Special Senses – Vision & Related Anatomy

Vocabulary flashcards covering key anatomical structures, nerves, muscles, and physiological concepts discussed in the lecture on special senses, with emphasis on vision and associated cranial nerves.

Fibrous Tunic

Outermost protective layer of the eye composed of sclera and cornea.

Sclera

Opaque ‘white of the eye’ where extrinsic eye muscles attach; 5/6 of fibrous tunic.

Cornea

Transparent anterior part of fibrous tunic that initiates light refraction.

Refraction

Bending of light as it passes between media of different densities (e.g., air → cornea).

Vascular Tunic (Uvea)

Middle, pigmented, vascular layer containing choroid, ciliary body, and iris.

Choroid

Highly vascular, dark-pigmented layer that nourishes retina and absorbs stray light.

Ciliary Body

Ring of smooth muscle and processes that alter lens shape via suspensory ligaments.

Iris

Colored diaphragm of smooth muscle that regulates pupil diameter.

Pupil

Central opening in iris through which light enters; not a physical structure.

Sensory Tunic (Retina)

Innermost layer housing photoreceptors that convert light to neural signals.

Lens

Biconvex, adjustable structure that fine-tunes focus by changing shape.

Aqueous Humor

Clear fluid in anterior segment; continuously produced and drained to nourish cornea & lens.

Vitreous Humor

Gel-like substance in posterior segment; maintains eyeball shape and supports retina.

Photoreceptors

Rods and cones of the retina that detect light stimuli.

Optic Nerve (CN II)

Cranial nerve transmitting visual information from each eye to the brain.

Optic Chiasm

X-shaped crossing where nasal retinal fibers decussate, separating visual fields.

Optic Tract

Pathway carrying visual field information (right or left) from chiasm to thalamus.

LR6 SO4 AO3

Mnemonic: Lateral Rectus–CN VI, Superior Oblique–CN IV, All Others–CN III.

Superior Rectus Muscle

Elevates the eyeball; innervated by oculomotor nerve (CN III).

Inferior Rectus Muscle

Depresses the eyeball; innervated by oculomotor nerve (CN III).

Medial Rectus Muscle

Adducts (moves eye medially); innervated by oculomotor nerve (CN III).

Lateral Rectus Muscle

Abducts (moves eye laterally); innervated by abducens nerve (CN VI).

Superior Oblique Muscle

Depresses & abducts eye via trochlea; innervated by trochlear nerve (CN IV).

Inferior Oblique Muscle

Elevates & abducts eye; innervated by oculomotor nerve (CN III).

Trochlea (Eye)

Fibro-cartilaginous pulley through which superior oblique tendon passes.

Lacrimal Gland

Parasympathetic (CN VII)-stimulated gland producing tears that drain into nasal cavity.

Parasympathetic Pupil Constriction

Rest-and-digest response that narrows pupil via circular iris muscles.

Sympathetic Pupil Dilation

Fight-or-flight response that widens pupil via radial iris muscles.

Chemoreceptors

Sensory receptors detecting chemical stimuli; used in taste and smell.

Mechanoreceptors

Receptors activated by mechanical deformation; essential for hearing & balance.

Baroreceptors

Pressure/stretch receptors in skin or vessels sensing mechanical force.

Nociceptors

Pain receptors responding to tissue-damage stimuli.

Proprioception

General sense of body/limb position detected by muscle & joint receptors.

Facial Nerve (CN VII)

Supplies taste to anterior 2/3 tongue, muscles of facial expression, and lacrimal gland.

Glossopharyngeal Nerve (CN IX)

Conveys taste & general sensation from posterior 1/3 tongue; innervates some pharyngeal structures.

Mandibular Division (V3)

Branch of trigeminal nerve carrying general sensation to anterior 2/3 tongue and muscles of mastication.

Hypoglossal Nerve (CN XII)

Motor nerve to intrinsic & extrinsic tongue muscles.

Styloglossus

Extrinsic tongue muscle that retracts and elevates tongue; CN XII.

Hyoglossus

Extrinsic tongue muscle that depresses tongue; CN XII.

Genioglossus

Extrinsic tongue muscle that protrudes tongue; CN XII.

Olfactory Nerve (CN I)

Sensory neurons in nasal mucosa conveying smell to brain.

Cribriform Plate

Perforated part of ethmoid bone through which olfactory nerve fibers pass.

Olfactory Bulb

Brain structure sitting atop cribriform plate where olfactory nerves synapse.

Olfactory Tract

Pathway carrying olfactory signals from bulb to primary olfactory cortex.

Oculomotor Nerve (CN III)

Innervates four recti, inferior oblique, and constricts pupil via parasympathetics.

Trochlear Nerve (CN IV)

Motor nerve to superior oblique muscle.

Abducens Nerve (CN VI)

Motor nerve to lateral rectus muscle enabling eye abduction.