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 (kī-ăz′mə) also chi·asm (kī′ăz′əm)
n. pl. chi·as·ma·ta (-mə-tə) or chi·as·mas also chi·asms
1. Anatomy A crossing or intersection of two tracts, as of nerves or ligaments.
2. Genetics The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over.

[Greek khīasma, cross-piece, from khīazein, to mark with an X, from khei, khī, chi (from the letter's shape).]

chi·as′mal, chi·as′mic, chi′as·mat′ic (-măt′ĭk) adj.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.chiasm - an intersection or crossing of two tracts in the form of the letter X
anatomical structure, bodily structure, body structure, complex body part, structure - a particular complex anatomical part of a living thing; "he has good bone structure"
chiasma opticum, optic chiasm, optic chiasma - the crossing of the optic nerves from the two eyes at the base of the brain


, chiasma
n. quiasma.
1. cruzamiento de dos vías o conductos;
2. punto de cruzamiento de las fibras de los nervios ópticos.
References in periodicals archive ?
For intra-extracranial tumors in the anterior skull base, the anterior limit of ETA is the frontal sinus, and the posterior limit is the optic chiasm and the anterior communication artery.
Diplopia/loss of vision###6###3###20###M=1,F=2###WM, BS, optic chiasm, MB, cerebral hemispheres, pituitary gland.
After 30 months, radiographic imaging demonstrated a reduction and stabilization of the tumors in the optic chiasm, hypothalamus, and left optic nerve.
The decussation or separation of optic nerve fibres at the optic chiasm means that the right hemifield is projected to the left striate cortex and the left hemifield is projected to the right striate cortex (see Figure 2).
There was associated mass effect on the optic chiasm, and superolateral displacement of the bilateral internal carotid arteries.
In sum, however, the volumes main points--that parallelism, chiasm, and concentrism are important features of the form and composition of the Quran--are indisputable.
Ischemic optic neuropathy (ION) refers to infarction of any portion of the optic nerve from the chiasm to optic nerve head.
Anterior visual pathways include retina, optic nerves and optic chiasm and the involvement results in moderate to profound visual loss along with impaired colour vision and loss of pupillary reflexes.
Emotions are likely not humanoid and wearing trousers and getting in physical conflicts with one another behind our optic chiasm.
Brain MRI showed thickening in the upper two thirds of pituitary stem, adjacent to the posterior optical chiasm.