Category: O

  • Organ of Jacobson

    A blind tubular sac that develops in the medial wall of the nasal cavity, becoming a functional olfactory organ in lower animals, but degenerating or remaining rudimentary in humans.  

  • Orf

    A contagious pustular dermatitis caused by the orf virus, a DNA virus of the Parapoxvirus genus, which is related to the vaccinia-variola subgroup of poxviruses. Orf mainly affects lambs and occurs in the spring. The disease rarely occurs in humans. When it does, it is usually confined to a single pustular lesion on a finger,…

  • Ordinate

    The vertical line parallel to the y-axis in a graph in which horizontal and perpendicular lines are crossed in order to provide a frame of reference. The abscissa is the horizontal line parallel to the x-axis.  

  • Orchichorea

    Involuntary jerking movements of the testicles.  

  • Orcein

    An orcinol stain specific for elastic connective tissue.  

  • Orbitopagus

    Conjoined twins in which the smaller fetus is attached to the orbit of the larger fetus.  

  • Orbitonasal

    Concerning the orbit and nasal cavity of the skull.  

  • Orbitale

    An anthropometric landmark, being the lowest point along the inferior margin of the orbit. It is one of two landmarks (the other is the porion) used to establish the Frankfort horizontal plane, most frequently in positioning the head for radiographs or measurements.  

  • Orbiculus oris

    The circular muscle surrounding the mouth. It is a muscle of facial expression, innervated by the facial nerve.  

  • Orbiculus ciliaris

    The portion of the ciliary body consisting of a bandlike zone lying directly anterior to the ora serrata.