Term
| 1. What components make up the external ear? What is the function of the external ear? |
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Definition
The outer ear consists of the ear flap (also called the pinna) which can be upright (a prick ear) or floppy. The ear flap funnels sound into the ear canal. Unlike humans that have a very short ear canal, dogs have a long narrow ear canal that makes almost a 90 degree bend as it travels to the deeper parts of the ear.
The outer ear cannel is separated from the middle ear by a thin membrane called the eardrum or tympanic membrane. The ear drum is very fragile and can be damaged by ear disease or during ear cleaning. |
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Term
| 2. What components make up the middle ear? What is its function? |
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Definition
| The middle ear consists of 3 small bones(malleus/hammer, incus/anvil, stapes/stirrup), , an air filled cavity called the bulla and a thin tube (the eustachian tube) leading from the bulla to the back of the mouth. The middle ear amplifies and transmits the vibrations from the eardrum to the inner ear. |
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Term
| 3. What components make up the inner ear? What is its function? |
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Definition
| The inner ear connects to the brain and contains nerves and centers for balance and hearing. The inner ear contains the actual sensory receptors that convert the mechanical vibrations to nerve impulses, along with receptors for the equilibrium sense. The hearing portion of the inner ear is contained in a snail-shell shaped spiral cavity in the temporal bone called the cochlea. Within the hollowed out bony cavity of the cochlea is a soft, multi-layered, fluid-filled portion that contains the receptor organ of hearing – the organ of Corti. |
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Term
| 5. What is the Eustachian tube and where is it located? |
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Definition
| The middle ear, connects the middle ear to the pharynx (throat) |
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Term
| 6. Name the auditory ossicles and where they are located. |
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Definition
Malleus, incus, stapes
The middle ear is an air-fi lled cavity within the
temporal bone between the tympanic membrane
and cochlea
Vibrations of the tympanic membrane are
transmitted to the cochlea by three small bones
collectively called the ossicles (Figure 12-5).
• The malleus attaches to the tympanic membrane
and forms a joint with the incus (Figure
12-6).
• The incus forms a joint with the stapes.
• The stapes is in contact with the oval window |
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Term
| 7. Which is the ossicle that you can see against the surface of the tympanic membrane? |
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Definition
The malleus attaches to the tympanic membrane
and forms a joint with the incus |
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Term
| 8. Which ossicle is nearest the inner ear? |
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Definition
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Term
| 1. List some of the causes of ear diseases. What is the most common cause? Discuss this with your preceptor |
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Definition
Atopic dermatitis and Otitis
Food allergy
Ear mites
Foreign body
Mass in vertical ear canal
Skin disorders
Types of ear problems encountered in dogs and cats include:
infection
foreign bodies
trauma to the ear flap
tumors inside the ear
tumors of the ear flap
aural hematoma |
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Term
| 6. What 2 nerves run through the tympanic bulla? If damaged by inflammation, what can occur? |
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Definition
| Because the facial and sympathetic nerves course through the middle ear, facial nerve paralysis or Horner’s syndrome (miosis, ptosis, enophthalmos, and protrusion of the nictitans), or both, may be present on the same side as the otitis media. |
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Term
| 3. List the diagnostic tests used to diagnose ear disorders. |
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Definition
Dx of otitis externa is straightforward, based on clinical signs (head shaking, scratching at the ear, visual redness of some portion of the ear surface, odor and/or discharge emanating from the ear, otoscopic eval of the ear canal integrity and cytological eval of swabs from the ear and ear canal (looking for presence of inflammatory cells and microorganisms, foreign bodies, masses and/or parasites) and sometimes ear cultures.
In addition to the above findings, if the hx consists of persistent ear inflammations (> 6 m), there is a 90% probability that both otitis externa and otitis media are present. In this case, complete medical resolution is unlikely, and only medical mgmt for the long term is possible. |
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