a. (sb.) Anat. 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 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. This [vascular] organ, generally called the ‘choroid gland’ by the older anatomists…, is 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, Expos. 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 sb. 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, 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, trans. 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. Imison, Sc. & Art (ed. Webster), I. 251. The whole of the choroides is opaque.
Hence Choroidal a., † a. belonging to the choroid membrane of the brain (obs.); b. belonging to the choroid coat of the eye; Choroidean a., pertaining to the choroid (plexus); choroidean artery = choroid artery, see 2; Choroiditis, Path. [see -ITIS], inflammation of the choroid coat.
1681. trans. 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. M. Hamilton, Nerv. Dis., 66. Blindness … which was the result of suppurative choroiditis.
