Eye and Ears Flashcards
(19 cards)
Describe the microscopical structures and functions of the 3 main layers of the eye
Retina- nervous layer, detect light (rods and cones) and transmit signals to the brain
Vascular coat- choroid, cilliary body and iris, supply nutrients, accommodate and regulate light
Corneoscleral coat- tough white fibrous sclera, protect and refract light (cornea)
Describe the microscopical structures and functions of the components of the uvea (choroid, ciliary body and iris)
Choroid- vascular, pigments layer, feeds retina and absorbs stray light
Cilliary body- cilliary muscles, lens accommodation, production of aqueous humor
Iris- coloured ring with smooth muscle, controls pupil size regulates light entry
Describe the layers of the cornea
Epithelium- strat squamous, non-keratinised layer, acts as a barier against pathogens
Bowman’s Layer- acellular collagen beneath epithelium, stengthens cornea
Stroma- thick, regular collagen with keratocytes, maintains transparency
Descemet’s membrane- thin basement membrane, supports endothelium
Endothelium- single layer of hexagonal cells, regulates fluid balance
Describe the mode of synthesis and drainage of aqueous humour
Synthesis- produced by ciliary processes, formed via active secretion and ultrafiltration from blood plasma
Drainage- flows from posterior chamber to pupil to anterior chamber, drains trabecular meshwork into Schlemn’s canal and into episcleral veins
Describe the microscopical structure and function of the different layers of the retina
- Neural retinal- non-photosensitve region anterior to ora serrata
Photosenstive region posterior to ora serrata - Retinal pigment epithelium
Outer layer of optic cup
Central retinal artery supplies blood to the inner retina
List the microscopical structure and function of the different layers of the retina
- Pigment epithelial layer
- Outer segments of rods and cones
- Outer limiting membrane
- Outer nuclear layer
- Outer plexiform layer
- Inner nuclear layer
- Inner plexiform layer
- Ganglion cell layer
- Optic nerve fiber
- Inner limiting membrane
Describe the microscopical structure of the lens
Capsule- elastic membrane surrounding lense
Cortex- outer, soft layer of lens fibres
Nucleus- dense core of tightly packed lens fibres
Lense fibres- transparent flattened cells wiht crystallins for clarity
Equator- midsection where fibres meet and grow
Describe the function of the lens
Refraction- focuses light onto retina
Accommodation- changes shape on near and far objects
Transparency- allows clear light passage for vision
Describe the microscopical structures and functions of the vitreous body
Spindle shaped cells= hyalocytes
Homogenous gel containing collagen fibrils and GAG’s
Maintains shape of the eye and helps keep the retina in place
Describe the microscopical structures and functions of the glands in the eyelid
Meibomian glands- produce oils for tear film stability
Zeiz glands- lubricate eyelashes
Moll glands- secrete sweat to maintain eye moisture
Lacrimal glands- produce aqueous tears for lubrication and protection
Describe the changes in, retinal detachment, corneal transplant, cataract, glaucoma and conjunctivitis
Retinal detachment- seperation of retina, leading to vision loss
Corneal transplant- replacement of damaged cornea to restore vision
Cataract- clouding of the lens causing blurred vision
Conjunctivitis- inflammation of conjunctiva , causing redness and discharge
Describe the microscopical structures and functions of the tympanic membrane
3 layers:
1- Outer epithelial layer
2- Middle fibrous layer
3- Inner epithelial layer
Function- sound transmission, protection from foreign objects and pressure equalisation
Describe the organisation on the middle ear (mainly auditory ossicles)
Tympanic membrane- separates external meatus from middle ear
Auditory muscles- malleus, incus and stapes
Auditory tube- connects middle ear to the nasopharynx
Where do we find endolymph and perilymph and what is the difference in the composition?
Found within the cochlea, vestibule and semi circular canals
Endolymph- rich in K+, low in Na+. slightly alkaline in pH
Perilymph- high Na+ ions and low K+ ions, slightly acidic in pH
Describe the microscopical structures and functions of Crista Ampullaris
Supporting cells- help maintain integrity of structure and facilitate regeneration of cells
Hair cells- detect mechanical changes in surrounding fluid caused by head movement
Cupla- when displaced, the stereocillia of hair cells, initiating and electrical signal that’s transmitted to the brain
Nerve fibres- transmit sensory signals generated by hair cells to the brain stem related to balance and orientation of the head
Describe the microscopical structures and functions of Macula of Utricle and Saccule
sensory epithelia containign hair and supporting cells
hair cells have stereocilia embedded in a gelatinus otolithic memebrane with otoconia (crystals)
Utriular- detects horizontal acceleration
Saccular- detects vertical acceleration
Describe the microscopical structures and functions of Cochlea (e.g. scalae, stria vascualaris)
Divided into 3 fluid-filled chambers: scala vestibuli, scala tympani, and scala media
Stria vascularis- specialised epithelium, produces endolymph and maintains high K+ concentration
Describe the microscopical structures and functions of Organ of Corti
Organ of corti- basilar membrane within the cochlear duct, contains inner and outer hair cells that transduce sound vibrations
Where do we find conductive hearing loss and sensorineural hearing loss and what is the difference?
Conductive- occurs in the outer/ middle ear, from blocked/ inefficient sound conduction
Seneorineural- inner er/ auditor nerve, due to damage to hair cells/ nerve pathways
