Visual, Vestibular, and Auditory Histology (Dr. Olinger) TEST 2 Flashcards
Gross Anatomy of the Eye
ANTERIOR CHAMBER:
- Everything Anterior t the Iris
POSTERIOR CHAMBER:
- Everything between the Iris and Lens
VITREOUS CAVITY:
- Located behind the Lens
Tunica
1) OUTER TUNICA (Sclera and Corena):
- CORNEA: is Transparent
- SCLERA: Opaque and LINED inside the Middle or Vascular Pigmented Layer that ABSORBS Light
2) MIDDLE TUNICA (Uvea):
- UVEA: Contains the Iris, the Ciliary Process, and the Choroid. All of the Blood Vessels run INTO the Choroid
3) INNER TUNICA (Retina):
- The RETINA contains Photoreceptor Neurons (Cones and Rods), Conducting Neurons (Bipolar and Ganglion), Association Neurons (Horizontal and Amacrine Cells), and a Supporting Neuroglia Cell (Müller Cell)
- Only CONE Cells are present in the FOVEA!!!
- Axons from the Retinal Ganglion Cells pass across the surface of the Retina, converge on the PAPILLA or OPTIC DISC, and leave the eye through many openings of the Sclera
Outer Tunica
- The LIMBUS is the Zone of transition of the Epithelium of the CONJUCTIVA with that of the Cornea
- The LUMBUS is also the boundary of the Transparent CORNEA with the Opaque SCLERA
Cornea
- BASAL Cells of the Corneal Epithelium are ANCHORED to BOWMAN’S LAYER by HEMIDESMOSOMES!!!
- CORNEAL ENDOTHELIUM Participates in the ACTIVE TRANSPORT of Materials from the AQUEOUS HUMOR into DESCENT’S MEMBRANE and part of the Corneal STROMA!!!
- Corneal Endothelial Cells contain ABUNDANT MITOCHONDRIA!!!
Cornea Layers
1) Corneal Epithelium
2) Hemidesmosomes
3) Bowman’s Layer
4) Stroma
5) Descent’s Membrane
6) Corneal Endothelium
7) Aqueous Humor
- The STROMA is formed by COLLAGEN LAMELLAE oriented at an angle to one another. FIBROBLASTS, surrounded by Extracellular Matrix, are present between Lameliae
- The transparency of the Cornea depends on the arrangement of the Collagen Lamellae and the affinity for Water of the Extracellular Matrix. BLOOD VESSELS ARE NOT PRESENT IN THE STROMA!!!!!!!!
- CORNEAL ENDOTHELIUM is PERMEABLE to AIR Oxygen used for Various Oxidative reactions, in particular Glutathione Reduction and Oxidation.
- The GLutahtione Pathway NEUTRALIZES Excess Active Oxygen in the Cornea. About 30% of Glucose is Metabolized in the Cornea by GLYCOLYSIS
Clinical Considerations: Corneal Transplants
- The MOST COMMON form os Tissue Allotransplantation with a SUCCESS RATE of over 90%!!!
Tunica
- CILIARY PROCESSES extend INWARD from the Ciliary Body. The Vascular Layer continues as the IRIS, whose free edge outline the PUPIL!!!!
- The ANTERIOR Portion of the CILIARY BODY contains Smooth Muscle:
1) MUSCLE of the CILIARY BODY
2) Dilator Muscle of the Iris
3) Constrictor Muscle of the Iris
**The Smooth Muscle of the Ciliary Body regulates the TENSION of the ZONULE or SUSPENSORY LIGAMENT of the Lends and therefore, is an IMPORTANT element in the mechanisms of ACCOMMODATION!!!!!!
Aqueous and Vitreous Humor
- AQUEOUS HUMOR: FLUID like, needs to be Circulated, and Regenerated!!!!!
- VITREOUS HUMOR: Gel like!!!!
Ciliary Body
1) DILATOR PUPILLAE:
- Consisting of MYOEPITHELIAL CELLS, contains Alpha Adrenergic Receptors and is Innervated by SYMPATHETIC NERVE FIBERS
- Contraction of the Dilator causes PUPIL DILATION or MYDRIASIS
2) SPHINCTER PUPILAE:
- Consisting of Smooth Muscle Cells, has ACETYLCHOLINE Receptors and is Innervated by PARASYMPATHETIC NERVE FIBERS
- Sphincter Contraction REDUCES the Diameter of the Pupil or MIOSIS!!!!
Inner Tunic
- RETINA runs all the way around the CHOROID!!!!
- FOVEA: Only CONES are present in the Fovea where FINE DETAIL VISION is BEST!!! It is hard to see light with the Fovea but it can see a LOT of COLOR!!!
- PAPILLA (Optic Disc): Axons from the Retinal Ganglion Celsl pass across the Surface of the Retina, CONVERGE on the Papilla (Optic Disc), and leave the Eye through many openings of the SCLERA (The Lamina Cribrosa) to from the OPTIC NERVE!!!!
Retina
Layers:
1) Inner Limiting Region
2) NERVE FIBER LAYER (Axons of Ganglion Cells):
- Layer that comes together to make the OPTIC NERVE
3) GANGLION CELL LAYER
- Cell Axons make the OPTIC NERVE
4) INNER PLEXIFORM LAYER
- Bipolar Cell Axons are Synapsing on Ganglion Cell Dendrites
5) INNER NUCLEAR LAYER
- Take info from Rods and Cones and send it up to the Ganglions (Bipolar Cells and Body Cell Layer)
6) OUTER PELXIFORM LAYER
- Photoreceptor Cell Axons are SYNAPSING on BIPOLAR Dendrites
7) OUTER NUCLEAR LAYER
- Contains cell bodies of Photoreceptor Cells
8) OUTER LIMITING MEMBRANE
9) INNER and OUTER SEGMENTS of RODS and CONES
- Actual SEEING!!!!!!
- Contains the Rods and Cones
10) PIGMENTED REPITHELIUM
Photoreceptors:
1) CONES: Color
2) RODS: Light
Fovea Centralis
- At the FOVEA CENTRALIS, tightly packed Cones are arranged at an ANGLE to the Pigmented Layer. Consequently, the OUTERN NUCLEAR Layer and the other layers of the Sensory Retina DO NOT OBSTRUCT the Light PATHWAY
- The Outer Segment of the Photoreceptor Cells receives Light that has NOT passed FIRST through the Other Layers of the Retina!!!
Optic Disc and Fovea
OPTIC DISC:
- The axons of the GANGLION CELLS turn into the OPTIC NERVE at the OPTIC DISC, which LACKS Photoreceptors and corresponds to the BLIND SPOT of the Retina
- When Intraocular Pressure INCREASE, the Disk of the Optic Nerve appears CONCAVE. The Disc becomes Swollen (Papilledema) and the Veins are DILATED when Intracranial Pressure INCREASES!!!
FOVEA:
- Previous Cell Layers are SLATED OUTWARD so that the most light is hitting the Cone Cells
- In its Center, the Fovea is for HIGH QUALITY VISION
- The rest of the Retina is for PERIPHERAL VISION.
Cones: Color Distinction
Rods: Movement Detection
Clinical Consideration: Detachment of the Retina
- Separationg of TWO Layers of the Retina
- Caused by Trauma, Vascular Disease, Metabolic Disorders, and Aging!!!!!
Rod Cells
INNER Segment of Rod Cells:
- MITOCHONDRIA Synthesize ATP required for the assembly of the Visual Pigment RHODOPSIN!!!!!
OUTER Segment of Rod Cells:
- Contains the PLASMA MEMBRANE that folds in on itself a Bunch of times. This INCREASES the changes of the Cell becoming excited in LOWER LIGHT by INCREASING the SURFAC AREA!!!
- Do all the SEEING in the OUTER SEGMENT!!!!**