lab test

non dysjunction

Non disjunction = inability of a pair of homologous chromosome to separate properly 

single nucleotide polymorphosim

Single nucleotide substitution of one nucleotide for another (point mutation) 

isochromosome

1 long (q) and 2 short arms (p)

non dysjunction examples

XXY = klinfelters = TRISOMY eg: micropthalmia/small eyes

XO. = turners MONOMSOMY eg: myopia/hyperopia/ptosis(droops)

XXX = metafemale syndrome

chromosome stucture

2 sister chromatids joined by centromere

one long (q) and one short arm (p)

longer q arm than p arm

DNA supercoiled into double helix around histone proteins from a nucleosome

what stage of mitosis needs arresting to see chromosomes

metaphase

stain to visualise chromsomes

stain with giemsa

what stages of mitosis are these?

axons vs dendrites

dendrites = point at which info enters neurons from nerve cells/environment

axons = elecrical signals leave cell body

ending in terminal arborizations

identify the stucture and its features

ventrol horn of spinal cord

stringy bits = neurites (axons/dendrites)

what makes up grey matter vs white matter of CNS

grey = cell bodies, glial cells, dendrites + soma of CNS neurones

axons have little myelination

white = myelinated axons of neurones - few soma

what cells myelinate PNS vs CNS and the differences between the way they myelinate

PNS = schwann cells

CNS = oligodendrocytes

oligodendrocytes create myelin for multiple axons but one schwann cell per axon

what glia maintains blood brain barrier

astrocytes

function of microglia

specialised macrophages maintaining homeostasis via repair

structure of nerves (+ neurones vs nerves )

nerves = collections of neurones

neurones surrounded by endoneurium

many neurones = fasicle wrapped in perineurium

many fasicles = wrapped in epineurium

identify the image and its stuctures

cross section of a nerve

axons = pale cicles

myelin sheath = purple ring (thicker if more myelinated)

darker purple cell bodies = schwann cell nuclei producing myelin

range of nerve cell axon diameters and function

1 to 15-20 micrometres

Large diamerer = faster conduction eg motor neurones 

Smaller = conduct slower eg: pain 

average size of cheek epithelial cell

50 -100 micrometres

identify structure and its features

large horn = ventral horn

circles = blood vessels

stringy region = neurites

white matter = myelinated axons

dots = soma of neurones comprising of grey matter

what type of neurones make up grey matter of CNS

multipolar neurones = single axon and multiple dendrites

olfactory nerve - role, foramen, damage caused , test

controls sensory sense of smell 

via olfactory receptors in nasal mucosa which attach to axons in olfactory filaments 

passing through cribriform plate (perforated region) of ethmoid bone to (destination) olfactory bulbs of brain 

(found in anterior fossa - opposite side to big hole of skull) 

Damage to axons by head injury = cannot regenerate so permanent loss of smell  = anosmia  

Test = pungent odour  

optic nerve 2 - role, foramen, damage caused , test

sensory control of vision 

made up of retina ganglion cell axons in retina 
optic nerve passes into skull via foramen of optic canal (perfect hole) at back of the orbit 

nerve continues to optic chiasm where nerve fibres cross over and continue as the optic tract (opposite side)

to lateral geniculate nucleus of the thalamus 

LGN axons pass through to area of brain responsible for conscious visual perception 

Pituitary tumour compresses tissue above it  

Pressure on axons of optic chiasm at midline so carry info of nasal retina so temporal vision loss = bi temporal hemi anopsia  

Test = visual fields  

field defect arising from midline compression of optic chiasm

loss of temporal vision = bitemporal hemianopsia

caused by pituitary tumour

direct vs consensual light reflexes

direct = constriction of pupil recieving light

consensual = simultaneous constriction of opposite pupil

oculomotor, trochlear, abducent nerve role, foramen, damage caused , test

control movement of the eye – innervate EOM  

Lr6So4R3  

Lateral rectus by abducent (6) 

Superior oblique by trochlear (4) 

Rest = oculomotor (3) 

all 3 nerves originate from specific motor nuclei and travel through superior orbital fissure in the back of orbit 

supplies specific EOM 

Test – ocular motility test – look for symmetry  

characteristics of oculomotor nerve palsies

oculomotor innervates LPS so causes ptosis (droppy eyelid) as LPS cant contract to open lid

only SO and LR working as 3rd nerve controls rest

LR over exerts = pulling eye out = exotropia

iris sphincter innervated by 3rd nerve = paralysed so dilated pupil = mydriasis

characteristics of abducent nerve palsies

esotropia = LR cant contract so cant oppose medial rectus so eye pulled inwards

trigeminal nerve -role, foramen, damage caused , test

 

Trigeminal: 

Opthalmic = eyes/cornea (superior orbital fissure)

maxillary = cheekbone (foramen rotundum)

mandibular = bottom jaw  branches (foramen ovale) 

mainly sensory and some motor nerves 

controls somatic sensory feelings (touch/pain/pressure) for face and head 

and controls muscles for mastication/chewing (mandibular) 

 

where in the eye are the most sensory receptors

fovea

facial nerve - role, foramen, damage caused , test

 

Facial:

internal acoustic meatus foramen + stylomastoid foramen? 
located in posterior fossa 

Innervates Orbicularis oculi 

Lacrimal gland and salivary gland controlled by facial nerve 

in petrous portion of temporal bone 
(2 lines on edge of hole) 

 

zygomatic branch of Facial nerve enters by internal acoustic meatus in petrous temporal bone and exits by stylomastoid foramen to reach obicularis oculi  

 

Damage  = lower lid drooping, dry eye, dry mouth = bells palsy

 

vestibulocochlear nerve - role, foramen, damage caused , test

sensory - posture + hearing 

cochlear nerve carries auditory info 
vestibular nerve - carries info about the position/movement of head 

foramen = internal auditory meatus 
located in posterior fossa 

 

Test = tuning fork behind ear on skull – can hear so problem with outer ear 

If cant hear = cochlea or vestibulo cochlear nerve damage 

otolithic organs vs semicircular canals for vestibulococlear system

• Semicircular Canals (aVOR): Detect rotational (angular) acceleration in three-dimensional space. 

• Otolith Organs (lVOR): Detect linear acceleration (translational motion) and gravity (tilt) 

glossopharyngeal nerve - role, foramen, damage caused , test

Glossopharyngeal: 

sensory, motor, autonomic nerves 

motor: 
nerve from nucleus ambiguous to stylopharyngeal muscles elevating larynx to swallow 

sensory: 
transmit somatic sensation from pharynx + posterior 1/3 tongue + taste buds to brain 

parasympathetic: 
otic ganglion supplies the parotid salivary gland 

foramen = jugular foramen

vagus nerve -role, foramen, damage caused , test

Vagus: 

role: 
sensory pathway for feelings from the throat, heart, and gut 
motor nerve for swallowing and speech 
as parasympathetic system, regulating involuntary functions such as heart rate -“rest and digest” 

foramen = jugular foramen 

location of cranial nerve foramen

pathway of blood and labels of heart

Deoxygenated blood enters the right atrium via the vena cava, passes to the right ventricle, and is pumped to the lungs via the pulmonary artery. Oxygenated blood returns via the pulmonary veins to the left atrium, moves to the left ventricle, and is pumped to the body through the aorta

3 differences between skeletal and cardiac muscles

cardiac = autonomic but skeletal = somatic/vountary

cardiac = branched + connected by intercollated discs with gap junctions (syncytium) but skeletal = long unbranched

cardiac = myogenic but skeletal = neurogenic

agglutinogens

antigens expressed on erythrocytes determining blood group

blood types and their agglutinogens

type A = blood has agglutinogens binding to antigen B (attack foreign B antigens)

type B = blood has agglutinogens binding to antigen A

type AB = no agglutinogens against A/B so no immune response

type O = have agglutinogen A and B

process of agglutination

plateletes + WBCs (Antibodies bind to B antigen) = cross linked complex activating specific proteins iin plasma membrane causing erythrocytes to rupture leaking haemoglobin into blood plasma = haemolysis = kidney damage

what is serum of the blood

plasma without any clotting proteins containing antibodies

what blood type is a universal donor vs universal recipient

O = universal donor - lacking AB antigens

AB = universal recipient - lacks antibodies to AB so recieved blood from any type

codominance

when more than one allele is expressed in the same phenotype

label the outer eye and lid

role of obicularis oculi and cranial nerve innervating it

zygomatic branch of facial nerve innervates sphincter muscle for eyelid closing

role of levator palpebrae superioris

elevates upper lid in blinking

maintains open palpebral aperture

levator originates from lesser wing of sphenoid at apex of orbit

runs over superior rectus and terminates as a broad aponeurosis tendon

levator inserts into the tarsal plate into the skin of the eyelid

innervated by oculomotor nerve

location of the superior tarsal muscle + function

arises from underside of levator and inserts into tarsal plate

smooth muscle with a secondary role in maintaining open palpebral aperture

identify the 6 tissue layers of microscopic structure of lower eyeld

3 principle glands of eyelids + role

meibomian gland (Produces outer lipid layer of tear film preventing ocular surface from drying out)

glands of zeiss (ciliary sebaceous glands lubricating lashes preventing drying)

glands of moll ( ciliary sweat glands =antimicrobial secreting imminuglobulins for ocular surfaces defence )

identify the meibomian flands of eyelid

in dense connective tissue in tarsal plates in upper eyelid

mode of secretion of meibomian glands and identify the stuctures on a microscopic section

Sebaceous glands consisting of multiple secretory acini which open onto a central duct 

Discharges contents onto lid margin 

identify the orbital vs palpebral regions of obicularis oculi

identify gland of zeiss and moll and eyelash follicle on a microscopic image

identify the 5 regions of the conjunctiva microscopically

orbital

limbal

bulbar

tarsal

marginal

identify the 5 regions of the conjunctiva on the eye

stucture of a goblet cell and function

triangular nucleus due to secretory granules in cytoplasm containing mucin

produce mucousal component of tear film

3 layers of tear film and gland responsible

lipid layer outer = meibomian

aqueous layer = lacrimal gland

mucus layer inner = goblet cells

relationship between levator aponeurosis and lacrimal gland

divides lacrimal gland into orbital lobe (upper 2.3rd) and palpebral lobe (lower 1/3rd)

pathway of lacrimal gland secretions

tubuloacinar gland

secretions from acini pass into intercalated ducts and into the main ducts which dischargex onto conjunctival surface

identify features of structure

acini of lacrimal gland

how do acini differ from ducts eg lacrimal gland

ducts lack secretory cells + higher density of myoepithelial cells

ducts modify composition f tear film by secreting electrolytes unlike acini

function of myoepithelial cells in lacrimal gland

        Wrap around acini where contractile force squeezes acinus triggering reflex tearing

function of lacrimal stroma lymphocytes

plasma cells secrete IgA in interstices of gland

transported across acini into tears

immunity protection + pathogen defence

lacrimal drainage system pathway

tears accumulate at inner corner of eye

puncta in eyelid margins connect to lacrimal sac via cannaliculi

lacrimal sac collects tears that travel down nasolacrimal duct into nose for drainage

(nasloacrimal canal connects lacrimal fossa to nasal region)

ptosis, proptosis, exopthalmos, enoptlhlamos, epiphora, ectropion, entropion, horedolum

ptosis = drooping of upper eyelid

proptosis + exopthalmos = Abnormal protrusion of eye  

 enophlamos = Sunken appearance of eye within socket 

 epiphora = Overflow of tears onto face caused by excessive tear production or blocked drainage ducts 

ectropion = Outward turning of lower lid (aging) exposing inner eyelid  

entropion = Lower eyelid turns inwards causing lashes/skin to rub against cornea 

hordeolum = Stye caused by bacteria  

identify stuctures of cornea

1 = pre corneal tear film 

2 = corneal epithelium 

3 = corneal stroma 

typical distance in microns from anterior to posterior surface of central cornea and significance of thickness on intra ocular pressure meaurement

0.52mm

thin cornea = artificially low IOP reading

thick cornea = higher eye pressure reading than it should be

how does the corneal endothelium change with age

Loss of endothelial cells with age 

Unable to replicate so increased variability in size and shape  

 

Hexagonal cells expand and flatten to fill gaps 

5 layers of cornea

epithelium

bowmans membrane

stroma

descemets membrane

endothelium

adv of having a stratified squamous non keratinised epithelium on anterior corneal surface

non keratinised = no latter scatter = transparant

stratified = renewable barrier from trauma

cell types in corneal epithelium

wing cells, basal cells, squamous cells

label features of the superficial cells of the cornea

tight junctions between superficial squamous epithelial cells = permeability barrier

glycocalyx facilitates attachment/spreading of tear film (Hydrophillic)

interdigitations and desmosomes between wing cells = intercellular adhesion reistsing force from eye movement

corneal bowmans membrane structure

cell free homogenous layer

lies under epithelium

consists of randomly orientated fine collagen fibrils

corneal stroma structure

regularly arranged lamellae of collagen fibres

paralle fibrils within each lamellae

sucessive lamellae orientate at angles

stucture name and label its features

corneal stroma

K = keratocytes = secretes extracellular matrix (collagen and proteoglycans)

stimulate repair

stucture and function

posterior layers of cornea = descemets membrane, stroma and endothelial cell arrowed

corneal endothelium = single layer of squamous cells lining posterior surface of cornea

descemets membrane = basement membrane of endothelium

relationship between organisation of corneal stroma and transparancy

Small diameter collagen fibrils = less light scattered and more light passes through

regular spacing between fibrils= light waves scattered by one fibril interact with others

regular spacing = scattered light waves cancel each other out = destructive interferance

so light passes through = no scatter
 

corneal collagen vs scleral collagen structure

Scleral vs corneal collagen: 

The cornea has narrow, uniformly packed collagen fibrils allowing transparency, while the sclera has larger, randomly arranged fibrils causing white opacity 

how is the corneal endothelium adapted for its role in maintaining physiological hydration and corneal transparancy

Monolayer = facilitates diffusion of nutrients + decreased scatter  

 

Tight junctions = endothelial barrier function so reduce water loss  

 

Numerous mitochondira = ATP for endothelial pump of ions creating osmotic gradient  

limbus microscopic structure - label structures 1-6

1 cornea 

2 conjunctiva 

3 episclera  

4 sclera  

5 trabecular meshwork  

6 iris  

relationship between limbus and corneal epithelialisation

Sub population of basal cells at limbus (so not only on epithelium) act as stem cells to replenish corneal epithelium 

identidy scleral structures

A = conjunctiva  

B = tenons capsule 

C = episclera  

D = sclera  

function of tenons capsule

Thin membrane which envelops eyeball from optic nerve to limbus  

Found between conjunctiva and episclera 

Protects eyeball by forming a socket seperating eyeball from surrounding orbital fat (outside sclera in orbit of eye) 

symptoms, causes, treatments of Fuchs corneal dystrophy

glare/blurred vision upon waking (improves over next hours)

causes

corneal endothelial cell loss form guttata (deposits on cornea)

compromised corneal endothelial pump

corneal oedema (inner corneal cells die causing fluid buildup and corneal swelling)

treatment

Eye drops for mild swelling to reduce corneal swelling  

 

Or replacement of damaged endothelial cell layer  (corneal transplant)

most common reaons for corneal transplant + alternatives

Corneal dystophies (fuchs. Keratoconus) or corneal scarring 

alternative = lamellar grafts and endothelial keratoplasty instead of full thickness graft

why does corneal transplant not need matching donor to host

cornea = immuno privelaged site

no BV so no immune response and no rejection

label structures of the anterior eye

why are the crests of ciliary processes of pars plicata white

pigment lost from outer epithelium

both epithelial = non pigmented

where do suspensory ligaments of zonules attach to ciliary body

begin at lens

run through pars plicata and attach to dentate processes of orra serrata

label structures of anterior eye - side profile

a = pars plicata

b = pars plana

h/i = iris

d= retina

identidy the structures of the microscopic structures of the ciliary body

identify the structures of the histology of the filtration angle

pathway of aqueous at filtration angle

Pars plicata epithelium secretes aqueous  

Flows along posterior surface of iris  

Through gap between iris and lens into anterior chamber through pupil 

Flows around and then leaves via canal of schlemm of trabecular meshwork  

scleral spur holds trabecular meshwork in place so aqueous can be fed through and into canal of schlemm for drainage

OR UVEO SCLERAL = leaves between muscle fibres of ciliary muscle

ciliary epithelium structure

structure of the pars plicata

includes blood vessels (dark blue) and melanocytes

function of the inner vs outer epithelium of the pars plicata of ciliary body

inner = non pigmented = produces aqueous humour

outer = pigmented = absorbs stray light = black box effecr

3 muscles of the ciliary muscle

longitudinal

radial

circular

ciliary muscle structure labels

role of ciliary muscle fibres in accomodation

ciliary muscles contract pulling cilliary body inwards

relieves tension on suspensory ligaments

opens trabecular meshwork increasing aqueous outflor into canal of schlemm

how is ciliary muscle innervated

parasympathetic NS