choroid, a. (n.) Anat.
(ˈkɔərɔɪd)
Also 7–8 -oide.
[ad. Gr. χοροειδής, corrupt reading for χοριοειδής (χ. χιτών ‘the choroid coat of the eye’ Galen), f. χόριον (see chorion) + εἶδος resemblance.]
Applied to certain structures resembling the chorion in form and vascularity; and to structures connected with these.
1. choroid coat (or choroid tunic): a vascular membrane lining the eye-ball, between the sclerotic coat and the retina, continuous in front with the iris, and containing numerous dark pigment cells. choroid gland: a gland-like plexus of blood-vessels of crescentic or annular form, imbedded in the choroid coat of the eye in osseous fishes. choroid membrane = choroid coat; see also 2. choroid muscle: the ciliary muscle of the eye.
| 1741 Monro Anat. Nerves (ed. 3) 44 The choroid Coat on the Outside of the Retina. 1764 Reid Inquiry vi. §12 The..function of the choroid membrane. 1778 Phil. Trans. LXVIII. 91 There was..a dispute..whether the choroid coat of the eye or the retina was the immediate cause of vision. 1836 Todd Cycl. Anat. I. 553/2 The so-called choroid gland in the eyes of Fishes. 1841–71 T. R. Jones Anim. Kingd. (ed. 4) 701 A vascular organ..called the ‘choroid gland’ by the older anatomists..of a crescentic form, and always of a deep red colour. 1881 Tylor Anthrop. 70 The black pigment lining the choroid coat at the back of the eye. |
2. choroid membrane: a name for the pia mater (Chambers Cycl.), and for the velum interpositum of the brain (Mayne Exp. Lex.); app. obs. in both senses; see also 1. choroid plexus: a plexus of blood-vessels connected by a thin membrane derived from the pia mater, in each lateral ventricle of the brain, forming a cord-like border on each side of the velum interpositum; also applied to similar structures in the third and fourth ventricles. choroid artery, posterior ch. a.: two arteries arising respectively from the internal carotid and the posterior cerebral arteries on each side, and contributing to form the choroid plexus. choroid vein: a vein connected with the choroid plexus.
| [1696 Phillips, Choroides, the folding of the Carotid Artery in the Brain. 1731 Bailey, Choroides Plexus. 1751 Chambers Cycl., Choroides is particularly used for the inner membrane which immediately invests the brain.] 1836 Todd Cycl. Anat. I. 493/1 After having given off the choroid artery, the internal carotid divides. 1842 E. Wilson Anat. Vade Mec. 377 The Choroid plexus is a vascular fringe extending obliquely across the floor of the lateral ventricle. 1881 Syd. Soc. Lex., Choroid vein of cerebrum, a vein in the outer border of each choroid plexus. |
3. ellipt. as n. The choroid coat or gland; see 1.
| 1683 Phil. Trans. XIII. 265 The Choroide is the seat of vision and not the retina. 1800 Young Mech. Eye in Ibid. XCI. 79 The horse-shoe-like appearance of the choroid of fishes. 1842 E. Wilson Anat. Vade Mec. 450 The Choroid is a vascular membrane of a rich chocolate-brown colour upon its external surface, and of a deep black colour within. |
† b. Formerly also choroides, choroeides.
(App. this was also used for the choroid membrane and the choroid plexus; see 2.)
| 1634 T. Johnson Parey's Chirurg. 183 Some call this coat Choroides, because it is woven with many veines and arteries, like the coat Chorion. 1676 Phil. Trans. XI. 746 Why the Uvea or Choroides is black in Men, but of divers colours in Brutes. 1822 J. Imison Sc. & Art (ed. Webster) I. 251 The whole of the choroides is opaque. |
Hence choˈroidal a., † (a) belonging to the choroid membrane of the brain (obs.); (b) belonging to the choroid coat of the eye; choˈroidean a., pertaining to the choroid (plexus); choroidean artery = choroid artery, see 2; choroiˈditis, Path. [see -itis], inflammation of the choroid coat.
| 1681 tr. Willis' Rem. Med. Wks. Voc., Choroeidal [mispr. chorodeidal], belonging to the net, like to the infoldings about the brain. 1875 H. Walton Dis. Eye Introd. 22 The choroidal pigment. Ibid. 713 Choroidal complications. 1842 E. Wilson Anat. Vade Mec. 282 The Choroidean is a small branch which is given off from the internal carotid. 1878 A. Hamilton Nerv. Dis. 66 Blindness..which was the result of suppurative choroiditis. |