What is the primary function of the eyelashes and eyebrows?
They help prevent foreign material from attaching to the eye surface.
What is the function of the Palpebrae (eyelids)?
They lubricate the eye surface and wipe it clean with each blink.
What is the Conjunctiva, and what does it do?
It is a mucous membrane (stratified squamous epithelial cells) that covers and protects the eye edges.
Where are tears produced, and what are they made of?
Tears are produced by the Lacrimal Glands. They consist of water and antibacterial enzymes (lysozymes).
Where do tears ultimately drain?
They drain into the Nasolacrimal Ducts, which empty into the nasal cavity (explaining a “runny nose” when crying).
What is the outermost layer (tunic) of the eye, and what is its main role?
The Fibrous Tunic. Its main role is protection.
What are the two major structures of the Fibrous Tunic?
The Sclera (the white of the eye) and the transparent Cornea (where light enters).
Which tunic is the middle layer, and what does it contain a high concentration of?
The Vascular Tunic (or Uvea). It has a high concentration of blood and lymph vessels.
What is the function of the Iris?
The Iris, which surrounds the Pupil, contains muscle fibers that regulate the amount of light entering the eye.
What does the Ciliary Body do?
It contains muscles and suspensory ligaments that anchor the lens and alter its shape for focusing (accommodation).
What is the Choroid Layer?
It’s the layer posterior to the ciliary body that contains a network of capillaries to deliver oxygen and nutrients to the photoreceptors.
Which tunic is the innermost layer and contains the photoreceptors?
The Neural Tunic, which is the Retina.
What is the two-part function of the Retina’s layers?
The outer layer uses pigmented cells to absorb light, and the inner layer contains the rod and cone photoreceptors to transduce light into neural signals.
What separates the anterior and posterior cavities of the eye?
The Lens and the Ciliary Body.
What fluid is found in the Anterior Cavity?
Aqueous Humor.
Where is Aqueous Humor formed, and how does it drain?
It’s formed at the ciliary body and drains through the Scleral Venous Sinus (Canal of Schlemm).
What condition can result from disrupted drainage of aqueous humor?
Glaucoma, which is characterized by increased fluid pressure in the eye.
What substance is found in the Posterior Cavity (Vitreous Chamber)?
The thicker, gelatinous substance called Vitreous Humor.
What happens during Pupil Dilation, and when does it occur?
The Radial muscles of the iris contract, pulling the iris outward, which increases pupil diameter to let more light in. This occurs in low light (Sympathetic activation).
What happens during Pupil Constriction, and when does it occur?
The Circular (Sphincter) muscles of the iris contract, pulling the iris inward, which decreases pupil diameter. This occurs in bright light (Parasympathetic activation).
How does the lens change shape for Near Vision Focus?
The Ciliary muscles contract, the suspensory ligaments relax, and the lens becomes rounder.
How does the lens change shape for Distant Vision Focus?
The Ciliary muscles relax, the suspensory ligaments pull on the lens, and the lens flattens.
What is Refraction?
The process where light rays are bent by the cornea and lens to focus at the fovea.
Where is the Fovea located?
It’s the region of the retina with the greatest density of photoreceptors and where the clearest vision is achieved.
