| hyaloid artery | <anatomy, artery> The terminal branch of the primitive ophthalmic artery, which forms in the embryo an extensive ramification in the primary vitreous and a vascular tunic around the lens; by 81/2 months, these vessels have atrophied almost completely, but a few persistent remnants are evident entoptically as muscae volitantes. Synonym: arteria hyaloidea. (05 Mar 2000) |
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| hyaloid | <anatomy> Resembling glass; vitriform; transparent; hyaline; as, the hyaloid membrane, a very delicate membrane inclosing the vitreous humor of the eye. Origin: Gr. Glassy, transparent; glass + appearance: cf. F. Hyaloide. Source: Websters Dictionary (01 Mar 1998) |
| hyaloid body | The transparent gel that fills the inner portion of the eyeball between the lens (lens, crystalline) and the retina. (12 Dec 1998) |
| hyaloid canal | A minute canal running through the vitreous from the discus nervi optici to the lens, containing in foetal life a prolongation of the central artery of the retina, the hyaloid artery. See: vitreous, hyaloid artery. Synonym: canalis hyaloideus, central canal of the vitreous, Cloquet's canal, Stilling's canal. (05 Mar 2000) |
| hyaloid fossa | A depression on the anterior surface of the vitreous body in which lies the lens. Synonym: fossa hyaloidea, lenticular fossa, patellar fossa of vitreous. (05 Mar 2000) |
| hyaloid membrane | A transparent homogeneous acellular layer between the substantia propria and the endothelial layer of the cornea; considered to be a highly developed basement membrane. Synonym: lamina limitans posterior corneae, membrana vitrea, Descemet's membrane, Duddell's membrane, entocornea, hyaloid membrane, lamina elastica posterior, limiting layers of cornea, membrana hyaloidea, posterior elastic layer, tunica vitrea, vitreous membrane. (05 Mar 2000) |
| persistent | Continuing to exist in spite of interference or treatment, tending to recur. (18 Nov 1997) |
| persistent anterior hyperplastic primary vitreous | A unilateral congenital abnormality occurring in full-term infants; characterised by a retrolental fibrovascular membrane formed by persistent primary vitreous with remnants of the hyaloid artery and tunica vasculosa lentis; associated with leukokoria, microphthalmos, shallow anterior chamber, and elongated ciliary processes. (05 Mar 2000) |
| persistent atrioventricular canal | A condition that is caused when the atrial and ventricular septa fail to meet, as in normal development, resulting in a low atrial and high ventricular septal defect or a common atrioventricular canal. Synonym: endocardial cushion defect. (05 Mar 2000) |
| persistent chronic hepatitis | A benign chronic hepatitis that may follow acute viral hepatitis A or B, or complicate bowel diseases; after six months, liver biopsy changes are mild, unlike active chronic hepatitis; rarely, if ever, progresses to cirrhosis, portal hypertension, or liver failure. (05 Mar 2000) |
| persistent cloaca | A condition in which the urorectal fold has failed to divide the cloaca of the embryo into rectal and urogenital portions. Synonym: sinus urogenitalis, urogenital sinus. (05 Mar 2000) |
| persistent ectopic pregnancy | An ectopic pregnancy which has persistent viable tissue, secreting hCG after conservative surgery. (05 Mar 2000) |
| persistent foetal circulation syndrome | <syndrome> A syndrome of persistent pulmonary hypertension in the newborn infant, without demonstrable cardiac disease. It is characterised by cyanosis and acidosis, severe pulmonary vasoconstriction, hypertrophy of pulmonary arterial muscle, and elevated pulmonary vascular resistance, with resultant right-to-left shunting of blood through a patent ductus arteriosus and at times a patent foramen ovale. (12 Dec 1998) |
| persistent generalised lymphadenopathy | A syndrome characterised by reactive hyperplasia of lymph nodes (of at least one month's duration and at two different body sites, not including the inguinal area) in patients infected with the human immunodeficiency virus. The lymph node lesions progress from benign reactive hyperplasia through a stage of mixed follicular hyperplasia, to follicular involution with lymphocyte depletion. Many go on to a malignant non-Hodgkin's lymphoma. (05 Mar 2000) |
| persistent mullerian duct syndrome | <syndrome> Familial disorder with presence of fallopian tube, uterus, and testis in a male. Deficient mullerian inhibitory substance secondary to Sertoli cell defect. Synonym: hernia uteri inguinale. (05 Mar 2000) |