BONE & CARTILAGE
A histology slide shows a bony matrix with rings of lamellae encircling a canal that carries a blood vessel down the long axis of the bone; naming this canal, not the perpendicular one, is the answer.
What is the Haversian (central) canal?
On an ATPase stain at pH 9.4, these fibers stain darkest—the same fibers that are pale, fast, powerful, and more fatigue-prone.
What are Type II fibers?
A burn victim loses their permeability barrier; the exam points to the filaggrin-rich layer just below the dead outer layer where transepidermal water loss is normally prevented.
What is the stratum granulosum?
A demyelinating vignette describes increased membrane leak and higher capacitance producing slowed conduction; naming this glial cell explains a Guillain-Barré pattern in the PNS.
What is the Schwann cell?
An asthma vignette wants the pathway: a beta-2 agonist raises cAMP and activates PKA, which inhibits this enzyme to relax bronchial smooth muscle.
What is MLCK?
An infant presents with dense, brittle bones, recurrent fractures, and marrow-failure anemia; biopsy shows thickened trabeculae and absent resorption bays because this cell type fails to do its job.
What is the osteoclast (osteopetrosis)?
On an ATPase stain at pH 9.4, these fibers stain darkest—the same fibers that are pale, fast, powerful, and more fatigue-prone.
What are Type II fibers?
A deep-dermis receptor with concentric onion-ring lamellae fires to vibration and deep pressure—not the fine-touch or Braille-texture receptors.
What is the Pacinian corpuscle?
This sodium-channel drug shows use-dependent block—repeated stimulation makes the block stronger—because it stabilizes the inactivated state.
What is lidocaine?
This osteoporosis drug is a monoclonal antibody against RANKL, preventing it from activating RANK on osteoclast precursors.
What is denosumab?
A tissue resists both compression and tensile load, contains Type I collagen, and would be the correct answer for a knee meniscus, an intervertebral disc, and the pubic symphysis alike.
What is fibrocartilage?
A vignette contrasts two muscle types: only this one requires extracellular calcium entering an L-type channel to trigger RyR2 and SR calcium release.
What is cardiac muscle?
A child has bleeding gums, loose teeth, and perifollicular hemorrhage; the defect is failed hydroxylation of proline and lysine, leaving this molecule underhydroxylated.
What is procollagen (vitamin C/scurvy)?
A farmer presents with salivation, lacrimation, diarrhea, pinpoint pupils, bronchospasm, and fasciculations; the mechanism is inhibition of this enzyme, treated with atropine plus pralidoxime.
What is acetylcholinesterase (organophosphate poisoning)?
A lateral skull fracture at this H-shaped junction of four bones threatens the middle meningeal artery and classically causes an epidural hematoma.
What is the pterion?
A postmenopausal woman has thin trabeculae with normal mineralization; the mechanism pairs decreased OPG with this increased ligand that drives osteoclast activation.
What is RANKL?
In smooth muscle, the exam wants the enzyme—activated by the calcium-calmodulin complex—that phosphorylates the myosin light chain to initiate contraction.
What is MLCK (myosin light chain kinase)?
A menkes-type copper transport defect (ATP7A) impairs this enzyme, blocking the covalent crosslinking of collagen in the extracellular space.
What is lysyl oxidase?
Two Na-channel toxins are contrasted: this one prevents channel inactivation, causing persistent depolarization—opposite to the pore-blocker that halts AP regeneration.
What is batrachotoxin?
A cardiac vignette describes disrupted direct ion passage between myocytes causing arrhythmia; naming this specific connexin explains the loss of synchronized conduction.
What is connexin 43 (Cx43)?
Three weeks after a tibial fracture, the fibrocartilaginous soft callus is being replaced by woven bone through this same process that also drives long-bone growth at the physis.
What is endochondral ossification?
A young athlete has exertional syncope, palpitations, and sudden death risk; imaging shows fibrofatty replacement of the right ventricle, tracing back to a mutation in this junctional protein complex.
What is the desmosome (ARVC)?
A dermis section shows Type I collagen bundles cut in many planes with fibers running in multiple directions to resist multidirectional force—naming this specific connective tissue, not the parallel tendon type.
What is dense irregular connective tissue?
During this phase, a second action potential is possible but only with a stronger-than-normal stimulus, because the membrane is hyperpolarized and K conductance remains high.
What is the relative refractory period?
A newer osteoporosis agent is an antibody against sclerostin, increasing Wnt signaling to boost osteoblast activity—distinct from the anti-RANKL and direct-osteoclast-inhibitor drugs.
What is romosozumab?