Iris and Ciliary Body: Anatomy and Physiology

Question 1

the uvea

Answer 1

-pigmented, vascular middle layer of the eye

Question 2

three components of the uvea

Answer 2

iris, ciliary body, choroid

Question 3

iris:

• heavily _____ circular structure
• _____ in diameter
• part of the ____, highly ____

Answer 3

pigmented;
12 mm;
uvea; vascularized

Question 4

iris is surrounded by _____;
____ is anterior to the iris;
____ is posterior to the iris

Answer 4

aqueous humor;
anterior chamber;
posterior chamber

Question 5

3 regions of the iris

Answer 5

1) iris root
2) pupillary margin
3) collarette

Question 6

iris root

Answer 6

peripheral region of the iris that is continuous with the ciliary body

Question 7

pupillary margin

Answer 7

• free edge of the iris

- rests on the crystalline lens

Question 8

collarette

Answer 8

• circular, jagged ridge ~1.5 mm from the pupillary margin
• attachment site for the fetal pupillary membrane (blood vessels) during embryologic development – vessels fragment and disappear by 8.5 months of gestation
• divides the iris into 2 zones: pupillary zone, ciliary zone (zones may differ in color)

Question 9

pupillary zone of iris

Answer 9

encircles the pupil

Question 10

ciliary zone of iris

Answer 10

extends from the collarette to the iris root

Question 11

layers of the iris

Answer 11

1) stroma
2) anterior pigmented epithelium
3) posterior pigmented epithelium

Question 12

iris stroma:

• most ____ layer
• composed of: _____

Answer 12

anterior;

loose connective tissue, pigmented cells, WBCs, the sphincter muscle, extensions of the dilator muscle

Question 13

iris stroma: loose connective tissue

• _____ form a meshwork over the collagen and ground substance
• collagen fibrils are arranged in _____ (most evident in light colored irises; appear as white fibers)
• anchor blood vessels (also arranged ____); protect arteries from ____

Answer 13

fibroblasts;
radial columns;
radially;
kinking and compression during extensive iris movement

Question 14

iris stroma: pigmented cells

• ____ are concentrated just under the meshwork of fibroblasts
• clump cells: _____ of free pigment within the iris similar to macrophages; concentrated ____

Answer 14

melanocytes;
scavengers;
just under the meshwork of fibroblasts in the pupillary zone

Question 15

iris stroma: WBCs

-involved in ____

Answer 15

the immune response

Question 16

iris stroma: sphincter muscle

• composed of ____ arranged smooth muscle fibrils in the ____ zone
• contraction causes ____; pulls the ___ toward the ___

Answer 16

circularly;
pupillary;
pupillary constriction (miosis);
pupillary zone; pupillary margin

Question 17

iris anterior pigmented epithelium:

• posterior to the ____
• composed of ____
• ____ join adjacent cells; regulates passage of ____

Answer 17

stroma;
a single layer of pigmented myoepithelial cells;
tight junctions;
aqueous humor from the posterior chamber into the iris

Question 18

iris anterior pigmented epithelium: dilator muscle

• arises from ____
• composed of ___ arranged smooth muscle fibrils in the iris root to a point just below the sphincter
• forms 3-5 layers that extend into the ____
• contraction causes ____; pulls the ___ toward the ____; ____ are visible in the ciliary zone

Answer 18

the basal surface;
radially; 
stroma;
pupillary dilation (mydriasis); 
pupillary zone; iris root;
circular contraction folds

Question 19

iris posterior pigmented epithelium:

• most ____ layer
• composed of ____
• basal surface lines ____
• apex faces the ____
• _____ join adjacent cells; regulates passage of ____

Answer 19

posterior;
a single layer of pigmented epithelial cells;
the posterior chamber;
apex of the anterior pigmented epithelium;
tight junctions;
aqueous humor from the posterior chamber into the iris

Question 20

the posterior pigmented epithelium with the anterior pigmented epithelium forms the ____; at the ___, 2 layers of epithelial cells curl around from the posterior iris to the anterior surface

Answer 20

pupillary ruff (pupillary frill);
pupillary margins

Question 21

iris blood supply: the ____ supplies the iris;
capillaries in the iris lack _____; contributes to ____; capillary endothelial cells are joined by ____; also contributes to ____

Answer 21

major and minor arterial circle of the iris;
fenestrations; the blood aqueous barrier;
tight junctions;
the blood aqueous barrier

Question 22

iris innervation:

• motor innervation of iris sphincter muscle by ____ fibers
• motor innervation of iris dilator muscle by ___ fibers

Answer 22

parasympathetic;

sympathetic

Question 23

2 iris muscles control the amount of light entering the eye:

• in bright light, the ____ contracts to constrict the pupil (miosis)
• in dim light, the ____ contracts to dilate the pupil (mydriasis)

Answer 23

sphincter;

dilator

Question 24

pupil diameter varies from ___ to ____ mm

Answer 24

1; 9

Question 25

melanin production contributes to ____; _____ plays a role in melanin production; ____ increases melanin production; nearly all infants have a _____ iris color; during the 1st 6 months, melanocytes produce more melanin and the iris can ____

Answer 25

``` iris color; sympathetic innervation; UV radiation; blue or blue-gray; darken ```

Question 26

ciliary body: - heavily ____, circular structure surrounding the ____ - part of the ____, highly ____

Answer 26

pigmented; lens; | uvea; vascularized

Question 27

outer to the ciliary body is the _____; inner to the ciliary body are the ____; anteriorly, continuous with the _____; posteriorly, continuous with the ____

Answer 27

sclera; posterior chamber and vitreous; iris, trabecular meshwork, and scleral spur; choroid and retina

Question 28

transition between the ciliary body and the retina/choroid is called the ____

Answer 28

ora serrata

Question 29

pars plicata: - wider ____ region - 70-80 _____ are located in this region

Answer 29

anterior; | ciliary processes

Question 30

ciliary processes are composed of projections of _____; extend into the _____; anterior portion of nonpigmented epithelium produces ____

Answer 30

ciliary stroma covered by pigmented and nonpigmented epithelium; posterior chamber; aqueous humor

Question 31

pars plana: - thinner, flatter ____ region - extends from the ____ to ____ - appears ____ in the area of ora serrata

Answer 31

posterior; | posterior pars plicata; ora serrata;

Question 32

layers of ciliary body

Answer 32

- nonpigmented epithelium - pigmented epithelium - ciliary stroma - ciliary muscle - supraciliaris

Question 33

ciliary body: nonpigmented epithelium - most ____ layer that lines the ____ - single layer of epithelial cells joined by ___; forms a ____; fluid and molecules must pass ____; contribute to ____ - _____ arise from the basement membrane of these cells; insert into the ____ - ____ production

Answer 33

inner; posterior chamber and part of the vitreous chamber; tight junctions; complete barrier; through cells, cannot pass between cells; blood aqueous barrier; zonules; equatorial regions of the lens; aqueous humor

Question 34

ciliary body: pigmented epithelium - outer to the ____ - single layer of epithelial cells that are _____ with the nonpigmented epithelium; ____ connect these cells

Answer 34

nonpigmented epithelium; apex to apex; gap junctions

Question 35

ciliary body: ciliary stroma | -composed of ____

Answer 35

vascularized, loose connective tissue (collagen, fibroblasts, ground substance) with melanocytes and WBCs

Question 36

ciliary body: ciliary muscle - composed of ____ - ____ attach to the scleral spur and TM - ____ are surrounded by stroma - ciliary stroma continues into the ____

Answer 36

smooth muscle fibers with longitudinal, radial, and circular orientations; longitudinal muscle fibers; muscle fibers; muscle layers

Question 37

ciliary body: supraciliaris - most ____ layer - ____ between ciliary body and sclera - continuous with the ____

Answer 37

outer; potential space; suprachoroid (space between choroid and sclera)

Question 38

ciliary body blood supply - the ____ supplies the ciliary body - capillaries are in the ____ - capillaries are ____, allows _____

Answer 38

major arterial circle of the iris (MACI) supplies the ciliary body; ciliary stroma; highly fenestrated; water, molecules, and ions to leak out of the capillaries and enter the stroma

Question 39

motor innervation of ciliary muscle by _____

Answer 39

parasympathetic fibers

Question 40

contraction and relaxation of the ciliary muscle controls ____

Answer 40

the shape of the lens

Question 41

ciliary processes in the _____ produce aqueous humor

Answer 41

anterior nonpigmented epithelium

Question 42

- aqueous humor is a filtrate of ____ - consists of ____ - nourishes the _____ and removes their waste - pressure gradient/exerts force on the internal surface area of the anterior eye- called the ____

Answer 42

blood; ions, water, and other molecules that leak out of capillaries in the ciliary stroma; avascular cornea and crystalline lens; intraocular pressure (IOP)

Question 43

trabecular drainage of aqueous: - _____% of aqueous drains through this route - route: _____

Answer 43

70-90; anterior chamber --> posterior trabecular meshwork --> Schlemm's canal --> aqueous veins and 25-30 intrascleral collector channels aqueous veins --> episcleral veins intrascleral collector channels --> intrascleral venous plexus --> conjunctival and episcleral veins

Question 44

uveoscleral drainage of aqeuous: - ____% of aqeuous drains through this route - route: ____

Answer 44

10-30%; anterior chamber --> iris root --> ciliary body --> supraciliaris --> suprachoroidal space --> vortex veins or absorbed into scleral stroma

Question 45

Anterior Segment OCT (AS-OCT): - details of structures above the ____ - cannot capture structures behind this - cannot completely visualize ____

Answer 45

pigmented epithelium of the iris; | the ciliary body