Facial Muscles, Eyelids and Ears Flashcards
Facial muscles
Muscles involved with facial expression
Different from muscles of mastication which raise and lower jaw
Innervated by cranial nerve VII - Facial nerve
Somatic muscles
Develop from somites
-Extrinsic eye muscles
-Tongue muscles
Visceral muscles
Develop from pharyngeal arches
-Muscles of facial expression
-Other muscles of the face
Facial nerve
Exits skull caudal to external acoustic meatus through stylomastoid foramen
Platysma m.
Cutaneous muscle
Innervated by dorsal and ventral buccal brs. and caudal auricular br. of facial n.
Draws commissure of lips caudally
Orbicularis oris m.
Located along free border of lips around angle of the mouth
N: dorsal and ventral buccal brs. of facial n.
A: Close mouth opening
Pull nose downward during sniffing
Dilates nostril
Buccinator m.
Forms foundation of cheek; located deep to platysma and partly deep to orbicularis oris m.
N: Dorsal and ventral buccal brs. of facial n.
A: Move food from vestibule to masticatory surface of teeth
Levator nasolabialis m.
Naso - nose, labia - upper lip
N: Auriculopalpebral br. of facial n.
A: Dilate nostril and raise upper lip
Zygomaticus m.
N: Auriculopalpebral br. of facial n.
A: Draw commissure of mouth dorsocaudally
Draw scutiform cartilage and ear rostrally
Parotidoauricularis m.
N: Facial n.
A: Depress the ear
Components of the eyelid
Palpebra (superior and inferior)
Palpebral fissure
-Opening between palpebrae
Commissure (medial and lateral)
-Corners
Lacrimal caruncle
-Triangular prominent structure located at medial angle of the eye; color usually relates to color of animal
Palpebral ligaments
-Medial attaches medial palpebral commissure to frontal bone
-Lateral attaches lateral palpebral commissure to zygomatic bone
Eyelashes
-Cilia present of superior palpebra but absent or few on inferior palpebra
Tarsal (meibomian) glands
Modified sebaceous glands that open at eyelid margin
Secrete lipids as part of superficial layer of tear film
Better developed in upper eyelid
Lacrimal gland
Located dorsolateral to the eye
Produces aqueous portion of tears
Innervated by facial n. (parasympathetic)
Superficial gland of the third eyelid
Located ventromedial to the eye
Produces aqueous portion of tears
Innervated by facial m.
Tear film
Superficial layer
-Lipids secreted by tarsal glands and ciliary glands located in palpebrae
-Limits evaporation of underlying aqueous layer
Middle aqueous layer
-Watery substance from lacrimal gland and superficial gland of third eyelid
-Flushes foreign material from conjunctival sac and lubricates palpebral/corneal interfaces
Inner mucoid layer
-Mucoprotein secretion from conjunctival cells
-Located between aqueous layer and cornea
-Binds aqueous film to cornea
Third eyelid and gland
AKA plica semilunaris/nictitating membrane
Composed of fold of palpebral conjunctiva and T shaped piece of cartilage
Lymphoid tissue located on medial surface
Superficial gland surrounds ventral portion of third eyelid
Conjunctiva
Mucous membrane
Composed of:
-Palpebral conjunctiva - covers inner surface of palpebrae
-Bulbar conjunctiva - covers rostral part of sclera and is continuous with outer layer of cornea substantia propria
Aqueous tear flow
Lacrimal gland -> conjunctival sac -> over anterior surface of eye -> lacrimal lake -> superior/inferior lacrimal puncta -> superior and inferior ducts (canaliculi) -> lacrimal sac (within lacrimal fossa) -> nasal vestibule via nasolacrimal ducts
Nasolacrimal duct
Begins at lacrimal sac in lacrimal fossa
Courses through osseous nasolacrimal canal of lacrimal and maxillary bones
Courses deep to nasal mucosa and ends in nasal vestibule on ventral aspect of alar fold
Orbicularis oris m.
Muscle of the eyelid
Encircles the eye
Closes palpebral fissure
Retractor anguli oculi lateralis m.
Muscle of the eylid
Covers lateral palebral ligament
Retracts the lateral angle of eye caudally (squinting)
Levator anguli oculi medialis m.
Muscle of the eyelid
Located dorsomedial to eye
Raises the eyelid
External ear
Auricle
-AKA pinna or ear flap
-Free part of the ear
Ear canal (external acoustic meatus)
-Mostly cartilaginous
-Two parts: vertical and horizontal
Cartilage of the external ear
Auricular cartilage
-Funnel shaped
-Forms vertical ear canal and part of horizontal ear canal
Annular cartilage
-Located between auricular cartilage and ear canal
-Forms terminal part of horizontal ear canal
Scutiform cartilage
-Small cartilaginous plate located in muscles rostral and medial to ear
Structures of external ear
Helix - Curved margins of auricular surface
Anthelix - Transverse ridge on inner aspect of auricle
Marginal cutaneous sac - Skin pouch
Tragus - Thick part of auricular cartilage located laterally
Antitragus - Ridge of cartilage located caudal to tragus
Intertragic incisure - Groove between tragus and antitragus
Pretragic incisure - Groove located rostral to tragus
Tympanic membrane (ear drum)
Located between external ear canal and middle ear
Part of malleus is fixed to tympanic membrane
Middle ear
Consists of tympanic cavity located in temporal bone
Tympanic cavity has small, dorsal epitympanic recess and large, ventral tympanic bulla
Location of auditory ossicles which transmit and amplify air vibrations from tympanic membrane to inner ear
Internal auditory (Eustachian) tube connects typmanic cavity with nasopharynx
Filled with air
Muscles of the middle ear
Tensor tympani m. - attaches to malleus
Stapedius muscle - attaches to stapes, smallest muscle in body
Aid in movements of tympanic membrane and auditory ossicles
Inner ear
Located within petrous portion of temporal bone
The semicircular canals and vestibule are cavities in petrous temporal bone - involved in vestibular system (organ of balance)
Cochlea - cavitiy in petrous temporal bone taht contains membranous cochlear duct; involved in hearing
Inner ear contains fluid (perilymph and endolymph)
Circumoral glands in cats
Large sebaceous glands around mouth, more numerous on lower lip
Secretions used for scent marking
