Ocular Anatomy and Tear Film Quiz

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Questions and Answers

What is the primary function of the aqueous humor in the anterior and posterior chambers?

To maintain structural integrity of the lens.

To anchor soft tissue to bone.

To provide illumination for the eye.

To provide nourishment for surrounding structures. (correct)

Which chamber is located between the ciliary body and the lens?

Posterior chamber (correct)

Vitreous chamber

Anterior chamber

Scleral chamber

What is the largest chamber of the eye?

Anterior chamber

Posterior chamber

Corneal chamber

Vitreous chamber (correct)

Which structure is responsible for providing sensory and motor innervation to the eye?

Nerves Signup and view all the answers

What is the primary role of the vitreous humor found in the vitreous chamber?

To provide cushion and insulation. Signup and view all the answers

What does the 'S' in the SCALP acronym stand for?

Skin Signup and view all the answers

Which layer of the skin is the outermost?

Epidermis Signup and view all the answers

What is the primary function of keratinocytes?

Provide water-resistant properties Signup and view all the answers

Which of the following is NOT a component of the epidermis?

Fibroblasts Signup and view all the answers

What does the term 'hypodermis' refer to?

Innermost skin layer Signup and view all the answers

Which cell type produces the majority of cells in the epidermis?

Keratinocytes Signup and view all the answers

Which component of the extracellular matrix is responsible for providing tensile strength?

Collagen Signup and view all the answers

What role do elastic fibers play in the skin?

They facilitate movement Signup and view all the answers

What structure supplies nourishment to the retina?

Choroid Signup and view all the answers

What is the function of the Meibomian glands?

To secrete oils onto the skin in front of the MCJ Signup and view all the answers

Which structure is the main refractive system of the eye?

Cornea Signup and view all the answers

Why is the iris considered part of the vascular layer of the eye?

It contains blood vessels. Signup and view all the answers

Which layer of the tear film is responsible for coating the ocular surface?

Mucoaqueous layer Signup and view all the answers

How is basal tear production initiated?

Spontaneously, by blinking Signup and view all the answers

When the ciliary muscle contracts, what happens to the zonules and the crystalline lens?

Zonules relax and lens accommodates. Signup and view all the answers

What is the average tear break-up time?

10 seconds Signup and view all the answers

What humor is present in the posterior chamber and what is it produced by?

Aqueous humor produced by the ciliary process. Signup and view all the answers

Which cranial nerve is primarily involved in the stimulation of reflex tears?

CN V Signup and view all the answers

What is the purpose of the fat in the orbit?

To provide cushion and insulation. Signup and view all the answers

Which receptor is the highest in the macula/fovea?

Cones Signup and view all the answers

What is the primary component secreted by emotional stimuli?

Emotional tears Signup and view all the answers

What happens to the lens during accommodation when looking at a near target?

The lens accommodates by adding more plus to the system. Signup and view all the answers

Which structure comes into contact with the globe during blinking?

Palpebral conjunctiva Signup and view all the answers

Which of the following types of tears are a direct response to irritants?

Reflex tears Signup and view all the answers

Which component of the tear film is primarily responsible for providing a protective lipid barrier?

Lipid layer Signup and view all the answers

What is the primary action of the parasympathetic system in relation to tear production?

Stimulates tear secretion Signup and view all the answers

What significant change occurred in the understanding of the tear film layers?

The aqueous and mucin layers were redefined as one layer Signup and view all the answers

Which region of the eyelid is known as the 'Lid wiper region'?

Area behind the MCJ Signup and view all the answers

What is a characteristic of the lipids secreted by the Meibomian glands?

Thick and viscous Signup and view all the answers

Which cranial nerve is involved in the secretion of basal tears?

CN VII Signup and view all the answers

What functions do capillary action serve in the drainage of tears?

Removes toxins and cellular debris Signup and view all the answers

Which structure connects the puncta to the lacrimal sac?

Lacrimal canaliculus Signup and view all the answers

What is the role of Horner's muscle in tear drainage?

Aids in pumping tears Signup and view all the answers

What happens during the evaporation of tears if there is a poor lipid layer?

Tear film ruptures Signup and view all the answers

What is the effect of aging on meibomian glands?

Keratinization and dropout of meibum Signup and view all the answers

How long do tears typically remain on the eyelid before evaporating?

10 seconds Signup and view all the answers

Which of the following statements about the lacrimal sac is true?

It collects tears through the nasolacrimal duct. Signup and view all the answers

What part does the valve of Hasner play in the nasolacrimal apparatus?

Prevents reflux of tears Signup and view all the answers

What does the mucoaqueous layer primarily do?

Maintains corneal health Signup and view all the answers

Which cranial nerve is responsible for the sensory innervation of the lacrimal gland?

CN V Signup and view all the answers

What is the function of Whitnall's ligament?

Maintain space between structures in the superior orbit Signup and view all the answers

What structure serves to cover the sclera and separate the globe from the orbit?

Tenon's capsule Signup and view all the answers

Which of the following is a primary function of orbital fat?

Acts as a cushion for the globe Signup and view all the answers

Study Notes

### Eyelid Structures

Palpebral Conjunctiva: Lining of the inner eyelid, continuous with the bulbar conjunctiva covering the eye
Lid Wiper Region: Elevated strip of palpebral conjunctiva along the eyelid margin, coming into contact with the globe during blinking
Ciliary and Lacrimal Portion of Eyelid Margin:
- Ciliary: Contains meibomian gland orifices, secreting oils (lipids) onto the skin in front of the margin.
- Lacrimal: Area closer to the lacrimal punctum.

Tear Film

Purpose: Coats the ocular surface (cornea and conjunctiva), preventing dryness and infection.
Average Tear Break Up Time: 10 seconds
Basal Tears: Secreted constantly to maintain a stable tear film, activated by the parasympathetic nervous system and CN7 (Facial Nerve).
Reflex Tears: Secreted in response to irritants and stimuli, activated by the parasympathetic nervous system and CNV (Trigeminal Nerve).
Emotional Tears: Secreted in response to emotions, activated by the limbic system and parasympathetic nervous system.
Types of Tears:
- Basal Tears: Lubricate and nourish the ocular surface.
- Reflex Tears: Wash away irritants and protect the eye.
- Emotional Tears: Release hormones and provide emotional relief.
Layers of Tear Film (Older Theory):
- Lipid Layer: Outermost layer, produced by meibomian glands, slows evaporation and creates a smooth surface.
- Aqueous Layer: Middle layer, produced by lacrimal glands, provides moisture and nutrients.
- Mucin Layer: Innermost layer, produced by goblet cells, provides adhesion to the corneal epithelium.
Layers of Tear Film (Newer Theory)
- Lipid Layer:
- Mucoaqueous Layer: More integrated than previously thought, combining the functions of both the mucin and aqueous layers.

Tear Film Production

Meibomian Glands: Located along the upper and lower eyelid margins, secrete lipids (oils).
Lacrimal Glands: Located within the lateral aspect of the upper eyelid, secrete aqueous fluid.
Goblet Cells: Scattered within the conjunctiva, produce mucin.

Eyebrow Structure (SCALP Acronym for Layers)

S: Skin
C: Connective Tissue (dense)
A: Aponeurosis (muscle)
L: Loose Connective Tissue
P: Periosteum

Skin Layers

Epidermis: Outermost layer of the skin:
- Keratinocytes: Major cell type, responsible for structural integrity and water resistance.
Dermis: Middle layer of the skin:
- Connective Tissue: Composed of fibroblasts, collagenous fibers, elastic fibers, and adhesive proteins.
Hypodermis: Subcutaneous tissue, composed of adipose (fat) and loose connective tissue.

Tears and Drainage

Tears are removed from the eye via capillary action and Horner's muscle.
Capillary action moves water without external force and helps clear cellular debris, toxins, and waste. Some tears also evaporate.
Horner's muscle aids in pumping tears through the nasolacrimal apparatus.
Tears normally last on the eyelid for 10 seconds.
A poor lipid layer leads to faster evaporation.
During evaporation, lipids diffuse towards the muco-aqueous layer, contaminating the mucin and causing the tear film to rupture.

Nasolacrimal Apparatus

Puncta: The openings in the eyelid margin that connect to the lacrimal canaliculi.
Lacrimal canaliculi: Tubes connecting the puncta to the lacrimal sac.
Lacrimal sac: A sac that collects tears, lined with epithelial cells that reabsorb tears.
Nasolacrimal duct: A duct lined with epithelium that carries tears into the nasal cavity.
The nasolacrimal duct has two portions:
- Intraosseous portion: Located in the nasolacrimal canal within the maxillary bone.
- Membranous/meatal portion: Located within the nasal mucosa, opening into the inferior meatus of the nasal cavity.
The valve of Hasner, a mucosal fold, prevents reflux of tears.

Tear Film Layers

Muco-aqueous layer: Maintains corneal and conjunctival health, provides nutrients, flushes debris and toxins, acts as the first line of defense against infections, provides a smooth refractive surface, protects against mechanical shock, and aids in lubrication.
Lipid layer: Prevents evaporation, creates a lid margin barrier, prevents spillover of tears, prevents skin lipids from migrating onto the ocular surface, forms a water-tight seal when eyelids are closed, and aids in lubrication.

Keratinization of meibomian gland (MG) ducts and MG dropout: Leads to a decline in meibum.
Decrease in sex hormones: Leads to a decline in meibum.
Lacrimal gland duct fibrosis: Leads to a decline in tear volume.
Decrease in number of goblet cells: Leads to a decline in mucins.
Decreased number of corneal nerves: Leads to reduced reflux tearing.
Eversion of lower puncta: Leads to poor drainage.

Lacrimal Gland Innervation

Sensory: CN V (ophthalmic nerve/lacrimal nerve)
Motor: Parasympathetic fibers

Horner's Muscle Innervation

Temporal and zygomatic branches of the orbicularis oculi muscle.

Orbital Bones

Bones of the cranium, face, and orbit contribute to the overall structure of the eye.
Foramina, fissures, and fossae (cavities) are important landmarks for understanding anatomical features.

Orbital Contents

The orbit contains the globe, connective tissues, blood vessels, orbital fat, and muscles.
Connective tissues:
- Tenon's capsule: Covers the sclera and EOM's, separating the globe from the orbit.
- Orbital septum (palpebral fascia): Separates the eyelids and lacrimal sac from the orbit.
- Periorbita: Covers the bone of the orbit, providing attachment for muscles, ligaments, and tendons.
Transverse dense connective tissue ligaments:
- Whitnall's ligament: Supports the superior orbit.
- Lockwood's ligament: Supports the inferior orbit.
- Medial check ligament: Prevents over-action of the medial rectus.
- Lateral check ligament: Prevents over-action of the lateral rectus.
Orbital septal system: A web of connective tissue septa that organizes, anchors, and supports orbital structures.

Orbital Nerves

Optic Nerve (CN II): Sense of sight.
Oculomotor Nerve (CN III): Innervates levator muscle and four EOMs (MR, SR, IO, IR).
Trochlear Nerve (CN IV): Innervates the Superior Oblique EOM.
Ophthalmic Nerve (CN V-V.1).
Maxillary Nerve (CN V-V.2)
Abducens Nerve (CN VI): Innervates the Lateral Rectus EOM.

Orbital Blood Vessels

Ophthalmic Artery: Supplies blood to the orbit.
Superior and Inferior Ophthalmic Veins: Drain blood from the orbit.

Orbital Muscles

Four Recti Muscles:
Orbital Fat: Provides cushion and insulation.
Bones: Provide protection.

Globe Divisions

Anterior chamber: Cavity between the cornea and iris/lens.
Posterior chamber: Cavity between the ciliary body and the lens.
Vitreous chamber: Largest chamber, located between the lens and retina.
Aqueous humor: Clear fluid produced by the ciliary process that nourishes surrounding structures.
Vitreous humor: Clear gel-like substance that maintains the eye's shape.

Accommodation System

The ciliary muscle contracts, causing the zonules to relax and the lens to accommodate (adding "plus" to the system) for near vision.
When looking at a distance, the ciliary muscle relaxes, causing the zonules to tighten and the lens to become less accommodating (less "plus" in the system).

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Description

Test your knowledge on eyelid structures and the tear film's role in ocular health. This quiz covers the anatomy of the eyelid including the conjunctiva and various tear types, such as basal, reflex, and emotional tears. Perfect for students studying ophthalmology or anatomy.