Anatomy Study Guide Chpt. 8 by Jenna Kozlowski
Terms in this set (60)
What are the five special senses?
Smell, taste, sight, hearing, and equilibrium
What are the accessory structures of the eye?
Extrinsic eye muscles, eyelids, conjunctiva, and lacrimal apparatus
The anterior of the eye is protected by what?
By the eyelids (protecting the borders of each eyelids are the eyelashes
Where is the conjunctiva found?
The conjunctiva lines the eyelids and covers part of the outer surface of the eyeball; it secretes mucus, which helps to lubricate the eyeball and keep it moist
What is conjunctivitis?
Is inflammation of the conjunctiva, and is often caused by pinkeye, an infectious form caused by bacteria or viruses
Where are the lacrimal glands found?
They are located above the lateral end of each eye,
What does the lacrimal glands produce?
continually release a dilute salt solution (tears); lacrimal secretions contain mucus, antibodies, and lysozyme, an enzyme that destroys bacteria
What is lysozyme and what does it do?
It is an enzyme that destroys bacteria
Why does your nose run when you cry?
Because the nasal cavity mucosa is continuous with that of the lacrimal duct system
How many extrinsic muscles are there?
There are 6 extrinsic (external) eye muscles attached to the outer surface of the eye
How many layers does the eyeball have?
What is the outermost larger of the eye called?
The fibrous layer
What is the sclera?
The sclera is a thick, glistening white connective tissue, "the white of the eye"
What is the cornea?
Light enters the eye through the cornea, which is well supplied with nerve fibers, mainly pain fibers
What is the middle layer of the eye called?
The vascular layer
What is the choroid?
Most posterior part of the eyeball is the choroid, a blood-rich nutritive tunic that contains dark pigments so that the light doesn't scatter inside the eye; the choroid is modified to form two smooth muscle structures, the ciliary body, to which the lens is attached and the iris
What is the iris?
the choroid is modified to form two smooth muscle structures, the ciliary body, to which the lens is attached and the iris
What is the pupil?
The pigmented iris has a rounded opening, the pupil, through which light passes
The innermost layer of the eye is what?
The innermost sensory layer of the eye is the two-layered retina
What is the retina?
The innermost sensory layer of the eye; which has two layers; The outer layer of the retina is pigmented, while the inner layer contains millions of receptor cells, the rods and cones
Where do you find rods and cones?
Rods and cones are distributed over the entire retina except at the optic disc (blind spot) where the optic nerve leaves the eyeball
What is the function of rods and cones?
Rods are denser at the periphery of the retina; these allow us to see in gray tones in dim light
Cones allow us to see color under bright light; they are densest in the center of the retina
What is your blind spot?
Rods and cones are distributed over the entire retina except at the optic disc (blind spot) where the optic nerve leaves the eyeball
The lack of cones result in what condition?
There are 3 types of cones, lack of any type of cone results in either partial or full color blindness
What does the lens do?
The lens focuses the light coming into the eye
Describe the two humors found in the eye.
The lens divides the eye into 2 segments; the anterior (aqueous) segment contains clear watery fluid called aqueous humor, while the posterior (vitreous) segment is filled with a gel0like substance called vitreous humor
What is glaucoma?
Glaucoma occurs when the aqueous humor is blocked and pressure builds up in the eye
How do cataracts occur?
As we age the lens becomes increasingly harder and opaque, resulting in cataracts
What is accommodation
The ability of the eye to focus specifically for close objects
Describe the real image formed on the retina.
The image formed on the retina as a result of the light-bending activity of the lens. IT is reversed from left to right, upside down, and smaller than the object
What happens at the optic chiasma?
The fibers from the medial side of each eye cross over to the opposite side of the brain
What is binocular vision?
Literally "Two-eyed vision", provides for depth perception
The reflexive movement of the eyes medially when we view close objects
What are the two reflexes of the eye? Describe how these reflexces work.
The photopupillary reflex and the accommodation pupillary reflex. Photopupillary works by being a protective reflex preventing excessive bright light from damaging the delicate photoreceptors. The accommodation relic provides more acute vision
What are mechanoreceptors?
Mechanoreceptors respond to physical forces, and are used in hearing and balance
What are the three parts of the ear?
The ear is divided into 3 major areas: the external (outer) ear, the middle ear, and the internal (inner) ear
What is the auricle?
Part of the external ear; also known as pinna; is the shell-shaped structure that surrounds the auditory canal opening
Describe the external acoustic meatus.
The external acoustic meatus (or auditory canal) is a short, narrow chamber carved into the temporal bone; part of external ear
What is the purpose of the ceruminous glands?
They secrete wavy yellow cerulean (earwax) which provides a sticky trap for foreign bodies and repels insects
What separates the external ear from the middle ear?
The tympanic membrane or eardrum separates the external ear front eh middle ear
Starting with the tympanic membrane, describe the path of sound waves in the middle ear.
The middle ear, or tympanic cavity, is a small, air-filled, mucosa-lined cavity within the temporal bone. It is flanked laterally by the eardrum and medially by a bony wall with two openings, the oval window and the inferior, membrane-covered round window.
The pharyngotympanic tube, or auditory tube, runs obliquely downward to link the middle ear cavity with the throat, and the mucosae lining two regions are continuous. The tympanic cavity is spanned by the three smallest bones in the body, the ossicles which transmit the vibratory motion of the eardrum to the fluids of the inner ear
These tiny bones, named for their shape, are the hammer, or malleus, the anvil, or incus, and the stirrup, or stripes.
When the eardrum moves, the hammer moves with it and transfers the vibration to the anvil. The anvil, in turn, passes the vibration on to the stirrup, which presses on the oval window of the inner ear. The movement at the oval window sets the fluids of the inner ear into motion, eventually exciting the hearing receptors.
What is the pharyngotympanic tube?
The pharyngotympanic rube or auditory tube runs obliquely downward to link the middle ear cavity with the throat
What are the three ossicles?
The tympanic cavity is spanned but he three smallest bones in the body, the ossicles, which transmits the vibratory motion of the eardrum to the fluids of the inner ear; these bones are the hammer (malleus), the anvil (incus), and the stirrup (stapes)
What parts make up the internal ear?
The internal ear is a maze of bony chambers called the bony (osseous) labyrinth; the 3 subdivisions of the bony labyrinth are the spiraling, peasized cochlea, the vestibule, and the semicircular canals
Describe the path of sound waves in the inner ear.
• The internal ear is a maze of bony chambers called the bony or osseous, labyrinth, located deep within the temporal bone behind the eye socket.
• The three subdivisions of the bony labryinth are the spiraling, peasized cochlea the vestibule and the semicircular canals. The vestibule is situated between the semicircular canals and the cochlea.
• The bony labryinth is filled with a plasmalike fluid called perilymph. Suspended in the perilymph is a membranous labryinth, a system of membrane sacs that more or less follows the shape of the bony labryinth. The membranous labryinth itself contains a thicker fluid called endolymph
What are the vestibular apparatus?
The equilibrium receptors in the inner ear (vestibular apparatus) can be divided into two functional arms-monitoring static equilibrium and dynamic equilibrium
Describe the differences between static and dynamic equilibrium.
• Within the membrane sacs of the vestibule are receptors called macular that are essential to our sense of static equilibrium.
• The macular report on changes in the position of the head in space with respect to the pull of gravity when the body is not moving. Because they provide information on which way is up or down, they help us help our head erect.
• The dynamic equilibrium receptors, found in the semicircular canals, respond to angular or rotary movements of the head rather than to straightline movements
• The semicircular canals (each about ½ inch or 1.3 cm around) are oriented in the three planes of space. Thus regardless of which plane you move in there will be receptors to detect movement
What is the organ of hearing?
The spiral organ of cortical
Describe how hearing works.
• Within the cochlear duct, the endolymph-containing membranous labryinth of the cochlea is the spiral organ of Cortical which contains the hearing receptors or hair cells.
• The chambers (scalae) above and below the cochlear duct contain perilymph. Sound waves then reach the cochlea through vibrations of the eardrum, ossicles,a nd oval window set the cochlear fluids into motion. As the sound of waves are transmitted by the ossicles front he eardrum to the oval window, their force (amplitude) is increased by the lever activity of he ossicles. In this way, nearly the total force exerted on the much larger eardrum reaches the tiny oval window, which in turn sets the fluids of the inner ear into motion, and these pressure waves set up vibrations in the basilar membrane.
• The receptor cells positioned on the basilar membrane in the spinal organ of cortical, are stimulated when their "hairs" are bent or tweaked by the movement of the fuel-like tectorial membrane that lies over them.
• The length of the fibers spanning the basilar membrane "tunes" specific regions to vibrate at specific frequencies. In general, high pitched sounds disturb the shorter, stiffer fibers of the basilar membrane and stimulate receptor cells close to the oval window, whereas low-pitched sounds affect longer, more floppy fibers and activate specific hair cells further along the cochlea
• Once stimulated, the hair cells transmit impulses along the cochlear nerve (a division of cranial nerve AVIII—the vestibulocochlear nerve) to the auditory cortex in the temporal lobe, where interpretation of the sound, or hearing occurs.
• Sound usually reaches the two ears at different times; functionally, this helps us to determine where sounds are coming from in our enviornment
• When the same sounds, or tones, keep reaching the ears, the auditory receptors tend to adapt, or stop responding, to those sounds, and we are no longer aware of them
• However, hearing is the last sense to leave our awareness when we fall asleep or receive anesthesia (or die) and is the first to return as we awaken.
What are chemoreceptors?
Receptors for taste and olfaction are classified as chemoreceptors because they respond to chemicals in solution
Where are olfactory receptors found?
Thousands of olfactory receptors occupy a postage stamp sized area in the roof of each nasal cavity
How do you smell?
• The thousands of olfacotry receptors, receptors for the sense of smell, occupy a postage stamp-sized area in the roof of each nasal cavity.
• Air entering the nasal cavity make a hairpin turn to enter the respiratory passageway below, so sniffing, which causes more air to flow superiorly across the olfactory receptors, intensifies the sense of smell.
• The olfactory receptor cells are neurons equipped with olfactory hairs, long cilia that protrude fronm the nasal epithelium and are continuously bathed by a layer of mucus secreted by underlying glands.
• When the olfactory receptors located on the cilia are stimulated by chemicals dissolved in the mucus, they transmit impulses along the olfactory filaments, which are bundled axons of olfactory neurons that collectively make up the olfactory nerve (cranial nerve I).
• The olfactory nerve conducts the impulses to the olfactory cortex of the brain. There the odor is interpreted, and an "odor snapshot" is made.
• The olfactory pathways are closely tied into the limbic system (emotional-visceral part of the brain). Thus, olfactory impressions are long-lasting and very much a part of our memories and emotions.
• Our reactions to odors are rarely neutral. We eith like or dislike certain odors and we change, avoid, or add odors according to our preferences.
• The olfactory receptors are exquisitely sensitive—just few molecules can activate them. Like the auditory receptors, the olfactory neurons tend to adapt rather quickly when they are exposed to an unchanging stimulus, in this case, an odor
The receptors for taste are what?
Taste buds which are widely scattered min the oral cavity, most are on the tongue
Describe the process of tasting.
• The taste buds, or specific receptors for the sense of taste, are widely scattered int eh oral cavity. Of the 10,000 or so taste buds that we have, most are on the tongue. A few are scattered on the soft palate, superior part of the pharynx,a nd inner surface of the cheeks.
• The dorsal tongue surface is covered with small peglike projections, or papillae. The taste buds are found on the sides of the large round gallate or cicumvallate papillae and on the tops of the more numerous fungiform papillae.
• The specific cells that respond to chemicals dissolved int eh saliva are epithelial cells called gustatory cells. Their long microvilli—the gustatory hairs—protrude through the taste pore, and when they are stimulated, they depolarize and impulses are transmitted ot he brain.
• Three cranial nerves—VII, IX, and X—carry taste impulses from the various taste buds to the gustatory cortex.
• The facial nerve (VII) serves the anterior part of the tongue. The other two cranial nerves—the glossopharyngeal and vagus—serve the other taste bud-containing areas.
• Because of their location, taste bud cells are subjected to huge amounts of friction and are routinely burned by hot foods. Luckily, they are amount themost dynamic cells in the body and they are replaced every 7 to 10 days by basal cells (stem cells) found in the deeper regions of the taste buds.
What are the five different taste sensations?
Sweet, sour, bitter, salty, and umami
When are sense organs formed in the embryo?
Very early in the embryonic development.
What is stabismus?
crossed eyes. Results from unequal pulls by the external eye muscles.
Describe presbyopia and when it occurs
Literally means old vision. It occurs after the age of 40
When you age or listen to music to loud, what can you develop?