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299 Cards in this Set
- Front
- Back
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What structure divides the main lacrimal gland into two parts?
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levator aponeurosis
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The superior portion of the main lacrimal gland is also called what?
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orbital portion
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The inferior portion of the main lacrimal gland is also called what?
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palpebral portion
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Name the large portion of the main lacrimal gland.
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superior (orbital) portion
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Name the small portion of the main lacrimal gland.
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inferior (palpebral) portion
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The main lacrimal gland is supplied by what artery?
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lacrimal artery
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The main lacrimal gland is drained by what vein?
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lacrimal vein
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The main lacrimal gland is innervated by what nerve(s)?
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lacrimal nerve and pterygopalatine ganglion
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The main lacrimal gland receives some (sympathetic, parasympathetic) nerve fibers.
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sympathetic
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Some sympathetics reach the main lacrimal gland by traveling with what structure?
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lacrimal artery
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The main lacrimal gland has about how many main ducts?
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12
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The main ducts of the main lacrimal gland enter into what structure?
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superior-lateral fornix
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The main lacrimal gland is an extension of ___________ into orbit and into _________________________ of lid.
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conjunctiva; submuscular areolar layer
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All ducts pass through what portion of the main lacrimal gland?
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palpebral portion
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What is the designation of the main lacrimal gland's secretory units?
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compound tubulo-alveolar (tubuloracemose) serous gland
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acinus
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cluster of cells that resembles a many-lobed berry, such as a raspberry
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The main lacrimal gland's acini contain what type of cells?
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secretory cells and myoepithelial cells
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Role of connective tissue in the main lacrimal gland?
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intralobular and interlobular
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The apices of main lacrimal gland cells point toward what structure?
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central lumen
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What are the only lymphatic vessels of the orbit?
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lymphatic vessels of the main lacrimal gland and optic nerve dura
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Lymph of the main lacrimal gland drains to what lymphatic node(s)?
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parotid nodes
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Function of accessory lacrimal glands?
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add to the volume of tear fluid produced
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Name 2 types of accessory lacrimal glands.
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Lacrimal glands of Wolfring
Lacrimal glands of Krause |
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Lacrimal glands of Wolfring
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conjunctival lacrimal glands of lids
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Lacrimal glands of Krause
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conjunctival lacrimal glands of fornix
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Where are lacrimal glands of Wolfring located?
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at attached border of tarsus in deep fibrous layer of orbital conjunctiva or between extremities or tarsal glands
(along orbital border of tarsal plate) |
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Where are lacrimal glands of Krause located?
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connective tissue of fornix
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How many lacrimal glands of Wolfring?
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approximately 2 to 5 in upper lid and 2 in lower lid
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How many lacrimal glands of Krause?
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42 in upper fornix and 6 to 8 in lower fornix
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lacus lacrimalis
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lacrimal lake; a tear reservoir located on the medial canthus. Plica makes up its floor; caruncle makes up its medial side.
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tear menisci
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strips of tears located at the posterior edges of both upper and lower eyelid margins; more easily seen on lower eyelid margin.
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Role of eyelids in distribution of tears?
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1. Precorneal tear film tends to break up between blinks, but blinking reforms preocular tear film.
2. Lateral parts of eyelids meet each other before medial parts, so tear film is pushed medially. |
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lacrimal papillae
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whitish elevated connective tissue ring that keeps the punctum open
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lacrimal puncta
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holes through which tears drain, located near medial canthus
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lacrimal canaliculi
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tubes in the upper and lower lids that join the puncta to the lacrimal sac
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Which is longer: the vertical part or the horizontal part of a lacrimal canaliculus?
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horizontal part
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The vertical part of a lacrimal canaliculus terminates as what structure?
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ampulla
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The horizontal part of a lacrimal canaliculus penetrates ________________ and then unites with other horizontal part to form a ______ ___________.
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lacrimal fascia; common canaliculus
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What muscle surrounds a lacrimal canaliculus?
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Horner's muscle
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A lacrimal canaliculus is lined by what type of tissue?
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stratified squamous nonkeratinized epithelial tissue
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The connective tissue of lacrimal canaliculi is rich in what type(s) of fibers?
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elastic fibers
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The common canaliculus terminates on what structure of the lacrimal drainage system?
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lacrimal sac
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How long is the lacrimal sac?
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10 or 12 mm
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Much of the lacrimal sac is directly underneath what structure?
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medial palpebral ligament
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The fossa in which the lacrimal sac lies is formed by what bones?
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frontal process of maxillary bone and the lacrimal bone
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Horner's muscle fibers originate from?
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lacrimal sac fascia and posterior lacrimal crest
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How does Horner's muscle drive or pump fluid into the lacrimal sac?
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by creating a positive pressure in the lacrimal canaliculus
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The lacrimal fossa is limited by?
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posterior lacrimal crest of lacrimal bone and anterior lacrimal crest of maxillary bone
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How do tears enter the lacrimal puncta?
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capillary attraction
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How long is the nasolacrimal duct?
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12 or 15 mm
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The nasolacrimal canal begins where?
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bottom of fossa for lacrimal sac
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The nasolacrimal canal is formed mostly by which bone structures?
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lacrimal groove of maxilla and lacrimal and inferior concha
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The duct of the nasolacrimal canal drains into?
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inferior meatus
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The nasolacrimal duct is composed of 2 parts. Name them.
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interosseous part
intrameatal part |
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The intrameatal part of the nasolacrimal duct runs under the mucous membrane of which meatus?
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inferior meatus
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What is the opening of the nasolacrimal duct called?
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ostium
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Valve of Hasner
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fold of mucosal tissue that prevents fluid of nasal cavity from entering nasolacrimal duct and prevents air from entering duct when sneezing or blowing nose
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The nasolacrimal sac and duct are lined by what tissue type?
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pseudostratified epithelium with goblet cells but no cilia
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The nasolacrimal duct is very close to which sinus?
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maxillary sinus
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The eye has how many tunics?
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3
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Name the tunics of the eye.
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Fibrous tunic
Middle (vascular) tunic Inner tunic |
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fibrous tunic
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cornea & sclera
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middle tunic
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choroid, ciliary body, & iris
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inner tunic
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retina & retinal parts of ciliary body and iris
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uvea (uveal tract)
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choroid, ciliary body, & iris
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What fraction of the fibrous tunic is sclera?
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5/6ths
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The eye has 3 chambers. Name them.
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Anterior chamber
Posterior chamber Vitreous chamber |
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What is the radius of sclera?
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11.5 mm
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What is the radius of cornea?
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7.8 mm
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Which has a steeper radius: cornea or sclera?
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cornea
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What major structures are found in the anterior segment of the eye?
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Cornea
Anterior sclera Angle Iris Ciliary body Lens |
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What major structures are found in the posterior segment of the eye?
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Choroid
Vitreous Retina Optic nerve Sclera (other than anterior sclera) |
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epiphora
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overflow of tears onto the face
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anterior pole of eyeball
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corneal center
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Location of ANATOMICAL posterior pole of eyeball?
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1mm above and 3mm temporal to optic nerve center
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geometric axis of eyeball
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line joining the anterior and posterior poles of eyeball
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visual axis
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line from an object to the fovea centralis
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What vessels are located near the equator of the eye?
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vortex veins
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Diameter of an adult eye?
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about 23 or 24 mm
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Anterior-posterior diameter of adult eye?
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24.0 mm
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Horizontal or transverse diameter of adult eye?
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23.5 mm
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Vertical diameter of adult eye?
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23.0 mm
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Which is the shortest diameter of the adult eye?
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vertical
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Why do the anterior and posterior surfaces of cornea differ in shape?
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Anteriorly, the limbus of sclera encroaches on the cornea more than it does posteriorly.
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Anterior surface of cornea is what shape?
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elliptical
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Posterior surface of cornea is what shape?
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circular
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Vertical diameter of anterior corneal surface?
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~ 11mm
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Horizontal diameter of anterior corneal surface?
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~ 12mm
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Diameter of posterior corneal surface?
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11.7 or 12 mm
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Central thickness of cornea?
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0.52mm (520 microns)
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Thickness of cornea at periphery?
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670 or 710 microns
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Why is cornea cold but iris warm?
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cornea is avascular but iris is vascularized
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Iris is approximately how many degrees warmer than cornea?
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5
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Why is the temperature difference between cornea and iris important?
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helps with circulation of aqueous
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Krukenberg's spindle
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a vertical fusiform area of melanin pigmentation on the posterior surface of the cornea in the pupillary area
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Pigmentary dispersion syndrome
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condition in which pigment cells flake off of the iris and float around in the aqueous humor
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Why is it important to monitor patients with Krukenberg's spindle or pigment dispersion syndrome?
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the sloughed-off pigment flakes in these patient's eyes may accumulate and clog the trabecular meshwork, leading to increased intraocular pressure and pigmentary glaucoma
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How can you identify Krukenberg's spindle with the slit lamp?
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Shine a narrow slit lamp beam right in the pupil and you should get a nice red retinal reflex. What characterizes this syndrome is that a spoke or two of red (due to missing pigment) will also be visible in the iris.
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Name the 5 layers of cornea, in order.
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1. Epithelium
2. Bowman's layer (anterior limiting lamina) 3. Stroma (substantia propria) 4. Descemet's membrane (posterior limiting lamina) 5. Endothelium |
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Which layer(s) of the cornea remain the same thickness throughout life?
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Epithelium
Bowman's layer Stroma |
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Which layer(s) of the cornea get(s) thicker with age?
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Descemet's membrane
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Which layer(s) of the cornea get(s) thinner with age?
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Endothelium
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Which corneal layer is composed of a single layer of cells?
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Endothelium
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Which corneal layer is composed of 4 to 6 layers of cells?
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Epithelium
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Which corneal layer makes up the majority of cornea?
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Stroma
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Which corneal layer is the basement membrane for corneal endothelium?
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Descemet's membrane
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Main functions of corneal epithelium?
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1. Form a barrier to pathogen invasion
2. Form a barrier to uptake of excess fluid by corneal stroma |
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How is basal lamina ofcorneal epithelium attached to Bowman's?
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tightly, by hemidesmosomes & anchoring fibrils
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The stratum basale or s. germinativum of corneal epithelium is how many cell layers?
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1
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Shape of cells in stratum basale of corneal epithelium?
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columnar
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How are cells held together in the stratum basale of corneal epithelium?
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desmosomes
gap junctions |
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Cytoplasm of cells in stratum basale of corneal epithelium contains?
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tonofibrils
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Which is the mitotically active portion of cornea?
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stratum basale (s. germinativum) layer of corneal epithelium
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Nonepithelial cells in s. basale of corneal epithelium?
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Melanocytes
Cells of Langerhans Lymphocytes or macrophages Sensory nerve fibers |
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Are the sensory nerve fibers in s. basale of corneal epithelium encapsulated or unencapsulated?
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unencapsulated
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Middle corneal epithelial layer is composed of what type(s) of cells?
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wing (umbrella) cells
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Middle corneal epithelial layer is composed of how many layers of cells?
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2 or 3
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Superficial cell layer of corneal epithelium is composed of what type(s) of cells?
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squamous
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Superficial cell layer of corneal epithelium is composed of how many layers of cells?
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2
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What features of surface corneal epithelial cells allow the mucous tear film layer to adhere to cornea and provide a smooth surface for tear film to rest upon?
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Microvilli and microplicae with glycocalyx
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What forms a selective semipermeable barrier for substances in precorneal tear film?
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zonula occludens (ZO)
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Bowman's layer is composed mainly of...?
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collagenous fibrils in ground substance
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How can you see the blending of Bowman's layer fibrils with stroma?
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by gently massaging cornea through lids and use of fluorescin dye and slit lamp
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Why is Bowman's layer considered acellular?
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because it lacks fibroblasts
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Nonepithelial cells found in Bowman's layer?
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Schwann cells and nerve fibers
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For corneal scarring to occur, which layer(s) must be penetrated?
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Descemet's and all layers above it
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Main function of corneal stroma?
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present a strong extracellular matrix that transmits light
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Another name for corneal stroma?
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corneal substantia propria
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Stroma forms what percentage of corneal thickness?
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90%
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Corneal stroma is composed mostly of...?
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collagenous lamellae (layers) and keratocytes or fibroblasts that constitute a dense regular connective tissue
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How does corneal stroma differ from sclera?
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Corneal stroma is dense REGULAR connective tissue; sclera is dense IRREGULAR connective tissue.
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Why is the regular arrangement of corneal stroma fibers essential?
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for transparency
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Which is thicker in diameter: corneal stroma fibers or scleral fibers?
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scleral fibers
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Why is the thin diameter of corneal stroma fibers essential?
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for transparency
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Why is the uniform interfibrillar distance of corneal stroma fibers unique and important?
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Other connective tissues do not have a uniform interfibrillar distance, but in corneal stroma this uniformity is essential for transparency.
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Ground substance of corneal stroma contains?
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glycosaminoglycans (GAGs) and proteoglycans
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In corneal stroma, fibroblasts and keratocytes are mostly between...?
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lamellae
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In corneal stroma, how do fibroblasts or keratocytes attach to each other?
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macula occludens (MO)
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Non-connective tissue cells found in corneal stroma?
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Nerve fibers
Schwann cells Wandering cells (lymphocytes, neutrophils & macrophages) |
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Main function of Descemet's membrane?
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to contribute structural strength to the cornea
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What is unique about the elastic properties of Descemet's membrane?
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no elastin
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How can Descemet's membrane indicate the age of the individual?
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thickness (gets thicker with age)
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Descemet's membrane is composed of?
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basement membrane collagen
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Descemet's membrane has 2 zones. Name them.
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1. Anterior fetal banded portion
2. Posterior nonbanded portion |
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Which zone of Descemet's membrane gets thicker throughout life?
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the posterior nonbanded portion
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fibronectin
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transmembrane protein that chemically attaches Descemet's membrane to corneal endothelium
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Hassal-Henle bodies
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"warts" that occur in PERIPHERAL cornea; protrustions of Descemet's membrane associated with a thinned endothelium; their incidence increases with age
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gutatta
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deposits of basement membrane found in CENTRAL cornea; indicative of endothelial dysfunction; associated with Fuch's dystrophy
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Main function of corneal endothelium?
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regulation of corneal hydration
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The basal part of each corneal endothelial cell rests on?
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Descemet's membrane
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The apical part of each corneal endothelial cell lines what structure?
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anterior chamber
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Which is a more complete barrier: macula occludens or zonula occludens?
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zonula occludens (ZO)
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Which has more mitochondria: endothelium or photoreceptors and RPE?
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photoreceptors and RPE
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Which corneal layer(s) have MO?
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Stroma
Endothelium |
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Which corneal layer(s) have ZO?
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Epithelium
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Which corneal layer(s) have gap juctions?
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Epithelium
Endothelium |
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Which corneal layer(s) have desmosomes?
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S. basale of epithelium
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Which corneal layer(s) have hemidesmosomes?
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Basal lamina of epithelium
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Which nerves supply sensory innervation to the cornea?
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long & short ciliary nerves
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Origins of the long & short ciliary nerves?
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V1 (Ophthalmic) division of CN5 (Trigeminal nerve)
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Describe sensory innervation of the cornea (Route 1).
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ophthalmic nerve, nasociliary nerve, long ciliary nerves
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Describe sensory innervation of the cornea (Route 2).
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ophthalmic nerve, nasociliary nerve, sensory root of ciliary ganglion, ciliary ganglion, short ciliary nerves
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Where are the cell bodies of long ciliary nerves located?
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semilunar ganglia
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Ciliary nerves entering the eyeball travel in the ______________ space.
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suprachoroidal
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Approximately how many sensory nerves enter the cornea?
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60 to 80
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Do sensory nerves enter central cornea or peripheral cornea?
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peripheral
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Are sensory nerves myelinated or unmyelinated as they enter the cornea?
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myelinated
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Sensory nerves that have penetrated the cornea further than about 2 mm are myelinated or unmyelinated?
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unmyelinated
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Do sensory nerves that have penetrated the cornea further than about 2 mm still have their Schwann cell covering?
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yes
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Most ciliary nerve branches enter peripheral cornea via ______, but some go through ____________ and __________ tissue to get to cornea.
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sclera; conjunctival; episcleral
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Nerve endings occur in which corneal layer?
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epithelium
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New corneal cells come from ______ conjunctiva and from corneal _____ cells.
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limbal; basal
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Location of corneal stem cells?
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limbal conjunctival s. basale
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Daughter cells of stem cells migrate to ______ to reside in _________________ where they divide to become __________.
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cornea; corneal s. basale; wing cells
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pleomorphism
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a change in cell shape
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polymegathism
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a change in cell size
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scleral thickness
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varies from 1mm at posterior pole to 0.3mm just posterior to recti insertions
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Why is sclera bluish white in infants?
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due to uveal pigmentation OR due to light passing through thin sclera, striking uvea and reflecting and absorbing light
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Why may sclera appear yellowish white in an elderly individual?
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due to trapping of lipids in dense irregular connective tissue
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Axenfeld's nerve loop
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Ciliary nerve loop that is visible in the sclera; may appear as clear-like spots if no migration of uveal melanocytes along the sides of this nerve, but is USUALLY marked by multiple focal pigmented areas at a constant distance from the corneoscleral junction. Present in ~ 12% of eyes.
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synonym for Nevus of Ota
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oculodermal melanocytosis
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Nevus of Ota
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An area of hyperpigmentation on the face, distributed along 1st and 2nd branches of CN 5. More common in people of Asian or African descent than in Caucasians. Can be congenital or acquired. Usually benign, but should be monitored in case it develops into melanoma. If recent onset, greater likelihood of melanoma.
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Synonym for suprachoroidal lamina?
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lamina fusca
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suprachoroidal lamina
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delicate layer of loose, pigmented connective tissue on the inner surface of the sclera
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suprachoroidal space
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space between sclera & choroid (not always present) where vessels & nerves run
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supraciliary space
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space between ciliary body and sclera (not always present)
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anterior scleral foramen
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hole that results if cornea is completely removed from eye; in normal eye, area where opaque sclera becomes clear cornea
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scleral emissaria
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passageways for vessels and nerves; also called scleral canals or channels
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Which vessels & nerves occur in the anterior scleral emissaria?
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1. Main trunks of the 7 anterior ciliary arteries
2. Tributaries of the 14 ciliary veins 3. Deep scleral venous plexus veins 4. Intrascleral venous plexus veins 5. Aqueous veins of Ascher 6. Nerve loops of Axenfeld |
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Which vessels & nerves occur in the middle scleral emissaria?
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1. Superior vortex veins
2. Inferior vortex veins |
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Which vessels & nerves occur in the posterior scleral emissaria?
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1. The 2 (nasal & temporal) long ciliary nerves
2. The 6-10 short ciliary nerves 3. The 2 long (nasal & temporal) posterior ciliary arteries 4. The numerous short posterior ciliary arteries |
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major anterior emissaria
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main trunks of the 7 anterior ciliary arteries; project into scleral proper at 4mm from corneal margin
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episcleral venous plexus
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not an emissarium, but receives blood from deep scleral venous plexus and intrascleral venous plexus (both anterior emissaria)
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episclera
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outermost part of sclera; composed of loose or dense connective tissues & vessels; anterior is more vascular than posterior
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Other terms for sclera?
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Scleral proper
Scleral stroma |
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Sclera is composed of what tissue type?
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dense irregular connective tissue
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sclera
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1. Dense irregular connective tissue
2. Collagenous fiber bundles are often in loops. 3. Fibroblasts produce the fibrils & ground substance. 4. There is a low density of pain nerve endings derived from long & short ciliary nerves. |
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What is the "weak spot" of the sclera?
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lamina cribrosa
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lamina cribrosa
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network of scleral tissue that can be considered part of the optic nerve
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Lamina cribrosa is formed by what type(s) of fibers?
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collagenous bundles & elastic fibers
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posterior scleral foramen
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hole that results if lamina cribrosa & optic nerve axons are removed
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scleral spurs
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fibers made of circularly arranged collaged with some elastin; posterior spur is origin of longitudinal ciliary muscle fibers; most trabecular meshwork sheets attach to anterior portion of spur
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internal scleral sulcus
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a slight, circular groove at the margin b/w the posterior surface of cornea and the sclera; contains canal of Schlemm & trabecular meshwork
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external scleral sulcus
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a slight groove on the external surface of the eyeball; indicates location of limbus; contains Tenon's and conjunctiva
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Shape of cornea depends on what factors?
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1. Curvature of cornea
2. Shape of iris 3. Size & position of lens (which changes with accommodation) |
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Volume of aqueous in the anterior chamber?
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~ 0.26 mL
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Diameter of cornea?
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12.5 mm
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Depth of cornea?
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~ 3.5 mm
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Location of trabecular meshwork?
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limbus and internal scleral sulcus
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limbus
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transition zone where corneal epithelium becomes conjunctival epithelium and where corneal stroma becomes sclera proper
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Trabecular meshwork is composed of what tissue type?
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a type of connective tissue that is neither typical sclera nor typical cornea, but is more fibrous tunic than middle tunic
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Where does trabecular meshwork terminate?
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anteriorly on Schwalbe's line; posteriorly at scleral spur, but a small amount of meshwork continues past this to attach to anterior face of ciliary body and sometimes to iris root
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Schwalbe's line (ring)
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termination of Descemet's membrane; composed of circularly arranged collagen fibers intermixed with elastic fibers & transitional endothelium; important to gonioscopy
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juxtacanalicular tissue
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tissue next to canal of Schlemm; externally, most of trabecular meshwork stops here
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Name landmarks used in gonioscopy.
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Schwalbe's line
Scleral spur Trabecular meshwork Ciliary body NOTE: These structures are listed in order of appearance when viewing from superior to inferior. |
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Components of trabecular meshwork?
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1. Iris processes
2. Uveal meshwork 3. Corneoscleral meshwork |
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iris processes
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iridic part of trabecuar meshwork; found only in 1/3 of eyes, which may have only a few processes; composed of iris tissue bridging from anterior surface of iris root to uveal meshwork
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Alternate terms for uveal meshwork?
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uveal trabeculae, uveal cords, inner sheets, uveal portion of meshwork
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Which meshwork is nearest to anterior chamber angle: iris processes, uveal meshwork, or corneoscleral meshwork?
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uveal meshwork
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Which is always the innermost 1-5 layers of the trabecular meshwork: iris processes, uveal meshwork, or corneoscleral meshwork?
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uveal meshwork
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Where does uveal meshwork begin anteriorly?
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Schwalbe's line
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Which of the meshworks (uveal meshwork, corneoscleral meshwork) is sheet-like? Which is cord-like?
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Uveal meshwork is cord-like; corneoscleral meshwork is sheet-like.
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When performing gonioscopy, where is Schlemm's canal in relation to the trabecular meshwork?
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Schlemm's lies behind the trabecular meshwork.
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What does it mean if Schlemm's Canal appears as a thin red line when you're performing gonioscopy?
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Blood is backed up in the canal because the examiner is exerting too much pressure on the eye with the gonio lens.
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How do you distinguish between iris processes and angle closure when performing gonioscopy?
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Iris processes appear as tiny, wispy structures rather than the large ridge seen in angle closure.
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angle recession glaucoma
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type of glaucoma in which the angle is too open due to a tear between iris and corneal sclera; results from trauma to the eye but may not manifest until years later; patients with a history of ocular trauma should therefore have gonioscopy performed on a yearly basis
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Alternate term for narrow angle glaucoma?
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angle closure glaucoma
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Why should you perform gonioscopy prior to dilation for narrow angle glaucoma suspects?
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Dilating a patient with narrow angle glaucoma may induce complete angle closure and a resulting spike in IOP.
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Alternate terms for corneoscleral meshwork?
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corneoscleral trabeculae
outer sheets |
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corneoscleral meshwork
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outer sheets of trabecular meshwork; composed of 8-15 layers
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Boundaries of the corneoscleral meshwork?
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Corneoscleral meshwork ends posteriorly on scleral spur and begins anteriorly at Schwalbe's line.
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Where are the uveal cords in relation to the corneoscleral meshwork?
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Uveal cords are inner to the corneoscleral meshwork.
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Where is the juxtacanalicular tissue in relation to the corneoscleral meshwork?
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Juxtacanalicular tissue is outer to the corneoscleral meshwork.
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Describe the outer wall of Schlemm's canal.
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Has efferents that drain aqueous, ordinary smooth lining of endothelium and a thin connective tissue that contacts limbal sclera.
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Key feature of inner wall of Schlemm's canal?
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Has unique endothelium that contacts juxtacanalicular tissue.
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Relative size of Schlemm's canal?
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Schlemm's canal occupies the posterior half of the distance between the scleral spur & end of Descemet's. Its anterior-posterior length is smaller than that of trabecular meshwork.
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Describe the drainage of aqueous.
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1. Efferents are small vessels directly draining Schlemm's canal
2. Deep scleral venous plexus recieves short efferents 3. Intrascleral venous plexus receives deep scleral venous plexus 4. Episcleral venous plexus receives intrascleral venous plexus and the long efferents called aqueous veins of Ascher. |
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uveal trabecular endothelial cells
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cover cord (trabeculae) & connect by cell junctions; may wander; phagocytize melanin granules carried in aqueous; synthesize extracellular matrix of cord.
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extracellular matrix of uveal cords
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basement membrane (cortical zone) is next to endothelium; core mostly of collagen fibrils w/ randomly arranged elastic tissue clumps & ground substance
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Why is juxtacanalicular tissue not considered part of the trabecular meshwork?
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no spaces b/w tissue layers
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Function of juxtacanalicular tissue?
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1. Cleans aqueous
2. May regulate passage of aqueous toward inner wall of Schlemm's canal by varying the amount & kind of ground substance |
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The endothelium of Schlemm's canal has 2 walls (inner & outer). Which wall has giant vacuoles?
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inner wall
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Circumference of Schlemm's canal?
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36 mm
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Inner wall of Schlemm's endothelium: vascular or avascular?
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vascular
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Alternate terms for canals of Sondermann?
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blind pouches
internal collector channels |
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Do anterior ciliary arteries deliver blood to Schlemm's lumen?
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no
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Canals of Sondermann are an extension of what structure?
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Schlemm's canal
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Alternate term for aqueous-draining efferents?
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external collector channels
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Function of giant vacuoules in Schlemm's endothelium?
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transport aqueous from juxtacanalicular tissue to lumen of Schlemm's canal
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What drives the vacuolation cycle?
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a pressure gradient created by aqueous in anterior chamber pushing against canalicular tissue
NOTE: The endothelium does not break; it just forms a channel. |
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List the 6 phases of the vacuolation cycle.
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1. Aqueous humor is traveling through trabecular meshwork
2. Endothelial cells of juxtacanalicular tissue begin to get an indentation 3. Aqueous enters the indentation 4. Indentation gets bigger 5. The endothelial layer on the outside (canal of Schlemm side) opens up into a hole and allows aqueous to travel through 6. The vacuole closes back up. |
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Why would an individual with albinism be prone to nystagmus and unlikely to acheive better than 20/70 vision?
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Absence of pigmentation prevents the macula from developing properly.
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Why does a blue iris appear blue?
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Few or no melanocytes lie in the anterior border and stroma layers of a blue iris. Stroma absorbs long wavelengths & pigmented epithelium reflects shorter blue waves back to the observer.
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collarette
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zigzag circular ridge of collagenous remains of vessels & active vessels; divides iris into pupillary & ciliary zones; thickest part of iris; previous (neonatal) attachment site of pupillary membrane to iris
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Fuch's crypts
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depressions or openings in the anterior iris surface on either side of the collarette; they allow the aqueous quick exit & entrance into spaces in the iris stroma as the volume of the iris changes with iris dilation or contraction
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Alternate term for radial streaks?
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white columns
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radial streaks
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radial white streaks in ciliary zone of anterior iris surface; due to collagen in outer walls of vessels; more obvious in blue iris
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A brown iris appears brown due to number of melanocytes or amount of melanin?
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number of melanocytes
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Anterior & posterior iris layers: positioned apex to apex or apex to base?
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apex to apex
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Location of minor arterial iris circle?
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iris stroma in region of collarette
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Location of major arterial iris circle?
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connective tissue of ciliary body near iris root (NOT actually in iris)
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Valleys between major ciliary processes of ciliary body have increased or decreased pigmentation?
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increased pigmentation
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Major ciliary processes of ciliary body have increased or decreased pigmentation?
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decreased pigmentation
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Schwalbe’s structural furrows
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what folds in iris when the pupil dilates and constricts; due to radial variations in thickness of posterior pigment epithelium & stroma
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Why are superficial layer and anterior border layer of iris not the same thing?
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The anterior border layer is included as part of the superficial layer.
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The superficial mesenchymal layer of iris is only found where?
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ciliary zone
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Why is the posterior leaf of iris stroma called the posterior retinal layer?
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It is continuous with epithelial cells that are continuous with ciliary body epithelial cells that are continuous with the retina. If you follow the posterior retinal layer it becomes the neurosensory retina.
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How many layers in the posterior retinal layer?
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2
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Anterior border layer of iris is composed of?
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Fibroblasts
Pigmented melanocytes Collagen fibrils |
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What's the difference between a melanocyte and a melanosome?
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A melanocyte produces melanin; a melanosome is a vacuole filled with melanin.
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What forms the blood-aqueous barrier of iris capillaries?
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zonula occludens (ZO)
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What's in iris stroma?
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aqueous, fibroblasts, melanocytes, lymphocytes, macrophages, mast cells, clump cells, ground substance, vessels, nerves, and sphincter
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clump cells
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round immune system cells that clump around the iris sphincter; increase in number with age
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How do mast cells increase vasodilation and inflammatory response?
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by triggering release of histamine and serotonin
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Patenol/Pataday
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brand names for combo antihistamine/mast cell stabilizing drops; useful for treating eye allergies
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Anterior iris epithelium and posterior iris epithelium: which is pigmented and which is nonpigmented?
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Anterior iris epithelium is pigmented; posterior iris epithelium is nonpigmented.
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Aqueous can only enter which side of the iris: anterior or posterior?
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anterior
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Why can't aqueous enter the posterior side of iris?
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tight junctions (ZO)
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iris cyst
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cyst caused by fluid buildup between the anterior and posterior iris epithelium
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Which should you use to distinguish between an iris cyst and a melanoma: pachymetry, A-scan, or B-scan? Why?
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B-scan, because it provides a 2-dimensional image that lets you know if the mass is full or optically empty (filled with fluid)
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A-scan assesses what?
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length of eye
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Normal pigment ruff at normal pupil is 100% epithelium or myoepithelium?
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epithelium
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Describe the blood supply & drainage of the iris.
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Blood is supplied to the iris by the radial arteries (derived from the major circle of the iris) and the minor circle of the iris (which are derived from radial arteries & give rise to arcades). Radial veins drain to ciliary body veins that drain to choroidal veins, then vortex veins.
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Parasympathetic innervation of the iris: long ciliaries, short ciliaries, or both?
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short ciliaries only
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Sympathetic innervation of the iris: long ciliaries, short ciliaries, or both?
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both long & short ciliaries
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Sensory innervation of the iris: long ciliaries, short ciliaries, or both?
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both long & short ciliaries
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The only synapses in the ciliary ganglion are between sympathetic or parasympathetic nerves?
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parasympathetic nerves
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How is the pupil displaced in relation to the center of the cornea?
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The pupil is displaced slightly downward & nasally in relation to the center of the cornea.
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miosis
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pupil constriction
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mydriasis
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pupil dilation
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Volume of fluid in the posterior chamber?
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0.065 mL
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List the anterior, posterior, and external boundaries of the posterior chamber.
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Anterior boundary: pigment epithelium of iris
Posterior boundary: lens & anterior zonules External boundary: ciliary process heads & valleys (of Kuhnt) between heads |
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Alternate term for canal of Hannover?
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circumlental space
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Effect of aging on zonules attached to lens equator?
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The zonules disappear with aging.
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Alternate term for canal of Petit?
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retrozonular space
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anterior hyaloid of vitreous
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face of vitreous
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canal of Petit
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the area from the most posterior zonules to the anterior hyaloid (face) of vitreous
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What are the two regions of the posterior chamber?
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canal of Hannover (zonular part, circumlental space) and canal of Petit (retrozonular space)
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Direction of aqueous movement: from anterior chamber to posterior chamber or from posterior chamber to anterior chamber?
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Aqueous moves from posterior chamber to anterior chamber.
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