Special Senses Week 12

OBJECTIVES Identify the macro-structures of the eye Diagrams Models Dissecting cow’s eye Identify the microscopic structures of the retina Identify the macro-structures of the ear Identify the microscopic structures of the cochlea

Objective 1: Structures of the Human Eye

Internal Eye Three concentric tunics (layers) of the eye: sclera Outer fibrous tunic – sclera and cornea Middle vascular tunic - choroid Inner sensory tunic - retina sclera choroid retina Optic Nerve (CN II)

Light

Retina

Human Retina Rods & Cones Retinal ganglion cells Nuclei of rods & cones Outer segments of rods & cones Bipolar cell nuclei Pigmented epithelial layer Vascular Tunic

Internal Eye Choroid Three concentric tunics (layers) of the eye: Iris Outer fibrous tunic Middle vascular tunic – choroid, ciliary body (ciliary muscle & process), iris Inner sensory tunic Ciliary Body Choroid Ciliary muscle Ciliary process Suspensory ligaments Iris Lens

Pupil dilation & constriction

Internal Eye Sclera Three concentric tunics (layers) of the eye: Outer fibrous tunic – sclera, cornea Middle vascular tunic – choroid, ciliary body (ciliary muscle & process), iris Inner sensory tunic - retina Sclera Cornea

Posterior Wall (fundus) of the Eye Retina Macula lutea Fovea centralis Optic disk (blind spot) Optic nerve

The optic disc is the region were: The optic nerve exits the eye The central artery and vein of the retina enter and exit the eye There are no photoreceptors, the “blind spot” Light

Ophthalmoscope View

Fovea centralis & Macula lutea The macula lutea is an oval region lateral to the optic disc, at it’s center lies the fovea centralis, the area of greatest cone density in the retina.

Segments of the Eye Vitreous humor Anterior segment: area in front of the lens, filled with aqueous humor Posterior segment: area behind the lens, filled with vitreous humor

Anterior Segment Anterior chamber: between the cornea and iris Posterior chamber: between iris and lens Suspensory ligaments Canal of Schlemm

Glaucoma Fluid drainage is blocked Optic nerve fibers damaged

Exterior Eye Anatomy 1? 2? 3?

Orbicularis oculi muscle Sclera Cornea Conjunctiva

Exterior Eye Anatomy (palpabrae) (palpabrae)

Exterior Eye Anatomy

Extrinsic Eye Muscles Lateral rectus Inferior rectus Superior rectus Inferior oblique Superior oblique Levator palpebrae superioris Medial rectus (not shown)

Objective 4: Ear Anatomy

1 2 3

External Auditory Meatus

Middle ear

Otitis media Normal Otitis media The tympanic membrane is bulging and hyperemic ( blood), and yellow purulent fluid is seen in the middle ear space.

Inner ear Vestibular & Cochlear nerves join to become the Vestibulocochlear Nerve (CN VIII) Cochlear nerve

Internal Acoustic Meatus

Internal Acoustic Meatus External Auditory Meatus (Canal) Petrous portion of Temporal bone Superior view Pharyngotympanic tube M I S Internal Acoustic Meatus External Auditory Meatus (Canal) Inner ear Tympanic membrane Middle ear

Petrous portion of Temporal bone Bony Labyrinth

Petrous portion of Temporal bone Membranous Labyrinth

Cochlea Endolymph

Cochlea histology

Cochlea, cs (Perilymph) (Endoymph) (Perilymph)

Identify given structures from models and slides Cochlea S.V. S.T. Identify given structures from models and slides

Hearing physiology

Balance & Equilibrium

Inner Ear

Vestibule – utricle & saccule Static equilibrium Responds to changes in linear movement (vertical & horizontal) Monitor head position, posture

Semicircular Canals - ampulla Dynamic equilibrium Responds to changes in rotational movement Balance

Objective 2: Cow Eye Dissection

lens retina Identify all external and internal structures listed! Follow the directions given in the Lab Manual!

Tapetum lucidum Iridescent portion (retina removed) Not present in humans

Objectives 3 & 5: Experiments

Lab Activity: On the Practical: Dissect cow’s eye Perform visual, auditory & balance experiments and analyze On the Practical: Identify the macro-structures of the eye from models and the cow eye Identify the macro-structures of the ear from models Identify the microscopic structures of the retina and cochlea