Part 3 - Utricle & Saccule

Question 1

The utricle and saccule are referred to as the ____ organs

Answer 1

Otolith

Question 2

What is the vestibule?

Answer 2

The part of the inner ear between the semicircular canals and the cochlea, containing the otolith organs

Question 3

How many ampullae are there?

Answer 3

3 - corresponding to the 3 semicircular canals

Question 4

What is the crus commune?

Answer 4

The joining of the non-ampullated ends of the anterior and posterior SCCs (semicircular canals)

Question 5

Which is more horizontally orientated and which is more vertically of the utricle and the saccule?

Answer 5

Utricle - more horizontal

Saccule - more vertical

Question 6

How is the sensory patch of the otolith organs different from the SCCs?

Answer 6

The sensory patch is called macula and is flat, so it’s not a crista anymore. Also, they have calcium carbonate crystals, called otoconia, on top of the gelatinous matrix

Question 7

What is an “otolith”?

Answer 7

The part of an otolith organ that contains the otoconia (calcium particles)

Question 8

What is the purpose of otoconia?

Answer 8

To add mass to the gelatinous matrix, which will make the hair cells responsive to static position changes of the head in the gravitational field

Question 9

What is the striola?

Answer 9

The central region of the otolithic macula

• the kinocilia of the utricle are oriented towards the striola and the orientation is away from the stroll in the saccule macula
• allows for excitation by some of the hair cells, regardless of the direction of motion

Question 10

What are the 3 types of static tilt?

Answer 10

Roll (side-to-side)
Yaw (“no”)
Pitch (“yes”)

Question 11

Of roll, pitch and yaw, which are encoded by which otolith organ?

Answer 11

Saccule: static upright tilt
Utricle: static roll and pitch

*Static yaw is not encoded by the otolith organs

Question 12

What is the name of the artery that supplies blood for the inner ear?

Answer 12

Basilar artery (arises from the junction of the 2 vertebral arteries)

Question 13

What is the name of the artery that provides oxygenated blood to the utricle, anterior SCC, and horizontal SCC?

Answer 13

Anterior vestibular artery (branches from the anterior inferior cerebellar artery (AICA) which comes from the basilar artery)

Question 14

What portion of the inner ear does the common cochlear artery supply?

Answer 14

The cochlea, saccule, and posterior SCC

Question 15

Neurons from what portion of the inner ear form the superior vestibular branch of the vesibulocochlear nerve?

Answer 15

Utricle
Anterior SCC
Horizontal SCC

Question 16

The saccule and posterior canal nerve fibres form which branch of the vestibulocochlear nerve?

Answer 16

The inferior branch

Question 17

Where are the first neurons of the vestibular component of the vestibulocochlear nerve located?

Answer 17

The scarpa ganglion outside of the vestibule

Question 18

The vestibular pathways start from the vestibular end organs, travel to the vestibular nuclei in the brainstem, and project to which 4 locations?

Answer 18

• the spinal cord
• the 3 extraocular motor nuclei controlling eye movements
• the cerebellum coordinating postural adjustments
• the thalamus, then cortex

Question 19

How do the vestibular responses from both sides complement each other?

Answer 19

By acting as a 3-way switch (both sides stimulate the same amount at rest, and when one side stimulates more, the other inhibits)