Flashcards in Cornea and Sclera Deck (86):
why is the sclera opaque
irregular array of collagen fibers and water content
the sclera is avascular except for the...
superficial vessels of the episclear and intrascleral vascular plexus
what type of collagen is the sclera 90% of
which collagen is expansible tissue.
which is control of fibril dimension.
which is the ability to resist tension
the large change in the refractive index of the cornea compared to air and by the corneal curvature produes the......
which is the most prominent interface w/in the cornea
the interface btwn the basal cells and the basement membrane
which wavelenths are absored more in the cornea
in wound healing, the goal is to promote_______ and not ______ by controlling fibroblast activatoin
to maintain cell regularity in corneal epithelial transparency, the cornea must prevent _______ from acculmualting and causing________ of cells and fibers
prevent water from accumulating and causing swelling/disorganization of cells and fibers
the cornea contains large concentrations of glycosaminoglycans which created an environment with a ______
high osmotic pressure
what maintain a barrier to fluid and ion transport in the cornea
what tight junction protein is at the site of the suprabasal epithelium
what is the basment membrane adhered to the basal cells by
hemidesmosomes and trans-plasma membrane collagen
the corneal epithelium has relatively low ________ through its _______cell membrane
the movement of sodium from the tears into the epithelium is by ______ but ______is required to move it into the stroma
what is ion transport into the cornea mediated by
NA/K ATPase and CA/Mg ATPase
what is the inward flux of sodium from the tears balnced out by
the outward movment of chloride into the tears
What is the driving force for the transport of chloride into the tears
the movemnt of sodium into the stroma by the pump
what pump in the basolateral membrane maintains the sodium gradient for the NaCl co-transport
how does chloride move into the cell against an electrochemical gradient
the Na-K-Cl co-transport
stimulation of the beta adrenergic receptors and serotonergic receptors increases ......
apical chloride conductance
the K channel is under _____ via _____ mediated pathway
what channel is mechano-senstivie
what causes an increase in current through the K channels as the cornea swells
what channel acts as a regulatory channel controlling osmolarity and cell volume
the K channel is sensitive to ___ changes
what is intracellular pH regulated by
lactate-H co tranport and Na H exchange
epithelial transport of water is ____ compared to endothelial pump
what is the water transporter that is important for the maintenance of normal corneal stromal thickness
what kind of innervation do the chloride channels do?
what kind of innervation do the potassium channels do?
where do the new basal cells originate from
stem cells at limbus
what is maintained by the shedding of superficial cells and proliferation of cells
there is no cell ______ in surface epithelial cells or wing cells
wehre do the basal cells migrate towards
center of cornea (123 mM per week)
how much basal cell division occurs per day
when do hemidesmosomes form during in a invasion-abrasion response
early period (18 hours)
the release of epidermal growth factor (EGF) initiates the production of fibronectin to cover the damaged area when what is damaged
what serves as a temporary matrix for cell adhesions
in the stroma, which collage is the one that regulates fibril thickness? which collagen is < 5nm in diameter?
which types of collagen are found in the normal basement membrane
4 and 7
why does the stroma need type 1 collagen filaments to be < 5 nm
corneal transparency. narrow diameter fibers dont cause light to scatter
type 1 collagen fibers make up ____% of collagen fibers in the stroma
in addidtion to types 4 and 7, what other unique collagen types are found in bowmans and descemets membrane
5, 8, 11, 12
in size theory of transparency, the fibril size is _____ and interfibril distance is less than ______
less than half the wavelenth of light
light scattered by fibrils of uniform diameter is cancelled by ______
do collagen fibrils have to be of equal diameter and equidistant from each other?
what is the principle that says when a wave passes through an opening the waves nearest the opening margins are slowed and the wavefront becomes curved
waht maintins the regular spacing and packing of the collagen fibrils
what do corneal GAGs exist in the native state as
how does the cornea maintain fibril spacing
GAGs connect their next nearest neighbor collagen fibrils and form a ring like structure around each fibril
what is involved in regulating collagen fiber diameter
what is involved in regulating interfibrillar spacing
collagen abnormalities and its relationship to proteoglycans can result in the loss of...
what is does abnormal keratan sulphate synthesis result in
what % is the cornea hydrated?
what % is the sclera hydrated
why will the cornea absorb more water if it is placed in saline
bc of the high concentration of GAGs
what does the swelling pressure produce?
inter-fibril tension that helps to maintain regular arrangemnt of fibrils
what is swelling pressure related to
what is the name for specialized fibroblasts residing in the stroma
corneal keratocytes (fibroblasts)
what are speciliized fibroblasts found in the stroma important in (3 things)
1. maintaining transparency
2 wound healing
3. synthesizing matrix components
keratocytes remain _____ until required
what do keratocytes express
what are responsible for the production and maintenance of the extracellular matrix of the stroma
tensile strength of keratocytes increases up to the ....
fourth postoperative year
______ incisions heal more slowly than _____ incisions
____ is a form of controlled cell death w/o the release of lysosomal enzymes or other intracellular components that could damage surrounding tissue
when do the dying stromal cells undergo necrosis
after the initial wave of apoptosis
are metabolic processes temperature dependent
the metabolic pump moves what?
ions NOT WATER
what balance does transparency depend on
leak/ion pump balance
why do cells enlarge w/ aging
w/ the loss of cells, cells from surrounding areas spread to fill the space
when are the pump and barrir restored in endothelial wound healing
when the single layer is restored
which pump sites are increased w/ endothelial wound healing
Na K ATPase
where is oxygen obtained from
tears, small amonts from aqueous and limbal vasculatoure
glucose, amino acids, and vitamins are obtained from...
the inflammatory response in contact lens inhibits the....
what can contribute to epithelial thinning associted w/ long term contact lens use
decreased mitosis rates
reduction in ______ is thought to be the result of prolonged epithelial edema in long term CL use
what causes keratinization of the ocular surface epithelium
vit a deficiency
the ionic barrier in the corneal epithelium generates a transepithelial potential of _________
25 - 35 mV
what is the xyz hypothesis of cell maintenance of epithelial wound healing
X = proliferation of basal cells
Y = Centripetal movement of cells
Z = Cell loss from the surface
How long would it take for a 6mm corneal would to heal?
How many different types of collagen have been detected in the eye?
light scatter only occurs when the distance between two regions of different refractive index become greater than ______