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Vellus hair
Vellus hair, or peach fuzz, is the fine, short, unpigmented, non-medullated body hair under 30 μm thick, distinct from terminal hair and lanugo; androgens drive its pubertal conversion and its miniaturization role in androgenetic alopecia.
Venography
Venography, also called phlebography, is an x-ray examination in which iodine-based contrast is injected into a vein to reveal clots, obstructions, and anatomic variants; first used in humans in 1923.
Venous hum
Venous hum (cervical venous hum): a continuous, innocent murmur of the internal jugular veins, loudest in the supraclavicular area, common in children, right-sided, louder sitting and in diastole, abolished by jugular compression or lying down.
Venous Pressure
Venous pressure is the blood pressure within the veins, also called venous blood pressure, assessed as central venous pressure, jugular venous pressure, or ambulatory leg venous pressure to gauge cardiac filling, fluid responsiveness, and venous disease.
Venous thrombosis
Venous thrombosis, blood clot formation in a vein (deep vein thrombosis, DVT; with pulmonary embolism forms VTE), explained by Virchow's triad, incidence about 1 per 1,000 adults yearly, treated with anticoagulants.
Venous ulcer
Venous ulcer (venous leg ulcer, stasis ulcer): open skin lesion near the ankle sustained by chronic venous insufficiency and venous hypertension; treated with strong compression therapy and endovenous ablation, with 26-69% recurrence within 12 months.
Ventilation/perfusion ratio
Ventilation/perfusion (V/Q) ratio: ratio of alveolar ventilation to pulmonary blood flow, about 0.8 overall, lower at lung bases; V/Q mismatch underlies hypoxemia, shunt, dead space, and the V/Q scan used to diagnose pulmonary embolism and CTEPH.
Ventral cochlear nucleus
Ventral cochlear nucleus (VCN), first relay of the central auditory system in the brainstem, subdivided into AVCN and PVCN; its octopus, bushy, and stellate cells run parallel timing and sound-localization pathways.
Ventricle (heart)
Ventricle (heart): the heart's two pumping chambers, the thick-walled left ventricle of the systemic circuit and the thin-walled right ventricle of the pulmonary circuit; differs from the atria, which only fill the ventricles.
Ventricular Function
Ventricular function: the hemodynamic and electrophysiological action of the heart ventricles, assessed by ejection fraction, global longitudinal strain, pressure-volume analysis, and diastolic indices; EF remains the heart failure classifier while GLS detects subclinical dysfunction.
Ventricular Pressure
Ventricular pressure, also called intraventricular pressure, is the pressure within a ventricle of the heart, measured by catheterization or imaging to evaluate heart and valve function.
Ventricular remodeling
Ventricular remodeling: pathological change in ventricular size, shape, and function after myocardial injury, driven by myocyte hypertrophy, apoptosis, and fibrosis; reversible in some patients as reverse remodeling or heart failure remission.
Ventricular system
Ventricular system: interconnected brain cavities (two lateral, third, fourth ventricles) that produce and circulate cerebrospinal fluid via the choroid plexus, foramina of Monro, Luschka, and Magendie; obstruction causes hydrocephalus.
Vergence
Vergence: disconjugate eye movements (convergence, divergence) rotating the eyes oppositely to fixate targets at different depths, driven by retinal disparity, cross-linked with accommodation, and disrupted in convergence insufficiency.
Vernal keratoconjunctivitis
Vernal keratoconjunctivitis (VKC) is a rare, chronic, sight-threatening allergic inflammatory eye disease of children, mainly boys in warm climates, marked by giant tarsal papillae, Horner-Trantas dots, shield ulcers, and Th2-driven inflammation.
Vernix caseosa
Vernix caseosa, also called vernix, is the waxy white biofilm coating fetal skin in the last trimester, made of about 80% water, 10% lipids, and 10% proteins; uniquely human, it waterproofs, protects against infection, and should not be washed off at birth.
Verrucous venous malformation
Verrucous venous malformation (VVM), formerly verrucous hemangioma, is a rare congenital venous malformation with MAP3K3 mosaic mutations, warty hyperkeratotic plaques mainly on the lower limbs, treated by wide excision.
Vertebra
Vertebra: the serial bones of the vertebral column; humans have 33 (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 4 coccygeal). Each has a body and arch; derived embryologically from sclerotomes of somites.
Vertebral artery
The vertebral artery (arteria vertebralis) is one of a pair of arteries that arises from the subclavian artery, ascends the neck, and supplies the posterior brain.
Vertebral artery dissection
Vertebral artery dissection (VAD), a tear in the vertebral artery wall causing intramural hematoma, stenosis, or aneurysm; a leading cause of stroke in young adults, treated with antiplatelet or anticoagulant drugs.
Vertebral venous plexuses
The vertebral venous plexuses, known as the Batson plexus after Oscar V. Batson, are valveless extradural veins around the spinal column that drain the spinal cord and vertebrae.
Vertebrobasilar insufficiency
Vertebrobasilar insufficiency (VBI), transient ischemia of the vertebrobasilar posterior brain circulation, coined by Milliken and Siekert in 1955; causes dizziness, vertigo, diplopia, ataxia; mainly atherosclerotic; diagnosed by angiography, MRA, CTA, Doppler.
Vertigo
Vertigo: the false sensation of spinning or motion, a subcategory of dizziness causing up to 8% of medical consultations. Key causes include BPPV, Meniere's disease, vestibular migraine, and stroke; diagnosed with Dix-Hallpike and HINTS exams.
Vestibular hair cell
Vestibular hair cell, also called vestibular sensory hair cell (type I and type II), is the inner ear mechanoreceptor that transduces head motion and gravity into vestibular nerve signals; type I cells have calyx endings, type II bouton endings, and mammals regenerate them poorly.
Vestibular implant
A vestibular implant is an implanted neurostimulator that restores balance by electrically stimulating the vestibular nerve in people with bilateral vestibular hypofunction, first implanted in 2007 and still investigational.
Vestibular migraine
Vestibular migraine (migrainous vertigo) is a migraine subtype causing recurrent vertigo, defined by Bárány Society/IHS criteria; affects 1–3% of people, treated with propranolol, valproate, venlafaxine, CGRP antibodies, and vestibular rehabilitation.
Vestibular nerve
Vestibular nerve: balance branch of cranial nerve VIII, with bipolar neurons in Scarpa's ganglion carrying signals from utricle, saccule, and semicircular canals to four vestibular nuclei; distinct from the cochlear (hearing) branch.
Vestibular neuritis
Vestibular neuritis, also known as acute unilateral vestibulopathy, is a sudden loss of vestibular nerve function on one side, causing severe vertigo for days while hearing stays normal.
Vestibular nuclei
Vestibular nuclei: four paired brainstem nuclei (superior of Bechterew, medial of Schwalbe, lateral of Deiters, inferior of Roller) under the fourth ventricle relaying vestibular nerve input for gaze, posture, autonomic, and perceptual functions.
Vestibular rehabilitation
Vestibular rehabilitation (VRT, vestibular physical therapy) is exercise-based physical therapy for peripheral vestibular hypofunction, using gaze stabilization, habituation, balance and gait exercises; strong guideline evidence supports it, unlike isolated eye-movement exercises.