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In anatomy a chiasm is the spot where two structures cross, forming an X-shape (from Greek letter χ, Chi). Examples of chiasms are: A tendinous chiasm, the spot where two tendons cross. For example, the tendon of the flexor digitorum superficialis muscle, and the tendon of the flexor digitorum longus muscle which even forms two chiasms.
The optic chiasm is found in all vertebrates, although in cyclostomes (lampreys and hagfishes), it is located within the brain. [2] [3] This article is about the optic chiasm of vertebrates, which is the best known nerve chiasm, but not every chiasm denotes a crossing of the body midline (e.g., in some invertebrates, see Chiasm (anatomy)).
The optic chiasm, or optic chiasma is the part of the brain where both optic nerves cross. It is located at the bottom of the brain immediately inferior to the hypothalamus . [ 7 ] Signs and symptoms associated with optic chiasm lesions are also known as chiasmal syndrome .
Chiasm (anatomy), an X-shaped structure produced by the crossing over of the fibers, with the prefix chiasm- means cross examples include: A nerval chiasm, where either two nerves cross in the body midline (e.g. Optic chiasma) A crossing of fibres inside a nerve reversing their mapping; A tendinous chiasm, the spot where two tendons cross.
Whereas a decussation refers to a crossing within the central nervous system, various kinds of crossings in the peripheral nervous system are called chiasma. Examples include: In the brain , where nerve fibers obliquely cross from one lateral side of the brain to the other, that is to say they cross at a level other than their origin.
The optic nerve component lengths are 1 mm in the globe, 24 mm in the orbit, 9 mm in the optic canal, and 16 mm in the cranial space before joining the optic chiasm. There, partial decussation occurs, and about 53% of the fibers cross to form the optic tracts. Most of these fibers terminate in the lateral geniculate body. [1]
The visual system is the physiological basis of visual perception (the ability to detect and process light).The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment.
Chiasmal syndrome is the set of signs and symptoms that are associated with lesions of the optic chiasm, manifesting as various impairments of the affected's visual field according to the location of the lesion along the optic nerve.