Vision, hearing and equilibrium Flashcards
Eyelids
- Aka palpebrae
- Continuation of the skin
- Continual blinking keeps eye surface lubricated and removes dust and debris
- can close firmly to protect eye
Palpebral Conjunctiva
-Covers inner surface of eyelids
Ocular conjunctiva
- Covers anterior surface of the eye
- Continuous with delicate corneal Epithelium
Eyelashes
- Long, thick hairs emerging from palpebral margins
- Prevent foreign matter from reaching the eye
- Root hair plexus triggers a blink response
-Tarsal glands Secrete waxy sebum
•keep eyelashes separate from each other
Lacrimal gland
- Daily produces 1ml of watery tears
- Tears lubricate, nourish, oxygenate corneal Cells, attack pathogens (antibodies, enzymes)
Lacrimal puncta
-Two small pores that drain the lacrimal lake
Lacrimal sac
-Small chamber nestled in lacrimal sulcus of orbit
Nasolacrimal duct
-Delivers tears to nasal cavity
The eyes consist of?
- Fibrous tunic
- Vascular tunic
- Neural tunic
Fibrous tunic
- Outermost layer of eye
- Consists of cornea (clear) and sclera (white)
- Functions
1) Supports and protects the eye
2) attachment site for extrinsic eye muscles
3) curvature of the cornea aids in focusing light onto the lens
Cornea
-Allows light to enter eye, so must be transparent and clear
-Dense matrix of multiple layers of collagen fibers
•Organized in way that will not interfere with light passage
-Avascular (no blood vessels to interfere with light passage)
•Receives oxygen and nutrients from tears
Vascular tunic
- Contains many blood vessels, lymphatic vessels, and intrinsic (smooth) muscles of the eye
- Functions:
1) Provides route for blood vessels and lymphatic supplying eye tissues
2) Regulates amount of light entering the eye
3) Secretes and reabsorbs aqueous humor (fluid) circulating in eye chambers
4) Controls shape of the lens (essential part of the focusing process)
Vascular tunic: IRIS
-Colored part of the eye
•Eye color determined by genes that influence density and distribution of melanocytes
-Contains blood vessels, pigment cells, and layers of smooth muscle fibers
•Contraction of muscle fibers changes diameter of pupil
Vascular tunic: Ciliary body and choroid
-thickened region bulging into interior cavity
Ciliary Muscle
-Smooth muscular ring projecting into interior of eye
Ciliary processes
-Secrete aqueous humor
Suspensory ligaments
-Hold the lens in position
Choroid
-Vascular layer covered by the sclera
-Has extensive capillary network
•Delivers oxygen and nutrients to neural tissue in neural layer
Neural tunic or retina
- Innermost layer of the eye
- Outermost pigmented layer
- Attached to choroid
- Absorbs light, protects, nourishes neural layer
- Thick, inner layer (neural part)
- Contains photoreceptors (Cells Sensitive to light)
Macula (spot) or macula lutea
-Area with highest concentration of photoreceptors
Fovea
-Central area (shallow depression) or fovea centralis
•Point of sharpest vision
Optic disk
-Where optic nerve exits retina (blind spot)
Anterior cavity
- Extends from cornea to lens
- Filled with aqueous humor
Posterior cavity
-Main volume of the eye
-Filled with gelatinous vitreous body
•Vitreous humor is fluid part of vitreous body
•Vitreous body does not regenerate
Rods
- Most numerous, highly sensitive (dim light)
- No discrimination among colors
- Density increases toward periphery of retina
Cones
- Provide us with color vision
- Give shaper, clearer images than rods
- Require more intense light
- Less numerous, denser closer to fovea
- Rods and cones synapses with bipolar cells
- Bipolar Cells synapse on ganglion Cells
- Amacrine and horizontal cells help process images
Stereocilia
-80-100 Long (resemble microvilli)
External ear
Visible portion of ear, collects and directs sound waves toward middle ear
Auricle
Composed of elastic Cartilage
External acoustic meatus
-passageway within the temporal bone
Ceruminous glands
Secrete waxy cerumen
Cerumen & hairs provide what?
-provide protection against entering foreign objects, insects, and microorganisms
Auditory tube
- Also called pharyngotympanic tube or eustachian tube
- Connects middle ear to nasopharynx
- Allows equalization of pressure on either side of tympanic membrane
- Can also allow microorganisms to invade and cause infection (otitis media)
Middle ear (or tympanic cavity)
-Air-Filled chamber
Tympanic membrane (tympanum or eardrum)
- Thin, semitransparent sheet
- Separates external ear from middle ear
Auditory ossicles
- Connect tympanic membrane with a receptor complex in the inner ear
- 3 tiny bones (malleus, incus, stapes)
Auditory ossicles details
-Joints between the bones are the smallest synovial joints of body
-Malleus(hammer)
•Attaches to tympanic membrane
-Incus (anvil)
•Attaches malleus to stapes
-Stapes (stirrup)
•Bound to oval window of cochlea
Middle ear muscles
-Tensor tympani Muscle
•Connects malleus to temporal bone
•Contraction stiffens tympanic membrane, reducing amount of vibration
-Stapedius Muscle
•Connects stapes to posterior wall of middle ear
•Reduces stapes movement at oval window
Internal ear
- Contains sensory organs for heating and equilibrium
- Superficial contours are established by layer of dense bone called bony labyrinth (labyinthos, network of canals)
Bony labyrinth
-Shell of Dense bone
-Surrounds and protects membranous labyrinth
-Space between bony labyrinth and membranous labyrinth filled with PERILYMPH
•Liquid closely resembling CSF
- Consists of 3 parts
1) Semicircular canals
2) Vestibule
3) Cochlea
