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Phase 1b - Neurology & Neuroscience > Visual System - Anatomy > Flashcards

Visual System - Anatomy Flashcards

(110 cards)

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1
Q

Which anatomical space does the eye reside within?

A
  • Orbit
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2
Q

Name structure 1.

A

Upper eyelid

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3
Q

Name structure 2.

A

Palpebral fissure

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4
Q

Name structure 3.

A

Lateral canthus

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5
Q

Name structure 4.

A

Lower eyelid

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6
Q

Name structure 5.

A

Pupil

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7
Q

Name structure 6.

A

Iris

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8
Q

Name structure 7.

A

Sclera

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9
Q

Name structure 8.

A

Medial canthus

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10
Q

Name structure 9.

A

Caruncle

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11
Q

Name structure 10.

A

Limbus (border between cornea and sclera)

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12
Q

What is the space between the lateral and medial canthus of the eye?

A
  • Palpebral fissure
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13
Q

What term refers to the lateral confluence of the upper and lower eyelid regions?

A
  • Lateral canthus
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14
Q

What term refers to the medial confluence of the upper and lower eyelid regions?

A
  • Medial canthus
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15
Q

What is the opening within the iris?

A
  • Pupil
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16
Q

Which globular nodule structure resides besides the medial canthus of the eye?

A
  • Caruncle
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17
Q

Which structure is the border between the cornea and sclera?

A
  • Limbus
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18
Q

Where is the lacrimal gland located?

A
  • Located within the orbit, latero-superior to the globe
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19
Q

What is the function performed by the lacrimal gland?

A
  • It continually releases fluid (tears) which cleanses & protects the eye’s surface as it lubricates and moistens it
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20
Q

How are tears drained by the lacrimal system (5 steps)?

A
  1. Tears produced by lacrimal gland
  2. Drain through the two puncta, opening on medial lid margin
  3. Flow through superior & inferior canaliculi
  4. Gather in tear sac
  5. Exit tear sac through tear duct into nasal activity
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21
Q

Which two superior and inferior eyelid structures are responsible for tear film drainage?

A

2 Puncta: Superior and inferior canaliculi

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22
Q

How are tears drained from the puncta to the tear sac?

A
  • Tears flow through the superior and inferior canaliculi to the tear sac
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23
Q

What is the fate of tears within the tear sac?

A
  • Exit the tear sac through the tear duct into the nasal cavity
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24
Q

What are the three types of tears?

A
  • Basal
  • Reflex
  • Emotional (crying)
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25
What are the functions of the basal tears (3)?
* Basal tears are your basic functional tear: * Released continuously in tiny quantities to **lubricate** the cornea and **keep it clear** of dust * **Vital to ensure good visual acuity and comfort** * Basal tears also fight against bacterial infection as a part of the **immune system**
26
Which tears are referred to the increased tear production in response to ocular irritation?
* Reflex tear
27
What does the tear pathway comprise of?
Afferent pathway → CNS → Efferent pathway → Lacrimal gland ## Footnote Neurotransmitter: acetylcholine
28
Which afferent nerve innervates the cornea?
* Sensory nerve fibres via the ophthalmic branch of **trigeminal nerve**
29
How is the efferent pathway mediated?
* Mediated by the **parasympathetic nerve**, innervating the **lacrimal gland**
30
What is the function of the tear film?
* Maintains **smooth cornea-air surface** * **Oxygen supply to Cornea** – normal cornea has no blood vessels * **Removal of debris** (tear film and blinking) * **Bactericide**
31
How many layers comprise the tear film? Name them.
Three: * **Superficial Lipid Layer** (to reduce tear film evaporation - produced by a row of Meibomian Glands along the lid margins) * **Aqueous Tear Film** * **Mucinous Layer Corneal Surface** (maintains surface wetting)
32
Which glands along the lid margins produce the superficial lipid layer of the tear film?
* Meibomian glands
33
What is the function of the lipid layer of the tear film?
* Responsible for **protecting** the tear film from **rapid evaporation**
34
What is the purpose of the mucinous layer corneal surface?
* Maintains surface wetting
35
Which tear film layer forms the main bulk of the tear film?
* The water layer
36
How do mucin molecules regulate surface wetting of the corneal epithelial surface?
* The mucin molecules act by **binding water molecules to the hydrophobic corneal epithelial cell surface**
37
Which thin transparent tissue covers the outer surface of the eye?
* Conjunctiva
38
Describe the anatomical course of the conjunctiva.
* Origin: Outer edge of the cornea * Anatomical relations: Covers visible part of the eye & Lines the inside of the eyelids
39
What function is performed by the conjuctiva (3)?
* The conjunctiva of the eye provides **protection** and **lubrication** of the eye by the production of mucus and tears * Prevents microbial entrance into the eye and plays a role in **immune surveillance** * It lines the inside of the eyelids and provides a **covering** to the **sclera**
40
How is conjunctiva nourished with nutrients and oxygen?
* **Tiny blood vessels**
41
What is the average antero-posterior diameter of the eye?
* 24mm in adults
42
What are the 3 layers of the eye?
* Sclera * Choroid * Retina
43
What is the function of the sclera?
* The outer **fibrous opaque layer** responsible for **protecting** the eye and **maintaining shape** (high water content)
44
Describe the water content of the sclera:
* High water content
45
How many layers form the cornea? Name them.
* **Epithelium** * **Bowman's membrane** * **Stroma** (its regularity contributes towards transparency) * **Descemet's membrane** * **Endothelium** (pumps fluid out of the cornea and prevent corneal oedema)
46
The regularity of which corneal layer contributes towards transparency?
* Stroma
47
Which corneal structure pumps fluid out of the cornea and prevents corneal oedema?
* Endothelium
48
Describe the water content of the cornea:
* Low water content
49
What property of the cornea provides 2/3 of the eye's focussing power?
* Refractive index
50
What provides oxygen supply to the anterior segment of the eye (cornea)?
* The **tear film** considering there are no blood vessels supplying the cornea
51
What is the uvea?
* The most **vascular coat of the eyeball** and lies **between the sclera & retina**
52
Where does the uvea reside?
* Between the sclera and retina
53
What three structures comprise the uvea?
* Iris * Ciliary body * Choroid
54
Which eye layer is pigmented and vascular?
* Choroid
55
Where does the choroid lie?
Between the retina and sclera
56
What is the function of the choroid?
* Responsible for providing **circulation** to the eye & **shielding out unwanted scattered light**
57
What is the iris?
Round opening in the centre is the pupil
58
What is the function of the iris?
Controls light levels inside the eye similar to the aperture on a camera
59
What is the outer capsule of the lens?
* Outer acellular capsule
60
Which fibres comprise the core of the lens?
* **Regular inner elongated cell fibres** - providing transparency
61
What are the 4 main functions of the lens?
* Provide **transparency** * **Regular structure** * **Refractive power**, 1/3 of the eye focussing power (higher refractive index than aqueous fluid and vitreous) * **Elasticity & accommodation**
62
What is the innermost neurosensory layer of the eye?
* Retina
63
Which nerve transmits electrical impulses to the visual processing centres of the brain?
* Optic nerve
64
What term describes the visual portion of the optic nerve?
* Optic disc
65
Where is the optic blind spot located?
* Where the **optic nerve meets the retina**, there are no light sensitive cells (Rods and Cones)
66
Where is the macula located?
* Centre of the retina, temporal to the optic nerve
67
What is the macula?
* A small and highly sensitive part of the retina responsible for detailed central vision
68
What is the fovea?
* A **small depression in the retina** of the eye where **visual acuity is highest** * **​**The centre of the field of vision is focused in this region, where retinal cones are particularly concentrated
69
Which structure is located at the very centre of the macula?
* The fovea
70
Which structure is the most sensitive part of the retina?
* The fovea
71
Which photoreceptor cells are found at their highest concentration within the fovea?
* **Cone cells** to perceive in detail
72
What is the corresponding landmark for the physiological blind spot?
* The optic disc
73
What is central vision?
* Central / Foveal / Macular vision is responsible for **detailed central fine vision** and **daytime colour vision** * Reading, fascial recognition
74
How is central vision assessed?
* Visual acuity assessment
75
What is associated with a loss of foveal vision?
* Poor visual acuity
76
What is peripheral vision?
* Specialises in **detecting shape &** **movement** in the environment * Night vision, navigation vision
77
What is associated with a loss of central vision?
* Problems with reading and recognising faces
78
How is peripheral vision assessed?
* Visual field assessment
79
An extensive loss of peripheral vision is associated with what?
* **Inability to navigate within the environment** * Needs white stick despite perfect visual acuity
80
What is the neuroretina?
* The inner thicker layer comprising of retinal ganglion cells, and photoreceptors
81
How many layers form the neuroretina?
Three: * Outer photoreceptor * Middle bipolar * Inner retinal ganglion cells
82
Which cells comprise the outer layer of the retina? What is their funciton?
* **Photoreceptors (1st order neurones)** ## Footnote Detection of light
83
Which cells comprise the middle layer of the retina? What is their function?
* **Bipolar cells (2nd order neurones)** ## Footnote Local signal processing to improve contrast sensitivity, regulate sensitivity
84
Which cells comprise the inner retinal layer?
* **Retinal ganglion cells (3rd order neurone)** ## Footnote Transmission of signal from the eye to the brain
85
What is the function performed by the retinal pigment epithelium?
* **Transports nutrient from the choroid to the photoreceptor cells**, and **removes metabolic waste** from the retina
86
What are the two main classes of photoreceptor cells?
* **Rod & cone cells**
87
What are the characteristics of rod photoreceptor cells (4)?
* 100 times more **sensitive** to **light** than cones * **Slow response to light** * **Scotopic vision** * **120 million rods**
88
What are the characteristics of cone photoreceptor cells (4)?
* **Less sensitive to light** * **Faster response** to light * Responsible for day light fine vision & colour vision (**photopic vision**) * **6 million cones**
89
Which photoreceptor cells are concerned with peripheral and night vision?
* Rod cells ## Footnote More photoreceptors, more pigment, higher spatial and temporal (time) summation Recognizes motion
90
Which photoreceptor cells are concerned with central and day vision?
* Cone cells ## Footnote Recognizes colour and detail
91
Where are the mitochondria located within the photoreceptors?
* Inner segments
92
What are the outer segments comprised of?
* Discs, that contain rhodopsin
93
Which pigment resides within the outer segment of rod cells?
* Rhodopsin
94
What are the 2 components of rhodopsin?
* Opsin and Retinal
95
Upon exposure to photons of light, rhodopsin exists in which form?
* From **cis-form to trans-form** upon exposure to photons of light
96
What happens to rhodopsin upon light exposure?
* **Bleaching:** Photon interactions result in isomerisation of retinal from the cis to trans-form, subsequently degenerating the rhodopsin molecule into it's constituent components, opsin and trans-retinal
97
What is the fate of deactivated photo-pigments in the outer segment (3 steps)?
1. **Phagocytossed** by the **retinal epithelial cells** 2. **Regenerated inside the retinal epithelial cells** 3. **T****ransported** back to the photo-receptors
98
Describe the density and distribution of rod photoreceptors:
* **Widely distributed throughout the retina** * Highest density outside the macula (absent within the macula), progressively decreasing towards the periphery
99
Where are cone photoreceptors located?
* Distributed **exclusively within the macula**
100
Where can one find the highest concentration of rod photoreceptors in the retina?
20-40 degrees away from the fovea
101
What are the 3 types of cone cells?
* S-cones * M-cones * L-cones
102
What is the peak light sensitivity of rod cells?
498nm
103
Which cone cells are sensitives to short wavelengths (blue)?
S-cones
104
Which cone cells are sensitive to medium wavelengths (green)?
M-cones
105
Which colour are L-cones sensitive too?
Red colour
106
Which cone cells are stimulated by yellow light?
M- and L-cones equally | Combination of green and red light
107
What is the commonest form of colour vision deficiency?
**Deuteranomaly** (Daltonism)
108
What is deuteranomaly?
Cannot perceive the colour red ## Footnote Caused by the shifting of the M-cone sensitivity peak towards that of the L-cone curve, causing red-green confusion
109
What is full colour blindness called?
Achromatopsia
110
What test is conducted to detect colour blindness?
Ishihara test

Phase 1b - Neurology & Neuroscience (18 decks)

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