Exam 1 Ocular Anatomy 2 PDF

Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Optic cup develops from ___. neuroectoderm In what day does the lens develop occur? 27th day 2nd month of development -Appearance of blood vessels in choroid 3rd month of development -Optic cup outer layer becomes anterio...

Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Optic cup develops from ___. neuroectoderm In what day does the lens develop occur? 27th day 2nd month of development -Appearance of blood vessels in choroid 3rd month of development -Optic cup outer layer becomes anterior iris epithelium & outer pigmented epithelium of ciliary body -Optic cup inner layer becomes posterior iris epithelium -Myofilaments of anterior epithelium form the iris sphincter muscle -Inner optic cup form inner nonpigmented epithelium of ciliary body ’ ciliary processes -Pupillary membrane forms between lens epithelium & cornal endothelium The lens develops from what? Surface ectoderm surface ectoderm ’ lens plate (placode) ’ invagination ’ lens pit ’ lens vesicle ’ posterior cells elongate & attach to anterior cells Lens development The pupillary membrane replaces the ___ in the choroid. vascular tunic 4th month of development -Neural crest forms stroma & ciliary muscle -Development of Bruch's membrane in choroid 5th month of development -Neural crest cells in peripheral aspect of cornea form the chamber angel, trabecular meshwork & Schlemm's canal -Vortex veins ’ large & medium layer of vessels in choroid 6th month of development -Anterior layer of iris epithelium develop into dilator muscle -Mesenchymal cells form the anterior border layer -Neural crest forms the stroma -Central vessels atrophy & become bloodless 8th month of development -Central vessels fragment & disappear & reabsorption of pupillary membrane occurs If the pupillary membrane does not reabsorb, what happens? Persistent pupillary membrane appears When does aqueous humor production begins? 4-6 months of gestation Optic cup is divided into ___ outer layer & inner layer The outer layer of the optic cup becomes: -Retinal pigmented epithelium (RPE) -Outer pigmented ciliary body epithelium -Anterior non-pigmented iris epithelium The inner layer of the optic cup becomes: -Neural retina -Non-pigmented ciliary body epithelium -Posterior pigment epithelium of iris The mesenchyme from the anterior segment forms the ___. choriocapillaries The epithelium of the iris and the ciliary body develop from neural crest cells. b. false; they develop from neuroectoderm a. true b. false Pupillary membrane -Transitory membrane composed from mesenchyme & branches from major circle of iris What are the 3 regions of the uvea? -Iris -Ciliary body -Choroid Uvea -Vascular middle layer of eye -Has fenestrations Iris -Circular structure anterior to the lens -Contains the pupil -Regulate amount of light entering the eye 1 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Pupil -Center aperture -Slightly nasal & inferior to the iris center -Size: regulates retinal illumination -Diameter: 1-9 mm depending on light -Border is more pigmented (cells from posterior pigmented epithelium) Iris root -Never attached to the lens -Thinnest part of iris -Approx. 0.5 mm thick -Joins iris to ciliary body -Circular ridge (ring like) approx. 1.5 mm from pupillary margin -Site of attachment for fetal pupillary membrane -Divides iris in pupillary zone & ciliary zone Collarette Diameter & thickness of iris 12 mm diameter; thickness vaires The iris divides the eye in (2) chambers, those are... Anterior chamber & posterior chamber (allows aqueous humor flow) -Anterior border layer -Stroma & sphincter muscle -Anterior epithelium & dilator muscle -Posterior epithelium Layers of iris (4) -Thin condensation of stroma -Absent in iris crypts -Composed of fibroblasts (surface), pigmented melanocytes (below) -Attachment to trabecular meshwork at the root Anterior border layer of iris -Composed of pigmented cells (melanocytes & clump cells) & non-pigmented cells (fibroblasts, lymphocytes, macrophages & mast cells) Iris stroma Clump cells Large & round; usually at the pupillary portion of the stroma of iris Minor circle of the iris -Incomplete circular vessel -Located iris stroma inferior to collarette -Non-fenestrated -Form part of blood-aqueous barrier (not allowing vascularization) 2 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Radial course from iris root to pupil margin -Anterior ciliary artery & long posterior ciliary artery anastomose to form the arteries of iris -Thick tunica adventitia (thick-walled blood vessels) -Encircled by bundles of collagen fibrils for protection from kinking & compression Major circle of the iris -Lies within the stroma & anchors firmly -Composed of smooth muscle cells joined by tight junctions -Circular muscle surrounding the pupil -Wide 0.75-1 mm -Innervated by the parasympathetic system -Contraction: pupil; constriction: miosis Sphincter muscle -Lies near stroma -Composed of: *myoepithelial cells *pigmented cuboidal epithelium (apical portion) joined by tight junctions & desmosomes *smooth muscle processes (basal portion) Anterior Iris Epithelum -Single layer -Columnar heavily pigmented cells joined by tight junctions & desmosomes -Periphery loose pigment continues into the ciliary body as nonpigmented epithelium -Thin basement membrane covers the basal aspect -Pupillary ruff (frill) Posterior Iris Epithelium -Epithelial cells curl around the anterior epithelium at pupillary margin encircling the pupil -Has serrated apperance Pupillary ruff -3-5 layers of muscle fibers extending into stroma joined by tight junctions -Innervation by sympathetic system -Present from iris root to midpoint of sphincter in the stroma -Contraction: miosis; pupillary enlargement Dilator muscle The anterior epithelium has ___ shape cells while the posterior has ___ shape cells. a. columnar, columnar 3 / 21 b. cuboidal (anterior) & columnar (posterior) Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf b. cuboidal, columnar c. columnar, cuboidal The sphincter & dilator muscles are separated by a band of ___. a. adipose tissue b. connective tissue c. nervous tissue b. connective tissue -Thick branching trabeculae encircling depressions in the surface -Located in both sides of collarette (Fush's crypt & peripheral crypts near the root) Crypts of iris The anterior iris surface contains (3): -Crypts -Light pigmented iris -Circular contraction folds for pupillary dilation Light pigmented iris -Thin, radial, collagenous columns of trabeculae -Smooth -Near the pupil small circular furrows (radial contraction furrows in pupillary zone or structural furrows deeper through ciliary zone into ciliary body) Posterior surface of iris Iris color -Determined by the number of melanin granules within the melanocytes & area they occupy -Reflection of light also contributes -Heavily pigmented: velvet, smooth & brown appearance -Light: trabeculae are evident Nevus -Area of hyperpigmentation; accumulation of melanocytes Ciliary body -Ring shaped structure (front) -Behind the iris -Width: 5.9 mm nasal & 6.7 mm temporal -Posterior area ends in ora serrata (flat) -Anterior ciliary body contains processes that extend to posterior chamber -Sagittal section has triangular shape with base anteriorly -One corner of the base lies at scleral spur -2 parts: pars plana & pars plicata Pars plana of ciliary body (orbicularis ciliaris) -Flat region -Extends until ora serrata -Zonule fibers insert into internal limiting membrane of pars plana & some attach on the valleys of pars plicata -Ciliary body is attached to vitreous base Pars plicata of ciliary body (corona ciliaris) -Wider part -Contains ciliary processes (70-80 of 2mm length, 0.5 mm width & 1mm height) 4 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Valleys of Kuhnt -Constant production of aqueous humor Ora serrata -Serrated pattern -Dentate process or teeth -Oral bays (rounded portions between teeth) Valleys of Kuhnt regions between ciliary processes on pars plicata Supraciliaris (supraciliary lamina) -Outermost layer adjacent to sclera -Ribbon-like layers of loose CT -Contains pigmented melanocytes, fibroblasts & collagen bands -Allow accumulation of fluids between layers -In case of trauma, it will detach from ciliary body The majority of the thickness of the ciliary body is in the ____. ciliary stroma Ciliary muscle -Smooth muscle fibers -Longitudinal, radial & circular direction Longitudinal muscle fibers of Burke (ciliary muscle) -Lie adjacent to supraciliaris & parallel to sclera -Base is at scleral spur -Apex is in choroid Radial fibers of ciliary muscle -Form wider, shorter, interdigitating VS -Originate as scleral spur & insert into CT near base of ciliary processes -Transition later from longitudinal to circular fibers Annular muscle of Muller -Circular bundles -Sphincter type action -Near the major circle of iris The ciliary muscle has ____ innervation. Autonomic nervous system; parasympathetic stimulation for muscle contraction Ciliary stroma -Highly vascularized loose CT -Lies between muscle & epithelial layers -Forms the core of each ciliary processes -Anteriorly: continuous with iris stroma -Posteriorly: continuous with choroidal stroma -Major arterial circle of the iris (stroma) anterior to circular muscle Ciliary epithelium -2 layers of epithelium connected by intercellular junctions, desmosomes & tight junctions -Cover ciliary body -Line the posterior chamber as part of the vitreous chamber -Gap junctions between apical surfaces provide communication between layers & formation of aqueous humor Pigmented ciliary epithelium - Outer layer -Pigmented cuboidal epithelium joined by desmosomes & gap junctions -Anterior: continuous with anterior iris epithelium -Posterior: continuous with retinal pigmented epithelium -Basement membrane attaches the pigmented epithelium to the stroma 5 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Non-pigmented ciliary epithelium -Inner layer -Lines the posterior chamber -Composed of columnar cells (pars plana) & cuboidal cells (pars plicata) -Lateral walls of cells contain interdigitations joined by desmosomes, gap junctions & zonula occludens -Diffusion barrier between blood & aqueous -High metabolic activity (‘ mitochondrias) -Active secretion of aqueous humor components -Anterior: continuous with posterior iris epithelium -Posterior: continuous with ora serrata & becomes neural retina What is the function of the tight junctions? They're a barrier to avoid fluid leaving or entering the tissue & prevent detachment Choroid -Extends from ora serrata to the optic nerve -Located between sclera & retina -Provides nutrients to outer retinal layers -LOTS of blood vessels (choriocapillaries) from short posterior ciliary arteries -3 layers Lamina fuscha (suprachoroid lamina) -Most external layer of choroid -Contains collagen bands & fibroblast (sclera) & melanocytes (choroidal stroma) -Loosement of tissue allows vascular swelling without dettachment -Suprachoroidal space carries the long posterior ciliary arteries & nerves Choroidal stroma -Pigmented, vascularized loose CT layer -Contains melanocytes, fibroblasts, macrophages, lymphocytes & mast cells -Collagen fibrils arranged circularly around the vessels (branches of short posterior ciliary arteries) -2 layers of vessels (Haller's & Sattler's) -Venules join ’ 4 vortex veins (no valves) -Innervation: autonomic N.S.; sympathetic & parasympathetic stimulation Parasympathetic stimulation of choroidal vessels -Nitrous oxide responsive vasodilation -Results in increase of choroidal blood flow Sympathetic stimulation of the choroidal vessels -Vasoconstriction -Decreased choroidal blood flow Haller's layer Outermost layer of the choroid, made up of large vessels with larger lumen Sattler's layer Medium sized vessels that branch out of the outer later & continue branching to form the capillary bed (choriocapillaris) What happens if the choroid separates from the sclera? Part of the suprachoroid will adhere to the sclera & part remain attached to the choroid Choriocapillaris -Single layer of anastomosing, fenestrated capillaries facing the retina to facilitate the movement of materials -Has wide lumen (3-4x than ordinary capillary & 2-3 RBCs pass through instead of 1) -Occasionally pericytes are found & have contractile function Pericytes 6 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Rouget cells that have contractile function & the ability to alter local blood flow Where are the choriocapillaris densest? In macula area (where vision occurs) Bruch's membrane (basal lamina) of choroid -Innermost layer -Fuses with retina -Runs from optic nerve to ora serrata -Multilaminated sheet containing a center layer of elastic fibers -5 components -Tight adhesion between choroid & outer pigmented layer of retina Mention the 5 components of Bruch's membrane -Interrupted basement membrane of choriocapillaris -Outer collagenous zone -Elastic layer -Inner collagenous zone -Basement membrane of RPE cells (attachment of RPE & Bruch's membrane) What is the function of the ciliary body? -Production & secretion of aqueous humor -Accommodation How does longitudinal fibers in ciliary body affect movement of aqueous humor? Since some longitudinal fibers are attached to ciliary muscles, the configuration of the trabecular meshwork changes & facilitates aqueous movement through anterior chamber angle structures Process of accommodation 1. Contraction of longitudinal fibers of ciliary muscle pulling choroid forward 2. Contraction of circular fibers draws ciliary body closer to the lens & “ diameter of the ring formed by ciliary body 3. Tension is released from zonular fibers & lens capsule adopt a more spherical shape 4. Lens thickens (increases anterior to superior) 5. Lens thins along equator 6. Anterior lens surface moves forward & anterior chamber becomes shallower 7. No change in posterior pole ___ and __ are significant factors in the production & secretion of aqueous humor -Ciliary body capillaries & ciliary epithelial layer The stroma of the ciliary processes contains a dense network of __ capillaries. a. fenestrated a. fenestrated b. non-fenestrated The number & shape of the processes provide a large surface secretion to the ___ chamber. a. anterior a. anterior b. posterior Where is the aqueous humor produced? non-pigmented ciliary epithelium What are the 3 mechanisms contributing to the production & secretion of AH? 1. diffusion 2. ultrafiltration 3. active secretion Diffusion -Passive movement of ions across a membrane related to size & solubility -[‘] ’ [“] movement Ultrafiltration -Passive flow of blood plasma from capillaries into ciliary stroma caused by hydrostatic pressure -Substances leave blood through diffusion & ultrafiltration but must be actively secreted across non-pigmented ciliary epithelium to become aqueous humor 7 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Molecules are transported across the membrane against a concentration gradient using energy -Production of 80-90% of aqueous humor -Enzymes that catalyze rxns in non-pigmented ciliary epithelium: Na/K ATPase & carbonic anhydrase that move Na & HCO3 into posterior chamber for aqueous production Active secretion Movement of Na+ & Cl- drives secretion into the ___ chamber with HCO3- having an ____ role by moderating Cl- flux a. anterior b. posterior c. direct d. indirect b. posterior; d. indirect Na/K ATPase -Enzyme in non-pigmented ciliary epithelium -Use ATP to pump out Na+ & H2O follows -Na+ is highly dependent on HCO3 for movement to posterior chamber Carbonic anhydrase -Enzyme in non-pigmented ciliary epithelium -Catalyze: CO2 + H2O ’ HCO3 -Used in glaucoma therapy to produce bicarbonate & aqueous humor production will be diminished What is the function of the aqueous humor? -To maintain pressure & round shape of the globe in the anterior chamber -Provide transparent refractive index -Provide nutrition to avascular structures (cornea, lens, anterior vitreous & TM) -Collection bin for metabolic waste products surrounding tissues & clear out inflammatory products & blood from globe The aqueous humor has ___ times greater concentration of ascorbate than plasma. a. 10 b. 20 c. 50 d. 90 b. 20 Ascorbate Vitamin C; antioxidant to protect the cornea & lens against oxidative damage; has higher concentration in the lens The aqueous humor has ___ times less protein than plasma. a. 10 b. 50 c. 100 d. 200 d. 200 -As a consequence of tight junctional barrier causing minimal light Why does aqueous humor has less concentration of proteins than scatter thus maximum light transmission. plasma? -If if has proteins, the lens will become opaque The aqueous humor is composed of... -Ascorbate -Proteins (should not have) -Waste products from cornea & lens (Cl-, aa, lactate) Lactate Metabolic waste product of anaerobic glycolysis of lens & cornea How much aqueous humor is produced per minute? 2.5 ul increasing during the night as it follows circadian rythm Viscosity of aqueous humor Relative to water: 1.02-1.040 Osmolarity of aqueous humor Slightly hyperosmotic to plasma Blood aqueous barrier -Controls secreted aqueous humor -Fenestrated capillaries (large molecules exit the blood) -Tight junctions of NPE prevent movement of molecules -Force molecules to pass through cell into posterior chamber 8 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Proteins pass out due to fenestrated vessels but do not pass into posterior chamber because of the tight junctions Iris capillaries are __. a. fenestrated b. non-fenestrated b. non-fenestrated; they prevent leakage out of iris blood vessels & zonula occludens junction in the endothelial cell to maintain barrier function What are the functions of the choroid? -Provide nutrients to outer retina (blood to RPE) -Absorption of excess light (dark pigments) -Suprachoroidal space provides pathway for posterior vessels & nerves that supply the anterior chamber -Egress for catabolites from retina passing through Bruch's membrane into choriocapillaries The uvea obtains blood supply from ___. -Short posterior ciliary arteries around optic nerve forming choroidal vessels -Long posterior ciliary arteries + anterior posterior ciliary arteries ’ major circle of iris ’ supply blood to iris & ciliary body Venous return for most of the uvea is through ___. vortex veins Sensory innervation of the uvea -Trigeminal nerve ’ nasociliary -Sympathetic fibers form the superior cervical ganglion via the ophthalmic & short ciliary nerves innervate the choroidal blood vessels for vasoconstriction while the long ciliary nerves innervate the iris dilation (contraction) & ciliary muscle (relaxation) -Parasympathetic fibers from ciliary ganglion innervate the ciliary muscle (contraction), iris sphincter muscle (contraction) & choroidal vessels (vasodilation) How does age changes the iris? -Loss of pigment from epithelium is evident at pupillary margin -Pigment deposition is seen on iris surface, anterior lens surface, posterior cornea & trabecular meshwork -Dilator muscle atrophies -Sphincter muscle becomes sclerotic (difficult to dilate with pharms) Aging changes in the ciliary body -CT of ciliary muscle increases (becomes sclerotic) -Ciliary muscle contraction diminish -Aqueous humor production decreases *By 80 yrs old, is approx. 25% of original AH Age changes in choroid -Drusen -Choriocapillaris decrease in density & diameter (“ blood flow) -Choroidal thickness “ -Excessive basement membrane deposited in inner collagenous zones of Bruch's membrane -Seen as small, pinhead-sized, yellow-white spots on fondus -Contains cellular fragments & accumulation of basal laminar material Drunsen Iridodialysis -Trauma to eye or head -Thin iris root tears away from ciliary body resulting in damage to vessels & nerves -Blood is seen in anterior & posterior chambers -Can cause sector paralysis of iris muscles 9 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Abnormal attachment between iris surface & another structure -Posterior (iris adherent to anterior lens surface, ‘ IOP) -Anterior (iris adherent to corneal epithelium or TM) Iris Synechia -Pigment granules shed from posterior iris surface & disperse into anterior chamber -Can be deposited on iris, lens, corneal epithelium & TM -Compromise aqueous outflow -Pigment loss is evident on transillumination of iris -Can ‘ IOP due to obstruction caused by the pigments Pigmentary Dispersion Syndrome Presbyopia -Loss of ability to accommodate & focus at near -Normal-age related -Loss of elasticity restricts muscle movement & hampers accommodation -Changes in ciliary body, zonules, lens capsule & lens Thyndall Phenomenom -Beam of light in anterior chamber (dark) with presence of visible particles -Uvea inflammation -Caused by disruption of zonula occludens between nonpigmented ciliary cells causing breakdown of blood aqueous barrier allowing immune factors & leucocytes enter the aqueous humor -Hypopion -Hyphema -Blood in the anterior chamber of the eye, usually caused by blunt trauma -Can occlude outflow of AH through angle & affect IOP Hyphema 10 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Accumulation of cells Hypopion -Degenerative process involving choroid & retina -Presence of multiple confluent Drusen -Detachment or atrophy of RPE with subsequent formation of disciform scars, loss of photoreceptors & neovascularization -Wet vs Dry -Metabolite products of choriocapillaris & waste products of retina must pass through Bruch's membrane, with age the phospholipids accumulate in membrane & it becomes hydrophobic impeding passage of water, resulting in RPE detachment Age-related macular degeneration (AMD) Malignant tumor of iris; darker color & ‘ in size Iris melanoma Stays the same size, usually vision is not impaired Iris mole Pupillary membrane should disappear around 6th month of development; all of the remnants are attached to the collarets always; pt can have normal or obstructed vision Persistent Pupillary Membrane Remnants (PPM) Cell shape of posterior wall of lens columnar Cell shape of anterior wall of lens cuboidal Lens vesicle Hallow ball of cells of anterior lens epithelium & posterior lens epithelium Lens growth after embryonic development of the nucleus is attributed to ___ fibers. secondary lens fibers 11 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Posterior lens epithelium -Differentiates into primary lens cells (crystallins) in embryological development -Primary fibers -Elongate towards the anterior lens epithelium -Form embryonic lens nucleus -Disappears after birth Anterior lens epithelium -Contains germinative zone anterior to the equator -Cuboidal cells; one layer -Becomes secondary fibers -Becomes fetal nucleus -Secrete anterior capsule throughout life -Metabolic transport mechanisms -Basal aspect adjacent to capsule Germinal zone of lens -In anterior epithelium -Pre-equatorial region -Site of mitosis -Cells differentiate in lens fibers -Basal stretches to posterior pole -Apical aspect towards anterior pole Order of growth of nuclei lens fetal nucleus ’ juvenile ’ adult ’ lens cortex Contain fibers formed after sexual maturation (2): a. fetal nucleus b. juvenile nucleus c. adult nucleus d. lens cortex c. adult nucleus & d. lens cortex After birth, only the ___ fibers remain. b. secondary (from anterior epithelium) a. primary b. secondary Hyaloid artery becomes ___ around the ___ month. central retinal artery; 4th month What type of fibers are younger, outer, nucleated & contain organelles? b. secondary a. primary b. secondary The cortex has ___ cells & the nuclei has ___ cells. b. newer; a. older a. newer b. older Y sutures are derived from... secondary fibers The lens is vascular & transparent. b. false; is avascular & transparent a. true b. false Mention the 3 parts of the lens -Capsule -Lens epithelium -Lens fibers Capsule of lens -Elastic -Acellular layer -Basement membrane of anterior epithelium cells -Allow passage of small molecules inside & outside of lens -Barrier against large molecules -Thickness varies in regions Thickest region of the lens capsule Anterior & posterior in the equator: 21-23 um The lens capsule is the ____ base membrane of the whole body. 12 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf a. thinnest b. thickest b. thickest Thinnest region of lens capsule Posterior pole: 4 mm; can break easily Lens epithelium -Single layer of cells which form new fiber cells Lens fibers -Main mass of lens -Form the basis of nucleus & cortex -Formed by mitosis in germinative zone -Nucleus is lost & lose attachment to basement membrane, become compacted as insoluble protein in nucleus -Hexagonal shape arranged in concentric rings/layers -Individual fibers are connected by ball & socket interdigitations -Attached to capsule anterior & posteriorly -Long crescent shape Mention the 3 types of crystallins/lens fibers Alpha, beta, gamma Cytoplasm of lens fibers -90% of crystallins (water-soluble proteins) -40% weight of fiber -Contribute to gradient refractive index -Microtubules & filaments (actins) to provide organization Location of lens -In posterior chamber behind the iris; anterior to vitreous chamber The lens if malleable. a. true a. true b. false The ciliary muscles contract & change lens shape to reduce the dioptric power and induce accommodation. b. false; increase dioptric power a. true b. false Wieger's ligament -Attaches the posterior surface of lens to the anterior vitreous (hyaloid capsular ligament) Space of Berger Area of non-adhesion between vitreous & lens The lens is a. concave b. convex c. biconcave d. biconvex d. biconvex Anterior radius of curvature of lens 8-14 um Posterior radius of curvature of lens 5-8 um Poles of lens Center of anterior & posterior surface The thickness of the lens increases ___ each year through life 0.02 um Lens diameter (nasal to temportal) -6.5 mm infants -9 mm teenagers & adults Equator of lens Largest circumference of lens between poles Refractive power in unaccommodated lens 20 D; higher power in center 1/3 of lens is composed of ____ proteins; but varies within the lens (1.50 nucleus & 1.37 in outer cortical surface) 2/3 of the lens is composed of ___ water The pH of the lens is 6.9 - which is lower than aqueous (7.6) or plasma (7.4) Divisions of the lens -Embryonic nucleus -Fetal nucleus -Adult nucleus -Lens cortex 13 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Center of lens -Formed by elongating posterior epithelium of primary lens fibers -Figure #5 Embryonic nucleus -Embryonic & fetal nuclei -Fibers formed from birth to sexual maturation -Figure #3 Adult nucleus -Embryonic nucleus & fibers surrounding it after birth -Only secondary fibers -Figure #4 Fetal nucleus -Fibers after sexual maturation -Divided into (3) zones: superficial, internal & deep Lens cortex -Junction of lens fibers when they reach the poles & meet with other fibers -Anterior & posterior -Y shape (inverted or straight) Suture 14 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Anterior suture -Joining of apical aspects of fiber -Upright Y shape Posterior suture -Joining of basal aspects of fibers -Inverted Y shape As growth, fibers get larger & sutures become ___. Asymmetric & disimilar Zonules of Zinn (suspensory ligaments of lens) -Thread-like fibers attaching the lens to the ciliary body -Microfibrils (extracellular matrix of fibrillin & elastin) -Arise from basement membrane of nonpigmented ciliary epithelium in pars plana -Column-like structures on both sides of the ciliary processes & end at lens capsule -Primary & secondary Primary suspensory ligaments Attach ciliary body to lens Secondary suspensory ligaments Attach ciliary body to primary suspensory ligaments Accommodation (eye viewing object at distant; unaccommodated lens) -Ciliary muscles relax -Diameter of ciliary ring is large -Zonules are stretched Accommodation (eye viewing object at near; accommodated lens) -Ciliary muscles contract -Increase refractive power of eye -Zonules are relaxed Accommodation -Ability of eye to change power & bring near objects into focus -Accomplished by increasing power of lens -Ciliary body contracts Stimulus initiating accommodative mechanism is... retinal blur Accommodation is ___ dependent. a. cone; little influence of rods a. cone b. rod Primary function of lens -Refraction of light into macula -Transparency What gives the transparency of the lens? -Absence of vessels -Few organelles -Organization of fibers -Short distance between components (close fibers) Metabolic activity of the lens is mostly in ___. a. anterior epithelium a. anterior epithelium b. posterior epithelium Where does the lens obtain its nutrients from? From the aqueous humor & small contribution of vitreous Source of energy of the lens to form new fibers Anaerobic glycolysis (70%) while aerobic glycolysis (Krebs cycle) is limited to epithelium or superficial fibers with mitochondria Part of lens that has no metabolic activity Nucleus Na+ & Cl- is more abundant (inside/outside) the lens. Outside K+ is more abundant (inside/outside) the lens. Inside Lactate is not necessary inside the lens. b. false; it is needed to use glucose & metabolism a. true b. false ATP activity in lens is higher in ____. Epithelial cells & newer fibers near cortex; lower at equator Excess of Na+ or Cl- will cause water to be ____ inside the lens. a. retained & will cause swelling a. retained b. eliminated 15 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf To maintain a dehydrated lens, ____ uses ATP to constantly move water out. Na/K pump The lens may have aerobic & anaerobic metabolism, where both require ____ to convert glucose to glucose-6-phosphate. a. hexokinase a. hexokinase b. sorbitol c. aldose reductase If hexokinase is not present what forms from glucose? Sorbitol An excess of sorbitol will create ____ & will favor movement of water inside the lens. an osmotic gradient Glutathione -Protein protector against oxidative damage -Transported by aqueous humor -Can be synthesized by epithelial cells of lens -Detoxifies free radicals preventing damage Absorbic Acid (Vitamin C) -Prevent oxidative damage -Found in aqueous humor also but more amount in lens Free radicals -Metabolism byproducts -Oxidative changes from UV light absorption -Disrupt cellular processes & amino acid shape in proteins that cause cellular damage As age increases, the lens will suffer changes also such as... -“in soluble lens proteins (alpha crystallins) -“ in ATP, K ions, amino-acids & inositol -“ in glutathione (less detoxification) -‘ Ca, Na & H2O (disruption ion balance & swelling) -Older nuclear fibers loose organelles Cataract -Lens opacity -Greatest cause of blindness -Risk factors: aging, disease, genetics, nutrition, metabolic deficiencies, trauma, congenital, environmental stress -Named according to location -Graded by severity -Causative mechanisms: fluid & ion imbalance, oxidative damage, protein modification & metabolic disruption -Embryonic or fetal nucleus -Center opacification -Fibers susceptible to oxidative damage (“ glutathione) -Yellow color (brunescence cataract) Nuclear cataract -Cortex -Spike-like shape (radiated pattern) -Thicker in the periphery, follows the shape of the fiber -Progress slowly Cortical cataract 16 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Beneath the posterior capsule -Impacts vision early -Epithelial cells migrate from equatorial region -Associated with long term use of steroids (topical) & radiation therapy (cancer) Posterior subcapsular cataract Phacoemulsification Use of high-frequency sound waves to break up cataract, which is then removed by suction with needle; usually due to secondary cataract (opacity of IOL after cataract extraction) -Trabecular Meshwork (TM) -Schlemm's canal -Scleral spur -Located at internal scleral sulcus (corneoscleral junction) Anterior chamber angle structures -At posterior edge on internal scleral sulcus -Posterior portion: attach longitudinal ciliary muscles fibers -Anterior portion: attach trabecular sheets Scleral spur Trabecular Meshwork -Mesh-like structure in the anterior chamber that filters the aqueous humor as it flows into the canal of Schlemm -Composed of flattened perforated sheets (3-5 at apex & branch 15-20 as they extend into scleral spur) -Intratrabecular spaces between sheets: spaces fontana -Collagen & elastic fibers embedded in ground substance; covered by basement membrane & endothelial cells -Occupy most of inner aspect of internal scleral sulcus -Triangular shape (base: scleral spur & apex: Schwalbe's line) -3 divisions Schwalbe's line Termination of Descemet's membrane What are the anatomic division of the trabecular meshwork? -Uveal -Corneoscleral -Juxtacanalicular 17 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf What happens if the endothelial cells of the trabecular meshwork Can cause endothelization, cover the T.M. obstructing its pathway increase in quantity? & cause glaucoma -Inner sheets with more openings -Attached to ciliary stroma & longitudinal muscle fibers -Cord-like -Larger pores -Figure #3 Uveal meshwork -Middle/outer region -Attach to scleral spur -Sheet-like -Figure #2 Corneoscleral meshwork -Most external -CT surrounded by endothelium -“ gaps in between to move the aqueous humor -Figure #! Juxtacanalicular meshwork -Circular vessel between cornea & sclera -Considered a vein; drains aqueous humor -Lumen lined with endothelial cells joined by zonula occludes Canal of Schlemm Juxtacanalicular Connective Tissue (cribriform layer) -Region separating endothelial cell lining of canal of Schlemm from TM allowing movement of aqueous humor -Consists of endothelial cells & fibroblasts embedded in matrix of collagen, elastic fibers & ground substances inside 18 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Vacuoles inside endothelial cells move aqueous humor by diffusion (inside/outside) the Canal of Schlemm to be drained. -Annular area behind iris -2 regions: canal of Hannover (zonlues are located) & canal of Peitit (retrozonular space) Posterior chamber of eye Aqueous humor is produced by ____. Pars plicata of ciliary body Aqueous humor is secreted to posterior chamber through ____ into ____. Non-pigmented ciliary epithelium in ciliary processes in between the lens & iris; into the anterior chamber through the pupil. Movement of aqueous humor in anterior chamber is through.... Convection currents moving down along the cooler cornea & up the warm iris exiting through periphery of chamber in 2 pathways Ciliary processes ’ posterior chamber ’ pupil ’ anterior chamber ’ angle spaces within uveal meshwork “ CT surrounding ciliary body muscle bundles ’ suprachoroidal space ’ absorbed through sclera -5-35% of AH Unconventional outflow Conventional outflow Ciliary processes ’ posterior chamber ’ pupil ’ anterior chamber ’ angle, uveal meshwork ’ corneoscleral meshwork ’ juxtacanalicular tissue ’ internal collector channels (Sonderman) ’ external collector channels ’ deep scleral plexus or intrascleral plexus OR aqueous veins of Ascher ’ episcleral veins ’ anterior ciliary veins ’ ophthalmic vein (superior or inferior) OR vortex vein ’ cavernous sinus ’ jugular vein -Through vacuoles -Passive diffusion -Depends on IOP Internal collector channels (of Sondermann) Juxtacanalicular tissue contains invaginations that help transport outflowing AH into the canal of Schlemm Endothelial cells lining the external wall are joined by ____. zonula occludens External collector channesl -25-35 -Distributed through Canal of Schlemm & empty into deep scleral plexus or intrascleral plexus of veins ’ episcleral veins & conjunctival veins Aqueous veins of Ascher Drain directly into episcleral veins Radial episcleral collecting veins 19 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf -Receive blood from conjunctiva, limbal arcades, anterior episcleral veins & perforating scleral veins -Form anterior ciliary veins Vortex veins -Posteriorly drain the venous system (choroid, ciliary body & iris) into superior & inferior ophthalmic veins -4-7 Internal jugular ein -Blood from ophthalmic veins ’ internal jugular vein -Descends alongside the internal carotid artery Function of the aqueous humor -Maintains the pressure needed to inflate the eye -Provides nutrition for the central cornea & lens -Carries away waste products of cornea & lens IOP is maintained by the equilibrium between rate of production & rate of exit by homeostatic mechanisms Production of AH is constant throughout the day with more production during the night. b. false; more production during the morning a. true b. false Many cases of increased IOP are caused by ____ aqueous out- decreased (most variations in conventional pathway but can also flow. be in unconventional) Little resistance to aqueous passage through sheets of TM except when there is ____. pigment or debris accumulated within the pores The Canal of Schlemm provides huge resistance to outflow. b. false; too wide & provides little resistance a. true b. false Higher resistance of AH movement is at ____. Juxtacanalicular tissue (75%) & endothelium of inner wall of Schlemm's Canal (25%) Pressure of episcleral veins 8-10 mmHg (if elevated will not allow passage of AH) Resistance of conventional aqueous drainage 3-4 mmHg/ul/min Average IOP 15.5 +/- 2.6 mmHg (normal IOP: 10-20) Aqueous humor flow is ___ in the mornings. higher (3.0 ul/min) Variation of aqueous humor within the day 2.4 +/- 0.6 ul/min Aqueous humor flow at the afternoon 2.4 ul/min During the night, AH flow is decreased to ____. 1.5 ul/min Diabetes -Neovascularization can occlude the angle -Excess glucose can affect correct O2 entrance & cause neovascularization in iris & angle Uveitis -Inflammation of uvea (iritis, cyclitic, iridocyclitis, choroiditis) -Breakdown in blood aqueous barrier -Unilateral (infectious diseases or idiopathic) or bilateral (autoimmune disease) -Isolated attacks or repeated episodes -Inflammatory cells can occlude the angle, impeding outflow or causing acute open angle glaucoma Fuchs Endothelial Dystrophy -Chronic corneal dystrophy & can lead to permanent damage of TM 20 / 21 Exam 1 Ocular Anatomy 2 Estudia en línea en https://quizlet.com/_cr3unf Most common disease to cause uveititis Rheumatoid arthritis -Acute inflammation of the TM leading to acute rise in IOP (40-50 mmHg) due to swelling & obstruction -Severe pain -Tx: corticosteroids to “ inflammation Glaucomatocyclitic crisis -Trauma to iris with separation of iris root -Microscopic damage to TM (scars) leading to glaucoma Angle recession glaucoma Grade 0 angle closure No structures seen; completely closed Grade 4 angle closure Completely open; all structures are visible -Aging epithelial cells of iris & lens capsule release pigment & pseudoexfoliative material occluding the angle Pseudoexfoliative Glaucoma True/False False; should not have pigments The angle can have pigmentation. -Pigment liberated from posterior layer of iris causes damage to trabecular fibrils causing glaucoma Pigment dispersion glaucoma 21 / 21