Flashcards in The Eye - HY Deck (60):
The optic sulcus ...?
Evaginates from the wall of the diencephalon as the optic vesicle consisting of neuroectoderm.
The optic vesicle ...?
Invaginates and forms a double-layered OPTIC CUP + OPTIC STALK.
The optic cup and derivatives - The double-layered optic cup consists of ...?
1. Outer pigment layer.
2. Inner neural layer.
The outer pigment layer of the optic cup gives rise to ...?
The pigment layer of the RETINA.
The intraretinal space separates ...?
The outer pigment layer from the inner neural layer.
Although the intraretinal space is obliterated in the adult ...?
It remains a weakened area prone to RETINAL DETACHMENT.
The inner neural layer of the optic cup gives rise to ...?
The neural layer of the RETINA (ie rods, cones, bipolar cells, ganglion cells).
Iris - The epithelium of the iris develops from ...?
The ANTERIOR portions of BOTH the outer pigment layer and the inner neural layer of the optic cup, which explains its histological apperance of 2 layers of columnar epithelium.
Iris - The stroma ...?
Develops from MESODERM continuous with the choroid.
The iris contains the ...?
Dilator pupillae muscle + Sphincter pupillae muscle.
The dilator pupillae + sphincter pupillae muscles are formed from ...?
The epithelium of the OUTER pigment layer by a TRANSFORMATION of these epithelial cells into CONTRACTILE CELLS.
Ciliary body - The epithelium of the ciliary body ...?
Develops from the ANTERIOR portions of BOTH the outer pigment layer + the inner neural layer of the optic cup --> Explains the histological appearance of 2 layers of columnar epithelium.
Ciliary body - The stroma develops from ...?
Mesoderm continuous with the choroid.
The ciliary body contains the ...?
The ciliary muscle is formed from ...?
Mesoderm within the choroid.
The ciliary processes are ...?
Components of the ciliary body.
The ciliary processes produce ...?
Aqueous humor, which circulates through the POSTERIOR and ANTERIOR chambers and drains into the venous circulation via the TRABECULAR MESHWORK and the canal of Schlemm.
The ciliary processes give rise to the ...?
Suspensory fibers of the LENS (ciliary zonule), which are attached to and suspend the lens.
The optic stalk contains ...?
1. The choroid fissure, in which the hyaloid artery and vein are found --> Later become the central artery and vein of the retina.
2. Axons from the ganglion cell layer of the retina.
The choroid fissure closes during ...?
Week 7 so that the optic stalk, together with the axons of the ganglion cells, forms:
1. Optic nerve.
2. Optic chiasm.
3. Optic tract.
The optic nerve is a tract of the diencephalon and has the following characteristics:
1. Not completely myelinated until 3 MONTHS AFTER birth - By oligodendrocytes.
2. Not capable of regeneration after transection.
3. Invested by the meninges and therefore is surrounded by a subarachnoid space that plays a role in papilledema.
The sclera develops from ...?
Mesoderm surrounding the optic cup.
The sclera forms ...?
An outer FIBROUS layer that is continuous with the dura mater POSTERIORLY and the cornea ANTERIORLY.
The choroid develops from ...?
Mesoderm surrounding the optic cup.
The choroid forms ...?
A vascular layer that is continuous with the pia/arachnoid POSTERIORLY and iris/ciliary body ANTERIORLY.
The anterior chamber develops from ...?
Mesoderm over the anterior aspect of the eye that is continuous with the sclera and undergoes vacuolization to form a chamber.
The anterior chamber essentially splits the mesoderm into 2 layers:
1. The mesoderm POSTERIOR to the anterior chamber is called the IRIDOPUPILLARY MEMBRANE --> Normally resorbed prior to birth.
2. The mesoderm ANTERIOR to the anterior chamber develops into the SUBSTANTIA PROPRIA of the cornea and corneal endothelium.
The cornea develops from ...?
BOTH surface ectoderm + mesoderm lying anterior to the anterior chamber.
The surface ectoderm forms the ... of the cornea, which has a high regenerative capacity.
ANTERIOR EPITHELIUM OF THE CORNEA.
The mesoderm forms the ... of the cornea (ie Bowman layer, stroma, and Descemet membrane) + ... .
Substantia propria of the cornea + Corneal endothelium.
The lens develops from ...?
Surface ectoderm, which forms the LENS PLACODE.
The lens placode invaginates to form ...?
The LENS VESICLE.
The adult lens is completely surrounded by a ...?
The lens epithelium is ...?
Simple cuboidal epithelium located beneath the capsule on the ANTERIOR surface.
The vitreous body develops from ...?
Mesoderm that migrates through the choroid fissure and forms a transparent GELATINOUS substance between the lens and the retina.
The vitreous body contains a portion of the ...?
Hyaloid artery --> Later obliterates to form the HYALOID canal of the adult eye.
The canal of Sclemm is found at the ...?
Sclerocorneal junction called the LIMBUS and drains the aqueous humor into the venous circulation.
An obstruction of the canal of Sclemm results in ...?
Increased INTRAOCULAR PRESSURE --> GLAUCOMA.
The EXTRAocular muscles develop from ...?
Mesoderm of somitomeres 1, 2, and 3, that surround the OPTIC CUP --> Also called preoptic myotomes.
Coloboma iridis is a ...?
Cleft in the iris caused by FAILURE OF THE CHOROID FISSURE to close in WEEK 7 --> May extend into the ciliary body, retina, choroid, or optic nerve.
A palpebral coloboma is a ...?
A notch in the eyelid --> Due to a defect in the developing eyelid.
Congenital cataracts are ...?
Opacities of the lens and are usually BILATERAL.
Congenital cataracts are ...?
Congenital caratacts may result from the following:
Congenital glaucoma (Buphthalmos) is ...?
Increased intraocular pressure due to abnormal development of the canal of Schlemm or the iridocorneal filtration angle.
An enlarged eye is suspected when the corneal diameter exceeds ...mm in a term newborn.
If the eye is enlarged, ...?
Infantile glaucoma should be suspected immediately.
Infantile glaucoma may also be present with ...?
4. Cloudy cornea.
Infantile glaucoma - The cornea often has ...?
Horizontal lines called Haab striae --> Due to disruption of the Descemet membrane.
Persistent iridopupillary membrane consists of ...?
Strands of connective tissue that partially cover the pupil --> Seldom affects vision.
Microphthalmia is a ...?
Small eye - Associated with intrauterine infections from the TORCH.
Anophthalmia is ...?
Absence of the eye - Due to failure of the optic vesicle to form.
Cyclopia is a ...?
Single orbit and one eye --> Failure of median cerebral structures to develop.
Retinocele results from ...?
Herniation of the retina into the sclera or from failure of the choroid fissure to close.
Retrolental fibroplasia (retinopathy of prematurity) is an ...?
Oxygen-induced retinopathy seen in premature infants.
Papilledema is ...?
Edema of the optic disk (papilla) due to increased INTRACRANIAL PRESSURE.
--> This pressure is reflected into the subarachnoid space, which surrounds the optic nerve.
Retinitis pigmentosa is a ...?
Hereditary degeneration + atrophy of the retina.
AD, AR, XR trait.
Retinitis pigmentosa is characterized by ...?
1. Degeneration of RODS.
2. Night blindness (nyctalopia).
3. "Gun barrel vision".
Retinitis pigmentosa may also be due to ...?
Abetalipoproteinemia (Bassen-Kornzweig syndrome) --> May be arrested with massive doses of vitA.