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Questions and Answers
What is the function of the medial rectus muscle?
What is the function of the medial rectus muscle?
- Moves the eye medially (correct)
- Moves the eye laterally
- Elevates the eye and turns it medially
- Depresses the eye and turns it laterally
Which cranial nerve controls the lateral rectus muscle?
Which cranial nerve controls the lateral rectus muscle?
- VI (Abducens) (correct)
- IV (Trochlear)
- III (Oculomotor)
- V (Trigeminal)
What is the main function of the inferior oblique muscle?
What is the main function of the inferior oblique muscle?
- Depresses eye and turns it medially
- Moves eye laterally
- Elevates eye and turns it medially
- Elevates eye and turns it laterally (correct)
What is the purpose of the pigmented layer in the retina?
What is the purpose of the pigmented layer in the retina?
Which term refers to the tiny pit containing only cones for the highest visual acuity?
Which term refers to the tiny pit containing only cones for the highest visual acuity?
What pigment is found in rods and is formed from Opsin and Retinal?
What pigment is found in rods and is formed from Opsin and Retinal?
Where are the lacrimal glands located?
Where are the lacrimal glands located?
What is the function of tarsal glands associated with the eyelid edges?
What is the function of tarsal glands associated with the eyelid edges?
What is the function of lacrimal canaliculi?
What is the function of lacrimal canaliculi?
Where is the lacrimal caruncle located?
Where is the lacrimal caruncle located?
What is the function of ciliary glands associated with the eyelashes?
What is the function of ciliary glands associated with the eyelashes?
Which structure drains lacrimal secretion into the nasal cavity?
Which structure drains lacrimal secretion into the nasal cavity?
Which eye structure contains only cones for the highest visual acuity?
Which eye structure contains only cones for the highest visual acuity?
What is the pigment found in cones and is essential for color vision?
What is the pigment found in cones and is essential for color vision?
The area of the retina that lacks photoreceptors, thus creating a blind spot, is known as the:
The area of the retina that lacks photoreceptors, thus creating a blind spot, is known as the:
Which part of the eye is responsible for fine-tuning the focus of light onto the retina?
Which part of the eye is responsible for fine-tuning the focus of light onto the retina?
What is the main photosensitive pigment found in rods, essential for vision in low light conditions?
What is the main photosensitive pigment found in rods, essential for vision in low light conditions?
The transparent structure of the eye that helps to refract light onto the retina is called the:
The transparent structure of the eye that helps to refract light onto the retina is called the:
Which eye structure secretes aqueous humor to maintain intraocular pressure?
Which eye structure secretes aqueous humor to maintain intraocular pressure?
Which eye component contains blood vessels and provides nourishment to the outer layers of the eye?
Which eye component contains blood vessels and provides nourishment to the outer layers of the eye?
What is the function of the iris in the eye's physiology?
What is the function of the iris in the eye's physiology?
What is the function of the suspensory ligament (zonular fibers) in relation to the lens?
What is the function of the suspensory ligament (zonular fibers) in relation to the lens?
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Study Notes
Eye Structure and Function
- Special sense receptors: large, complex sensory organs or localized clusters of receptors
- Accessory structures: extrinsic eye muscles, eyelids, conjunctiva, and lacrimal apparatus
Eyelids and Eye Muscles
- Canthus: medial commissure and lateral commissure
- Palpebral fissure: space between the eyelids in an open eye
- Tarsal glands: modified sebaceous glands associated with eyelid edges, producing oily secretions to lubricate the eye
- Ciliary glands: modified sweat glands between eyelashes, with ducts opening at eyelash follicles
- Lacrimal caruncle: raised area containing sebaceous and sweat glands, producing oily, whitish secretion to lubricate the eye
Lacrimal Apparatus
- Lacrimal glands: located above the lateral end of each eye, continually releasing dilute salt solution (tears) onto the anterior surface of the eyeball
- Lacrimal canaliculi: tears flush across the eyeball into these canaliculi
- Lacrimal sac: after canaliculi
- Nasolacrimal duct: finally enters the inferior meatus of the nasal cavity
Extrinsic Eye Muscles (External Eye Muscles)
- Lateral rectus: moves eye laterally (cranial nerve VI: Abducens)
- Medial rectus: moves eye medially (cranial nerve III: Oculomotor)
- Superior rectus: elevates eye and turns it medially (cranial nerve III: Oculomotor)
- Inferior rectus: depresses eye and turns it medially (cranial nerve III: Oculomotor)
- Inferior oblique: elevates eye and turns it laterally (cranial nerve III: Oculomotor)
- Superior oblique: depresses eye and turns it laterally (cranial nerve IV: Trochlear)
Eyeball Structure
- Fibrous layer: outermost layer
- Sclera: protective layer, visible as the "white of the eye"
- Cornea: transparent, crystal clear, well-supplied with nerve endings
- Vascular layer: middle of the eyeball, divided into three distinguishable regions
- Choroid: blood-rich nutritive tunic containing dark pigment, preventing light scattering inside the eye
- Ciliary body: attached to the lens by the ciliary zonule, and the iris
- Pupil: pigmented iris with a rounded opening, allowing light to pass
Retina
- Sensory layer: delicate two-layered retina, extending anteriorly only to the ciliary body
- Pigmented layer: composed of pigmented cells, absorbing light and preventing scattering inside the eye
- Neural layer: transparent inner of the retina, containing millions of receptor cells (rods and cones)
- Fovea centralis: lateral to each blind spot, a tiny pit containing only cones, with the greatest visual acuity
- Rhodopsin: purple pigment found in rods, formed from opsin (protein) and retinal (modified vitamin A product)
Lens and Accommodation
- Lens: flexible biconvex crystal-like structure, focusing light onto the retina
- Anterior (aqueous) segment: anterior to the lens, containing aqueous humor
- Posterior (vitreous) segment: posterior to the lens, containing vitreous humor
- Accommodation: the eye's ability to focus specifically for close objects
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