Chapter 17: Special Senses Flashcards
Meibomian Glands
Produce an oily secretion
Ciliary Glands
Modified sweat glands between the eyelashes.
Conjunctiva
A transparent membrane that lines the eyelids as the palpebral conjunctiva. Covers the whites of the eyes as the ocular conjunctiva. Lubricates and protects the eye.
Lacrimal Apparatus
Consists of the lacrimal gland and associated ducts
What does lacrimal glands secrete?
Tears, which contain mucus, antibodies, and lysozyme.
Enter via excretory ducts
Exit via lacrimal punctum
Drains into nasolacrimal duct
How many muscles surround the eye?
6 muscles
Four recuts muscles
Two oblique muscles
Accessory structures of the eyes.
Eyebrows, eyelids, conjunctiva, extrinsic muscles
Lens
a biconvex transparent, flexible, avascular structure. Allows precise focus of light onto the retina.
Three tunics
Fibrous- outside layer
Vascular tunic- middle layer
Sensory tunic- inside layer
Sclera
White connective tissue, “ white of the eye”
Cornea
Transplant, central anterior portion. Allows for light to pass through.
Repairs itself easily.
Vascular Tunic (Uvea)
Has three regions, choroid, ciliary body and iris.
Choroid Region
A dark brown membrane that forms the posterior portion of the uvea. Supplies blood to all eye tunics.
Ciliary Body
A thickened ring of tissue surrounds the lens.
Smooth muscles
Anchors suspensory ligaments that hold the lens in place.
Changes the shape of the lens for near or far vision
Iris
Pigmented part of the eye- responsible for the color of the eye.
Pupil
The central opening of the iris. Regulates the amount of light entering the eye
Sensory Tunic (Retina)
Two-layered membrane.
Pigmented layer of Retina
Outer layer that absorbs light and prevents it from scattering.
Neural Layer of the Retina
Contains the photoreceptors- rods and cons.
How do the signals pass?
Two neuron chain, bipolar neuron to ganglion cells.
Rods
Found on the edges of the retina. Sensitive to dim light and best suited for night vision. Black and white vision
Cones
Found in the center of the retina. Bright light for activation of color vision Three cones, blue red and green
Fovea Centralis
Center of the visual field, area of the retina with only cones. High visual acuity.
Optic Disk
No photoreceptors are not found here
What separates eye into anterior and posterior chambers?
lens
Posterior Segment
Filled with a clear gel called vitreous humor.
Vitreous humor
Transmits light, supports the posterior surface of the lens, holds the neural retina firmly against the pigmented layer, and contributes to intraocular pressure.
Anterior Segments is composed of two segments-
Anterior- between the cornea and the iris
Posterior- between the iris and the lens.
Glaucome
Excessive production of aqueous humor
Accommodation
Changing the lens shape by ciliary muscles to increase the ability of the lens to bed light rays (refractory power)
Constriction
The pupillary reflex constricts the pupils to prevent divergent light ray from entering the eye
Convergence
Medial rotation of the eye balls toward the object being viewed.
Emmetropia
Normal vision
Myopia or nearsightedness
Light rays from distant objects fall in front of the retina. Light rays from near objects are focused correctly. Corrected with a concave lens.
Hyperopia or farsightedness
Light rays from near objects fall behind the retina.
Light rays from distant objects are focused correctly. Corrected with a convex lens.
Visual pathways
-Photoreceptors of the retina
- Optic nerve
- Optic nerve crosses at the optic chiasma
-Optic tracts
-Thalamus
-Visual cortex of the occipital lobe.
The ear is divided into three areas.
Outer ear, middle ear, and inner ear.
External ear
Involves hearing only
Pinna (auricle)
Exterior part of the ear, is the earlobe.
External auditory canal
Narrow chamber in the temporal bone, Lined with skin. Ceruminous (wax) glands are present.
Where does the external ear end?
Tympanic membrane.
Tympanic membrane
Thin connective tissue membrane that vibrates in response to sound. Transfers energy to ossicles.
Sound waves turn into…
Mechanical energy
Middle ear or tympanic cavity
only involved in hearing
The tympanic or middle ear cavity connect to the throat via
pharyngotypanic or auditory (eustachian) tube
Function of the pharyngotympanic or auditory (eustachian) tube.
Allows for equalizing pressure during yawning or swallowing. Otherwise this tube will collapse.
Three bones in the middle ear
Malleus (hammer)
Incus (anvil)
Stapes (strirup)
What is the function of the 3 ossicles?
Transfer sound to the inner ear.
Stapes will cause fluid vibration on the oval window.
Inner ear
Sense organ for hearing and balance.
What are the bony chambers of the inner ear?
Cochlea, vestibule and semilunar canals.
What is the receptor for hearing?
Hair cells on the basilar membrane. It is a gel-like membrane capable of bending hair cells.
How are these impulses transmitted?
Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal bone.
Organs of equilibrium
Semicircular canals and vestible.
Semicircular canals
Filled with fluid called endolymph.
Crista ampullaris - a tuft of hair cells
Patch of receptor that detect body motion. A sensory neuron wraps around the base of each receptor.
Vestibule
Bony structure between the semilunar canals and cochlea.
Two fluid chambers.
Mechanoreceptors and small pieces of bones.
Sensory neurons wrap around the base of each mechanoreceptor.
Semicircular canals and movement
Detection of rotational movement of the head.
Causes endolymph to move, stimulates receptors which then excite sensory neurons that send impulses to midbrain.
Vestibule and movement
Head movement is detected by the ear stones. When head tips forward of backward they move. Stimulates receptors, send impulses to midbrain.
Taste has what kind and how many receptors ?
Chemoreceptors and four types
Location of taste buds
Tongue, fost palate and cheeks
Filiform papillae
Sharp with no taste buds
Fungiform
Rounded with taste buds
Circumvallate papillae
large papillae with taste buds
Gustatory Cells
Have long microvilli
Stimulates by chemicals dissolved in saliva.
What cranial nerves receive the taste bud signals?
Facial, glossopharyngeal nerve and vagus
What are the basic flavors
Sweet, sour, bitter , salty and umani.
