Flashcards in The Eye Deck (68):
The orbit is formed by which bones?
Frontal, maxillary, zygomatic bones and lacrimal
The orbit's boundaries - roof
frontal anf sphenoid
The orbit's boundaries - medial border
maxilla, lacrimal and ethmoid
The orbit's boundaries - lateral border
zygomatic and sphenoid
The orbit's boundaries - floor
maxilla and palatine
Why is the orbit concave?
to increase field of vision
Lateral margin of the orbit is at the junction of the...
frontal and zygomatic bones
The infraorbital margin extends upward to form what?
the anterior lacrimal crest
The supraorbital margin extends downward to form what?
the posterior lacrimal crest.
What is the purpose of the lacrimal apparatus?
to produce and drain lacrimal fluid (tears)
What do tears contain?
salt, mucous and lyzosymes
What is the function of the lacrimal gland?
Lubricates, moistens and cleans the conjunctiva
What does the lacrimal gland contain?
water, salt, mucin, and a bacterocidal enzyme
Explain what happens to the tears in the general process of removing them
half of them from the lacrimal gland evaporate. The remainder enter the papilla for drainage into the lacrimal sac. The lacrimal sac is connected to the nasolacrmal duct. Then it enters the nasal cavity and is covered by a mucous membrane.
What are the functions of the eyelashes/eyebrows?
Protects eyevall from foreign things, protects from perspiration, shades the eye from direct sun rays.
Which glands are at the base of the eyelids? What do they do?
Sebaceous (ciliary) glands are at the base, used to release a lubricating fluid into the hair follicles to avoid infection (like sty)
What do the sebaceous glands located between the eyelid and conjunctiva serve to do?
prevent sticking of eye
Which other glands are there of the eye?
suderiferous (sweat) glands
What does the lacrimal caruncle secrete?
sebacious and suderiferous glands
Which cranial nerve is associated with orbicularis occuli?
What does the levator palpebrae superioris (CIII) do?
raises upper lid
What are the 3 layers of the eyeball?
Fibrous, vascular and nervous tunic
What is the purpose of the sclera?
gives shape to and protects inner structure of eyeball.
What is the purpose of the cornea?
helps focus light through to the retina
Cornea has a (greater/lesser) convex curvature than the sclera.
Why is the choroid darkly pigmented?
For light absorption
What does the choroid do?
Provides nutrients to the retina
The ciliary body is layers of __________ muscle.
What does the ciliary body do?
Alters the shape of the lens (refraction or accommodation)
What does the iris do?
Responds to change in the light levels and controls the amount of light entering. dilating or constricting of the pupil.
How many layers does the retina have?
2, 1) external (non-visual portion) and 2) internal (seen)
What contains rods and cones?
in dim light, and are more sensitive to light and let us see shapes and images.
in light and give us visual acuity (colour and visual sharpness)
Most acute vision is focused on the ______________________.
macula lutea (fovea centralis)
What gives us our visual axis?
The angle through the lens to the macula lutea gives us our visual axis.
What is considered the eye's blind spot?
There are no photoreceptors on which part of the eye?
The optic disc
Which artery and vein are located in the optic nerve?
Central retinal artery and vein
Explain melanin. Where is it found?
It gives pigment to hair colour and skin. It's found in the choroid.
What does melatonin do in the choroid?
Absorbs stray light rays - prevents reflection and scattering of light within the eyeball.
- the image cast by the retina remains sharp and clear
- gives eye colour to iris
What is the retina's function?
processes the visual data before transmitting nerve impulses in the thalamus.
Is the lens vascular?
What is the lens composed of?
The lens is held in place by what?
the suspensory lig.
What does the lens do?
fine tunes focusing of light rays and facilitates clear vision.
Where is the aqueous humour secreted into?
into the ciliary processes
What is the aqueous humour mostly made up of?
Where does the psoterior chamber flow?
into the anterior chamber, filers into the Canals of Schlemm
If you have no drainage of the aqueous humour(?) what does this mean?
What is the function of the vitreous humour?
Helps to retain the shape of the eyeball, helps to keep both layers of the retina together, helps to maintain intraoccular pressure with the aqueous layer
Explain the visual pathway in the retina.
axons of trtinal ganglion cells provide output from retina to brain. rods and cones release neurotransmitters which lead to generation of nerve impulses
Explain the visual pathway in the brain.
Axons in optic nerve pass through optic chiasma. Some fibers cross to other side, other remain uncrossed. The fibers then form the optic tract, enter the brain and terminate in the thalamus. Optic radiations project to visual areas in the occipital loves of the cerebral cortex (after synapsing in the thalamus)
Superior rectus, cranial nerve and action
CIII, elevates eye
Inferior rectus, cranial nerve and action
CIII, depresses eye
Medial rectus, cranial nerve and action
CIII adducts eye
Inferior rectus, cranial nerve and action
depresses eye, CVI (abducens)
Inferior oblique, cranial nerve and action
elevates, laterally rotates, CIII
Superior oblique, cranial nerve and action
IV, depresses, laterally rotates
Nearsightedness. Where object focuses IN FRONT of retina.
Correction of myopia is...
Farsightedness. Focusing is BEHIND retina.
For myopia is accomodation/refraction too strong or too weak? How about hyperopia?
Myopia - too strong
hyperopia - too weak
How to correct hyperopia?
Astigmatism, what is it? what happens?
When cornea or lens is oddly shaped. Focusing on light rays will not be on the fovea centralis.
How to correct astigmatism
What causes colour blindness?
Lack of photopigments in the eyes choroid and retina.