![]() Six extrinsic, or external, eye muscles are attached to the outer surface of the eye these muscles produce gross eye movements and make it possible for the eyes to follow a moving object these are the lateral rectus, m edial rectus, superior rectus, inferior rectus, inferior oblique, and superior oblique. Lacrimal secretion also contains antibodies and lysozyme, an enzyme that destroys bacteria thus, it cleanses and protects the eye surface as it moistens and lubricates it. The tears flush across the eyeball into the lacrimal canaliculi medially, then into the lacrimal sac, and finally into the nasolacrimal duct, which empties into the nasal cavity. ![]() The lacrimal glands are located above the lateral end of each eye they continually release a salt solution ( tears) onto the anterior surface of the eyeball through several small ducts. The lacrimal apparatus consists of the lacrimal gland and a number of ducts that drain the lacrimal secretions into the nasal cavity. A delicate membrane, the conjunctiva, lines the eyelids and covers part of the outer surface of the eyeball it ends at the edge of the cornea by fusing with the corneal epithelium. Modified sebaceous glands associated with the eyelid edges are the tarsal glands these glands produce an oily secretion that lubricates the eye ciliary glands, modified sweat glands, lie between the eyelashes. Projecting from the border of each eyelid are the eyelashes. ![]() Anteriorly, the eyes are protected by the eyelids, which meet at the medial and lateral corners of the eye, the medial and lateral commissure (canthus), respectively. The accessory structures of the eye include the extrinsic eye muscles, eyelids, conjunctiva, and lacrimal apparatus. Vision is the sense that requires the most “learning”, and the eye appears to delight in being fooled the old expression “You see what you expect to see” is often very true. Vision is the sense that has been studied most of all the sensory receptors in the body 70% are in the eyes. Touch or somatosensory, also called tactition or mechanoreception, is a perception resulting from activation of neural receptors, generally in the skin including hair follicles, but also in the tongue, throat, and mucosa. Smell or olfaction is the other “chemical” sense odor molecules possess a variety of features and, thus, excite specific receptors more or less strongly this combination of excitatory signals from different receptors makes up what we perceive as the molecule’s smell. Taste refers to the capability to detect the taste of substances such as food, certain minerals, and poisons, etc. Hearing or audition is the sense of sound perception. Sight or vision is the capability of the eye(s) to focus and detect images of visible light on photoreceptors in the retina of each eye that generates electrical nerve impulses for varying colors, hues, and brightness. The functions of the five special senses include:
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