent bone
Pathologic fracture
Weakness in the bone structure due to conditions such as a tumor or osteoporosis
Stress fracture
From repeated excessive stress
Depressed fracture
Occurs in the skull when the broken section is forced inward on the brain
Spiral fracture
A break that angles around the bone
Colles’ fracture
a break in the distal radius at the wrist, commonly occuring when a person attempts to break a fall by extending the arm and open hand
Pott’s fracture
A fracture of the lower fibula due to excessive stress on the ankle
Steps to bone healing
A hemotoma or clot forms in the medullary canal
Necrosis occurs at the ends of the broken bone
Inflammatory response as a reaction to trauma and debris
The hematoma becomes a fibrin network into which granulation tissue grows.
New capillaries extend into the tissue
Phagocytic cells and fibroblasts (lay down new collagen fibers) migrate.
Chondroblasts begin to form cartilage
The two bone ends become splinted together by a procallus or fibrocartilagionous callus.
Osteoblasts from periosteum and endosteum begin to generate new bone, forming a body callus.
Subsequent motnhs - repaired bone is remodeled by osteoblastic and osteoclastic actviity in response to mechanical stresses
Steps to bone healing summarized
Hematoma, granulation tissue, procallus (fibrocartilage) bony callus, remodeling.
Complications related to healing of bone:
Muscle spasm - can pull bone fragments out of position
Infections such as tetanus or osteomyelitis - threat to compound fractures or when surgery needed
Ischemia - cast can compromise circulation
Compartment syndrome - may develop shortly after the fracture occurs when there is inflammation, such as with crush injuries. Increased pressure of fluid within the fascia compresses the nerves and blood vessels cause ischemia of the muscle.
Fat emboli - when fatty marrow escapes from the bone marrow into a vein - can travel to the lungs and cause obstruction - behavioural changes, confusion, disorientation
Nerve damage
Failure to heal
Fractures in and near a joint may have long-term effects like osteoarthritis or stunted growth if near epiphyseal plate.
Physiological manifestations of severe pain
Pallor, diaphoresis, hypotension, tachycardia
Reduction of a fracture
Puts the bones back into alignment
Subluxation
If a bone is only partially displaced, with partial loss of contact between the bones.
Sprain
A tear in a ligament
Strain
Tear in a tendon
Avulsion
When ligaments and tendons are completely separated from their bony attachments
Degrees of muscle tears
First - small % of muscle
Second - stops short of being a complete tear. Muscle can only partially contract
Third - complete tear across muscle width, muscle unable to contract
Repetitive strain injury
Disorders affecting muscles, tendons, and nerves. Repeated forceful or precision movements. Rapid repetition of certain movements interferes with circulation to the area and damages soft tissues with cumulative effects.
Pain, weakness, numbness.
Tendinitis
A repetitive strain injury. Inflammation or injury of the tendon and sheath
Risk factors for osteoporosis
Aging - decreased osteoblast activity Decreased mobility Hormonal factors = hyperparathyroidism, Cushing's syndrome, glucocorticoids like prednisone Deficits of calcium, D, protein Smoking Caffeine Light bone structure
Therapeutic measures for osteoporosis
Supplements of calcium and vit D
Fluoride supplements promote bone deposition
Bisphoshonates can inhibit osteoclast activity
Calcitonin
Injected human parathyroid hormone to decrease bone resorption
Weight bearing exercise
Surgery to reduce kyphosis.
Rickets and Osteomalacia
Result from deficit of Vit D and phosphates required for bone mineralization
Leads to lack of calcification of cartilage leading to weak bones and deformities
Paget’s disease
Progressive
Excessive bone destruction
Bone replaced by fibrous tissue and abnormal bone
Structural abnormalities, thickening
Osteomyelitis
Bone infection caused by bacteria, sometimes fungi
Local inflammation and bone pain
Fever and excessive sweating, chills, malaise
Lordosis
Spine curving significantly inward at lower back
Caused by achondroplasia, obesity, discitis, slipping forward to vertebrae
Kyphosis
Hunchback
Poor posture, spina bifida, congenital defects, spinal tumors or infections, Scheuermann’s disease
Scoliosis
Curve to spine.
Can be inherited
Osteosarcoma
A primary malignant neoplasm that usually develops in the metaphysis of the femur, tibia, or fibula
Ewing’s sarcoma
A malignant neoplasm occurs in diaphysis of long bones
Chondrosarcoma
Arise from cartilage cells, usually pelvic bone or shoulder girdle at points of muscle attachment and eventually metastasize to the lung.
Muscular Dystrophy
A group of inherited disorders
Degeneration of skeletal muscle
Duchenne’s or pseudohypertrophic is the most common
Affects young boys
Caused by a deficit of dystrophin (a muscle cell membrane protein) leads to degeneration and necrosis of the cell
Muscle fibers are replaced by fat and fibrous connective tissue
Signs of muscular dystrophy in children
Motor weakness
Waddling gait
Difficulty attaining upright posture
Tendon reflexes reduced
Majority develop cardiac abnormalities and mental retardation
Death usually by 20 from respiratory or cardiac failure.
Primary Fibromyalgia Syndrome
Group of disorders
Pain and stiffness affecting muscles, tendons, and surrounding soft tissues
No obvious signs of inflammation or degeneration
Cause not known
Aggravated by: sleep deprivation, stress and fatigue.
Osteoarthritis
Degenerative, “wear and tear” joint disease
Articular cartilage of weight-bearing joints like hips and knees are damaged and lost through structural fissures and erosion resulting from excessive mechanical stress.
Surface of cartilage becomes rough and worn and interferes with joint movement
Tissue damage causes the release of hormones, which accelerates the disintegration
Subchondral bone may be exposed and damaged, cysts and osteophytes or new bone spurs develop
Pieces of the osteophytes and cartilage break off into the synovial cavity causing further irritation
joint space becomes narrower
Congenital abnormalities can predispose
Joint movement limited, the joint can appear enlarged and hard as osteophytes develop
Rheumatoid Arthritis
Autoimmune
Chronic systemic inflammatory disease
Progressive damage to joints
Abnormal immune response, causing inflammation of the synovial membrane with vasodilation, increased permeability and formation of exudate, causing typical red, swollen, painful joint called synovitis.
Characterized by remissions and exacerbations
How does rheumatoid arthritis progress?
Synovitis - inflammation, synovial cells proliferate
Pannus formation - granulation tissue from the synovium spreads over the articular cartilage, releases enzymes destroying cartilage.
Cartilage erodes
Pannus cuts off nutrients from synovial fluid
Pannus between the bone ends becomes fibrotic and limits movements, then calcifies and removes joint space.
Ankylosis - joint fixation and deformity develop
Other complications from rheumatoid arthritis
Atrophy of muscles
Alignment of bones in joint shifts
Inflammation and pain can cause muscle spasm further drawing bones out of allignment
Contractures and deformity
Systemic effects from circulating immune factors, causing fatigue, depression, malaise, anorexia, fever, iron deficiency,
Juvenile Rhematoid Arthritis
Usually more acute than adult form, systemic effects are more marked, rheumatoid nodules are absent. Large joints frequently affected.
Infection Septic Arthritis
Usually develops in a single joint
Red, swollen, painful, decreased range of movement.
Purulent exudate
Caused by blood-borne baceria
Lyme disease
Caused by a spirochete and transmitted by ticks
Characterized by a migratory arthritis and rash developing several weeks to months after the tick bite
Knee and other large joints most often involved
Gout (gouty arthritis)
Results from deposits of uric acid and urate crystals in the joint that then cause an acute inflammatory response
Uric acid is usually excreted through the kidneys, excess amount causes hyperuricemia.
Often affects a single joint, damages articular cartilage, redness and swelling.
Tophus
A large, hard nodule consisting of urate crystals that have been precipitated in soft tissue or bone causing a local inflammatory reaction. Usually occur after first year of gout
Ankylosing Spondylitis
Chronic, progressive inflammatory condition, affects the sacroiliac joints, intervertebral spaces, and costovertebral joints.
Autoimmune disorder.
Vertebral joints become inflamed, then fibrosis and calcification or fusion of joints follows.
Ankylosis means fixation
Causes a straight back as spine fuses.
Kyphosis develops from postural changes necessary because of rigidity of spine
Osteoporosis
Bursitis
Inflammation of the bursae associated with bones, muscles, tendons and ligaments of various joints. Can be caused by regular repetitive movements.
Synovitis
Inflammation of the synovial membrane lining the joint
Movement of joint is restricted and painful due to swelling as the synovial sac fills with fluid. Joint becomes swollen, red, and warm.
Tendinitis
Irritation or inflammation of tendon.
Dull ache at site of tendon attachment, tenderness, milk swelling.
Likely from repetitive motions or actions.
What characteristic do rheumatoid arthritis, juvenile arthritis, and ankylosing spondylitis have in common that often requires aggressive treatments?
These joint disorders all have systemic effects. Rheumatoid arthritis causes fever, fatigue, and anorexia. Juvenile arthritis forms cause uveitis, fever, rash, lymphadenopathy, hepatomegaly, and joint involvement. Ankylosing spondylitis can cause osteoporosis and restrict lung expansion.
