MSK Blue Boxes Midterm Flashcards
CNS Damage: physiological response
Proximal stumps of injured axons begin to regenerate
Send sprouts to area of lesion
Growth blocked by ASTROCYTE PROLIFERATION at injury site
Axonal sprouts retracted
Result: permanent disability
Rhizotomy
spastic paralysis
Intractable pain vs Rhizotomy
Sensory/motor fibers of spinal nerves are ONLY segregated at the POST/ANT ROOTS
At these sites the doctor can selectively section each to relieve either intractable pain (sensory/post root) or rhizotomy (motor/ant root)
Adult neuron proliferation
only in the olfactory epithelium (smell)
others destroyed by disease/trauma-> not replaced
Nerve Degeneration
Nerves stretched/crushed/severed
Axons degenerate distal to nerve lesion
Intact cell body + damaged axon = possible regeneration/return of fxn
Best chance of survival w/compressed nerve (paresthesia)
Paresthesia
pins-and-needles sensation due to compressed nerve
ex- when you sit too long with legs crossed
Crushing nerve injury
Damages/kills axon distal to injury site
Nerve cell bodies usually survive
Nerve conn tissue coverings intact-> guide growth of axons to distal targets-> no surgery needed
Cutting nerve injury
Sprouting occurs at proximal ends of axons (but may not reach distal target)
Requires surgery b/c regeneration requires apposition of cut ends (sutures in epineurium)-> realign nerve bundles
Anterograde/wallerian degeneration
Degeneration of axons detached from their cell bodies
Axon and myelin sheath degenerate (despite sheath not being injured)
Compression of vasa nervorum
Cuts off a nerve’s blood supply (ischemia)
Prolonged ischemia-> nerve degeneration (can be just as severe as crushing/cutting the nerve)
Ischemia
inadequate blood supply
Saturday night syndrome
drunk person passes out w/limb dangling off side of bed-> nerve ischemia-> paresthesia (often permanent)
Transient paresthesia
common in dental surgery anesthetics
Accessory/Supernumerary Bones
Develop when additional ossification centers appear-> form extra bones
Normal: several centers of ossification-> develop many bones-> bones fuse
Extra: bones don’t fuse-> appearance of “extra” bone (missing part of main bone)
Common in foot
Sutural bones in cranium
Sutural Bones
Small, irregular, worm-like bones
Circumscribed areas of bone along suture of cranium (where flat bones abut, esp parietal)
Heterotropic Bones
Bones form in soft tissues where not normally present
ex- horse riders develop in their thighs due to chronic muscle strain-> small hemorrhagic areas-> calcification-> ossification
Fracture Reduction
Broken ends of bone brought together to heal
Normal position approximated
Bone healing
Surrounding fibroblasts proliferate-> secrete collagen-> collar of callus (holds bones together)
Bone remodeling-> callus calcifies-> callus resorbed/replaced by bone
Fractures heal faster in growing bones (children)
Collar of Callus
Forms around broken bones due to fibroblast proliferation and their secretion of collagen
Holds bones together
Calcifies, then resorbed and replaced by bone
Green-stick fractures
incomplete breaks caused by bending of the bones
Osteoporosis
Reduction in quantity of bone or atrophy or skeletal tissue
Dec in organic/inorganic bone components-> brittle bones-> lose elasticity-> fracture more easily
Assessed by bone scanning
Sternal Puncture
Wide-bore needle inserted through cortical bone into spongy bone
Sample of red bone marrow aspirated w/syringe-> evaluate for hematological diseases
Sternum used because close to surface and easily accessible
ex- bone marrow transplantation for leukemia patients
Bone Age
determined by
1. appearance of calcified material in diaphysis/epiphyses
2. disappearance of epiphyseal plate (no dark line-> fusion)
Helps predict adult height and approximate age of skeletal remains
Lines of arrested growth
Bone with thickened trebeculae
Dense line of provisional calcification caused by cartilage degeneration in columns of bones
Bone injury adult v child
Adult: fracture
Child:: epiphysis displacement
Avascular necrosis
Loss of arterial supply to bone tissue-> tissue death
Fracture-> areas of adjacent bone necrotize (OSTEOCHONDROSIS)
Osteochondrosis
avascular necrosis of epiphyses in children
Calvaria
skullcap
Fontanelles
wide areas of fibrous tissue at sutures where cranial bones do not make full contact w/each other (in newborn)
Anterior is most prominent (“soft spot”), usually flat
Feel like ridges due to cranial bone overlapping (during passage through birth canal)
Bulging=> increased intracranial pressure (or baby is crying)
Depressed=> dehydration
Pulsates w/cerebral arteries
Osteoarthritis
Degenerative Joint Disease
Sx: stiffness, discomfort, pain
common in older people, weight-bearing joints
Substances in blood stream easily enter joint cavity
Traumatic joint infection-> arthritis, inflammation, septicemia
Arthroscopy
Examination of synovial joint cavity
Insert cannula and arthroscope
Enables orthopedic surgeons to examine joints and perform certain surgeries (allows more rapid healing than traditional joint surgery)
Absence of muscle tone
Normal: gentle force that helps maintain pressure on other structures
Absent: may allow joints to dislocate, antagonist muscle may cause limb to assume abnormal resting position
Denervated muscle-> fibrosis, loses elasticity-> abnormal resting position
Muscle soreness
Due to excessive/novel eccentric contractions (lengthening type more likely to create micro-tears/periosteal irritation)
Pulled muscles
Skeletal muscles have limited ability to lengthen (+ ~1/3)
Skeletal attachments usually prevent excessive lengthening except in hamstring (w/knee ext, hamstring reaches max length before hip fully flexes-> common hamstring tears)
Satellite cells of skeletal muscle
turn into new muscle fibers that individually replace skeletal striated muscle fibers (fibers can’t divide)
Source of myoblasts (which can fuse together to create new muscle fibers)
Hypertrophy of existing fibers
Lengthens and increases myofibrils w/in muscle fibers
Increases amount of work muscle can perform
Occurs in response to frequent strenuous exercise
Muscle testing
Helps diagnose nerve injury
2 types: patient resists examiner (power) or examiner resists patient (compare bilateral pairs)
Electromyography (EMG)
Place surface electrodes over muscle, patient performs movements, examiner amplifies/records electrical action potentials
Normal resting: baseline activity (muscle tone, disappears during deep sleep/paralysis/anesthesia)
Contracting: variable peaks of phasic activity
Analyze activity of individual muscles during different movements
Help restore muscle activity
