83 Questions
Which muscle is the main elevator of the eyebrows and forehead?
Frontalis
At what stage of development do the eyelids form from the folds of surface ectoderm filled with mesenchyme?
2nd month
Which cranial nerve innervates the muscles responsible for eyebrow movements?
CN VII (Facial)
What is the primary function of the eyelids?
Cover the globe for protection
Which nerve is innervated first for reflex blinking due to touch or irritation?
CN V
What is the most common blink rate per minute during spontaneous blinking?
15
Which glands contribute to the lipid layer of tears?
Meibomian and Zeiss glands
What is the role of the muscle of Horner in tear drainage?
Surrounds the canaliculi, aids in pumping tears into the lacrimal sac
What is the function of eyelashes in the eye?
Screen and sense the environment, induce blink reflexes
What is the cause of lagophthalmos?
Physiological, mechanical or paralytic (VII CN palsy)
What is the characteristic feature of xanthelasma?
Yellow plaques of lipid near the inner canthus
What is madarosis associated with?
Loss of eyelashes
What is the clinical significance of trichiasis?
Misdirected growth of eyelashes
What is the cause of poliosis?
Depigmentation of the hair
What is the characteristic feature of ectropion?
Eversion of the eyelid margin
What is the cause of external hordeolum?
Acute inflammation of an eye gland, usually caused by staphylococci
What is the function of the plica semilunaris (semilunar fold)?
It allows lateral movement of the eye
Where is the caruncle located?
Just medial to the plica semilunaris
What is the function of the lacrimal punctum?
To drain tears from the eye into the lacrimal sac
Where are the pores of the meibomian glands located?
At the eyelid margin
Which layer of the eyelids contains the tarsal plate?
Orbicularis layer
What separates the tarsal and orbital portion of the upper eyelid?
Superior palpebral crease
What is the function of the malar crease?
To separate the tarsal and orbital portion of the lower eyelid
Where do the upper and lower eyelids meet?
At the corners of the palpebral fissure in the lateral and medial canthus
What is the function of the lacrimal lake?
To pool tears
What is the function of the lacrimal papilla?
To contain the lacrimal punctum
What is the function of the superior palpebral sulcus?
To separate the tarsal and orbital portion of the upper eyelid
Where are the fibers of the superior palpebral levator muscle inserted?
Into the skin
What is the composition of the tarsal plate?
Dense irregular connective tissue and palpebral ligaments
Which glands are large sebaceous glands located posterior to the eyelashes and housed inside the tarsal plates?
Meibomian glands
What is the function of the orbital septum?
To serve as a barrier and restrict fat from falling onto the lids margins
Which muscles are part of the posterior muscular system of the eyelids?
Superior levator palpebrae muscle and superior and inferior tarsal muscle of Muller
Which nerve provides sensory innervation to the eyelids?
Trigeminal nerve
What are the glands of Zeis associated with?
Eyelash follicles
What is the blood supply to the eyelids?
Medial palpebral artery, lacrimal artery, and peripheral arcades
Which type of blinking is associated with the palpebral portion of the eyelids?
Spontaneous blinking and reflex blinking
What does the palpebral conjunctiva consist of?
Stratified columnar epithelial layer and a submucosa layer
What provides sensory innervation to the eyelids?
Trigeminal nerve
Which specialized areas are included in the palpebral portion of the eyelids?
Muscle of Riolan and muscle of Horner
What is the composition of the palpebral portion of the eyelids?
Dense irregular connective tissue and palpebral ligaments
Which layer of the tear film contains antibacterial substances such as lysozyme, beta-lysin, and lactoferrin?
Aqueous layer
Which gland provides stability to the tear film?
Meibomian gland
Which layer of the tear film is primarily responsible for trapping debris and removing sloughed epithelial cells and debris?
Mucous layer
Which layer of the tear film is only 1% of the thickness of the tear film and contains waxy esters, cholesterol, and free fatty acids?
Lipid layer
What is the normal Tear Break Up Time (TBUT)?
Between 15 and 45 seconds
What is the primary cause of Congenital Nasolacrimal Duct Obstruction?
An imperforate valve of Hasner
What is the characteristic symptom of Canaliculitis?
Pain, swelling, erythema, and discharge
What is the main feature of Dacryoadenitis?
Inflammatory enlargement of the lacrimal gland
What is the common cause of Dacryocystitis?
Obstruction of the nasolacrimal duct
What is the recommended treatment for Acute Canaliculitis with a pouting puncta?
A posterior cut down of the canaliculus and curettage of the granules
What is the primary symptom of Congenital Dacryostenosis?
Lacrimation
What is the most common congenital lacrimal abnormality?
Congenital Nasolacrimal Duct Obstruction
What is the total volume of tears on the ocular surface?
7 to 10 μl
Where is the lacrimal gland located?
Temporal fossa
What is the average pH of the tear film?
7.45
What is the primary function of the lacrimal gland?
Produce tears
What is the composition of the lacrimal gland secretion?
Water, electrolytes, and mucus
What is the main function of the conjunctival goblet cells?
Produce mucus
What is the average tear production per minute?
1 μl/min
What is the primary innervation of the lacrimal gland?
Parasympathetic nerves
What triggers reflex tearing?
Tactile stimuli
What contributes to the osmolarity of the tear film?
Salt content
Where does tear film distribution involve the secretion of fluid?
Upper fornix
What is the capacity of the eye to hold tears at once?
20-30 μl
What is the primary function of the lacrimal sac?
To store tears
What is the length of the interosseous part of the nasolacrimal duct?
12 mm
What is the function of the valve of Hasner in the nasolacrimal duct?
To prevent retrograde movement of fluid up from the nasal cavity
What contributes to the lateral displacement of the lateral wall during tear drainage?
Contraction of the orbicularis muscle
What is the primary role of the canaliculi in tear drainage?
To transport tears to the lacrimal sac
Where does the lacrimal sac empty into?
Inferior meatus of the nose
What prevents reflux and acts as the first valve in the nasolacrimal drainage system?
Valve of Rosenmuller
What is the function of the valve of Krause in the nasolacrimal drainage system?
To aid in tear drainage
What is the primary factor causing tears to drain into the nasolacrimal duct?
Gravity
What causes the expansion of the lacrimal sac during tear drainage?
Contraction of the lacrimal sac
What is the function of the common canaliculus in the nasolacrimal drainage system?
To transport tears to the lacrimal sac
What is the function of the lacrimal punctum in the nasolacrimal drainage system?
To drain tears
What supplies blood to the bulbar conjunctiva?
Anterior ciliary arteries
What is the main retractor of the inferior eyelid?
Interior tarsal muscle
What are the two medial depressor muscles of the eyelids?
Porcerus and Corrugator
In a normal patient, you should be able to see the superior limbus.
False
What is the vertical measurement of the palpebral fissure?
10 mm
What nerve innervates the muscle of Müller innervated?
Sympathetic nervous system
The palpebral conjunctiva is made up of non-keratinized stratified columnar epithelium cells.
True
Study Notes
Anatomy of the Eyelids: Key Facts
- The palpebral portion of the eyelids is used for spontaneous and reflex blinking
- The orbital septum is a dense irregular connective tissue that serves as a barrier and restricts fat from falling onto the lids margins
- The posterior muscular system includes the superior levator palpebrae muscle and the superior and inferior tarsal muscle of Muller
- The tarsal plate is composed of dense irregular connective tissue and palpebral ligaments that hold it in position
- The palpebral conjunctiva consists of stratified squamous epithelial layer and a submucosa layer
- The meibomian glands are large sebaceous glands located posterior to the eyelashes and occupy the length of the tarsal plate
- The glands of Zeis are modified sebaceous glands associated with eyelash follicles
- The trigeminal nerve provides sensory innervation to the eyelids, while the facial nerve supplies the orbicularis muscle
- The blood supply to the eyelids includes the medial palpebral artery, lacrimal artery, and peripheral arcades
- The eyelids have two types of blinking: spontaneous blinking and reflex blinking
- The palpebral portion of the eyelids includes two specialized areas: the muscle of Riolan and the muscle of Horner
- The tarsal plate is composed of dense irregular connective tissue and palpebral ligaments that hold it in position
Tear Film and Lacrimal Gland Overview
- Mucous layer, produced by conjunctival goblet cells, constitutes 30-40% of the total tear film and helps in adhesion and trapping of bacteria and viruses.
- The total volume of tears on the ocular surface is 7 to 10 μl, with normal tear production at about 1 μl/min, and the eye's capacity to hold 20-30 μl at once.
- Normally, the tear film is isotonic and has an average pH of 7.45, with electrolytes contributing to its osmolarity.
- Tear film properties, including salt content and osmolarity, vary based on factors such as blink rate, humidity, ocular pathology, and contact lens use.
- The lacrimal secretory system consists of the main and accessory lacrimal glands, meibomian glands, and conjunctival goblet cells, serving a dual function of tear formation and drainage.
- The lacrimal gland, located in the temporal fossa of the orbital plate, has orbital and palpebral portions, each with distinct characteristics and locations.
- The secretion of the lacrimal gland consists of water, electrolytes, and antibacterial agents, and reflex secretion increases in response to stimuli.
- The lacrimal gland is supplied by the lacrimal artery and innervated by sensory, vasomotor sympathetic, and secretomotor parasympathetic nerves.
- Reflex tearing occurs in response to external stimuli, with the afferent pathway through the trigeminal nerve and the parasympathetic pathway through the facial nerve.
- Tear film distribution involves the secretion of fluid into the upper fornix, spreading across the globe's anterior surface, and being forced out of pores by orbicularis contraction.
- Both upper and lower eyelid margins have a tear meniscus, with the upper tear meniscus continuous with the lower meniscus and leading to punctum in the medial canthus for drainage.
Test your knowledge of the anatomy of the eyelids with this quiz. Explore key facts about the structures and functions of the eyelids, including muscles, glands, blood supply, and innervation.
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