ABO Exam Prep – Anatomy fully solved

Fibrous Tunic Vascular Tunic Nervous Tunic What three layers are the eye made up of? Fibrous Tunic Consists of the sclera and the cornea. Vascular Tunic Consists of the iris, the choroid, and the ciliary body and is responsible for nourishment Nervous Tunic The inner layer of photoreceptors and neurons which consists of the retina; Contains rods and cones Rods Lets us see at twilight and in dimly lit rooms; does not discriminate between different colors of light. About 120 million rods Cones Cones require brighter light to function than rods do; Discriminate colors. About 6 million in Fovea Macula Where light will focus in a healthy eye Fovea The highest concentration of cones is found at the fovea which is the center of the macula Optic Disc (Blind Spot) The point where the optic nerve enters the eye; Does not contain receptor cells so it is sometimes called the "blind spot" What are the three fluid-filled chambers in the eye? Anterior Chamber Posterior Chamber Vitreous Chamber Anterior Chamber Located between the cornea and the iris Posterior Chamber Located between the iris and the lens Vitreous Chamber Located between the retina and the lens; Is filled with a thicker gel-like substance called Vitreous humor which maintains the shape of the eye Aqueous Humor Watery fluid produced by the ciliary body. It maintains pressure (called intraocular pressure or IOP) and provides nutrients to the lens and cornea. Canal of Schlemm Where the Aqueous Humor is continually drained from the eye. Cornea A transparent dome shaped layer that sits in front of the eye and lets light enter through 5 Distinct Cornea Layers Memory Hint: B comes before D and think "end" for last layer. Epithelium Bowman's Membrane Stroma Descemet's Membrane Endothelium Epithelium The outer most layer of the cornea which rests on Bowman's membrane Bowman's Membrane Acts as a protective barrier of the Cornea Stroma Located between the two membranes makes up 90% of the thickness of the cornea Descemet's Membrane Separates the stroma and the endothelium of the Cornea Endothelium The inner most layer of the Cornea which removes water from cornea helping to keep the cornea clear Dilator Muscle Opens the iris allowing more light in Sphincter Muscle Closes the iris Iris has the ability to change the pupil size from ___ millimeters to ___ millimeters. Iris has the ability to change the pupil size from 2 millimeters to 8 millimeters. Crystalline Lens Focuses light on the retina. Sits just behind the pupil. Accommodation The process of focusing on objects based on their distance. The closer an object is to the eye the more power is required of the crystalline lens to focus the image on the retina. BONUS) The lens achieves accommodation with the help of the ciliary body which surrounds the lens. Ciliary Body the structure between the choroid and the iris that anchors the lens in place Zonules fbrous strands connecting ciliary body and lens When the ciliary body contracts, the zonules _____ allowing the lens to _______, adding power, allowing the eye to focus up close Relax; Thicken When ciliary body relaxes, the zonules ________, drawing the lens outward, making the lens _______, and allowing the eye to focus at distance. Contract; Thinner Palpebrae Another term for eyelid Medial Canthus This is the point where the upper and lower eyelids meet near the nose. In layman terms, "the corner of your eye." Lateral Canthus This is the point where the upper and lower eyelids meet towards your ear. Eyelashes Strong hairs that run along the upper and lower palpebral margins. They are there to filter debris from entering the eye. Meibomian Glands Located along the inner margin of the eyelids the glands secrete a liquid that keeps the eyelids from sticking together. These secretions make up part of the tear film. Emmetropia All the rays of light entering the eye all focus on the retina right where they need to be to provide crisp sight without the need of corrective lenses