It is inclosed in a membranous covering (capsule) and is maintained in position by a membrane (suspensory ligament) which extends from the margin of the lens outward to the sclerotic at the point of junction of the choroid and iris.
They are found in one or both of the lateral ventricles, enveloped in the folds of the choroid plexus.
This is owing to a comparative absence of pigment in the choroid coat inside the upper part of the eyeball, and enables the animal to see and advance with security in darkness where the human eye would be of little use.
Tumors of thechoroid plexus, known as brain sand, are frequently met with on post-mortem examinations, but seldom give rise to any appreciable symptoms during life.
In severe inflammations pus may form in the choroid or iris, and escaping into the cavity of the aqueous humor show as a yellowish-white stratum below.
Between the retina and the choroid there is a very delicate membrane, which is usually (but wrongly) associated with the latter.
It proceeds from the optic thalami (the second cerebral vesicle) to the eye; penetrates its outer envelopes, and then spreads out like a net between the choroid and the corpus vitreum.
The inner membrane becomes the choroid or vascular coat, and in front the ciliary corona and iris.
In Amia and in Teleosts a network of capillaries forming the so-called choroid gland surrounds the optic nerve just outside the retina.
This movement is brought about by the contraction of smooth muscle fibres contained in the processus falciformis, a projection from the choroid which terminates in contact with the lens in a swelling, the campanula Halleri.
The retina, being transparent, offers no obstruction to the passage of the light onward to the black surface of the choroid coat, from which the vibrations are, in all probability, communicated to the retina and conveyed to the brain.
The choroid coat, which lies immediately behind the retina, is regarded by Mariotte and Bernoulli as the more probable seat of vision.
The choroid c c, is embued with a black liquor, which serves to absorb all the rays that are irregularly reflected, and to convert the body of the eye, into a more perfect camera obscura.
Minute bands of muscle in the choroid can alter the convexity of the lens, and thus adapt its focus to the position of objects at different distances.
About the place where the sclerotic passes into the cornea the choroid becomes continuous with the iris, a round curtain, the structure seen through the cornea, differently coloured in different individuals.
Within the sclerotic coat, and so to speak lining it, comes the choroid coat.
This coat contains the nerve endings of the optic nerve which, coming through the opening in the bony orbit, passes through the sclerotic andchoroid coats.
This ciliary body is a ring of tissue lying behind the iris connected with the anterior portion of the choroid coat of the eye.
Whence it is evident that vision exists where the choroidcoat is not present, and consequently that the choroid coat is not the organ of vision.
From this he concludes, that the defect of vision is owing to the want of the choroid coat, and, consequently, that this coat is the proper organ of vision.
Mariotte was led, from some curious circumstances, to think that vision was not performed by the retina, but by the choroid coat.
These circumstances, in my opinion, render it certain, that the retina, and not the choroid coat, is the organ of vision.
The choroid or vascular coat, is the respiratory system or lung in the eye.
The vascular or choroid coat of the eye is the continuation of the encephalic pia mater.
The choroidcoat incloses also an osseous mass, the lens--a vertebral body.
If this accident should happen, the portion of the sclerotic and choroid left behind should be carefully sought for and removed.
Suprachoroidal lymph-space which extends backwards between the choroid and sclerotic.
As the choroid approaches the front part of the eyeball, its parts become folded upon themselves into a series of ridges, called ciliary processes.
All around the edge, where the cornea, sclerotic, and choroid meet, is a ring of involuntary muscular fibers, forming the ciliary muscle.
For instance, a layer near the choroid is made up of nerve cells arranged in innumerable cylinders called "rods and cones," and packed together not unlike the seeds of a sunflower.
The pigmented layer of the choroid coat represents this blackened lining.
This pigment layer and that of the choroid and retina absorb the light entering the eye, so that little is reflected.
It also serves to hold the choroid and the retina in position, and to maintain the proper relations of the inner structures of the eye.
The circular space thus left in front by the termination of the choroid is occupied by the iris, a thin, circular curtain, suspended in the aqueous humor behind the cornea and in front of the crystalline lens.
The choroid plexuses contain the small choroidal arteries; and the blood from these is returned by small veins, which join to form the veins of Galen.
Resting on the upper surface of the thalamus is the vascular fringe of the velum interpositum, named choroid plexus, and immediately internal to this fringe is the free edge of the white posterior pillar of the fornix.
The choroid plexus of the pia mater turns round the gyrus hippocampi, and enters the descending cornu through the lateral part of the great transverse fissure between the taenia hippocampi and optic thalamus.
Some of them, like the choroidal on the mesial surface, are developed very early, while the vesicle is little more than epithelial, and contain between their walls an inpushing of mesoderm to form the choroid plexus.
This fossa is roofed over by the epithelium lining the cavity of the ventricle, by pia mater and blood-vessels constituting a choroid plexus (fig.
Its apex, where the two choroid plexuses blend with each other, lies just behind the anterior pillars of the fornix.
The albinos, in whom these dark cells of the choroid are wanting, have imperfect vision, especially in the daytime and in strong lights.
The choroid layer turns up anteriorly, making a free edge comparable to an iris.
To these distinctive characters he adds, in an appendix to his paper, the presence of the spiral valve, and the absence of a processus falciformis and a choroid gland.
A large pupil is left, but is divided by two flaps, continuations of the choroid coat, projecting from either side and overlapping.
It rests upon the choroid coat and spreads over about two thirds of the back surface of the eyeball.
Near where the sclerotic coat joins the cornea, the choroid coat separates from the outer wall and, by folding, forms many slight projections into the interior space.
The choroid coat lies immediately beneath the sclerotic coat at all places except a small margin toward the front of the eyeball.
The iris is a continuation of the choroid coat across the front of the eyeball.
The Middle Coat* consists of three connected portions—the choroid coat, the ciliary processes, and the iris.
Op represents part of the optic vesicle to one side of the choroid slit.
Horizontal section through a part of the choroid slit at stage P.
With reference to the later stages in the development of the eye, the only subject with which we propose to deal is the growth of the mesoblastic processes which enter the cavity of the vitreous humour through the choroid slit.
No mesoblast can be seen passing round the outside of the optic cup; and the only mesoblast which enters the optic cup passes through the choroid slit.
To these distinctive characters, he adds in an appendix to his paper, the presence of the spiral valve, and the absence of a processus falciformis and a choroid gland.
The artery bringing the blood to the above vascular membrane is bound up in the same sheath as the optic nerve, and passes through the choroid slit very close to the optic nerve.
Thus the optic nerve (opn) and choroidslit (ch) are both exhibited.
The figure contains the eye cut through in the plane of the choroid slit.
The mesoblast, though it projects between the lips of the ridge near the lens, only extends through the choroid slit into the cavity of the vitreous humour in the neighbourhood of the optic nerve.
It is covered by the choroid plexus, a thick vascular membrane, and gives rise dorsally to the stalk of the pineal body.
On its roof the pia mater forms a very vascular choroid plexus.
Just as the nerve processes arising in the retina are continued to the optic centre in the cerebrum, so must we look for the origin of the corresponding blood process not in the choroid itself, but in the lower regions of the organism.
What we call 'seeing' is far more the result of an interplay between the retina carrying the nerves, and the choroid carrying the blood-vessels.
In cases of doubt ophthalmoscopic examination of thechoroid and iris may reveal tubercle.
Secondary cataract is due to abnormalities in the nutrient matter supplied to the lens owing to disease of the ciliary body, choroid or retina.
Between the sclerotic and the subjacent choroid coat is a lymph space traversed by some loose pigmented connective tissue,--the lamina fusca.
On the deep surface of the choroid is a structureless basal lamina.
Many lizards have a vascular projection of the choroid into the vitreous, foreshadowing the pecten of birds and homologous with the processus falciformis of fishes.
The pigment deposit in the choroid is excessive and gives, as a background to the retina, a beautiful silvery sheen when examined with the ophthalmoscope.
The retina is a thin coat, lying inside the choroid at the back of the eyeball, and having the form of a hollow hemisphere.
He described the eye and especially the vitreous body, the choroid and the retina.
If a portion of the retina is disengaged from the choroid and raised up, it bleaches, though the remainder, still attached portion, retains its color.
The source of the color was found to be the inner surface of the choroid upon which the retina lies.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "choroid" in a variety of sentences. We hope that you will now be able to make sentences using this word.
