Ch 15-The Special Senses Flashcards
What do the accessory structures include
eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles
Coarse hairs that overlie the supraorbital margins
Functions include: Shading the eye; Preventing perspiration from reaching the eye
Eyebrows
Protect the eye anteriorly
Palpebrae (Eyelids)
separates eyelids
Palpebral fissure
medial and lateral angles (commissures)
canthi
contains glands that secrete a whitish, oily secretion (Sandman’s eye sand)
Lacrimal caruncle
Project from the free margin of each eyelid
Initiate reflex blinking
Eyelashes
Protects eyes from foreign objects
Prevents drying of the eye
Eyelashes
Transparent membrane that lines the eyelids as the palpebral conjunctiva
Conjunctiva
Covers the whites of the eyes as the bulbar conjunctiva; Lubricates and protects the eye
Conjunctiva
Consists of the lacrimal gland and associated ducts
Lacrimal Apparatus
secrete tears
Lacrimal glands
Contain mucus, antibodies, and lysozyme (destroys bacteria)
tears
Enable the eye to follow moving objects
Maintain the shape of the eyeball
Extrinsic Eye Muscles
thin, skin-covered folds.
eyelids
A slightly irregular hollow sphere with anterior and posterior poles
eyeball
The wall of the eyeball is composed of three tunics
fibrous, vascular, and sensory
The internal cavity is filled with fluids called
humors
The lens separates the internal cavity into
anterior and posterior segments
Forms the outermost coat of the eye and is composed of Opaque sclera (posteriorly); “whites of the eyes”
protects the eye and anchors extrinsic muscles
Fibrous Tunic
lets light enter the eye
Clear cornea (anteriorly)
Middle coat of the eyeball.
Pigmented layer.
Vascular Tunic (Uvea): Choroid Region
What are the three parts of Vascular Tunic (Uvea): Choroid Region
choroid, ciliary body, and iris
A dark brown membrane that forms the posterior portion of the uvea
Vascular Tunic (Uvea): Choroid Region
Supplies blood to all eye tunics
Vascular Tunic (Uvea): Choroid Region
Helps absorb light, preventing it from scattering and reflecting within the eye.
Vascular Tunic (Uvea): Choroid Region
Anteriorly, the choroid becomes
the ciliary body
Controls lens shape
Ciliary Body
A thickened ring of tissue surrounding the lens
Ciliary Body
The visible, colored part of the eye
Iris
Lies between the cornea and the lens & is continuous with the ciliary body posteriorly
Iris
central opening of the iris
pupil
Run along the inner surface of the retina
Leave the eye as the optic nerve
Ganglion cell axons
Is the site where the optic nerve leaves the eye Lacks photoreceptors (the blind spot)
The optic disc
Photoreceptors of the retina
rods, cones
Respond to dim light
Are used for peripheral vision
rods
Respond to bright light
Have high-acuity color vision
Are found in the macula lutea
Cones
separates the internal eye into anterior and posterior segments
The lens
The anterior segment is composed of two chambers
anterior and posterior
between the cornea and the iris
anterior
between the iris and the lens
posterior
A biconvex, transparent, flexible, avascular structure that:
Allows precise focusing of light onto the retina
Lens
Pathway of light entering the eye
cornea, aqueous humor, lens, vitreous humor, and the neural layer of the retina to the photoreceptors
Arranged in a stack of disklike infoldings of the plasma membrane that change shape as they absorb light
Photoreceptors
Sensitive to dim light and best suited for night vision
rods
Absorb all wavelengths of visible light
rods
Perceived input is in gray tones only
rods
The three types of cones
blue, green, and red
Functional characteristics
Need bright light for activation (have low sensitivity)
Have pigments that furnish a vividly colored view
Cones
to substances dissolved in saliva
taste
to substances dissolved in fluids of the nasal membranes
smell
gustation
taste
olfaction
smell
gustation and olfaction are what type of senses
chemical senses
The organ of smell is the
olfactory epithelium
What does the olfactory epithelium cover
superior nasal concha
found in papillae of the tongue mucosa
Taste buds
which papillae contain taste buds
Fungiform and circumvallate
Part of the outer ear-auricle composed of
helix, lobule, external auditory canal, tympanic membrane
Auricle is called
pinna
what is the helix
rim
what is the lobule
earlobe
Short, curved tube filled with ceruminous glands
External auditory canal
Thin connective tissue membrane that vibrates in response to sound
Transfers sound energy to the middle ear ossicles
Boundary between outer and middle ears
Tympanic membrane
Eardrum
Tympanic membrane
A small, air-filled, mucosa-lined cavity
Flanked laterally by the eardrum
Middle Ear
connects the middle ear to the nasopharynx
Pharyngotympanic tube
Equalizes pressure in the middle ear cavity with the external air pressure
Pharyngotympanic tube
Inner Ear is also called
Bony labyrinth
Contains the vestibule, the cochlea, and the semicircular canals
Inner Ear
Channels worming their way through the temporal bone
Inner Ear
The central cavity of the bony labyrinth
The Vestibule
Suspended in the vestibule perilymph are two sacs
the saccule and utricle
what do the two sace in the vestibule do
House equilibrium receptors called maculae
Respond to gravity and changes in the position of the head
A spiral, conical, bony chamber that:
Extends from the anterior vestibule
The Cochlea
The cochlea is divided into three chambers
Scala vestibuli
Scala media
Scala tympani
A pressure disturbance (alternating areas of high and low pressure) originating from a vibrating object
Sound
The route of sound to the inner ear follows this pathway: outer
pinna, auditory canal, eardrum
The route of sound to the inner ear follows this pathway: middle
malleus, incus, and stapes to the oval window
The route of sound to the inner ear follows this pathway: inner
scalas vestibuli and tympani to the cochlear duct
