Allied Chap. 10 Sense Organs

Front 1

senses

Back 1

* provide an important dimension to our enjoyment of life and supply the brain with important information about the condition of the body so that homeostasis can be maintained.
* Our eyes paint the colors of nature and our environment for our pleasure and yet warn us of any threatening images.
* Our ears transmit melodious music and the joy of conversation and caution us regarding noises that threaten our safety.
* Our sense of smell allows us to coordinate odors with wonderful experiences such as the scent of perfume and the smells of favorite foods and alerts us to odors that might be threatening such as lethal gases.
* Our sense of taste allows us to enjoy food more fully and makes dining a daily pleasure and can prevent us from swallowing toxic materials or foods by transmitting distasteful messages.
* Finally, our general sense organs allow us to experience touch, pressure, vibration, pain, temperature, and information concerning position and movement of different body parts. These receptors are distributed throughout the body and are found in the skin, muscles, joints, and visceral organs.
* ability to sense changes in our external and internal environments is a requirement for maintaining homeostasis and for survival.

Front 2

General Sense Organs

Back 2

* All sense organs must be able to detect stimuli in the environment and conduct the information to the central nervous system for interpretation
* They are widely distributed throughout the body and detect stimuli such as touch, pressure, temperature, position, and pain.
* found mostly in the skin.
* sense organ receptors are often classified according to the type of stimuli that activates them:
1. encapsulated-covered by a "capsule," -
2. unencapsulated-free of any covering - Unencapsulated receptors have naked nerve endings that are free of any covering. They are the simplest, most common, and most widely distributed sensory receptors.
ie. Free nerve ending or Naked nerve ending - sense discriminative touch, tickle, temperature and pain,

Front 3

proprioceptors

Back 3

* specialized receptors found near the point of junction between tendons and muscles and others found deep within skeletal muscle tissue
* located in muscles
* When stimulated, they provide us with information concerning the position or movement of the different parts of the body as well as the length and the extent of contraction of our muscles.

Front 4

Converting a Stimulus into a Sensation

Back 4

* The sense organs must be able to sense or detect stimuli in their environment.
* Each sense organ contains specific receptors that detect different types of stimuli.
* Receptors produce (change into) an electrical signal or nerve impulse.
* This impulse is conducted by a sensory nerve (transmitted over a nervous system pathway) to the appropriate area of the brain, where the sensation is perceived and interpreted.

Front 5

General Sense receptors (organs)

Back 5

* encapsulated-covered by a "capsule,"
* nerve endings that have some type of connective tissue capsule surrounding their terminal or dendritic end.
* located at the tips of dendrites of sensory neurons.
1. Pacinian corpusle or Lamellar (Pacini) corpuscle - sense pressure and high-frequency vibration
2. Krause's end bulb or Bulboid (Krause) corpuscle - sense touch and possibly cold
3. Meissner's corpusle or Tactile corpuscle - sense touch and low frequency vibration
4. Muscle spindle - sense proprioception (sense of muscle length)
5. Ruffini's corpusle (Ruffini ending) or Bulbous corpuscle - sensetouch and pressure
6. Golgi tendon receptor - sense proprioception (sense of muscle tension)

Front 6

Special Sense Organs

Back 6

* tongue, nose, eye, and ear
* Large complex organs or localized groupings of specialized receptors in areas such as the nasal mucosa or tongue
* five special senses:
1. sight
2. hearing
3. smell
4. taste
5. balance
ie. eye, ear, nose and taste buds.

Their receptors are groups of highly specialized and localized cells that are typically associated with each sense.
Specialized receptors include:
Chemoreceptors
Photoreceptors
Mechanoreceptors

Front 7

Chemoreceptors

Back 7

* a Specialized sense organ receptor
* Chemoreceptors respond to chemical stimuli. These sensory receptors are stimulated by the chemical concentration of substances.
* Gustatory cells, smell, olfactory cells, taste
* other chemical receptors are located in the aorta and other arteries
*ie. nose - olfactory cells - smell & taste buds - gustatory cells - taste

Front 8

Photoreceptors

Back 8

* a Specialized sense organ receptor
* Photoreceptors respond to light stimuli. They are located in the retina of the eye and are known as the rods and cones.
* Photoreceptors account for nearly 70 percent of the sensory receptors in our body.
ie. eye -rods and cones - vision

Front 9

Mechanoreceptors

Back 9

* a Specialized sense organ receptor
* Mechanoreceptors respond to mechanical stimuli.
* These sensory receptors are stimulated by changes in pressure or movements of body fluids.
ie. ear - organ of Corti (spiral organ) - hearing & ear - Cristae ampullares - balance

Front 10

Taste

Back 10

* The sense of taste is the gustatory sense.
* Chemoreceptors (gustatory cells) on the tongue are sensitive to the chemicals in our food and pick up the sensations that allow us to enjoy our meals.
* When the chemoreceptors are stimulated, the impulses travel along the facial (VII) and glossopharyngeal (IX) cranial nerves to the appropriate areas of the brain such as the parietal and temporal lobes of the cerebral cortex.

Four basic taste sensations are concentrated on a particular area of the tongue:
1. Bitter
2. Sour
3. Salty
4. Sweet

Front 11

smell

Back 11

* chemoreceptors for the sense of smell are the olfactory receptors (olfactory cells).
* After the olfactory cells are stimulated by odor-causing chemicals, the resulting nerve impulse travels through the olfactory nerve in the olfactory bulb and tract and then enters the thalamic and olfactory (sensory processing) centers of the brain where the impulses are interpreted as specific odors.
* pathways and location of olfactory nerve impulses are closely associated with the areas of the brain that are imortant to memory and emotion.

Front 12

pain receptors

Back 12

receptors that respond to physical damage or injury

Front 13

thermoreceptors

Back 13

receptors that respond to temperature

Front 14

two-point discrimination

Back 14

* the ability to distinguish one touch stimulus from two
* lesions to the parietal lobe of the brain will impair two-point discrimination
* neurologist test - touch two different parts of the skin at the same time to see if both parts can be felt.

Front 15

touch receptors

Back 15

* located in the skin
* fingertips - 2 - 8 mm apart, distributed closely together
* palms - 8 - 12 mm apart - relatively close together
*back of the torso - 40 - 60 mm apart - quite far apart

Front 16

stretch receptors

Back 16

* located deep in the stomach - signals when you are full
* stretch (pressure) receptors - in most hollow organs of the body

ie. stomach, intestines, arteries, vagina (birth canal), and urinary bladder that enable normal functioning of the organ

Front 17

disruption of general sense organs

Back 17

* can occur by burns, diabetes, cardiovascular disease, stroke, spinal cord or brain injury or disease
* occurs from crossing legs tightly (falls asleep)
* occurs when blood flow to the organ is slowed

Front 18

eye structure

Back 18

* designed to ensure that light is transmitted successfully to photoreceptors and the brain for interpretation.
* Photoreceptors account for nearly 70 percent of the sensory receptors in our body.
* Accessory structures such as the eyebrow, eyelid, eyelashes, the lacrimal apparatus that secretes and drains tears, and the extrinsic eye muscles serve us by protecting and assisting the eye to perform its functions effectively

Front 19

anatomy of the Eye

Back 19

* eye is shaped like a sphere and is approximately one inch in diameter.
* The tough, white outer layer of the eyeball is the sclera.
* The middle layer is a soft, blood-rich, nourishing layer, known as the choroid. (Two involuntary muscles make up the front part of the choroid: the iris and the ciliary muscle.)
* The innermost layer around the sides and back of the eye is the retina.
* At the front of the eye is the clear, dome-shaped cornea, through which light rays enter. Light then passes through the pupil, which is a hole in a ring of muscle known as the iris, or colored portion of the eye.
* Next, the light rays pass through the bulging lens and are bent or focused to form a clear picture on the retina. The lens is held in place by suspensory ligaments that extend from the ciliary body (ciliary muscle) and blend with the capsule of the lens.
* In the anterior cavity in front of the lens is a watery fluid known as the aqueous humor, which is constantly being formed, drained, and replaced. The bulk of the eyeball is filled with a clear jellylike substance called vitreous humor.

Front 20

Retina

Back 20

* The retina layer contains the photoreceptors known as rods and cones, which detect patterns of light rays and convert them to nerve signals or nerve impulses.
* The nerve signals then travel along the optic nerve to the brain. No rods or cones are present in the area of the retina where the optic nerve fibers exit. The result is a "blind spot" known as the optic disc.
* Damage to the retina impairs vision because even if an image is in focus, damage to rods or cones located on the retina can interfere with proper vision

Front 21

choroid

Back 21

* The middle layer of the eye is a soft, blood-rich, nourishing layer,
* contains a dark pigment that prevents the scattering of incoming light rays
* front part of the choroid is made from two involuntary muscles; the iris and the ciliary muscle
* choroid coat - the dark pigmented middle layer of the eye that prevents the scattering of incoming light.

Front 22

cornea

Back 22

* At the front of the eye is the clear, dome-shaped through which light rays enter.
* "window of the eye"
* covered by thin membrane that may be damaged by foreign objects, chemical irritants, or trauma.
* contains rods and cones - rods are receptors for night vision, cones are receptors for daytime.

Front 23

pupil

Back 23

* where light enters the eye and is then refracted
* a black hole in the center of the iris (or colored portion of the eye)
* the pupil dilates when the spoke like fibers of the iris contract letting in more light rays - in dim light
* the pupil contracts (constricts) when the circular fibers of the iris contract letting in fewer light rays - in bright light

Front 24

iris

Back 24

colored portion of the eye.

Front 25

lens

Back 25

* light rays pass through and are bent or focused to form a clear picture on the retina
* The lens is held in place by suspensory ligaments that extend from the ciliary body (ciliary muscle) and blend with the capsule of the lens.
* lens becomes fatter or thinner to affect the greatest degree of refraction allow to focus close up or far away
* structures on which ciliary muscles pull to help the eye focus

Front 26

suspensory ligaments

Back 26

The suspensory ligaments are strands of tough, fibrous tissue that radiate from the ciliary body of the eye to the lens and hold the lens in place.

Front 27

ciliary body

Back 27

* The ciliary body is a section of the eye formed by a thickening of the choroid that fits like a collar into the area between the anterior margin of the retina and the posterior margin of the iris.
* The ciliary muscle is composed of both radial and circular smooth muscle fibers and lies in the anterior part of the ciliary body.

Front 28

aqueous humor

Back 28

In the anterior cavity (anterior chamber) in front of the lens is a watery fluid known as the aqueous humor which is constantly being formed, drained, and replaced

Front 29

vitreous humor

Back 29

The bulk of the eyeball is filled with a clear jellylike substance (thick) called vitreous humor

Front 30

lacrimal

Back 30

a gland that forms tears in the eye

Front 31

optic disk (optic nerve head)

Back 31

* the location where ganglion cell axons exit the eye to form the optic nerve
* There are no light sensitive rods or cones to respond to a light stimulus at this point
* This causes a break in the visual field called "the blind spot" or the "physiological blind spot"
* represents the beginning of the optic nerve and is the point where the axons of retinal ganglion cells come together
* also the entry point for the major blood vessels that supply the retina

Front 32

optic nerve (cranial nerve 2)

Back 32

* transmits visual information from the retina to the brain

Front 33

posterior chamber

Back 33

* a narrow space behind the peripheral part of the iris, and in front of the suspensory ligament of the lens and the ciliary processes
* consists of small space directly posterior to the iris but anterior to the lens

Front 34

macula lutea

Back 34

* "spot" "yellow"
* an oval-shaped highly pigmented yellow spot near the center of the retina of the human eye
* contains the parafovea and perifovea
* contains cones only, no rods

Front 35

fovea (fovea centralis)

Back 35

* meaning pit or pitfall
* part of the eye, located in the center of the macula region of the retina
* responsible for sharp central vision which is necessary in humans for reading, watching, driving

Front 36

anterior chamber

Back 36

The anterior chamber (AC) is the fluid-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium.

Front 37

Visual Pathway of light

Back 37

* Light enters the eye and progresses through a series of structures until it is bent or refracted so that it focuses on the retina
* The innermost layer of the retina contains photoreceptors (rods and cones) that respond to light stimuli by producing nervous impulses
* The photoreceptor cells synapse with neurons in the bipolar and ganglionic layers of the retina
* Nervous signals eventually leave the retina through the optic disc and form the optic nerve, which eventually travels to the visual cortex of the occipital lobe. It is here that visual interpretation occurs.
1. enters in the transparent cornea
2. aqueous humor
3. pupil
4. lens - refraction
5. vitreous humor
6. retina then cones and rods - which produces a nervous impulse
7. optic nerve
8. brain
9. visual cortex of the optic lobe
10. visual interpretation

Front 38

processes for vision

Back 38

Three processes are necessary for vision:
* Refraction
* Stimulation of rods and cones
* Conduction of nerve impulses to the brain

Front 39

Refraction Visual Disorders

Back 39

* Anything that disrupts Refraction, Stimulation of rods and cones, or Conduction of nerve impulses to the brain processes naturally impacts our vision either temporarily or permanently

Front 40

Refraction visual disorders are common and include:

Back 40

* Myopia
* Hyperopia
* Astigmatism
* Presbyopia
* Cataracts

Front 41

Myopia (nearsightedness)

Back 41

* If our eyes are elongated, the image focuses in front of the retina instead of on it. The retina receives only a fuzzy image, and as a result, only near objects can be seen.
* Treatment is Radial Keratotomy (RK)

Front 42

Hyperopia (farsightedness)

Back 42

If our eyes are shorter than normal, the image focuses behind the retina. The retina receives a fuzzy image, and as a result, only far objects can be seen.

Front 43

Astigmatism

Back 43

a distortion caused by an irregularity of the cornea or lens. One part of the cornea or lens is usually flatter than another part, resulting in an uneven refraction of light waves and an image that cannot be properly focused on the retina.

Front 44

Presbyopia (oldsightedness)

Back 44

Adults usually use reading glasses to compensate for this common form of farsightedness that occurs during the aging process.

Front 45

Cataracts

Back 45

* Cataracts can cause focusing problems as a result of cloudy spots that develop in the eye's lens.
* Most cataracts are caused by degenerative changes, most often occurring after 50 years of age.
* The condition is treated by lens implant surgery.

Front 46

Other Visual Disorders

Back 46

* involve the stimulation of rods and cones and the conduction of nerve impulses to the brain.
* involve damage or degeneration in the optic nerve, the brain, or any part of the visual pathway between them that can impair vision.

Some examples of diseases caused by these two disorders are:
* Disorders of the retina
* Disorders of the visual pathway

Front 47

Disorders of the retina

Back 47

* Retinal detachment is often due to aging, eye tumors, or head trauma.
* Diabetic retinopathy occurs from hemorrhages and growth of abnormal vessels associated with diabetes mellitus (a disorder involving the hormone insulin)
* Glaucoma is excessive intraocular pressure caused by abnormal accumulation of aqueous humor. As the fluid increases, blood flow through the retina is decreased, causing retinal degeneration and a loss of vision.
* Macular degeneration is a progressive degeneration of the central part of the retina leading to blindness. it is the leading cause of blindness in the elderly.
* color blindness - inherited caused by genes on the X chromosome that produce abnormal photopigments in the cones. usually deficient in green or red sensitive photopigment.

Front 48

Disorders of the visual pathway

Back 48

* Degeneration of the optic nerve resulting from diabetes, glaucoma, and other causes can impair vision.
* Strokes can damage visual processing centers and impair vision.
* Scotoma is the loss of the central visual field when certain nerve pathways are damaged.

Front 49

Surgical Treatments for Visual Disorders

Back 49

* Radial keratotomy (RK), a surgical procedure to treat myopia, involves the surgical placement of six or more radial incisions in a spokelike pattern around the cornea. As a result, the cornea flattens and the ability to focus improves.

* Laser thermal keratoplasty (LTK) is a laser surgery most recently approved by the FDA for treating hyperopia. During this procedure, ultra-short bursts of laser energy are used to reshape the surface of the cornea. No surgical incision is necessary.

Front 50

Nyctalopia

Back 50

Night Blindness

Front 51

Trachoma

Back 51

chronic chlamydial infection

Front 52

Strabismus

Back 52

* convergence disorder of the eyes
* an improper alignment of the eyes; can cause them to converge (cross)

Front 53

corneal ulcers

Back 53

can develop from wearing contact lenses that are dirty of left in longer than intended

Front 54

palpebral fissue

Back 54

* the opening outlined by the eyelash lined upper and lower eyelids
* significant changes to the size can be a sign of endocrine or nervous system disease.

Front 55

lacrimal caruncle

Back 55

* Pink part in the corner of the eye
* glandular structure located at the medial angle
* lacrimal caruncle and the sebaceous secreting tarsal (or meibomian) glands, which line the inner surface of the eyelids, can sometimes become infected frequently with staphylococcal organisms.
* common infections involves the hair follicles of the eyelashes

Front 56

medial angle

Back 56

the junction of the upper and lower lids near the nose

Front 57

conjunctiva

Back 57

* a mucus membrane that lines the underside of the eyelids and covers the sclera in the front.
* kept moist by tears formed in the lacrimal gland located in the upper lateral portion of the orbit.

Front 58

rods and cones

Back 58

* in the retina
* rods are receptors for night vision, absent in the fovea and macula but found in increasing numbers near the periphery of the retina.
* cones are receptors for daytime and red, green and blue color vision; less numerous and more densely concentrated in the fovea.
* no rods or cones in the optic disc area of the retina

Three types of cones each is sensitive to a different color: red, green, or blue. These cones allow us to distinguish between different colors.

Front 59

opthalmoscope

Back 59

used to examine the retinal surface (or fundus) and internal eye structures.
can also see the optic disc and the retinal blood vessels

Front 60

shaken baby syndrome

Back 60

characteristic of multiple hemorrhages of the retina

Front 61

conjunctivitis

Back 61

* infection starting at the conjunctiva, producing an inflammation response
* pink eye
* can be caused by the bacteria chlamydial conjunctivitis or trachoma
* drainage or mucus pus is commonly caused by staphylococcus and haemophilis.
* can produce lesions on the eyelid tat can damage the cornea and impair vision.

Front 62

subconjunctival hemmorrhage

Back 62

trauma to the eye that may cause bleeding below the conjunctiva

Front 63

depth perception

Back 63

* the visual ability to perceive distance of an object

Front 64

strabismus or squint

Back 64

* the positioning of the eyes cannot be coordinated to focus on the same thing.
* usually the brain will compensate for the missing or unusual elements in the visual field
* an improper alignment of the eyes; can cause them to converge (cross)
* usually caused by paralysis, weakness, or other abnormality affecting the external muscles of the eye.

Front 65

divergent squint

Back 65

the eyes may diverge outward to the side

Front 66

convergent squint or cross-eye

Back 66

if one or both eyes converge toward the nose

Front 67

color blindness

Back 67

* inherited caused by genes on the X chromosome that produce abnormal photopigments in the cones
* usually deficient in green or red sensitive photopigment
* can see different colors but can not distinguish between the colors.
* more common in men than women
* not considered a clinical disease

Front 68

ear

Back 68

* the organ of hearing or organ of Corti
* necessary to maintain our sense of equilibrium. * Hearing is the result of sound vibrations initiating impulses that are transmitted to the temporal lobe of the brain via the eighth cranial nerve for interpretation of the sound.
* Both of these senses are detected by mechanoreceptors that are located deep within the ear.

The ear is divided into three main parts, each of which plays a vital role in transmitting sounds so that we can hear successfully:
* External ear
* Middle ear
* Inner ear

Front 69

external ear

Back 69

* has two parts: the auricle (pinna) (top of the ear) and the external acoustic canal or external acoustic meatus.
* Located in the external ear are short hairs and ceruminous glands that produce a waxy substance called cerumen.
* Cerumen may collect in the canal and impair hearing by absorbing or blocking the passage of sound waves.
* has structures that allow it to successfully move sound waves along the canal and forward to the areas necessary to interpret the sound waves.
* the external ear ends at the tympanic membrane according to the book.

Front 70

middle ear

Back 70

* has three very small bones collectively known as the ossicles.
* These bones describe their shape and are known as the malleus (hammer), incus (anvil), and stapes (stirrup)
* The eustachian or auditory tube connects the throat with the middle ear, explaining the frequent spread of infection from the throat to the ear.
* has structures that allow it to successfully move sound waves along the canal and forward to the areas necessary to interpret the sound waves.

Front 71

inner ear

Back 71

* consists of three spaces in the temporal bone assembled in a complex maze called the bony labyrinth
* It is filled with a watery fluid called perilymph and contains the vestibule, semicircular canals, and cochlea
* The vestibule constitutes the central section of the bony labyrinth that is filled with a thick fluid called endolymph.
* The sense organs for equilibrium are located in the semicircular canals, and the cochlea (snail shaped) contains the "organ of Corti", sometimes referred to as the "organ of hearing."
* semicircular canals contain receptors
* has structures that allow it to successfully move sound waves along the canal and forward to the areas necessary to interpret the sound waves.
* Impulses are transmitted from the inner ear to the brainstem by way of the cochlear nerve

Front 72

tympanic membrane (eardrum)

Back 72

* partition between the external and middle ear
* passageway leading to the tympanic membrane is the external acoustic canal.

Front 73

crista ampullaris

Back 73

* receptor located within the semicircular canals
* generate nerve impulses when you move your head
* Sensory cells in the cristae ampullaris have hairlike extensions that are suspended in the endolymph and are stimulated during head movement. This, in turn, causes the hairs to bend and send the impulse through the vestibular nerve to the brain. Eventually the impulse reaches the cerebellum and medulla.

Front 74

endolymph

Back 74

fluid that fills the bony labyrinith

Front 75

Pathway of Sound Waves

Back 75

* Sound waves flow into the outer ear and pass along a narrow tube, the external auditory canal or ear canal causing the tympanic membrane to vibrate then travel to a small patch of elastic skin at its end, the eardrum. The sound waves bounce off the eardrum and produce vibrations.

* The eardrum is connected to a row of three tiny bones linked together: the malleus (hammer), incus (anvil), and stapes (stirrup). The vibrations pass along these bones until the stirrup presses against the oval window. The vibration of the membrane of the oval window causes the perilymph in the bony labyrinth of the cochlea to move, which causes the endolymph of the cochlear duct to move.

* The cochlea is a small, fluid-filled, snail-shaped organ deep inside the ear. The vibrations flow as ripples into the fluid inside the cochlea. Here, they bend thousands of tiny hairs (organ of Corti) that emerge into the fluid from hair cells. As the hairs bend, the hair cells create nerve signals that go along the cochlear nerve to the eighth cranial nerve and on to the auditory cortex of the temporal lobe, where they are interpreted as sound.

Front 76

Balance and Equilibrium

Back 76

* Mechanoreceptors for balance are located within the vestibule and semicircular canals of the inner ear.
* Each canal is surrounded by perilymph and contains endolymph
* The receptors are called cristae ampullaris, and they generate nerve impulses when you move your head.
* Sensory cells in the cristae ampullaris have hairlike extensions that are suspended in the endolymph and are stimulated during head movement. This, in turn, causes the hairs to bend and send the impulse through the vestibular nerve to the brain. Eventually the impulse reaches the cerebellum and medulla.

Front 77

Hearing Disorders

Back 77

Hearing disorders usually fall into one of two categories:
* Conduction impairment - refers to the blockage of sound waves as they travel through the external and middle ear to the sensory receptors of the inner ear (the conduction pathway)
* Nerve impairment - results in insensitivity to sound because of inherited or acquired nerve damage.

Front 78

Otosclerosis

Back 78

* Conduction impairment
* inherited disorder that impairs the conduction ability of stapes
* usually appears during childhood or early adulthood as tinnitus

Front 79

Otitis Media

Back 79

* Conduction impairment
* middle ear infection
* untreated otis media can lead to Mastoiditis

Front 80

External otitis

Back 80

* Conduction impairment
* Swimmer's ear

Front 81

Presbycusis

Back 81

* Nerve impairment
* hearing loss due to aging

Front 82

Tinnitus

Back 82

* Conduction impairment
* ringing in the ear

Front 83

Meniere's disease

Back 83

* Nerve impairment
* Chronic ear disease of unknown cause that results in nerve damage and loss of hearing
characterized by tinnitus and vertigo a sensation of spinning

Front 84

tophi

Back 84

small nodules filled with uric acid appear on the upper edge of the helix in people who have gout.

Front 85

dawin tubercle

Back 85

nodule found on the helix, its considered a variation of normal and requires no treatment.

Front 86

otoscope

Back 86

used to examine the external ear canal and outer surface of the tympanic membrane.

Front 87

Fungiform Papillae

Back 87

* mushroom shaped papillae (projections) on the tongue
* They are located on the top (dorsal) surface of the tongue, scattered throughout the filiform papilla but mainly at the tip and lateral margins of the tongue
* They have taste buds on their superior (upper) surface which can distinguish the five tastes: sweet, sour, bitter, salty, and umami
* They have a core of connective tissue.
* They are innervated by the seventh cranial nerve,

Front 88

foliate papillae

Back 88

* short vertical folds found on the lateral margins of the tongue
* Taste buds, the end-organs of the gustatory sense, are scattered over the mucous membrane of their surface
* Serous glands drain into the folds and clean the taste buds.

Front 89

palatine tonsil

Back 89

* occasionally called the faucial tonsils
* are the tonsils that can be seen on the left and right sides at the back of the throat.

Front 90

circumvallate papillae (or vallate papillae)

Back 90

* dome-shaped structures on the human tongue that vary in number from eight to twelve.
* situated on the dorsum of the tongue immediately in front of the foramen cecum and sulcus terminalis, forming a row on either side; the two rows run backward and medially, and meet in the midline
* Each papilla consists of a projection of mucous membrane from 1 to 2 mm. wide

Front 91

lingual tonsil

Back 91

* rounded masses of lymphatic tissue that cover the posterior region of the tongue.
* Their lymphatic tissue are dense and nodular, their surface is covered with stratified squamous epithelium which invaginates as a single crypt into each lingual tonsil.
* They are partially surrounded by connective tissue placing them in the group of Partially Encapsulated Lymphatic Organs, tonsils, the only one of its kind.

Front 92

Tonsillitis

Back 92

* an inflammation of the tonsils and will often, but not necessarily, cause a sore throat and fever. In chronic cases tonsillectomy may be indicated