The Special Senses - Answers

Arlo Guthrie — Thu, 02 Apr 2009 15:09:07 GMT

Current Revision posted to Revision Guide For Student Nurses - Part 1 by Arlo Guthrie on 4/2/2009 3:09:07 PM

ANSWERS

List the special senses.
- Olfaction (smell).
- Vision.
- Hearing.
- Balance.
- Taste.
- Touch.
What are the names of the bones located at the back of the nasal cavity, which are covered by a mucous epithelium housing the bipolar receptor cells of the olfactory system?
Ethmoturbinate bones.
Which of the cranial nerves is responsible for the sense of smell?
I - Olfactory.
List 6 parts of the anatomy that help to protect the eye from injury.
- The orbits (eye sockets).
- The zygomatic arch of the skull.
- The eyelids.
- The third eyelids.
- The lacrimal apparatus (responsible for tear production).
- Eyelashes.
What is meant by lacrimation?
The production of tears.
What is the name of the fibrous tissue of which the eyelids are made?
The tarsal plate.
What are the names of the angles where the upper and lower eyelids meet?
The medial and lateral canthus.
What are the names of the glands whose ducts open onto the edge of the eyelid (these secrete a fatty material that contribute to the composition of tears)?
The Meiobian (or tarsal) glands.
Give another name for the eyelashes.
Cilia.
The globe of the eye has 3 layers; describe them briefly.
- Outer layer - fibrous for protection.
- Middle layer (known as the uvea or uveal tract) - vascular & pigmented.
- Inner layer (the retina) - comprised of receptor cells.
The outer layer of the eye comprises the sclera and the cornea. Which part gives the white colour of the eye?
The sclera.
What is the name of the junction between the sclera and the cornea?
The limbus.
The uvea (middle layer of the eye) comprises 5 structures. Can you list them and briefly state the function of each?
- Choroid - a dark lining at the back of the eye which contains blood vessels which supply all the ocular internal structures.
- Tapetum - an area of light reflecting cells located on the inner surface of the choroid thought to improve night vision.
- Ciliary body - the inward projection of the uvea from the lining towards the centre of the eye; contains smooth muscle enabling the lens to change shape and thus focus.
- Suspensory ligament - supports the lens.
- Iris - contains 2 layers of muscular tissue which vary the amount of light reaching the retina via the pupil.
How does the pupil differ in cats and dogs?
When the iris of a dog is fully closed the pupil is round; however in cats, the pupil becomes a vertical slit.
Describe the 3 layers which make up the retina (inner layer of the eye).
- Outer layer of photoreceptor cells (rods & cones).
- Middle layer of bipolar receptor cells.
- Inner layer of ganglion cells which carry information to the optic nerve.
Describe the aqueous humour.
A watery fluid filling the space between lens and cornea. It serves to nourish both lens and cornea aswell as helping to maintain the shape of the cornea.
Describe the vitreous humour.
A jelly-like substance which fills the space between the lens and the back of the eye.
Describe in 6 brief steps how the eye functions.
- Light enters via the cornea and is focused onto the retina.
- The amount of light allowed into the eye is controlled by the iris which adjusts the size of the pupil.
- The lens focuses light onto the retina (focusing is controlled by the ciliary muscle which alters the curvature of the lens).
- Light passes through the retinal layers and produces and upside-down image on the light-receptive cells.
- The tapetum reflects light that missed the rods and cones on the way through back onto the retinal layers.
- The image is transmitted by the bipolar receptor cells and ganglion cells through the optic nerve, optic chiasma, midbrain and culminating at the cerebral cortex.
The ear is divided into 3 main parts. Can you name them?
- External ear.
- Middle ear.
- Inner ear.
List the 3 components of the external ear.
- Pinna (the cartilaginous ear flap which serves to funnel sound and is also used as a means of expression).
- Vertical canal.
- Horizontal canal.
What do the ceruminous glands secrete?
Ear wax.
What is the correct name for the eardrum?
The tympanic membrane.
What is the name of the passage where the external ear ends and the tympanic membrane lies across the entrance to the middle ear?
The external auditory meatus.
What is the name of the air-filled space that is connected to the pharynx by the auditory tube and houses the middle ear?
The tympanic bulla.
What is another name for the auditory tube?
Eustachian tube.
Name the 3 small bones that lie across the middle ear which serve to transmit vibrations from the tympanic membrane to the inner ear.
- Malleus.
- Incus.
- Stapes.
What is the collective name for the 3 small bones given in answer to Q26?
Ossicles.
In addition to the tympanic membrane, 2 other membranes are located within the middle ear. Can you name them?
- The oval window.
- The round window.
What is the name of the fluid that is found between the bony labyrinth and membranous labyrinth of the inner ear?
Perilymph.
What is another name for the auditory nerve that carries nervous impulses from the inner ear to the brain?
The vestibulocochlear nerve.
What is the name of the fluid that is found within the membranous labyrinth?
Endolymph.
The membranous labyrinth comprises 4 parts. Name them and briefly describe of each.
- Utricle - a delicate membranous sac located in the bony vestibule of the ear beneath the cavity that houses the semicircular canals.
- Saccule - as above but smaller.
- Semicircular canals - 3 arch-shaped, fluid filled canals (vertical, horizontal & transverse); these register impressions of changes of position in the body by oscillation of the fluid and convey the information to the cerebellum.
  The semicircular canals sense movements rather than position (see Q34).
- Cochlea - the spiral canal of the internal ear concerned with hearing.
What is the function of the crista located at each ampulla (at the base of the semicircular canal)?
This comprises hair cells embedded in a jelly-like cupula that swings to and fro as the endolymph moves within the canal and registers turning movements.
What are the receptors located within the utricle and saccule responsible for monitoring the position of the head known as?
Maculae.
What is the function of the spiral organ (or organ of Corti) located within the cochlea?
This contains sensory hairs that react to different frequencies as a sound travels through the endolymph up the spiral of the cochlea.
What is the medical name for the sensation of taste?
The gustatory sensation.
What is the collective name given to the sensory nerve ending responsible for taste, and where are they located?
Taste buds; these are found over the tongue and the mucous membranes of the palate, pharynx and epiglottis.
List the cranial nerves that pass stimuli from the taste buds to the brain.
- VII - Facial.
- IX - Glossopharyngeal.
- X - Vagus.