Pouch on caudal border (lateral helix) of ear -- formed by an indent called the lateral incisure in underlying auricular cartilage
The inner ear communicates with the pharynx by way of ____________.
Auditory tube (Eustacian tube)
the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a system of passages comprising two main functional parts: - The cochlea, dedicated to hearing and the vestibular tube which is dedicated to balalce.
What is the purpose of the auditory tube?
equalize the pressure in the middle ear cavity with external, atmospheric pressure. If pressure is not equal on both sides of the tympanic membrane, there is a painful distortion of it
Malleus (hammer), incus (anvil), and stapes (stirrup). They amplify sound waves to the inner ear.
How are excessively loud noises damped?
By 2 skeletal muscles in the ear: tensor tempani; stapedius (smallest skeletal muscle in body)
Attached to stapes. Contraction tenses stapes to reduce its movement. Degree of stretch determined by loudness of sound waves. The more taut the muscle, the less vibration, the more damper on the loudness...
2 parts of the inner ear and their functions
1. Vestibular portion - sensory for position and equilibrium 2. Cochlear portion - sensory for sound
Origin of the cochlear nerve?
Branch of the vestibulocochlear nerve (cranial nerve VIII)
Membranous labryrinth contains what fluid?
fluid inside the membranous labyrinth which consists of low sodium/high potassium electrolyte concentration similar to intracellular fluid
-contains water, LOW POTASSIUM, high sodium, high calcium, and protein -similar to cerebral spinal fluid
membranous sac in the vestibule; connected to semicircular canals. both ends of each semicircular canal open into the utricle
the smaller of two sacs within the membranous labyrinth of the vestibule in the inner ear (sacculus = small bag)
sense of up or down movement
Site of active absorption of endolymph
Sensory receptors that sense equilibrium - located in the ampullas of the semicircular canals
Sensory receptor areas in the utricle and saccule -- patches of epithelium containing hair cells -- sensation contributes to orientation and balance
These are calcium carbonate crystals that stick to the goop on the walls of the utricle and saccule walls. They have greater density than the surrounding endolymph, so they lag under head acceleration.
What part(s) detect rotational acceleration or deceleration involving the head?
Ampullary crista of corresponding semicircular duct. When the head is moved, hair cells of crista stimulated.
2 parts of the cochlea
Scala vestibuli Scala tympani
Duct at the apex of the cochlea where perilymph from the scala vestibuli is allowed to flow into the scala tympani. Only communication between 2 parts of the cochlea
receptor site for vibrations and relays them to auditory nerve fibers
converts sound waves to nerve impulses - > then transmit to cerebral cortex for interpretation
measures the amplitude and frequency of sound waves.
Where are high-frequency sounds dissipated?
Near the base of the cochlea near the vestibule
Which component of the ear relies on fluid conduction of sound waves for its function?
The first fluid displaced by the inward movement of the stapes is ______________________.
Perilymph in the vestibule
The sensory receptor of the inner ear that converts sound energy to a nerve impulse is _____________.
Organ of Corti
What makes up the pinna?
Skin with a cartilaginous core
Ceruminous glands are what type of glands?
modified apocrine sweat glands
2 layers of epithelium separated by connective tissue
consists of semicircular canals, their ampullas and utricle and saccule.
These are all involved in the sense of equilibrium.
Each of the inner ear regions contains mechanoreceptors.
Tympanic cavity lined by what type of cells?
Simple squamous or cuboidal epithelium
Tympanic membrane composed of which type of cells?
2 layers of simple squamous epithelium with fine connective tissue between epithelia
Auditory tube is lined with which type of cells?
Ciliated pseudostratified epithelium
T or F: Inner ear has both osseous and membranous labyrinths?
Oval vestibular window is closed by
Cochlear (round) window covered by __________.
the porous, perforated bony core of the cochlea
what the cochlea wraps around
adds protection to the blood vessels
What nerve innervates the stapedius muscle?
Facial nerve (CN VII)
What innervates the tensor tympani muscle?
Branch of the Trigeminal Nerve (Cranial Nerve V) - Mandibular Division
Where does the auditory tube originate?
Rostral portion of the tympanic cavity
Give the origin, insertion, innervation, and action of the tensor veli palatini muscle.
Origin: scaphoid fossa at the base of the medial pterygoid plate, spine of the sphenoid bone, and lateral aspect of the auditory tube
Insertion: its tendon turns around the pterygoid hamulus inserting as the palatine aponeurosis
Innervation: mandibular division of trigeminal (V3)
Action: tenses the soft palate, tigthens the soft palate as in blowing, primary opener of the auditory tube
Give the origin, insertion, innervation, and action of the levator veli palatini muscle
Origin: inferior surface of the petrous portion of the temporal bone in front of the carotid canal and cartilage of the auditory tube
(enters pharynx from the gap above the superior constrictor muscle)
Insertion: upper surface of palatine aponeurosis
Innervation: pharyngeal branch of vagus
Action: raises and retracts the soft palate, bringing it close to the posterior wall of the pharynx; active in phonation and sucking liquid
What attaches the stapes to the vestibular window?
Helix of the ear
Lateral and medial edges of the pinna
Scapha of the ear
Inner portion of the pinna
the small eminence rising from the cheek and protecting the erar passage
transverse ridge on the internal, concave wall of the auricular cartilage at the level of the beginning of the external acoustic meatus
region posterior and inferior to the tragus
Small, boot-shaped cartilaginous plate located in the muscles rostral and medial to the external ear
Isolated cartilage interposed in the auricular muscles
Through what foramen does the facial nerve exit the skull?
Name 2 parasympathetic ganglia present in region of middle and inner ear.
1. Geniculate ganglion - found on facial nerve where major petrosal nerve branches off 2. Otic ganglion - located lateral to the wall of the auditory tube. (also innervates parotid salivary gland)