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Anatomy and Physiology > Special Senses > Flashcards

Special Senses Flashcards

1
Q

What is the function of the eye?

A

Converts light into nervous impulses for processing in the brain. Responsible for vision.

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2
Q

Describe the palpebrae?

A

Eyelids
Contain skeletal muscles
Outer surface is skin; inner surface is conjunctiva
Eyelids present on the free edge of the upper lid only
The angle that forms the junction between the two palpabra is the canthus

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3
Q

What is the correct name and function of the third eyelid?

A

Nictitating membrane
Extra protection
Distributes even tear coat

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4
Q

Where are the Meibomian glands found?

A

Small sebaceous glands situated beneath the conjunctiva of the eyelids

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5
Q

What is the fornix?

A

The angle formed by the reflection of the conjunctiva

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6
Q

Where is the lacrimal apparatus found?

A

Under the upper eyelids

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7
Q

What is the function of the lacrimal apparatus?

A

Produce tears

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8
Q

How do tears drain?

A

Drain via naso-lacrimal duct system. There are 2 small openings in the lids called the lacrimal punctata which lead to a pair of ducts called the lacrimal canniliculi, which join together to form the lacrimal duct which opens into the nasal cavity.

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9
Q

What makes up the outer layer of the eye?

A

The sclera
- tough fibrous tissue which helps maintains eye shape
- appears white except over the aqueous humour (appears translucent) where its called the cornea
-provides a place for extra-ocular muscles to attach
(control movement of eye)
-the sclera and cornea meet at the limbus
-the cornea is an avascular membrane
-Helps focus the light

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10
Q

What does the Middle layer (UVEA) of the eye consist of?

A

Choroid
Iris
Tapetum Lucidum
Ciliary Body

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11
Q

Describe the structure of the choroid?

A

Has an area of light reflecting cells

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12
Q

Describe the structure of the iris

A

Has central hole - pupil
Very vascular
- contraction and relaxation of smooth muscle of iris, alters size of pupil - controls the amount of light entering the eye/reaching the retina.

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13
Q

Describe the Tapetum lucidum

A

lies amongst the innermost layer of the retina
Has an area of light reflecting cells, which reflects light back onto the retina - improving night vision.
Function is to optimise low levels of light

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14
Q

Describe the ciliary body

A 
Smooth muscle fibres
Control the thickness and shape of lens
Control how the eye focuses:
- distance - lens narrows
- close - lens fattens and rounds
It projects towards the centre of the eye and creates a point of attachment for the lens
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15
Q

What attaches to the ciliary body?

A

The suspensory ligament

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16
Q

What makes up the inner layer of the eye?

A

The retina - converts light to nervous impulses which then travel to optic disc where the optic nerve carries the info to the brain

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17
Q

What makes us the retina?

A

2 layers of Photoreceptors

18
Q

Name and describe the photoreceptors

A

Rods

  • sensitive to low light, not colour
  • provide white and black and night vision
  • located at periphery of retina

Cones

  • sensitive to bright light
  • provide colour vision
  • located centrally
19
Q

Describe the make up of photoreceptors in dogs and cats

A

95% Rods and 5% Cones

20
Q

Name the 3 media found inside the eye

From front to back

A

Aqueous humour
Lens
Vitreous humour

21
Q

Describe the aqueous humour

A

Watery fluid circulates the anterior chamber
Provides nutrients to the lens
Produced by continuous cells of the ciliary body

22
Q

What is glaucoma?

A

When the aqueous humour isn’t reabsorbed properly, the fluid volume increases and increases the intraocular pressure and the eye will appear larger

23
Q

What is the vitreous humour

A

Semi-fluid transparent gel which separates the posterior aspect of the lens from the retina
Maintains the globe shape

24
Q

Describe the structure and function of the lens?

A

Solid, biconvex transparent structure situated behind the iris.
It is attached to the ciliary body by the suspensory ligament.
Made of elastic tissue
Responsible for more exact focusing of light onto the retina.

25
Q

What is opacity and how does it change with age?

A

Non-Transparency (cloudiness)

Lens becomes more transparent as animal gets older

26
Q

What is a cataract?

A

An abnormal opacity that will affect vision

27
Q

Describe the two reflexes of the eye used in practise

A
  1. The Menace Reflex
    - Object waved in front of an animals face will cause the animal to blink
  2. The pupillary reflex
    - Bright light shone into eye will cause the pupil to constrict (under ANS control)
28
Q

Describe how vision works?

A
  1. Light enters the eye through the cornea where is starts to become focussed
  2. The light then passes through the pupil
  3. The iris controls the size of the pupil and therefore regulates the amount of light entering the eye
  4. Light the passes through the lens where it focusses more finely
  5. The light then hits the photoreceptors in the retina where it produces an upside down image
  6. Any light that has missed the photoreceptors is reflected back onto the retina by the tapetum lucidum
  7. The image is received via the optic nerve and interpreted in the cerebral hemisphere
29
Q

Describe the make up and functions of the external ear

A

Pinna of ear

  • external ear flap
  • composed of a layer of skin and a layer of cartilage with blood vessels in between
  • directs sound waves into ear canal

External Auditory Meatus

  • opening leading to the auditory canal
  • contains ceruminous glands which produce ear wax
30
Q

Name the boundaries between the:
External and Middle Ear
Middle and Inner Ear

A

Tympanic membrane

Oval Window

31
Q

Describe the make up and functions of the middle ear

A

Auditory Ossicles: Malleus, Incus, Stapes
Transmits vibrations from tympanic membrane to oval window

Eustachian tube leaves middle ear and runs to pharynx - plays a role in equalising pressure on each side of the tympanic membrane

32
Q

What is the correct name for a middle ear infection and how could infection access this area?

A

Otitis media

Via pharynx and eustachian tube or via external ear

33
Q

Where is the inner ear located?

A

Deep within the temporal bone

34
Q

What process occurs in the cochlea?

A

Vibrations are converted to nerve impulses
Contains the Organ of Hearing (corti)
contains sensory hairs bathed in endolymph which react to different frequencies.
Send impulses via cranial nerve 8 whose fibres start here

35
Q

Apart from the cochlea, what other structures are found in the inner ear?

A

Utricle, Saccule and Semi-circular canals

36
Q

What is the function of the saccule and utricle

A 
Movement of calcium particles stimulates the hairs to pass info to cranial nerve 8. This info is processed by the brain to recognise the position of the head.
Contain Maculae (receptors) that detect the position of the head relative to gravity
37
Q

What is the structure and function of the semi-circular canals?

A

At the base of each canal is an ampulla which has a group of sensory hair cells.
When the head moves, the endolymph flows past the hairs in the ampulla pulling them. These sensory cells then send messages to the auditory nerve which regulates head position.

38
Q

Why are the semi-circular canals arranged in 3 planes?

A

To recognise all directions of head movement

39
Q

Where are taste buds found close to?

A

Papillae of tongue
MM & soft palate
Pharynx
Epiglottis

40
Q

What nerves are involved in taste?

A

Facial (7), Glossopharyngeal (9) and Vagus (10)

41
Q

Where are the sensory nerve endings for smell found?

A

The ethmoturbinate bones at back of nasal cavity

42
Q

Where is the olfactory nerve located?

A

Runs from nose, passes through the mesethmoid bone into the Olfactory Bulb of the brain

Anatomy and Physiology (15 decks)

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