Lecture 9: 12/14 Flashcards
what are the two zones on the anterior surface of the iris
- central pupillary zone
2. peripheral ciliary zone
junction between the 2 zones of the iris is called
the collarette
the collarette is the thickest part of the iris and is _____ thick
0.6mm thick
appearance and location of the collarette
a zigzag, circular ridge easily seen about 1.5mm peripheral to the pupillary margin
explain the pupillary ruff
an extension of the two posterior epithelial layers which folds up around the pupillary margin and is visible as a heavily pigmented border
the three areas of the ciliary zone
- an inner area adjacent to the collarette
- a furrowed central area
- a marginal cribiform area next to the ciliary body
the dark pits that appear to go deep into the iris are called
Fuch’s crypts
Fuch’s crypts are adjacent to the _____ and are the result of _____
adjacent to the collarette and result of the erosion
the marginal cribriform area (most peripheral) can be seen only with what equipment?
ginioscopy
what are two things unique about the marginal cribriform area?
- small little crypts called ciliary crypts
- iris pectinate fibers seen in this area
what is special about the central area (furrowed zone) of the ciliary zone?
there are contraction furrows that run concentric with the pupil
what is found in the inner area of the ciliary zone?
smooth, slight radial ridges
what are the three types of zones/furrows on the posterior surface of the iris?
- contraction folds of Schwalbe
- circular folds
- structural folds of Schwalbe
the contraction folds of Schwalbe are:
grooves that run from the pupillary margin peripherally to the collarette
circular folds are:
concentric around the pupil
radial folds (most peripheral) run
radially on in to the ciliary body, are valleys between ciliary processes
4 layers of the iris, from anterior to posterior
- anterior limiting layer
- stroma
- posterior membrane (anterior epithelium)
- posterior pigmented epithelium
what 2 iris layers were derived from mesoderm?
- anterior limiting layer
- stroma
what 2 iris layers were derived from neuro-ectoderm?
- posterior membrane (anterior epithelium)
- posterior pigmented epithelium
what layer of the iris is a big determinant in the color of the iris?
anterior limiting layer
which layer of the iris is absent or thinned at the crypts?
anterior limiting layer
2 main cell types in the anterior limiting layer of the iris?
- fibroblasts
- melanocytes
location of the fibroblasts in the anterior limiting layer of the iris
from the most anterior layer, located root to margin
location of the melanocytes of the anterior limiting layer of the iris
posterior, pigment cells with have “arms” that tend to connect with each other
are capillaries present in the anterior limiting layer of the iris and if so, how dense?
yes they are common and may increase in size and number in response to pathologies such as iritis and diabetes
the layer of the iris that is loosely arranged collagenous connective tissue network which comprises most of the thickness of the iris
stroma
list some important structures embedded in the stroma layer of the iris
blood vessels and nerves, pigmented (melanocytes) and unpigmented (fibroblast) cells, sphincter muscle
sphincter muscle width (cross section) is _____ mm
0.75 mm
location and action of the sphincter muscle
it is a flat muscle that runs radially around the pupil
-when it contracts, it makes the pupil smaller
the sphincter muscle is bound firmly on its posterior side to:
to a layer of connective tissue which is continuous with the dilator muscle
what is the sphincter muscle composed of and what is it innervated by?
the sphincter is composed of smooth muscle cells and is supplied by parasympathetic nerve fibers in the short ciliary nerves
blood vessels of the iris reside in the ______
stroma
blood vessels enter the iris from the :
major arterial circle of iris
at the region of the collarette the arteries form an incomplete circular anastomosis called the:
minor arterial circle of the iris
the 2 types of pigment cells found in the stroma layer of the iris
melanocytes (most cells) and clump cells (spherical, without processes, darker, most frequent in pupillary region)
origin and path of the 2 anastomoses of the stroma layer of the iris
originate at the anterior ciliary arteries an long posterior ciliary arteries and run in a radial direction towards pupillary margin
what kind of muscle is the posterior membrane (anterior epithelium)?
non-striated, smooth muscle
cells found in the posterior membrane (anterior epithelium) layer of the iris ?
myoepithelial cells
apex and base of the myoepithelium cells contains
apex: forms the epithelium, faces posteriorly
base: forms the smooth muscle fibers, faces anteriorly
what is the extent of the dilator muscle?
extends from root of iris to mid sphincter
what are the 3 groups of spurs on the dilator
- Grunnert’s
- Von Michel’s
- Fuchs
location of Grunnert’s spurs on the dilator
most peripheral, at root of iris
location of Von Michel’s spurs on the dilator
peripheral edge of sphincter
location of Fuchs spurs on the dilator
midpoint of sphincter
what innervates the dilator muscle?
sympathetic NS
pupils dilate in ‘flight of flight’ response
the posterior pigment epithelium layer of the iris is an extension of the
anterior non-pigment epithelium
in which direction does the apex and base face for cells in the posterior pigmented epithelium of the iris?
apex faces anteriorly
base faces posteriorly (basement membrane)
