chiasma

/kahy-az-muh/US // kaɪˈæz mə //UK // (kaɪˈæzmə) //

芝华士,芝罘区,芝华仕,脊柱

Definitions

n.名词 noun

1
plural chi·as·mas, chi·as·ma·ta [kahy-az-muh-tuh]. /kaɪˈæz mə tə/.
- : Anatomy. a crossing or decussation, as that of the optic nerves at the base of the brain.
- : Cell Biology. a point of overlap of paired chromatids at which fusion and exchange of genetic material take place during prophase of meiosis.

We know that they are directly connected by fibres that arch round through the chiasma.
Pressure on the optic chiasma, for example by a tumour of the pituitary body, is associated with bilateral temporal hemianopsia.
At the base of the section are seen the optic nerves and their chiasma.
The optic chiasma, where present, is involved in the floor of the thalamencephalon and forms a large, upwardly-projecting ridge.
The nerves are fibrous, and a commencement of the chiasma is certainly present.