Eye & Visual System

Lacrimal Gland

Sits above the eye and has several ducts that provide tears to continually flush the living cells of the cornea, preventing infection

Sjorgen Syndrome (SS)

Autoimmune CT disorder of exocrine glands, primarily salivary and lacrimal glands.

Outer Cornea

Stratified squamous epithelium innervated by free nerve endings of the trigeminal nerve

Stroma

The middle layer of the cornea,

Inner Aspect of Cornea

Endothelium

Light Passes Through

1. Cornea

2. Aqueous Humor

3. Pupil (in Iris)

4. Lens

5. Vitreous Humor

6. Retina - the fovea

Vitreous Chamber

Gooey humor that does not get replaced

Aqueous Humor

Undergoing constant replacement being generated by ciliary body

Generation and Flow of Aqueous Humor

Ciliary process → posterior chamber → iris/lens → pupil → anterior chamber → trabecular meshwork → Schlemm’s canal → collector vessel → veins

Iris

Circular and radial smooth muscle, circular contracting decreases pupil size, radial contract increases pupil size

Parasympathetic Input

Pupil Constricts

Sympathetic Input

Pupil dilates

Photoreceptors

Red, Green, Blue - a combination of these creates colors (at the bottom of the retina)

Pigmented Epithelium

Absorbs the remaining photon, blood vessels (nutrient supply) for the photoreceptor cells

Opsins

Photosensitive pigments located in outer segment membranes

Photoreceptor Cells

Rod or Cone

Cone

Red, blue, and green colors, one type of opsin

Rods

Black and White vision

Fovea

Arrangement of cone photoreceptor cells, with interspersed colors. Region of highest acuity without blood vessels

Optic Disc

Optic nerve axons penetrate the retina to reach the optic nerve. Entry point for most of the blood supply to the retina (no photoreceptors). All blood vessels are going in.

Retinal Detachment

Outer segments and the pigmented epithelium detach, losing nutrient supply to the photoreceptors

Anterior Portion of Lens

Cuboidal Cells

Most of Lens

Anucleate crystallin cells (transparent). Cells at equator of epithelium layer elongate and produce more lens fiber cells

Photoreceptor Outer Segments

Photoreceptor cells present, sensing light and then relaying info to interneuron

Inner Nuclear Layer

Bipolar neuron transmit information from photoreceptors to ganglion

Retinal Pigment Epithelium (RPE)

Phagocytose (shed) distal ends of the outer segment (used

Ganglion Cell Layer

Collect data from bipolar neurons (only if there is a color contrast) and then transmit it to ophthalmic cortex in brain through optic nerve (CN II)