Structure and Function Week #4 Flashcards
(37 cards)
what is laboratory medicine
Practices for the assessment, diagnosis, treatment, management or prevention of health-related conditions
why is screening important
to check for “occult” or hidden diseases in asymptomatic people.. examples- pap smear, HIV, TB, PKU, etc. Classifies people as likely or unlikely to have the disease. Goal: reduce mortality and morbidity
what is a sequence of developments form earliest pathological change to resolution or death
natural history or progression of disease
What is a case where early detection is not useful?
Cervical cancer- HPV can cause some changes to cervical cells that will if left alone regress.
What are the four requirements for a screening program?
1) suitable disease 2) suitable test 3) suitable program (reaches target audience) 4) Good use of resources-cost, benefit
What is difference between reliable and valid?
reliable is if you get the same results each time (test is repeatable) may or may not be valid
valid is if you get the correct result
what is sensitivity
correctly classifies cases cases found/all cases
percentage of people with the disease who have positive test results
what is specificity
correctly classifies non-cases.. non cases/all non-cases
percentage of individuals without the disease who have a negative test result
what is predicitive value
probability that those tested are correctly classified PPV= true positives/all positives NPV- true negatives/all negatives
reference ranges
established range of normal values in healthy people and anything out of range should be examined. they are not perfect as there may be small amount of people with normal results with undetectable disease, the sample size to calculate reference may have been small, population may not be representative, normal ranges vary
what is the most common source of invalid results
pre-analytical errors
What causes lack of regeneration in axons?
absence of schwann cell tubes, basal lamina and laminin. Need these components to repair axon.
dislocation of distal axon
What contributes to slow regeneration of axons?
1) exposure to growth inhibiting extracellular matrix (chrondotin sulfate, proteglycans)
2) insufficient clearing of debris blocks regrowth
What is a positive neuropathy symptom
tingling, paraesthisa, has feeling but feels different or pain
what is a negative neuropathy symptom
no feeling at all, numbness
What are the main causes of neuropathy?
axonal injury
demylination- causes change in conduction and message
diabetic neuropathy- starts with vascular pathology
What is the basal lamina and where does it come from?
secreted by schwann cells and is the interface between the schwann cell and the endoneurium layer of connective tissue. the basal lamina is important because it contains laminin and fibronectin needed for regeneration of axons
What is a fasicle?
it is a bundle of related axons, separate out as individual nerves to either muscle or skin. is surrounded by perineurium and multiple fasicles are wrapped together by epineurium.
What is the contents of a peripheral nerve?
sensory neurons (info to CNS), motor neurons (to skeletal muscle) and sympathetic neurons (pre-ganglionic CNS-ganglion) (post-ganglionic ganglion to organ)
What is a ganglion
cluster of nerve bodies in PNS
What is a dendrite
tapering processes that arise from cell body, receives messages from receptors
what is an axon
long thin extension of nerve cell that projects to different regions
What are schwann cells
they are glia cells that surround axons in PNS. can be myelinated or unmyleinated. If myleinated form around single segment. Gaps in between or called nodes of ranvier
what are the 3 layers of connective tissue around nerves
endoneurium- 1st layer surrounding axon, has capillaries to feed axon.
perineurium- wraps around fasicles
epineurium- wraps multiple fasicles together
