ABO Ocular Anatomy & Physiology 3 — Questions and Answers
Question 1: Which portion of the aqueous humor drainage system is located in the angle of the anterior chamber?
- Canal of Schlemm
- Episcleral veins
- Trabecular meshwork (Correct answer)
- Collector channels
Correct answer: Trabecular meshwork
The trabecular meshwork lines the angle of the anterior chamber and is the primary site of aqueous humor outflow resistance.
Question 2: The choroid's primary physiological role is to:
- Provide structural support to the globe
- Supply oxygen and nutrients to the outer retina (Correct answer)
- Regulate intraocular pressure
- Produce melanin for UV protection only
Correct answer: Supply oxygen and nutrients to the outer retina
The choroid is a highly vascular layer that provides oxygen and nutrients to the outer retinal layers, including the photoreceptors.
Question 3: Which cranial nerve controls the superior oblique muscle responsible for intorsion and depression of the adducted eye?
- CN III
- CN IV (Correct answer)
- CN VI
- CN V
Correct answer: CN IV
The trochlear nerve (CN IV) innervates the superior oblique muscle, which intorts and depresses the eye especially when adducted.
Question 4: The limbus is clinically important because it contains:
- Only corneal stem cells
- Only trabecular meshwork
- Corneal stem cells, aqueous drainage structures, and is a surgical landmark (Correct answer)
- Only melanocytes
Correct answer: Corneal stem cells, aqueous drainage structures, and is a surgical landmark
The limbus contains corneal epithelial stem cells (at the palisades of Vogt), drainage structures, and is used as a landmark for surgical incisions.
Question 5: What type of collagen predominates in the corneal stroma and contributes to its transparency?
- Type I collagen in irregular arrangement
- Type IV collagen in a random network
- Type I collagen in regular orthogonal lamellae (Correct answer)
- Type II collagen in a fibrous network
Correct answer: Type I collagen in regular orthogonal lamellae
The corneal stroma contains type I collagen arranged in precise orthogonal lamellae of uniform diameter, which minimizes light scattering and ensures transparency.
Question 6: The vitreous humor is attached most firmly to the retina at which location?
- Posterior pole near the fovea
- Equator of the globe
- Vitreous base straddling the ora serrata (Correct answer)
- Optic nerve head only
Correct answer: Vitreous base straddling the ora serrata
The vitreous base, which straddles the ora serrata, is the site of the firmest vitreoretinal attachment and does not detach even in advanced PVD.
Question 7: Which cells in the retina are responsible for phagocytosing shed outer segment discs of photoreceptors?
- Müller cells
- Microglia
- Retinal pigment epithelium (RPE) (Correct answer)
- Astrocytes
Correct answer: Retinal pigment epithelium (RPE)
RPE cells phagocytose and digest shed outer segment tips of photoreceptors daily, which is essential for maintaining photoreceptor health.
ABO Ocular Anatomy & Physiology 3
Which portion of the aqueous humor drainage system is located in the angle of the anterior chamber?