Basic Science Flashcards
(42 cards)
An 80 year old woman presents with loss of vision in her right eye, scalp tenderness and jaw claudication. Which of the following is most likely false in regards to the microscopic findings of the condition that has led to these symptoms?
false- giant cells have to be present for Dx
The symptoms described are typical of giant cell arteritis.
In this condition, there is inflammatory cell infiltration (lymphocytes, plasma cells, eosinophils and macrophages) in the media. But the inflammation may be patchy with skip lesions. This is why biopsy length of ⩾ 2cm to avoid likelihood of skip lesions.
Multinucleated giant cells are typically located close to fragmented internal elastic lamina, but giant cells are only present in about 50% positive biopsies.
The lumen may become obliterated by fibrin thrombus, which becomes organised and recanalised.
The adventitia and small periarterial vessels are frequently affected in the chronic inflammatory process.
lymph drainage
Most lateral ocular structures drain into superficial parotid nodes. Most medial ocular structures drain into submandibular nodes.
Structures draining into superficial parotid nodes
Lateral eyebrow, lateral eyelid, lateral conjunctiva, lacrimal gland
Structures draining into submandibular nodes
Medial eyebrow, medial eyelid, medial conjunctiva, lacrimal carbuncle, maxillary sinus, frontal sinus
Structure draining into retropharyngeal nodes
sphenoid sinus
Which of the following substances in the aqueous humour is found in lower concentrations in comparison to plasma?
Aqueous humour
Lacks protein, and is therefore transparent Has excess ascorbate, chloride and hydrogen Protein composition includes albumin, growth factor, enzymes like carbonic anhydrase and lysozyme, steroid hormones, catecholamines, hyaluronic acid and cAMP
A good way to remember this: The AC is full of Acid (ascorbic acid) and Chloride
If a man has red-green colour blindness and his partner is not a carrier, what is the likelihood that his daughters are carriers?
100%
Green and red genetic colour deficiency is X-linked recessive. Therefore affected fathers will pass the gene to his daughters, but these carriers will not have colour vision deficits.
image formed by a prism?
although this seems more of a Part 1 FRCOphth style question, a similar question has appeared in a recent FRCOphth Part 1 examination.
The image formed by a prism is virtual, erect and displaced towards the apex of the prism.
Which culture medium below is best for isolating Neisseria gonorrhoea?
Thayer-Martin medium
Neisseria gonorrhoea are aerobic Gram-negative cocci. The endotoxin activity and IgA proteases they have enables cleavage of immunoglobulin.
Chocolate Agar is a non-selective medium for the cultivation of fastidious bacteria, especially Neisseria and Haemophilus spp.
Thayer-Martin is a type of agar typically containing chocolatised (heated) equine or bovine blood and antibiotics used for the selective isolation of pathogenic Neisseria (e.g. Neisseria gonorrhoea, Neisseria meningitidis) from specimens with mixed flora of bacteria and fungi.
McCoy agar is usually used for growing obligate intracellular bacteria such as Chlamydia trachomatis and Sabouraud is used to grow fungi.
Which of the following zones of the Descemet’s membrane grows with age?
A useful mnemonic for this:
Anterior
Banded
Congenital
Does not grow
Descemet’s membrane
3-4 microns at birth, and grows to 10-12 microns in adults
Basement membrane of the corneal endothelium
Type IV collagen
Two zones
Anterior banded zone which develops in utero
Posterior non-banded zone which is deposited by endothelial cells throughout life
What is the most common inheritance pattern of Marfan’s syndrome?
Marfan’s syndrome is most commonly due to a mutation in the FBN1 gene on chromosome 15.
In the majority of cases, it is genetically inherited and follows follows an autosomal dominant inheritance pattern however there is about 25% patients that are effected by a sporadic mutation.
If genetically inherited, it is subject to pleiotropy and variability expressivity, resulting to a broad phenotypic continuum and there is a high degree of clinical variability.
ocular trauma
A few useful anatomical facts about the sclera:
Thinnest (0.3mm) just behind the insertions of the recti muscles Thickest (1.0mm) at the posterior pole around the optic nerve head It is 0.4–0.5 mm thick at the equator and 0.6 mm thick anterior to the muscle insertions
Because of the above, the most common sites of scleral rupture following blunt trauma are:
in the superonasal quadrant, close to the limbus in a circumferential arc parallel to the corneal limbus opposite the site of impact behind the insertion of the rectus muscles
The Bruch’s membrane can buckle as a result of traumatic mechanical event at site of contusion or away from the impact. When a rupture occurs through the choroid/Bruch’s membrane/RPE but the sclera stays intact, this is termed a choroidal rupture. The rupture is often concentric to the disc. There is no treatment for this but a CNV is a late complication and may be treated the conventional way.
Best disease:
Second most common hereditary macular dystrophy
Autosomal dominant
Mutations in the VMD2 gene (aka BEST 1 gene)
Highly variable expression
Usually asymptomatic in early stages
Surprisingly good prognosis, most patients retain reading vision beyond 5th decade
Develops yolk-like lesion at posterior pole but this may later be replaced by scarring, atrophy or CNV (which will cause vision to drop)
Classically EOG shows reduced Arden ratio (<1.5) but ERG is normal
regarding the image formed by a prism?
The image formed by a prism is virtual, erect and displaced towards the apex of the prism.
regards to cotton wool spots?
Cotton wool spots:
Believed to occur due to ischaemia from retinal arteriole obstruction
Represent nerve fibre layer infarct
Represented by hyper-reflectivity of the inner retina on OCT
Decreased perfusion in the inner retina -> ischaemia of nerve fibre layer -> disrupts axoplasmic flow -> axoplasmic debris
accumulates in retinal ganglion cell axons which is thought to interfere with signal conduction
Cytoid bodies are considered to be histological hallmark of CWS
Cytoid bodies are eosinophilic segments of swollen ganglion cell axons due to defective axoplasmic flow
Reference(s)/further reading:
Gomez, M. L., Mojana, F., Bartsch, D. U., & Freeman, W. R. (2009). Imaging of long-term retinal damage after resolved cotton wool spots. Ophthalmology, 116(12), 2407-2414. https://doi.org/10.1016/j.ophtha.2009.05.012
Congenital stationary night blindness inheritance
It has various forms in AD, AR and X-linked.
maternally inherited?
Kearn-Sayre syndrome
Melas syndrome
Leber Hereditary optic neuropathy
regarding the retinal pigment epithelium (RPE)
The RPE is immune provilege. It remains so by secreting immunosuppressive factors. It doesn’t secrete cytokines.
This is understandably an unpleasant topic to learn and may bring back bad memories from Part 1. However, a very similar question was asked in the FRCOphth Part 2 exam. We have summarised the key points below.
RPE function
Blood retinal barrier.The RPE lies in the interface between the neural retina and the choriocapillaris where it forms the outer blood retinal barrier. To limit transepithelium diffusion between cells, the cells of the epithelium are bound together by a partially occluding seal, the tight junction. The tight junction subdivides the plasma membrane into two functionally distinct domains. The apical membrane faces the photoreceptors of the neural retina, while the basolateral membrane faces the fenestrated choriochapillaris. Light absorption. As a layer of pigmented cells the RPE absorbs the light energy focused by the lens on the retina Nutrient transport. To regulate transport across the monolayer, various pumps, channels, and transporters are distributed specifically to either the apical or the basolateral membrane. The RPE transports ions, water, and metabolic end products from the subretinal space to the blood and, conversely, takes up nutrients such as glucose, retinol, and fatty acids from the blood and delivers these nutrients to the photoreceptors. Visual cycle modulation. To maintain photoreceptor excitability retinol is constantly transported from the photoreceptors to the RPE where it is reisomerised to 11-cis-retinal and transported back to the photoreceptors. This is the key component of the visual cycle.
Another function that contributes to the maintenance of photoreceptor excitability is the phagocytosis of the shed photoreceptor outer segments.
The photoreceptor outer segments are digested, and essential substances such as retinal are recycled and returned to the photoreceptors for rebuilding light-sensitive outer segments from the base of the photoreceptors
Nutrient support. The RPE is able to secrete a variety of growth factors as well as factors that are essential for the maintenance of the structural integrity of the retina and the choriocapillaris Immune privilege. The secretory activity of the RPE plays an important role in establishing the immune privilege of the eye by secreting immunosuppressive factors.
from superficial to deep?
skin
subQ tissue
orbicularis oculi
neovascualr bundle
orbital septum
smooth muscle
conjunctiva
Think of the upper lid in 3 parts
The lower part is 5 mm has 4 layers: skin, orbicularis, tarsus and conjunctiva.
The middle part is another 5 mm has 5 layers: skin, orbicularis, levator aponeurosis, tarsus and conjunctiva.
Above 10 mm, the upper eyelid has 7 layers: skin, orbicularis, septum, preaponeurotic fat, levator aponeurosis, Muller’s muscle, and conjunctiva.
definitions
Umbo - the center of the foveola. A 150-micron diameter depression observed clinically as the normal light reflex.
Foveola - the foveal floor. A 350-micron diameter region representing the “floor” of the fovea. The foveola does not have inner nuclear or ganglion cell layers. The foveola is approximately equal to the foveal vascular zone.
Foveal avascular zone (FAZ) - the macular center and fixation point. A region devoid of retinal vessels.
Fovea (fovea centralis) - A 1,500-micron diameter (approximately 1 disc diameter) region superimposed on the foveola. Contains only cones (no rods) and processes of Muller cells.
Parafovea - 500 micron width ring around the fovea. The parafovea has the thickest ganglion cell, inner nuclear and outer plexiform layers.
Perifovea - 1,500 micron width ring around the parafovea. The perifovea is roughly bordered by the optic disc and temporal vascular arcades.
regarding granular corneal dystrophy?
inherited in AD manner
stains w masson trichroma
can recur in graft
Granular corneal dystrophy is characterised by opaque granules containing non-birefringent hyaline bodies in stroma and Bowman’s layer, not in endothelium and Descemet membrane.
The table below summarises the various types of corneal dystrophy:
From the middle cranial fossa to the apex of the orbit, which of the following is the best description of the course of the optic canal?
anteriorly, inferiorly and laterally
Which of the following zones of the Descemet’s membrane grows with age?
posterior non banded
useful mnemonic for this:
Anterior
Banded
Congenital
Does not grow
Descemet’s membrane
3-4 microns at birth, and grows to 10-12 microns in adults
Basement membrane of the corneal endothelium
Type IV collagen
Two zones
Anterior banded zone which develops in utero
Posterior non-banded zone which is deposited by endothelial cells throughout life
lymph drainage
Most lateral ocular structures drain into superficial parotid nodes. Most medial ocular structures drain into submandibular nodes.
Structures draining into superficial parotid nodes
Lateral eyebrow, lateral eyelid, lateral conjunctiva, lacrimal gland
Structures draining into submandibular nodes
Medial eyebrow, medial eyelid, medial conjunctiva, lacrimal carbuncle, maxillary sinus, frontal sinus
Structure draining into retropharyngeal nodes
sphenoid sinus
medial wall of the orbit?
*A useful mnemonic to remember the structures forming the walls of the orbit roof:
FRONT-Less (Frontal Bone, Lesser Wing of Sphenoid)
Floor: Zip My Pants (Orbital surface of Zygomatic bone, orbital plate of Maxilla, orbital process of Palatine bone)
Medial wall: SMEL (Body of Sphenoid, frontal process of Maxilla, orbital plate of Ethmoid, Lacrimal bone)
Lateral wall: Greatz: Greater wing of sphenoid, Zygomatic*
)
Which of the following structures travel through the foramen rotundum?
Superior orbital fissure - Ophthalmic nerve (CN V1)
Foramen Rotundum - Maxillary nerve (CN V2)
Foramen Ovale - Mandibular nerve (CN V3)
Foramen Lacerum - Does not transmit structures
Foramen Spinosum - Middle meningeal artery
Foramen Petrosum - Lesser petrosal nerve (but this nerve can alternatively travel through the foramen ovale)
culture medium below is best for isolating Neisseria gonorrhoea?
Thayer Martin
Neisseria gonorrhoea are aerobic Gram-negative cocci. The endotoxin activity and IgA proteases they have enables cleavage of immunoglobulin.
Chocolate Agar is a non-selective medium for the cultivation of fastidious bacteria, especially Neisseria and Haemophilus spp.
Thayer-Martin is a type of agar typically containing chocolatised (heated) equine or bovine blood and antibiotics used for the selective isolation of pathogenic Neisseria (e.g. Neisseria gonorrhoea, Neisseria meningitidis) from specimens with mixed flora of bacteria and fungi.
McCoy agar is usually used for growing obligate intracellular bacteria such as Chlamydia trachomatis and Sabouraud is used to grow fungi.
Reference(s)/further reading:
Papp, J. R., Schachter, J., Gaydos, C. A., Van Der Pol, B. (14 March 2014). Recommendations for the Laboratory-Based Detection of Chlamydia trachomatis and Neisseria gonorrhoeae — 2014 Recommendations and Reports. Centres for Disease Control and Prevention, Atlanta, USA. Retrieved 25 August 2024, from https://www.cdc.gov/mmwr/preview/mmwrhtml/rr6302a1.htm?uid=5c51b88cbef4db3007eed34ead618843244c9647
Clinisciences: Reagents and instruments for immunology, cell biology and molecular biology. Retrieved 25 August 2024, from https://www.clinisciences.com/en/buy/cat-thayer-martin-agar-selective-solid-5525.html
