Sensory Systems Flashcards
What are functions of the ear?
- collect auditory stimuli
- transduce auditory to mechanical and then nervous stimuli
- transmit nerves impulses to the CNS via the vestibulocochlear nerve (CN VIII)
What are the anatomical divisions of the ear and their features?
- external ear: auricle or pinna, external auditory meatus
- middle ear: tympanic cavity,tympanic membrane (eardrum), three auditory ossicles, associated ligaments + muscles. Connected to pharynx via auditory (eustachian) tube
- inner ear: composed of membranous labyrinth enclosed in temporal bone
T/F: the inner ear functions for sound collecting and conducting,while the external and middle ear functions in both hearing and equilibrium
- false;
- the external/middle ear functions for sound collecting and conducting,
- while the inner ear functions in both hearing and equilibrium (vestibular system)
What are the parts of the external ear?
- pinna/auricle
- external auditory meatus: vertical canal, horizontal canal, annular cartilage
What is this structure? What are some features?
- pinna/auricle
What is this structure? What do the various arrows indicate?
- cross section of a ear
- black arrows:annular cartilage
- arrowheads: auricular cartilage
- asterisks: external acoustic meatus
- white arrow: incudostapedius joint
** tympanic membrane removed
What structure is shown? Label the numbers.
What kinds of glands are present in ears? What do they secrete?
- ceruminous glands
- type of apocrine gland
- secrete cerumen (ear wax)
What are features of the middle ear?
- tympanic membrane + cavity
- auditory ossicles
- auditory (eustachian) tube
What feature is shown? What are some features?
- tympanic cavity
What structure is shown? What are the differences between A and B in regards to species and form?
- tympanic membrane
- A; horse; tympanum is more round and the manubrium of the malleus forms a very shallow and and is centrally located to the tympanum
- B; dog; tympanum is oval or comma shaped and the manubrium of the malleus is C-shaped
What is this structure? What are the labeled features?
- tympanic membrane
What is this structure? What species is it found in?
- guttural pouch: ventral expansion of the auditory tube
- horses
What is this structure? What are some features?
What are the parts of the inner ear?
- in petrous temporal bone
- vestibular apparatus
- cochlea
What are the organs of equilibrium and motion detection of the vestibular apparatus? What specialized structures do they contain?
- utricle, saccule, 3 semicircular ducts
- macula utriculi
- macula sacculi
- crista ampularis (sensitive to angular changes in acceleration)
What is the organ of hearing?
- cochlea
What is in the spiral organ of the cochlea?
- hair cells
What is this structure?
- spiral organ/organ of corti
What are features of the maculae?
- maculae that run perpendicular to each other are within the utricle (horizontal) and saccule (vertical)
- otoliths are located within a gelatinous membrane and their movement bends the sterocilia of neurosensory hair cells
- detects static equilibrium and linear acceleration
What are features of the semicircular ducts?
- at the base of the semicircular ducts are ampullae containing a crista ampullaris
- the cupula is gelatinous and movement is detected by stereocilia of neurosensory hair cells
- detects rotational movement
What is this structure? What are labeled features?
What is endolymph?
- fluid within the membranous labyrinth of the inner ear
- high in potassium
- bathes inner ear cells and allows normal function
- large diverticula (sacs) in reptiles possibly involved in calcium homeostasis
What are special features of the endolymphatic system in amphibians and reptiles?
- result in sac-like structures behind eyes
- functions in controlling pressure, fluid, and ion concentration (esp. calcium) homeostasis
- neuroectoderm
What is a special sensory adapation of fish and aquatic amphibians?
- lateral line system
- tactile sense organs: detect movements and pressure changes in surrounding water
What is this structure?
- lateral line organ
What is a special sensory adaptation of snakes? What is its function?
- vomernasal / jacobson’s organ
- smell via taste
What is a specialized chemoreception organ found in mammals and reptiles
- vomernasal
What parts of the eye are ectoderm derived? Mesoderm derived?
- ectoderm
- lens
- outer epithelium of cornea
- epithelium of palpebrae (eyelids)
- mesoderm
- corneal stroma
- sclera
- extraocular muscles
- ciliary muscles
- tunica vasculosa
What part of the eye are neuroectoderm derived?
- neuroectoderm of dienchephalon:
- optic cup connected by optic stalk
- optic cup: retina + pigment layer
- optic stalk: optic nerve
What is the eyeball or globe composed of?
- lens
- 3 layers:
- outer fibrous tunic
- middle vascular (uveal) tunic
- inner retinal (neuroepithelial) tunic
- located in the orbit
What is the adnexa?
- accessory ocular structures
- palpebrae (eyelids)
- third eyelid + conjunctiva
- lacrimal apparatus
What are the tunic layers of the eye?
- fibrous tunic
- sclera
- cornea
- limbus
- vascular (uveal) tunic
- iridocorneal angle
- iris
- ciliary body
- choroid
- neuroepithelial (retinal) tunic
What are features of the sclera?
- part of fibrous tunic
- posterior portion of the eye
- functions:
- protects the eye
- maintains the shape of the eye
- provides insertion points for tendon of extra ocularmuscles
What is this structure? What are some features?
- cornea
- part of the fibrous tunic
- anterior portion of the eye
- avascular and transparent
- richly supplied by sensory nerves (ophthalmic branch of CN V)
- relatively dehydrated to maintain transparency
- large regenerative capacity
- 5 layers
What feature of the eye is this? Label layers
- cornea
- 1: anterior corneal epithelium
- 2: anterior limiting lamina/subepithelial basement membrane, supporting lining epithelium
- 3: substantia propria (corneal stroke, mostly type 1 collagen)
- 4: posterior limiting lamina/membrane; Desemet’s membrane, supporting endothelium
- 5: posterior epithelium/corneal endothelium
What is this structure? Label the numbers. What are some features?
- cornea
- descemet’s membrane in grey
What factors contribute to corneal transparency?
- lack of blood vessels (avascular)
- collagen arrangement
- proteoglycans between collagen
- Na+/K+ ATPase (adenosine triphosphate) and carbonic anhydrase pumps transport water out
- located in anterior + posterior corneal epithelium
What is displayed here?
- corneal ulcer
What are features of the limbus?
- part of fibrous tunic
- corneoscleral junction
- where opaque sclera overlaps the transparent cornea. Area has small blood vessels
- nutrition for the cornea comes from microvasculature of limbus + aqueous humor
What is this structure? Identify some features
- limbus (corneoscleral junction: CSJ)
- region where transparent cornea merges with sclera (S)
- small blood vessels
- epithelium of the limbus is continuous with the conjunctiva (C) that lines the eyelids
- I: iris
- AC: anterior chamber
- PC: posterior chamber
What are features of the iris?
- part of the vascular tunic/uvea
- stroma
- pigmented loose connective tissue
- iridial melanin present in the stromal cells determines eye color
- dilator and sphincter papillae muscles
- posterior epithelium
- iridium granules (corpora nigra) are present in equids + ruminants at the dorsal and ventral pupillary margins
- iridocorneal angle (filtration or drainage angle)
What is this structure? Label the features
- iris
What determines eye colour?
- blue: minimal pigment in stroma of iris
- increasing pigment in stroma:
- green < blue grey < brown
- albinism: partial or total lack of melanin pigment in eyes, skin, hair. Recessive gene
- have melanocytes (melanin producing cells) but not genes for tyrosinase
- “red” color due to hemoglobin in RBCs
What are features of the iridocorneal angle?
- at the convergence of corneoscleral junction (limbus), ciliary body, and iris
- composed of:
- pectinate ligament
- trabecular meshwork
- trabecular (aqueous) veins
- draining point for aqueous humor
What is this structure? Label the numbers?
- eye
- 1: ciliary body
- 2: iris
- 3: cornea
- 4: lens
- 5: optic nerve
What are features of the ciliary body?
- part of vascular tunic/uvea
- anterior expansion at the choroid level of the lens
- mechanical and secretory functions
- houses the ciliary muscle
- smooth muscle
- contracts during accommodation, reduces tension of the zonular fibers of the lens
- surrounded by loose CT (elastic fibers, vessels, melanocytes)
- receives innervation from CN III (oculomotor n)
What structure is indicated? What are some features?
- ciliary processes
- located at base of the iris
- epithelial surface
- 2 layers of low columnar epithelium
- nonpigmented: ion transporting forming aqueous humor
- pigmented: basement membrane extends to form zonular fibers that suspend the lens
What is this structure? Label the numbers
- ciliary process
- 1: non-pigmented epithelial cells (form aqueous humor)
- 2: pigmented cells
- 3: in the aqueous humor
- 4: ct w/ vessels
Label the structures
- 1: body of lens
- 2: lens epithelium
- 3: ciliary processes
What is this structure? Somme features?
- ciliary body
- CB: ciliary body
- SL: suspensory ligaments
- ICA: iridocorneal angle
- CS: canal of schlemm
- posterior pigmented epithelium of iris are continuous with nonpigmented epithelium of ciliary body
What are features of the aqueous humor?
- occupies anterior and posterior chambers
- nourishes the cornea + lens
- maintains intraocular pressure
- formed by non-pigmented cells of ciliary processes
- constant drainage required at iridocorneal angle
What is the drainage pathway of aqueous humor?
Label the structures
- R: retina
- P: pigment epithelium
- Ch: choroid
- S: sclera
What part of the eye is indicated? What are some features?
- choroid
- part of vascular tunic/uvea
- highly vascularized
- anterior: continuous w/ stroma of ciliary body
- external: connected to sclera
- internal: connected to retinal pigment epithelium
- internal to vascular layer: tapetum lucidum
What are features of the tapetum lucidum?
- reflective carpet: shiny eyes
- increase light perception under poor illumination
What are features of the retina?
- neuro-epithelial (retinal) tunic
- 1: sensory/optical part: contacts the choroid
- 2: non-sensory/ciliary part: inner non-pigmented + outer pigmented ciliary epithelium “pars ciliary retinae”
- 3: non-sensory/iridial part: posterior pigmented epithelium “pars iridica retinae”
The retina is nourished by:
- vessels of the choroid and by retinal vessels entering via the optic disk
What structure is indicated by the red arrow? Black arrow? What tunics are visible?
- choroid
- retinal pigment epithelium
- fibrous: sclera
- vascular: choroid
- nervous: retina (+choroid)
What tunics are visible? Name some features.
- nervous + vascular
What are features of the sensory/optical retina?
- sends visual images to the brain
- 10 layers
- held in place by vitreous body
- combined nerve fiber layers converge on the optic disk to form the optic nerve
Label the nervous features indicated
How do the neurons of optical retina function? (pathway)
- light passes through layers of retina,stimulates photoreceptor cells (rods + cones)
- impulse is passed to bipolar neurons, then to ganglia cells
- axons of ganglion cells form the nerve fiber layer. These fibers converge at optic disk (papilla) and leave eye as the optic nerve (CN II)
- additional cells with supporting roles include: amacrine cells (interneurons), horizontal cells (regulate input from photoreceptor cells), muller cells (glial cells)
What is the path of light and visual perception?
- enter through tear film > cornea > aqueous humor > pupil > lens > vitreous humor > first 8 layers of retina > stimulate photoreceptors(rods + cones) > absorbed by retinal epithelium
- visual impulse created then passes in reverse order from rods and cones > bipolar cells > ganglion cells > optic nerves > brain
What are features of the retinal pigmented epithelium?
- outermost layer of retina
- consist of flat polygonal cells resting on a basement membrane
- transport of nutrients and metabolites to the rods + cones, light absorption, phagocytosis
What are features of the photoreceptor layer?
- neurons: rods + cones
- rods + cones have outer and inner segments connected through a cilium
What are features of rods + cones?
- rods:
- inner segment is long + thin
- contain flattened membranous disks containing pigment rhodopsin (vitamin A)
- responsible for vision in dim light (more in nocturnal species)
- 120 mil/retina
- cones:
- inner segment has a broad base
- disks contain lodopsin
- responsible for vision in bright light + colour
- 60 mil/retina
- *retinal detachment @ arrow
What is the fovea?
What is this structure?
- optic nerve
What are the refractive media of the eye?
- vitreous body
- lens
What are features of the vitreous body?
- occupies space between lens + retina; 4/5th of eyeball
- 99% water, rich in hyaluronic acid
- gel cortex, liquid center
- aids in maintaining shape and retinal apposition
What are features of lens?
- entirely surrounded by capsule (THICK on anterior surface)
- anterior epithelium
- simple cuboidal cells
- apical towards lens fibers
- at the equator, elongate + differentiate into lens fibers
- lens fibers
- prism-shaped cells, lack nuclei, interdigitate extensively and have gap junctions (transparent)
- differentiation and growth of lens throughout life
The lens and ciliary body are attached via _______
- zonular fibers
What structure is shown?
- ciliary zonular fibers
Label the image
- 1: zonular fibers
- 2: vitreous humor
- 3: pigmented epithelium
- 4: sclera venous sinus
- 5: non-pigmented epithelium
- 6: ciliary processes
What is this image showing?
- lens
- anterior lens epithelium refelects into the surface of the lens
- cells elongate to form lens fibers that comprise the lens (lose nucleus/organelles when mature)
- entire lens is contained in a capsule (thicker on anterior surface)
- 10: germinalzone
- 13: lens capsule
- 14: lens epithelium
- 15: new lens fibers
- 16: old lens fibers
Label the structures
- lens
- A: capsule
- B: subcapsular epithelium
- C: lens fibers
What are accessory ocular structures?
- eyelid
- conjunctiva
- cilia (eyelashes)
- tarsal (meibomian) glands - sebaceous
- third eyelid (nictitating membrane) unique to animals
- lacrimal (tear) apparatus
- lacrimal glands
- lacrimal sac
- nasolacrimal duct
What are features of the conjunctiva?
Anemia can be detected via observation of mucous membranes such as a :
- conjunctiva + third eyelid
Label structures
- eyelid (palpebrae)
What are features of the nictitating membrane?
- third eyelid
- protects eye, removes foreign material
- corresponds to a fold of conjunctiva formed by
- hyaline cartilage in ruminants + dog
- elastic cartilage in horses, pigs, + cats
- lined by conjunctiva
- aggregated lymphoid nodules are located under the conjunctival surface, can give cobblestone appearance
- gland of third eyelid contributes 30-50% of the aqueous portion of the tear film via small ductules.
What is this? Some features?
- lacrimal glands
- tear film moisturizes, lubricates, and protects the eyes
- have tubuloalveolar seromucinous acini compose of secretory cells filled with small granules
- myoepithelial cells are present at the base
What are the layers of the tear films?
- oily potion is produces by the Meibomian (tarsal) glands, oily portion is superficial layer of the tear film
- aqueous potion consisting of sero-mucous material is produced by the lacrimal glands and glands of the third eyelid
- mucous portion produced by goblet cels in the conjunctiva
What is pecten?
- special adaptation of reptiles + birds
- vascular structure that extends from the optic disc to the vitreous body that helps nourish the inner eye/retina
- birds have cartilage in the sclera that occasionally ossicles
