Organ of Vision

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Questions and Answers

What are Zeis's glands primarily classified as?

Mucous glands

Modified sweat glands

Accessory lacrimal glands

Sebaceous glands (correct)

Which part of the lacrimal gland is larger and deeper?

Palpebral part

Accessory part

Orbital part (correct)

Conjunctival part

What is the primary function of the lacrimal gland?

To protect the eye from foreign bodies

To produce tears for eye lubrication (correct)

To absorb light for vision

To provide nutrients to the eye

Which structure collects tears before they flow into the lacrimal sac?

Lacrimal punctum Signup and view all the answers

Which part of the conjunctiva covers the sclera?

Bulbar conjunctiva Signup and view all the answers

What is the role of lysozyme found in tears?

To serve as an antibacterial agent Signup and view all the answers

Where is the lacrimal sac located?

In the lacrimal fossa of the lacrimal bone Signup and view all the answers

What are the small accessory glands in the conjunctival fornices called?

Krause’s glands Signup and view all the answers

What is the primary function of the eyelids?

To protect the eye and distribute tears Signup and view all the answers

Which muscle is responsible for retracting the eyelid?

Levator palpebrae superioris Signup and view all the answers

What anatomical feature separates the two eyelids?

Palpebral fissure Signup and view all the answers

What are tarsal plates primarily composed of?

Condensed fibrous tissue Signup and view all the answers

What is the location of the lacrimal punctum?

At the inner canthus of the eyelids Signup and view all the answers

Which structure helps to maintain the moisture of the cornea?

Meibomian glands Signup and view all the answers

What role do eyelashes play in eye protection?

Heightening protection from debris Signup and view all the answers

What anatomical term refers to the eyelid?

Palpebrae Signup and view all the answers

What is the main function of the sclera in the eye?

To protect the eye and maintain its shape Signup and view all the answers

Which layer of the eye is responsible for its vascularity?

Vascular middle tunic Signup and view all the answers

What separates the cornea from the iris?

Anterior chamber Signup and view all the answers

Which part of the eye is avascular and nourished by lymph fluid?

Cornea Signup and view all the answers

What are the components of the cornea identified in the content?

Corneal epithelium and Bowman’s membrane Signup and view all the answers

What structure pierces the sclera at the back of the eye?

Optic nerve Signup and view all the answers

What is the role of Tenon’s capsule?

To cover the sclera and provide protection Signup and view all the answers

Which aspect of the eye's anatomy helps maintain its shape?

Aqueous humor Signup and view all the answers

What is the primary function of the ciliary body?

To suspend the lens and assist in accommodation for near vision Signup and view all the answers

Where does the choroid layer end anteriorly?

At the ora serrata, merging with the sclera Signup and view all the answers

What is the composition of the iris primarily made of?

Connective tissue, smooth muscle fibers, and blood vessels Signup and view all the answers

How is the ciliary muscle arranged, and what is its function?

In radial, circular, and longitudinal layers to alter lens shape Signup and view all the answers

What is the significance of the suprachoroidal lamina?

It separates the choroid from the sclera and contains ciliary vessels and nerves Signup and view all the answers

What structure is formed by the attachment of the iris to the ciliary body?

Iridocorneal angle Signup and view all the answers

Which part of the ciliary body contributes to the accommodation process of the eye?

Ciliary muscle Signup and view all the answers

What distinguishes the sclera from the episclera?

The sclera is dense while the episclera is loose connective tissue and vascular Signup and view all the answers

What is the primary function of the sphincter pupillae muscle?

To constrict the pupil Signup and view all the answers

Which part of the retina is known as the blind spot?

Optic disc Signup and view all the answers

What structure separates the anterior and posterior segments of the eye?

Lens Signup and view all the answers

Which layer of the retina is sensitive to light?

Optic part of the retina Signup and view all the answers

What characterizes the fovea centralis?

Has the highest concentration of cones Signup and view all the answers

What is the primary role of the dilatator pupilae muscle?

To dilate the pupil Signup and view all the answers

Which of the following statements about the retina is correct?

The outer surface of the retina is attached to the choroid. Signup and view all the answers

What is the shape of the lens when it is under constant tension?

Globular Signup and view all the answers

What occurs when the ciliary muscle contracts?

The lens thickens in response. Signup and view all the answers

Which function does aqueous humor NOT perform?

Helps in vision adjustment. Signup and view all the answers

What causes the formation of floaters in the vitreous body?

Formation of clumps of gel or crystal-like deposits. Signup and view all the answers

What is the role of the suspensory ligaments?

They maintain the curvature of the lens. Signup and view all the answers

Which of the following best describes accommodation?

The ability of the lens to adjust shape for focusing. Signup and view all the answers

What is the structure of the vitreous body attached to in the eye?

Lens and ciliary processes. Signup and view all the answers

Which of the following muscles is NOT part of the extrinsic muscles of the eye?

Levator palpebrae. Signup and view all the answers

How does the ciliary muscle affect vision for distant objects?

It remains relaxed increasing tension on suspensory ligaments. Signup and view all the answers

Study Notes

Structure of Eyeball:
- The eyeball is a spherical structure, approximately 2.5cm in diameter.
- It has three distinct layers: outer tunic (fibrous), middle tunic (vascular), and inner tunic (nervous).
- The spaces within the eyeball are filled with fluids, supporting the wall and internal parts, maintaining its shape.
Visual Accessory Organs:
- Eyelids (Palpebrae): Thin skin folds covering and protecting the eye.
  - Levator palpebrae superioris muscle retracts the eyelid.
  - Eyelashes along the edges provide additional protection from foreign objects.
- Conjunctiva: Mucous membrane lining the inner surface of eyelids, folds back to cover the anterior surface of the eyeball excluding the cornea.
- Lacrimal Apparatus:
  - Lacrimal gland and ducts
  - Conjunctival sac
  - Lacrimal puncta and canaliculi
  - Lacrimal sac
  - Nasolacrimal duct
- Extrinsic Muscles: Responsible for eye movement.
  - Four recti muscles (superior, inferior, medial, lateral)
  - Two oblique muscles (superior, inferior)
Eyeball Development:
- Complex interaction between neighboring tissues during embryonic development forms the eye.
- Neuroectoderm of the forebrain forms the sensory retina and accessory pigmented structures.
- Surface ectoderm forms the lens and anterior corneal epithelium.
- Neural crest cells contribute to the fibrous coats of the eye and tissues in the anterior segment.

Structure of Eyelids

Skin: Thin and loose.
Superficial fascia: Contains the palpebral part of orbicularis oculi muscle.
Palpebral fascia: Forms orbital septum, thickens to form tarsal plates.
Tarsi: Thin plates of condensed fibrous tissues at the edges of the lids.
Tarsal glands: Meibomian glands embedded in the posterior surface of the tarsi.
Conjunctiva: Lines the posterior surface of the tarsi.

Glands of Eyelids

Zeis's glands: Large sebaceous glands at the lid margin.
Moll's glands: Modified sweat glands closely associated with Zeis's glands; located at the lid margin.
Meibomian glands: Sebaceous or tarsal glands.

Lacrimal Apparatus

Lacrimal gland: Produces tears.
- Orbital and palpebral lobes.
- Excretory ducts.
Lacrimal punctum: Opening of drainage ducts.
Lacrimal canals: Collect tears.
Lacrimal sac: Store and drain tears to the nasolacrimal duct.
Nasolacrimal duct: Drains tears into the nasal cavity.

Orbit

Bony cavity: Houses the eye, lacrimal gland, and extrinsic muscles.
Periosteum: Lines the bony orbit.
Fat: Supports and cushions the eye.
Blood Vessels: Supply the eye and surrounding structures.
Nerves: Control and support the eye

Structure of the Eye

Outer Tunic (Fibrous Tunic):
- Sclera: Forms the posterior 5/6 of the eyeball, composed of dense fibrous tissues.
- Cornea: Transparent anterior portion, replacing the sclera.
Middle Tunic (Vascular Tunic):
- Choroid: pigmented layer separating the sclera from the retina; carries blood vessels.
- Ciliary body: Thickened part of the middle tunic containing the ciliary muscle.
- Iris: Colored portion of the eye containing muscles (sphincter and dilatator pupillae) controlling the size of the pupil.
Inner Tunic (Nervous Tunic):
- Retina: Innermost layer containing photoreceptors (rods and cones).
- Macula lutea: Region with high concentration of cones.
- Fovea centralis: Center of the macula containing only cones – sharpest vision.
- Optic disc: Contains no photoreceptors (blind spot) where the optic nerve exits.

Lens

Transparent, biconvex structure: Located between the anterior and posterior segments.
Suspensory Ligaments: Maintain constant tension to the lens shape.
Ciliary muscles: Change the shape of the lens to adjust focus (accommodation).

Aqueous Humor

Clear fluid: Fills the anterior and posterior chambers.
Secretion by ciliary processes: Flows through the pupil into the anterior chamber.
Drainage through the canal of Schlemm: Maintains the shape of the eye's front and nourishes the cornea and lens.

Vitreous Body

Clear, jelly-like substance: Fills the posterior segment of the eyeball.
Hyaloid membrane: Encloses the vitreous body.
Maintains eyeball shape: Anchors the retina in place.

Extrinsic Muscles

Four recti muscles: Superior, Inferior, Medial, Lateral – responsible for moving the eye.
Two oblique muscles: Superior and Inferior – responsible for moving the eye.

Blood Supply

Ophthalmic artery: Primary source of blood to the eye.
Branches of ophthalmic artery and other arteries provide blood supply to different parts of the eye.

Second Cranial Nerve (Optic Nerve)

Axons of ganglion cells: Carry visual information from the retina.
Optic Chiasm: Partial crossing of nerve fibers.
Optic Tracts: Continue to transmit the information.

Lesions of Visual Pathway

Total anopsia: Complete loss of vision in one eye.
Bitemporal hemianopsia: Loss of temporal vision in both eyes.
Contralateral homonymous hemianopsia: Losses of corresponding halves of the visual field.

Eyeball Development

Inductive interactions: Neighboring tissues interact to develop the eye.
Neuroectoderm, surface ectoderm, and mesenchyme: Contribute to the formation of the eye, including the sensory retina, lens, cornea, and other tissues.
Optic vesicles: form the optic cup, nerve, optic chiasm, and optic tract, forming the components of the eye.

Questions

Retina Layers: Ten layers
Fovea Centralis Receptors: Cones
Muscle attached to lens: Ciliary body
Innermost tunic of the eye: Retina
White portion of the eye: Sclera

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Description

Explore the intricate structure of the eyeball and its visual accessory organs. This quiz covers the layers of the eyeball, eyelids, conjunctiva, lacrimal apparatus, and extrinsic muscles. Test your knowledge about how these components work together to facilitate vision.

Organ of Vision - Eye Structure and Components

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