12.2 The Sense Organs Flashcards
The special senses have sense organs that contain the receptors for stimuli:
- eye
- ear
- nose
- taste buds
organ of sight and vision
eye
organ of hearing
ear
organ of smell
nose – olfactory
organ of taste
taste buds – gustatory
It is spherical in shape except anteriorly where it bulges forward
Eye
It measures about 1 inch in diameter
Eye
fill the cavity of the eyeball
Refracting Media
They are transparent so that light may pass through them to reach the retina
Refracting Media
Their function is to change the direction of the light waves so as to focus the image on the inner surface of the retina
Refracting Media
Refracting Media
- Cornea
- Vitreous body
- Lens
- Aqueous humor
is the point of crossing of the medial nerve fiber
Optic chiasma
It resembles the letter “X” a letter in the Greek alphabet called chi
Optic chiasma
are two bundles of nerve fibers that emerge from the optic chiasma and pass obliquely across the cerebral peduncles to enter the brain
Optic tracts
Extrinsic Muscles of the Eye
o Superior rectus o Inferior rectus o Medial rectus o Lateral rectus o Superior oblique muscle o Inferior oblique muscle
upper and lower protect the eyes and cover them during sleep
eyelids
eyelids parts
- Medial canthus
* Lateral canthus
squint or crossed eyes is a condition in which both eyes do not move in the same direction at the same time
Strabismus
is a thin transparent membrane that covers the inner surface of each eyelid, and is reflected over the anterior surface of each eyeball
Conjunctiva
is a special radiographic test to see if there is blockage of the tear canals
dacrocystography
Responsible for the formation, circulation, disposal of tears
Lacrimal Apparatus
has a lacrimal gland with its excretory ducts, 2 lacrimal ducts, a lacrimal sac, and nasolacrimal duct
eye
is the organ of hearing and equilibrium
ear
It is contained within the petrous part of the temporal bone. In sound waves are transformed into nerve impulses
ear
Auditory ossicles
- Malleus or hammer
- Incus or anvil
- Stapes or stirrup
an infection of the middle ear
Otitis media
an infection of mastoid cells
Mastoiditis
smell
Olfactus
are tufts of hairs in the lining membrane of the upper part of each nasal cavity
Receptors or endorgans
are the expanded anterior ends of the two olfactory tracts, two club-shaped structures that lie on the inferior surface of the frontal lobes of the cerebrum
Olfactory bulbs
Gustatory Organs
Organs of Taste
to taste, hence gustation and gustatory
Gustatio
are minute elevations on the tongue that are the cause of roughness of this organ
papillae
nipple or nipplelike
Papilla
are oval shaped bodies located on the sides of the papillae
taste buds
They have elongated central cells with hair at their surfaces
taste buds
covers the posterior five-sixths of the eyeball, and is white
Sclera
covers the remaining one-sixth of the eyeball.
Cornea
This layer is transparent
so that light may pass through it.
Cornea
is rich in blood vessels
The Vascular coat or middle layer
includes the posterior two-thirds of this middle layer
Choroid covering
a thickened ring of tissue that encircles the eyeball in front of the
choroid proper.
Ciliary body
Contains the ciliary muscles. This muscle regulates the covexity
of the lens by pulling on the suspensory ligament attached to the lens.
Ciliary body
is a colored membrane that surrounds the pupil
Iris
It is attached along its
outer margin to the ciliary body
Iris
Pigment in the ___ determines the color of the eyes
iris
is the circular opening in the center of the colored iris, and appears black
Pupil
the inner coat
retina
made of rods and cones
Visual layer
is a yellow spot on the posterior and inner surface of the retina opposite the pupil
Macula lutea
It is composed of cones with no rods and is the most sensitive area of the retina to light
Macula lutea
is a small depression at the center of the macula, opposite
the pupil and very sensitive to light
Fovea centralis (central pit)
is a small circular area on the inner surface of the retina where
the optic nerve enters the retina. It has neither rods nor cones
Blind spot or optic disc
lies posterior to the cornea in the anterior part of the eyeball. It is a
thin clear fluid
Aqueous humor
lie vertically in the anterior part of the eyeball, behind the iris
and the aqueous humor
lens and its capsule
is a transparent jellylike material that fills the cavity behind the
lens
Vitreous humor or body
is the point at the medial border of the eyeball
where the upper and lower eyelids meet
Medial canthus or internal canthus
is the point where the upper and lower eyelids
meet at the lateral margin of the eye
Lateral canthus or external canthus
lies behind the outer part of the supraorbital margin of the orbit
Lacrimal gland
one for each eyelid begin as small openings on the free margins of the
eyelids close to their medial ends and joins the lacrimal sac close to the nose
Lacrimal ducts
passes down in the nasolacrimal groove and opens into the nasal
cavity
Nasolacrimal duct
is a trumpetlike cartilaginous part that protrudes from the side of the head. It helps to direct sound waves into the ear canal
auricle or pinna
is the canal extending from the opening in
the auricle to the ear drum. It is about 2.5 cm (1 inch) in length. It is lined with skin that
contains modified glands – ceruminous glands – that secrete wax into the canal
external acoustic meatus (OT. Auditory)
is a small hollow space between
the external and internal ear. It is filled with air and contains three minute bones, the auditory
ossicles
middle ear, auris media, (tympanic cavity)
is a thin membrane stretched across the opening
between the inner end of the external acoustic meatus and the middle ear
Tympanic membrane – or ear drum
are three very minute bones in the middle ear
Auditory osscles
is attached by its handle to the inner surface of the
tympanic membrane
Malleus – or hammer
is attached at one end to malleus, by its other end to the stapes
Incus – or anvil
extends from the incus to an opening into the inner ear,
the vestibular opening or the fenestra ovalis, this opening is closed by the
footpiece of the stapes
stapes – or stirrup
of the auditory tube is its opening into the middle ear
Tympanic opening
is an opening from the middle ear
into this cavity or antrum
Aditus of the mastoid or tympanic antrum
Aditus of the mastoid or tympanic antrum also called
aditus and antrum
is located
between the middle ear and cochlea of the internal ear
Fenestra rotunda – or round opening or cochlear opening
is located between the
middle ear and vestibule of the internal ear
Fenestra ovalis – or oval opening or vestibular opening
lies medial to the middle ear
Internal ear (labyrinth)
a maze or complicated series of communicating cavities
labyrinthos
is a small cavity with walls of bone lying between the semicircular
canals and the cochlea is in front of the semicircular behind it
bony labyrinth
are curved passages within the petrous bone, each
forming more than a half circle, and shaped like the letter “C”. They open at
each end into the vestibule
three semicircular canals
consists of a spiral passage or canal similar to a spiral staircase,
with almost three complete turns. It has a central core of bone, the modiolus,
around which the windings are built
cochlea
is contained within the body labyrinth and has a
membranous covering that separates it from the osseous labyrinth
Membranous Labyrinth
fluid that surrounds the bony wall
Perilymph
fluid that fills the ducts and sacs
Endolymph
one inside of each semicircular canal, have five openings into
the utricle within the vestibule
Three semicircular ducts
lies within the spiral bony cochlea and follows its course from base to
apex
Cochlear duct
forms the floor of the cochlear duct
Basilar membrane
a gelatinous membrane that covers the hair
Tectorial membrane
is a small membranous sac in the vestibule of the bony labyrinth
Utricle
is a smaller membranous sac in the vestibule
Saccule