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Neuro > Histology > Flashcards

Histology Flashcards

1
Q

Corneoscleral Coat

A

Modifications
Cornea - anterior 1/6, transparent, convex
Substantial propria - middle, collagen fibres, vascular
Area cribrosa - posterior, perforate passes for optic nerve and retinal vessels.

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2
Q

Cornea

A

Diam: 11mm, Thickness; 0.5 mm centrally to 1mm at edges. No bv’s, transparent

  1. Anterior corneal epithelium - 5 layers stratified squamous, microvilli superficially (vermiform ridges), basal cells mitotic, regeneration, free nerve endings
  2. Bowman’s membrane - Homogenous collagen fibres, stability and strength, does NOT regenerate.
  3. Corneal stroma - 60 lamella of collagen fibrils, right angles. Fibroblasts - keratocytes - flattened between. Keratin and chondroitin sulfates. Transparent
  4. Descemet’s Membrane - Homogenous collagen filaments, mesh work, FENESTRATIONS
  5. Posterior corneal endothelium - simple squamous, abundant NA/K pumps, maintains hydration of stroma.
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3
Q

Sclera

A

Dense CT, extension of DURA. Collagen type I, elastic fibres.
1. Episcleral layer
Tenon’s space between -
Attachment site for ocular muscles
2. Substantial propria
3. Suprachoroidal lamina
Perforated posteriorly for exit of optic nerve fibres and entry of central retinal vessels.

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4
Q

UVEA (Tunica Vasculosa)

A

Iris, ciliary body, choroid

Features: vascular, loose CT, pigmented cells

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5
Q

Choroid

A

Choroid Proper - closest to sclera (outside), presence of large blood vessels
Chorio-capillary layer - continuos capillaries
Bruch’s membrane - between choroid and RPE - component of blood-retinal barrier

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6
Q

Ciliary Processes

A
  1. Provide attachment to the capsule of the lens by zonule fibres - ligaments of Zinn - oxytalan elastic fibres
  2. Secrete aqueous humour
  3. Fenestrated capillaries
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7
Q

Iris

A

Anterior extension of choroid, ANTERIOR to lens
Anterior surface: irregular, epithelial cells, stellate fibroblasts, stellate melanocytes
Stroma: loose CT, collagen, vascular, fibroblasts, melanocytes
Posterior: two epithelium: - inner (posterior) pigmented epithelium, continuation of RPE
Outer epithelium - pigmented myoepithelial cells *make up dilator pupillae muscle

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8
Q

Drainage of Aqueous Humour

A

Sclerocorneal junction

Spaces of fontana –> canal of schlemm –> aqueous humour drained into ciliary veins

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9
Q

Retina

A

Derived from ectoderm, anterior portion is non-photosensitive lining inner ciliary body and posterior iris.
Junction of anterior and posterior is ORA SERRATA.

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10
Q

Retinal pigment epithelium

A

Single layer of cuboidal cells
Synthesise melanin
Adjacent cells - junctional complex connection
Abundant microvilli, surround and phagocytose shed discs of rods and cones
Establish blood retinal barrier
Estérification of vitamin A

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11
Q

Photoreceptors

A

Light sensitive photoreceptor discs
Flattened membranous disk contains photosensitive pigments
Tips that contain disks are embedded within microvilli of RPE

Inner segments: cell organelles, metabolic processing

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12
Q

Rods

A

120 millions rods,
Disks: Visual Purple/Rhodopsin: contains scotopsin protein + retinal (chromophore, vitamin a derived, covalently attached)

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13
Q

Cones

A

7 million
Thicker and shorter,
Discs: pigment is called iodopsin. Contains photopsin
Sensitive only to light - better visual acuity.

3 types: S cones (short, blue), M cones (medium, green), L cones (long, red) for colour vision. Maximum absorptions at different wavelengths.

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14
Q

Bipolar cells of the retina

A

Extend between inner and outer plexiform layers
Axons synapse with several ganglion cells
Helps in communication with multiple cells
In fovea, however, ONE bipolar cell to ONE ganglion cell increases the visual acuity.

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15
Q

Other cells of the retina

A

Association neurons: horizontal cells, amacrine cells, in the bipolar cell layer
Supporting cells: Muller’s cells on the side, extend from outer limiting membrane (layer 3, next to outer rods and cones) all the way down to inner limiting membrane (layer 10, below optic nerve fibre layer)

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16
Q

Outer synaptic plexiform layer

A

Synapse between bipolar cells and photoreceptors

17
Q

Inner synaptic plexiform layer

A

Synapse between bipolar cells and ganglion cells

18
Q

Where do you find the cell bodies of muller’s cells?

A

In the inner nuclear layer with cell bodies of bipolar, horizontal, amacrine as well

19
Q

Layers of the retina

A
  1. Pigment epithelial layer (RPE)
  2. Outer segment of rods and cones
  3. Outer limiting membrane (outer limit of muller cells)
  4. Outer nuclear layer (inner segments of rods and cones)
  5. Outer plexiform layer (synapses of photoreceptors and bipolar cells
  6. Inner nuclear layer (cell bodies of bipolar, horizontal, amacrine, and muller cells)
  7. Inner plexiform layer (Synapses of bipolar cells and ganglion cells)
  8. Ganglion cell layer
  9. Optic nerve fibre layer (axons of ganglion cells)
  10. Inner limiting membrane (inner limit of Muller cells)
20
Q

Blood supply to the retina

A

First five layers (ie RPE, outer rods, outer limiting, outer nuclear, to outer plexiform (layer 5)) by choriocapillaries

Layers 6-10 (ie inner nuclear layer, inner plexiform, ganglion, optic nerve fibre, inner limiting layer) - by central retinal artery

21
Q

Macular Lutea

A

Center of the posterior retina at the visual axis of th eye

Fovea central is: small depression in the centre of the macula lutea, area of highest visual acuity, contains ONLY CONES

22
Q

Lens features

A

Biconvex
AVASCULAR
Held in place by RADIALLY oriented group of zonule fibres - oxytalan, elastic fibres. arise from ciliar processes, play a part in change of shape of lens during process of accomodation. (Ie tight when lens is flat and ciliary muscles are relaxed ie distant )
(Relaxed when ciliary muscles rae contracted and lens is convex, for near sight)

23
Q

Layers of the Lens

A
  1. Lens capsule - thick BL of 10-20microm, produced by ANTERIOR lens cells, attached to zonule fibres
  2. Subcapsular epithelium - single layer of simple cuboidal, ONLY on ANTERIOR surface of lens. Source of lens fibres
  3. Lens fibres - thin, flattened structures. Lose the organelles and accumulate crystallins (proteins)
24
Q

Vitreous Body

A

Between lens and retina, 4 mL capacity.
Spindle shaped cells - hyalocytes
Fine collagen fibrils in the matrix
ECM rich in GAGs especially hyaluronic acid

25
Q

Conjunctiva

A

Lines inside of eyelids and visible part of sclera, secretes MUCIN

26
Q

Glands of the eyelid

A

Meibomian glands - Sebaceous, within tarsal plate. Lubricates - delays drying of tears

Glands of Zeiss - Sebaceous glands within eyelids (where eyelashes come out)

Glands of Moll - sweat glands at the lid margins.

27
Q

Lining of the tympanic membrane

A

External: thin skin
Internal: simple squamous epithelium

Membrane itself consists of collagen fibres

28
Q

Inner Ear

A

Bony labyrinthe: 3 semicircular canals, vestibule, cochlea

Membranous labyrinthe: semicircular DUCTS, vestibular LABYRINTH, cochlear labryinth.

29
Q

Membranous labryinths

A

Communicating sacs and ducts with ENDOLYMPH
Vestibular: semicirc ducts, utricle, saccule
Cochlear: cochlear duct

Endolymph: SImilar to ISF - low in Na high in K

30
Q

Bony labryinths

A

Contain perilymph - similar to ECF (and CSF) high in Na low in K

31
Q

Cristae

A

Sensory hair cells - 3 cristae ampullaris (ampullary crests) of semicircular ducts. Detect angular acceleration.
Cupula: gelatinous protein - polysaccharide mass, projects into the lumen, surrounded by endolymph and attached to each crista.

32
Q

Macula

A

Hair cells within utricle and saccule. Sense gravity and linear acceleration of head.
Cells of the epithelium face the endolymph.
Otolithcic membrane - gelatinous polysaccharide material over the epithelium. Outer limit is crystalline bodies of calcium carbonate and protein otoconia

33
Q

Stria Vascularis

A

In cochlear duct. Responsible for ionic composition of endolymph

34
Q

Sound conduction

A

Sound waves within cochlea, vibrate organ of corti, basilar membrane more elastic than tectorial membrane, vibration of basilar membrane causes hair cells to displace, shearing force created against tectorial membrane creates a nerve impulse.
High frequency sound - maximum displacement of basilar membrane at base
Low frequency sound - apex of cochlea.

35
Q

Sensorineural Deafness

A

Destruction of nerve (sensory neuroepithelial) cells or central pathway to the brain

Level at which sustained exposure may cause hearing loss - 90-95 dB (normal convo is 60-70 dB, rock concert 115, pain begins 125)
Death of hearing tissue - 180
Loudest sound possible - 194

36
Q

Corneal Transplant

A

Indications: keratitis, trauma, keratoconus, corneal degeneration, etc.

Types: penetrating kératoplastie, lamellar kératoplastie, endothelial kératoplasty

37
Q

Lens - cataract

A

Lens = mostly water and protein
Crystalline keeps it clear
Ageing leads to clumping of protein –> cloudy appearance
Visual acuity and contrast sensitivity is lost (contours, shadows, colour vision lost)

Some causes; diabetes, homocysteinuria, fabry’s
Congenital: congenital herpes, congenital syphilis, CMV - cytomegalovirus inclusion disease, rubella
Drugs: corticosteroids, haloperidol

38
Q

Glaucoma

A

Increased intraocular pressure
Symptoms: headache, eye pain, loss of vision, vomiting, halo around light
Signs: peripheral field of vision is decreased, redness, raised intraocular pressure (tonometry - used to measure IOP)
Can cause optic nerve compression, can lead to permanent vision loss

39
Q

Most common site of retinal detachment

A

Between RPE and rods & cones layer

Some causes: cataract surgery, trauma, extreme dehydration, retinal tears

Neuro (6 decks)

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