Eyes and Ears Flashcards
The fibrous coat of the eye is also called the _____?
Sclera
What structure is responsible for the majority of light refraction?
The cornea
Where does the cornea draw it’s nutrients from?
The aqueous humor by diffusion
What is the external portion of the cornea called?
The conjunctiva
What is the purpose of the conjunctiva?
Along with the lacrimal gland, produce a fluid that bathes the anterior surface of the eye and keeps it nourished and moist
What is the layer of numerous anastomosing blood vessels called?
The choroid layer
What’s the structure that controls the refraction of light from the lens?
The ciliary body
What are the two muscles that control pupil size? What are their actions and innervations?
The sphincter pupillae - constricts, parasympathetically innervated
The dilator pupillae - dilates, sympathetically innervated
What structure accounts for two thirds of the eye’s optical (refractory) power?
The cornea
What nerve innervates the cornea?
CN V
What are the three main components of the cornea?
Epithelium, collagen, and endothelium
The lens is composed of _____?
Stiff, elongated prismatic cells known as lens fibres
The lens has less optical power than the cornea, but is superior how?
It is adjustable by the ciliary muscles
What is the condition associated with age and far-sightedness?
Presbyopia
What fluid is the anterior chamber filled with, and where is it produced?
It is filled with the aqueous humor and is produced by the ciliary body
Where is the aqueous humor of the anterior chamber drained?
The canal of Schlemm
What happens in glaucoma?
Increased pressure in the anterior chamber transfers pressure back to the optic nerve and results in damage to the optic nerve and blindness
The nervous coat of the eyeball is called the?
Retina
What are the two photosensitive cells of the eye and what do they detect?
Rods - more sensitive to light, do not respond to red light
Cones - detect colors (red, blue, green)
What is the protein required for rod and cone function and what vitamin is it a metabolite of?
Retinal - Vitamin A
Why should the optic nerve be called a tract?
The meninges surround the nerve up to the sclera, the subarachnoid space is filled with CSF, and the ganglion cells of the retina are myelinated by oligodendrocytes and fed by astrocytes
Papilledema is a condition of??
Increased CSF limiting venous return from retina and causes edema under optic disc. Visible by blurred disc margins where the optic disc is raised.
What is the function and composition of the vitreous body?
It functions to support the retina and applying pressure against the shape of the globe. It is composed of hyaluronic acid and type II collagen fibrils
The hyaloid canal is a vestige of what embryonic structure?
The hyaloid artery
What is the pathway of nerve impulses from the retina?
The optic nerve to the optic chiasm to the lateral geniculate body of the thalamus to optic radiations to the primary visual cortex
What muscle(s) does the abducens nerve (CN VI) innervate and what is/are their action(s)?
Lateral rectus - abducts the eye
What muscle(s) does the trochlear nerve (CN IV) innervate and what is/are their action(s)?
Superior oblique - internally rotates, depresses and abducts
What muscle(s) does the oculomotor nerve (CN III) innervate and what is/are their action(s)?
Inferior oblique - externally rotates, raises and adducts
Medial rectus - internally rotates
Inferior rectus - depresses
What is the name for the ear canal?
The auditory meatus
What is the function of cerumen?
To protect the ear from irritation and infection
What is the pathway from the tympanic membrane to the oval window?
Tympanic membrane –> malleus –> incus –> stapes –> oval window
What kind of joints are in the middle ear?
Synovial joints
What muscles contract to reduce the movement of the ossicles in order to protect the ear from excessive noise?
Tensor tympani - malleus
Stapedius - stapes
What are the three parts of the inner ear?
The cochlea, the vestibule, and the semicircular canals
Movement of the stapes at the oval window moves the perilymph of?
The scala vestibuli
The movement of the perilymph in the scala vestibuli vibrates what?
The endolymph in the scala media, the basilar membrane, and the Organ of Corti
What organ translates the movement of hair cells to electrical impulses?
The Organ of Corti
Describe the auditory pathway.
The cochlear division transmits nerves to it’s nucleus then to the superior olivary nucleus. This information ascends to the inferior colliculus then goes to the thalamus (which allows us to localize sound). From the thalamus, this info is sent to the primary auditory cortex located in the temporal lobe
What systems keep us in balance?
The vestibular system, the visual system, and pressure/proprioceptors
What are the parts of the vestibule?
The saccule, the utricle, and the 3 semicircular canals
What are the hair structures that transmit information on movement?
The otoliths - which are composed of calcium carbonate
What structure is at the base of each semicircular canal?
The ampulla, which contains the hair cells responsible for nerve transmission
What is BPPV?
Benign Paroxysmal Positional Vertigo - a condition in which the patient is overcome by a sudden sensation of spinning
How is BPPV diagnosed and treated?
It is diagnosed with the Dix-Hallpike manuever (the roll test) and treated with the Epley or Semont Manuever
