vagal activity: Parasympathetic activity.
vagina: The genital canal in the female extending from the uterus to the vulva; the birth canal.
vagus: The tenth cranial nerve, chief mediator of the parasympa thetic nervous system.
vallecula: The groove between the base of the tongue and the epiglottis.
Valsalva maneuver: A forced exhalation against a closed glottis, the effect of which is to stimulate the vagus nerve and thereby slow the heart rate.
variant angina: See Prinzmetal's angina.
vasoconstriction: Narrowing of the diameter of a blood vessel.
vasoconstrictor: A substance that causes narrowing of the diameter of blood vessels; an alpha sympathetic agent.
vasodilation: Widening of the diameter of blood vessels.
vasodilator: A substance that causes widening of the diameter of blood vessels.
vasopressor: An agent that raises the blood pressure by causing vasoconstriction.
vasovagal: Having vascular and vagal components; often used to refer to a syndrome consisting of precordial distress, anxiety, nausea, and sometimes syncope.
VD: An abbreviation for venereal disease.
vein: A blood vessel that carries blood to the heart.
venae cavae: The largest veins of the body, which return blood to the right atrium.
venipuncture: The puncture of a vein to obtain a blood sample or to introduce a catheter.
venom: A poison, usually the poisonous substances derived from snakes, spiders, bees, wasps, and other such creatures.
venous blood: Blood poor in oxygen, containing hemoglobin in the reduced state.
ventilation: Breathing, moving air in and out of the lungs.
ventral: Referring to the front of the body; anterior.
ventricle: A thick-walled, muscular chamber that receives blood from the atrium and pumps it into the pulmonary or systemic circulation.
ventricular aneurysm: A localized bulge in the wall of the ventricle, often the late result of myocardial infarction.
ventricular arrhythmia: A dysrhythmia arising in the His-Purkinje system.
ventricular ectopic activity: Initiation of electric impulses by a secondary pacemaker in the ventricles.
ventricular fibrillation: Rapid, tremulous, and ineffectual contractions of the cardiac ventricles; cardiac arrest.
ventricular standstill: Asystole with sinus p waves.
ventricular tachycardia: Rapid, repetitive firing of a ventricular ectopic focus; a life-threatening dysrhythmia.
venule: A very small vein.
vernix: A white, cheesy substance covering the skin of the newborn.
vertebra: One of the 33 bones of the spinal column.
vertebral: Pertaining to the spinal column.
vertex: The top of the head.
vertigo: Dizziness; a hallucination of movement; a sensation that the external world is spinning around.
VHF: Very high frequency; the portion of the radio frequency spectrum between 30 and 300 mHz.
viable: Capable of living.
vial: A glass container storing a sterile powdered or liquid drug for parenteral use, sealed with a rubber stopper, and often containing multiple doses.
visceral: Pertaining to organs of the body.
visceral pleura: The outer, membranous covering of the lungs.
vital capacity: The volume of air that can be forcefully exhaled from the lungs following a full inhalation.
vital signs: Measurements of body functions, including pulse, respirations, and blood pressure.
vitreous fluid: A jellylike, transparent substance filling the inside of the eye.
vocal cords: Paired structures in the larynx whose vibrations produce sound.
volar: Pertaining to the palm side of the arm.
volume expander: An intravenous fluid that stays in the vascular space, usually a colloid or crystalloid.
voluntary commitment: A situation in which a patient signs himself into a psychiatric facility of his own free will.
voluntary muscles: The muscles that function under the conscious control of the brain.
vomiting: A forceful, active expulsion of stomach contents through the mouth (as opposed to regurgitation, which is passive).
vomitus: The matter ejected from the stomach by vomiting.
vulnerable period: An interval during the relative refractory period of the ventricular repolarization, corresponding to the upstroke of the T wave, near its peak, in which an ectopic impulse or an unsynchronized current can produce ventricular tachycardia or fibrillation.
vulva: The external parts of the female genitalia.
watt: A unit of electric energy obtained by multiplying amperes times volts.
watt-seconds: Units of electric energy expressed as watts delivered for 1 second; joules.
wheeze: A high-pitched, whistling sound characterizing obstruction or spasm of the lower airways.
white blood cell: Leukocyte; the cellular element of the blood that produces antibodies and participates in the inflammatory response.
willis, circle of: Arterial loop under brain that is responsible for autoregulation and constant perfusion of cerebral arteries.
withdrawal: Symptoms produced by abstinence from a drug to which one is addicted.
xiphoid: The small, cartilaginous, and bony portion of the sternum attached to the lower end of the body of the sternum.
Xylocaine: A trade name for lidocaine.
zygoma: The cheek bone.