Chapter 10 Head, Eyes, Ears, Nose, and Throat FINAL EXAM Flashcards
(260 cards)
Facial muscles are innervated by what cranial nerves?
V (Trigeminal)
VII (Facial)
The opening between the eyelids is termed?
Palpebral fissure
Two thin, transparent mucous membranes termed _______ lie between the eyelids and the eyeball
Conjunctivae
1) Bulbar conjunctiva-covers the scleral surface of the eyeballs
2) Palpebral conjuunctiva-lines the eyelids and contains blood vessels, nerves, hair follicles, and sebaceous glands. One of the sebaceous glands, the meibomian gland, secretes an oily substance that lubricates the lids, prevents excessive evaporation of tears, & provides an airtight seal when the lids are closed
Tears, formed by the lacrimal glands, combine with sebaceous secretions to maintain?
A constant film over the cornea
In the inner (or medial) canthus small openings termed the ______ _______ drain tears from the eyeball surface through the lacrimal sac into the nasolacrimal ducts
Lacrimal puncta
The globe of the eye, also known as the “eyeball” is surrounded by three separate layers:
1) sclera
2) uvea
3) retina
Describe the sclera of the eye
tough, fibrous outer layer commonly referred to as the white of the eye. Merges w/cornea in front of the globe at the junction termed limbus. Cornea covers iris & pupil. It is transparent, avascular, and richly innervated with sensory nerves via the ophthalmic branch of the trigeminal nerve V. Constant wash of tears provides cornea w/oxygen supply and protects its surface from drying. An important corneal function is to allow light transmission through the lens to the retina
Describe the uvea of the eye
Middle layer, consists of the choroid posteriorly & the ciliary body and iris anteriorly
- choroid layer is highly vascular & supplies retina w/blood.
- iris=circular, muscular membrane that regulates pupil dilation & constriction via the oculomotor nerve III.
- central opening of iris, the pupil, allows light transmission to the retina through the transparent lens
- ciliary body is a thickened region of the choroid that has two functions: (1) adjusts shape of lens to accommodate vision @ varying distances, (2) produces transparent aqueous humor (fluid the helps maintain intraocular pressure & metabolism of the lens & posterior cornea). Aqueous humor fills the anterior chamber between the cornea & lens and flows between the lens and the iris
Describe the retina of the eye
Inner layer, an extension of CNS
- transparent layer has photoreceptor cells, rods & cones, scattered throughout its surface. These cells perceive images & colors in response to varying light stimuli
- rods=low levels of light
- cones=higher levels of light
- macula lutea densely packed peripherally w/rods
- fovea centralis (small depression in center of macula lutea on the posterior wall of the retina) concentrated w/cones NO rods
- perforating retina is optic disc, head of the optic nerve II. Contains NO rods or cones, causing a small blind spot located 15 degrees laterally from center of vision
- The central retinal artery and central vein bifurcate at the optic disc and feed into smaller branches throughout the retinal surface
Vision, the primary function of the eyes, occurs when?
Rods and cones in the retina perceive images and colors in response to varying stimuli
The lenses are constantly adjusting to stimuli at different distances through?
Accommodation
When the lenses bring an image into focus what happens?
Nerve impulses transmit the information from the retina along the optic nerve and optic tract, reaching the visual cortex (located in the occipital lobe of each cerebral hemisphere) for cognitive interpretation
Six extraocular muscles and three cranial nerves allow for eye movement in six directions
1) The medial, inferior, & superior rectus muslces and the inferior oblique muscles, guided by the oculomotor nerve (cranial nerve III), control upward outer, lower outer, upward inner, & medial eye movements
2) The superior oblique muscle controls lower medial movement, innervated by the trochlear nerve (cranial nerve IV)
3) The lateral rectus muscle controls lateral eye movement, innervated by the abducens nerve (cranial nerve VI)
The external ear is composed of the?
Auricle (pinna) and the external auditory ear canal
The auricle (pinna) is composed of?
Cartilage and skin
External ear: the helix is the prominent outer rim; the concha is the ?
Deep cavity in front of the external auditory meatus
The bottom portion of the ear is referred to as the?
Lobule
The auricle (pinna) is attached to?
The head by skin, extension cartilage to the external auditory canal cartilage, ligaments, & muscles (the anterior, superior, and posterior auricular muscles)
The auricle (pinna) serves three main functions
1) Collection and focus of sound waves
2) location of sound ( by turning the head until the sound is loudest)
3) protection of the external ear canal from water and particles
The adult’s external ear canal is an?
S-shaped pathway leading from the outer ear to the tympanic membrane (TM), commonly known as the eardrum
The lateral one third of the ear canal has a cartilaginous portion framework; the medial two thirds of the canal are surrounded by bone The skin covering the cartilaginous portion of the auditory canal has hair follicles surrounded by sebaceous glands that secrete?
Cerumen (earwax). The hair follicles and cerumen protect the middle ear & inner ear from particles & infection
The middle ear is an?
Air filled cavity separated from the external ear canal by the tympanic membrane (TM). The TM, composed of layers of skin, fibrous tissue, & mucous membrane, is shiny & pearl gray. It is translucent, permitting limited visualization of the middle ear cavity
- middle ear contains 3 tiny bones: malleus, incus, & stapes (ossicles)
- lying between the nasopharynx and the middle ear is the eustachain tube. It opens briefly during yawning, swallowing, or sneezing to equalize the pressure of the middle ear to the atmosphere
- function of middle ear: amplification of sound. Sound waves cause the TM to vibrate; this vibration is transmitted through the ossicles to inner ear. The amplification results from the ossicles and from the size (area) difference between the TM and the oval window, an oval shaped aperture in the wall of the middle ear leading to the inner ear
The inner ear is encased in a bony labyrinth that contains three primary structures:
1) The vestibule
2) Semicircular canals
3) cochlea
The vestibule (inner ear) & the semicircular canals (inner ear) contain?
Receptors responsible for balance & equilibrium