Podcast
Questions and Answers
Which muscle is the main elevator of the eyebrows and forehead?
Which muscle is the main elevator of the eyebrows and forehead?
- Procerus
- Corrugator
- Frontalis (correct)
- Orbicularis Oculi
At what stage of development do the eyelids form from the folds of surface ectoderm filled with mesenchyme?
At what stage of development do the eyelids form from the folds of surface ectoderm filled with mesenchyme?
- 6 months
- 4.5 months
- 2nd month (correct)
- 1st month
Which cranial nerve innervates the muscles responsible for eyebrow movements?
Which cranial nerve innervates the muscles responsible for eyebrow movements?
- CN V (Trigeminal)
- CN VII (Facial) (correct)
- CN VI (Abducens)
- CN III (Oculomotor)
What is the primary function of the eyelids?
What is the primary function of the eyelids?
Which nerve is innervated first for reflex blinking due to touch or irritation?
Which nerve is innervated first for reflex blinking due to touch or irritation?
What is the most common blink rate per minute during spontaneous blinking?
What is the most common blink rate per minute during spontaneous blinking?
Which glands contribute to the lipid layer of tears?
Which glands contribute to the lipid layer of tears?
What is the role of the muscle of Horner in tear drainage?
What is the role of the muscle of Horner in tear drainage?
What is the function of eyelashes in the eye?
What is the function of eyelashes in the eye?
What is the cause of lagophthalmos?
What is the cause of lagophthalmos?
What is the characteristic feature of xanthelasma?
What is the characteristic feature of xanthelasma?
What is madarosis associated with?
What is madarosis associated with?
What is the clinical significance of trichiasis?
What is the clinical significance of trichiasis?
What is the cause of poliosis?
What is the cause of poliosis?
What is the characteristic feature of ectropion?
What is the characteristic feature of ectropion?
What is the cause of external hordeolum?
What is the cause of external hordeolum?
What is the function of the plica semilunaris (semilunar fold)?
What is the function of the plica semilunaris (semilunar fold)?
Where is the caruncle located?
Where is the caruncle located?
What is the function of the lacrimal punctum?
What is the function of the lacrimal punctum?
Where are the pores of the meibomian glands located?
Where are the pores of the meibomian glands located?
Which layer of the eyelids contains the tarsal plate?
Which layer of the eyelids contains the tarsal plate?
What separates the tarsal and orbital portion of the upper eyelid?
What separates the tarsal and orbital portion of the upper eyelid?
What is the function of the malar crease?
What is the function of the malar crease?
Where do the upper and lower eyelids meet?
Where do the upper and lower eyelids meet?
What is the function of the lacrimal lake?
What is the function of the lacrimal lake?
What is the function of the lacrimal papilla?
What is the function of the lacrimal papilla?
What is the function of the superior palpebral sulcus?
What is the function of the superior palpebral sulcus?
Where are the fibers of the superior palpebral levator muscle inserted?
Where are the fibers of the superior palpebral levator muscle inserted?
What is the composition of the tarsal plate?
What is the composition of the tarsal plate?
Which glands are large sebaceous glands located posterior to the eyelashes and housed inside the tarsal plates?
Which glands are large sebaceous glands located posterior to the eyelashes and housed inside the tarsal plates?
What is the function of the orbital septum?
What is the function of the orbital septum?
Which muscles are part of the posterior muscular system of the eyelids?
Which muscles are part of the posterior muscular system of the eyelids?
Which nerve provides sensory innervation to the eyelids?
Which nerve provides sensory innervation to the eyelids?
What are the glands of Zeis associated with?
What are the glands of Zeis associated with?
What is the blood supply to the eyelids?
What is the blood supply to the eyelids?
Which type of blinking is associated with the palpebral portion of the eyelids?
Which type of blinking is associated with the palpebral portion of the eyelids?
What does the palpebral conjunctiva consist of?
What does the palpebral conjunctiva consist of?
What provides sensory innervation to the eyelids?
What provides sensory innervation to the eyelids?
Which specialized areas are included in the palpebral portion of the eyelids?
Which specialized areas are included in the palpebral portion of the eyelids?
What is the composition of the palpebral portion of the eyelids?
What is the composition of the palpebral portion of the eyelids?
Which layer of the tear film contains antibacterial substances such as lysozyme, beta-lysin, and lactoferrin?
Which layer of the tear film contains antibacterial substances such as lysozyme, beta-lysin, and lactoferrin?
Which gland provides stability to the tear film?
Which gland provides stability to the tear film?
Which layer of the tear film is primarily responsible for trapping debris and removing sloughed epithelial cells and debris?
Which layer of the tear film is primarily responsible for trapping debris and removing sloughed epithelial cells and debris?
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?
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?
What is the normal Tear Break Up Time (TBUT)?
What is the normal Tear Break Up Time (TBUT)?
What is the primary cause of Congenital Nasolacrimal Duct Obstruction?
What is the primary cause of Congenital Nasolacrimal Duct Obstruction?
What is the characteristic symptom of Canaliculitis?
What is the characteristic symptom of Canaliculitis?
What is the main feature of Dacryoadenitis?
What is the main feature of Dacryoadenitis?
What is the common cause of Dacryocystitis?
What is the common cause of Dacryocystitis?
What is the recommended treatment for Acute Canaliculitis with a pouting puncta?
What is the recommended treatment for Acute Canaliculitis with a pouting puncta?
What is the primary symptom of Congenital Dacryostenosis?
What is the primary symptom of Congenital Dacryostenosis?
What is the most common congenital lacrimal abnormality?
What is the most common congenital lacrimal abnormality?
What is the total volume of tears on the ocular surface?
What is the total volume of tears on the ocular surface?
Where is the lacrimal gland located?
Where is the lacrimal gland located?
What is the average pH of the tear film?
What is the average pH of the tear film?
What is the primary function of the lacrimal gland?
What is the primary function of the lacrimal gland?
What is the composition of the lacrimal gland secretion?
What is the composition of the lacrimal gland secretion?
What is the main function of the conjunctival goblet cells?
What is the main function of the conjunctival goblet cells?
What is the average tear production per minute?
What is the average tear production per minute?
What is the primary innervation of the lacrimal gland?
What is the primary innervation of the lacrimal gland?
What triggers reflex tearing?
What triggers reflex tearing?
What contributes to the osmolarity of the tear film?
What contributes to the osmolarity of the tear film?
Where does tear film distribution involve the secretion of fluid?
Where does tear film distribution involve the secretion of fluid?
What is the capacity of the eye to hold tears at once?
What is the capacity of the eye to hold tears at once?
What is the primary function of the lacrimal sac?
What is the primary function of the lacrimal sac?
What is the length of the interosseous part of the nasolacrimal duct?
What is the length of the interosseous part of the nasolacrimal duct?
What is the function of the valve of Hasner in the nasolacrimal duct?
What is the function of the valve of Hasner in the nasolacrimal duct?
What contributes to the lateral displacement of the lateral wall during tear drainage?
What contributes to the lateral displacement of the lateral wall during tear drainage?
What is the primary role of the canaliculi in tear drainage?
What is the primary role of the canaliculi in tear drainage?
Where does the lacrimal sac empty into?
Where does the lacrimal sac empty into?
What prevents reflux and acts as the first valve in the nasolacrimal drainage system?
What prevents reflux and acts as the first valve in the nasolacrimal drainage system?
What is the function of the valve of Krause in the nasolacrimal drainage system?
What is the function of the valve of Krause in the nasolacrimal drainage system?
What is the primary factor causing tears to drain into the nasolacrimal duct?
What is the primary factor causing tears to drain into the nasolacrimal duct?
What causes the expansion of the lacrimal sac during tear drainage?
What causes the expansion of the lacrimal sac during tear drainage?
What is the function of the common canaliculus in the nasolacrimal drainage system?
What is the function of the common canaliculus in the nasolacrimal drainage system?
What is the function of the lacrimal punctum in the nasolacrimal drainage system?
What is the function of the lacrimal punctum in the nasolacrimal drainage system?
What supplies blood to the bulbar conjunctiva?
What supplies blood to the bulbar conjunctiva?
What is the main retractor of the inferior eyelid?
What is the main retractor of the inferior eyelid?
What are the two medial depressor muscles of the eyelids?
What are the two medial depressor muscles of the eyelids?
In a normal patient, you should be able to see the superior limbus.
In a normal patient, you should be able to see the superior limbus.
What is the vertical measurement of the palpebral fissure?
What is the vertical measurement of the palpebral fissure?
What nerve innervates the muscle of Müller innervated?
What nerve innervates the muscle of Müller innervated?
The palpebral conjunctiva is made up of non-keratinized stratified columnar epithelium cells.
The palpebral conjunctiva is made up of non-keratinized stratified columnar epithelium cells.
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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.
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