Week 12: Skin, Muscle and Bone Flashcards
Describe the following tests of damage: CK; myoglobin
Serum creatinine kinase: diseased or damaged muscle fibers leak CK into serum
Myoglobin: detectable in urine after crush/traumatic muscle injury, associated with ischemic disorders or extreme exertion
Describe the following tests of muscle function: EMG; strength/range of motion
EMG: records summation of APs of the muscle fibers in each motor unit, abnormalities help differentiate muscle, peripheral nerve disorders or neuromuscular junction disorders
strength/range of motion: done manually or with myometers
Describe the following tests of muscle metabolism: forearm ischemic test
forearm ischemic test: helps determine integrity of glycolytic pathways and enzyme systems that function during intense exercise
Describe the following tests of muscle structure: biopsy, genetics
Biopsy: histological exam that helps define myopathic and neuropathic disorders
Genetics: discovers genetic changes associated with a variety of muscle disorders
How does muscle hypertrophy vs. atrophy occur?
Hypertrophy: caused by excessive stress to muscle
Atrophy: caused by insufficient stimulation to muscle
How does endurance vs. strength training change muscle fibers?
Endurance: low intensity, long duration - increased mitochondria and capillaries, decreased fiber diameter
Strength: high intensity, short duration - increased glycolytic activity, fiber diameter, muscle strength
Define sarcopenia
How much of skeletal muscle mass and strength is lost and when?
Sarcopenia = age-related loss of skeletal muscle, causes decrease in strength
30-40% of skeletal muscle mass and strength lost in third to ninth decade
What are the major ways skeletal muscle disorders can occur (6)?
Alteration of nerve supply or conduction: Trauma Defect in muscle structure Energy utilization Psychogenic Unrelated to the muscle
Give an example(s) of: Alteration of nerve supply/conduction (3) Trauma (1) Defect in muscle structure (1) Energy Utilization (1)
Alteration of nerve supply or conduction: denervation atrophy, myasthenia gravis, periodic paralysis
Trauma: myoglobinuria
Defect in muscle structure: muscular dystrophy
Energy utilization: McArdle’s disease
Define weakness vs. fatigue
Weakness: failure to generate force
Fatigue: failure to sustain force
Primary hyperkalemic periodic paralysis: etiology, what does the affected gene normally do?
Etiology: autosomal dominant genetic disorder affecting sodium channels in muscle cells, typically SCN4A gene
SCN4AA gene: encodes voltage-gated sodium channel in the NMJ
Primary hyperkalemic periodic paralysis. What is the major s/s? What are some triggers (5)?
S/S: periodic paralysis
Triggers: Rest after exercise, potassium-rich foods, stress, fatigue, fasting
Patho of primary hyperkalemic periodic paralysis
- Sodium normally enters voltage-gated channels in NMJ and depolarizes muscle fiber
- Mutations result in failure to inactivate channels, which prevents potassium efflux and depolarization
- Muscle fiber cannot relax, new signals have no effects, resulting in paralysis
Treatment of primary hyperkalemic periodic paralysis
Glucose or other carbs
Avoid unknown triggers
Define muscular dystrophy, etiology
genetically caused myopathies with progressive degeneration of skeletal muscle fibers
Etiology: Gene for dystrophin absent or nonfunctional
What is the most common and severe type of muscular dystrophy? What is the inheritance pattern?
Duchenne muscular dystrophy
X-Linked trait
Patho and s/s (3) of muscular dystrophy
Patho: dystrophin protein absence or decreased levels leads to issues with mechanical stabilization and calcium regulation within the muscle fibers
S/S: calf muscles enlarged due to fat cell infiltration, cardiac failure, pulmonary infection
Define rhabdomyolysis, patho
acute muscle destruction associated with myoglobinuria
Patho: excessive myoglobin excretion damages renal tubule, leading to ATN which can lead to renal failure
Traumatic vs. nontraumatic causes (5) of rhabdomyolysis
Traumatic: extensive trauma with crush injuries
Non-traumatic: increased muscle O2 consumption, decreased muscle energy production, muscle ischemia, infection, direct toxins
What are some causes of: Increased muscle O2 consumption (3) Decreased muscle energy production (3) Muscle ischemia (3) Infection (2)
increased muscle O2 consumption: heat stroke, severe exercise, seizures
Decreased muscle energy production: hypokalemia, hypophosphatemia, genetic enzymatic deficiencies
Muscle ischemia: arterial insufficiency, drug overdose with coma and muscle compression
Infection: influenza, Legionnaires’ disease
What is the hallmark sign of rhabdomyolysis?
Elevated creatinine kinase levels
Define fibromyalgia
poorly characterized chronic disorder associated with general pain, stiffness, dysfunctional sleep, fatigability
What do we know about fibromyalgia? (5)
- Chronic pain in muscles and surrounding structures
- Does not appear to be inflammatory process
- Etiology unknown but believed to involve psychological, genetic, neurobiological and environmental factors
- Frequent comorbidity of depression, anxiety, stress-related disorders (PTSD)
- Treatment focuses on alleviating sx
Define glycogen storage disorders
group of defects in processing, synthesis or breakdown of glycogen
McArdle’s disease: definition and characteristics
McArdle’s: defect in muscle glycogen phosphorylase
Characteristics: Muscle energy disorder characterized by muscle pain, exercise intolerance, myoglobinuria, susceptibility to fatigue
Cori disease: definition and characteristics
Cori disease: defect in glycogen debranching enzyme
Characteristics: progressive skeletal weakness and atrophy and/or cardiomyopathy
Von Gierke’s disease: definition and characteristics
Von Gierke’s disease: defect in glucose-6-phosphatase
Characteristics: causes growth failure and lactic acidosis
What is the difference in bone marrow between adults and infants
Adults: yellow marrow or medullary cavity
Infants: Red marrow or hematopoietic tissue
What is the role of osteoclasts vs. osteoblasts?
Osteoblasts: bone-building cells
Osteoclasts: bone-chewing cells
Define lacunae
arranged in concentric circles called lamellae around central Haversian canals
Describe the feedback regulation loop for calcium
- Low calcium levels stimulates PTH which stimulates osteoclasts to break down bone to release calcium into plasma
- High calcium levels stimulates calcitonin which stimulates uptake of calcium by osteoblasts
Which joint type is associated with most pathology? How can they be impacted by arthritis?
Synovial joints: between articulating bones, separated by a fluid-containing joint cavity
Arthritis: inflammation of the synovial sac between the joints
Basic steps of bone repair (4)
- hematoma forms when blood vessels rupture
- fibrocartilage callus forms to splint break
- bony callus made of spongy bone forms, replacing fibrocartilage as more osteoclasts and osteoblasts move to area
- bone remodeling - occurs in response to mechanical stresses, forming a strong, permanent patch
Define the 3 types of alterations in bone union
Delayed union: increased healing time, inadequate immobilization, breakdown in hematoma formation, infection
Nonunion: failure to unite, infection, mobility
Malunion: union in abnormal position, compromise in function, deformity at fracture site
What is a fat embolism; how do they form; what are the risks?
Fat embolism: microemboli that lodge in small vessels
Formation: fat globules released into circulation from stores in fractured bone, globules attract platelets and create microemboli that lodge in small vessels
Risks: Injury to vasculature, ARDS, DIC, cerebral edema
How can nerve damage result from bone fracture?
What is compartment syndrome and how can this lead to amputation of a limb?
Nerve damage: bone fragments can rupture and compress nerves
Compartment syndrome: fascia and skin internally encapsulate compartments of leg and forearm, compressing the blood supply resulting in nerve damage and functional loss
How can pyogenic infection occur and result in bone damage?
caused by microorganisms introduced during trauma, surgery or bloodstream from other sources
Growth of microorganism causes cell death, inflammation and bone destruction
Define osteomyelitis. causes, common pathogen
acute or chronic pyogenic infection of bone and marrow
Causes: direction extension or contamination of open fracture or wound, seeding from blood or skin
Common pathogen: Staph aureus
Define osteomalacia
softening of bone due to inadequate mineralization of bone matrix, caused by deficiency of calcium or phosphate
Define rickets, what is the common sign?
inadequate calcium absorption and impaired mineralization of bone
Bowing legs in children - due to growth at the epiphyseal plate
Define Rheumatoid arthritis
systemic inflammatory disease, immune complexes deposit in synovium, immune cells attack and destroy cartilage and subchondral bone
What is rheumatoid factor
reacts with a fragment of IgG to produce immune complexes
Define osteoarthritis
Imbalance between mechanical stress and joint’s ability to resist stress causes articular cartilage to deteriorate
Causes of osteoarthritis
Post inflammatory disorders Posttraumatic disorders (fracture)
Prevention of osteoarthritis (4)
weight loss, injury prevention, muscle strengthening, task modifications
What are the basic considerations of skin lesions? (6)
- Characteristics
- Distribution/configuration
- Length of time present and recurrence
- Medications
- Family hx
- Environmental exposures
Define impetigo, what is the typically infectious organism
superficial skin infection with vesicles/pustules that rupture and leave golden brown crust, may result in ecthyma
Staph aureus
Define folliculitis, what is the typically infectious organism (2)
infection of hair follicles with erythematous papules and pustules
Staph aureus, P.aeruginosa
Define furunculosis
deeper infections of hair follicle, inflammatory nodules with pustule drainage can coalesce to form carbuncles
Define cellulitis, what is the typically infectious organism
cutaneous skin infection that is warm, tender, erythematous, rapidly spreading; can become necrotic if untreated
Staph aureus
Define necrotizing fasciitis, what is the typically infectious organism
rare infection of subcutaneous tissue and fascia that causes necrosis
S. pyogenes
What are common fungal infections (6)
- tinea pedis (athlete’s foot)
- tinea cruris (jock itch)
- tinea capitis (scalp)
- tinea corporis (body)
- c. albicans - causes skin infection, vaginal yeast infection, thrush
- tinea versicolor - skin infection occurring in hot, humid climates
What are common viral infections (3)
Herpes simplex
Herpes zoster
HPV
What are the different kinds of dermatitis? (5)
contact dermatitis drug-related eczematous dermatitis photoeczematous dermatitis primary irritant dermatitis atopic dermatitis
What is atopic dermatitis?
heritable condition, erythematous plaques, associated with family hx of asthma/hay fever
What is psoriasis?
chronic, genetic disease of epidermal proliferation
Define seborrheic keratosis, risk factors
keratinocytes become raised and light brown with sharp border demarcation
Risk factors = age, sun exposure
Define hemangioma, when do these usually resolve by?
idiopathic tumor of newly formed blood vessels
Often resolves by age 10
Define keratoacanthoma, what are risk factors, what percentage becomes malignant?
originates from neck of hair follicle, firm, raised nodule with central keratin plug
Risk factors = sun exposure, age
6% become squamous cell carcinoma if untreated so usually removed
Define Actinic keratosis, characteristics, risk factors.
most common premalignant tumor
characteristics: sharp border demarcation, rough, red, yellow, brown or gray
Risk factors = sun exposure, age
What are the major types of skin cancer and what skin layer to they affect (3)?
- Which one is most invasive and metastatic?
- Which is more common?
Basal cell carcinoma - stratum basale
Squamous cell carcinoma - stratum spinosum
Malignant melanoma - melanocytes
- Malignant melanoma
- basal cell carcinoma
What does ABCDE stand for when evaluating skin tumors?
Asymmetry Border irregularity Color Diameter Evolving over time
