structures of the eye Flashcards
What act to protect the eye from foreign objects, perspiration and direct sun ray
Eyebrows and eyelashes
What shades the eyes during sleep, protect it from excessive light and spread lubrication over the eyeballs by blinking?
Eyelids
What is a group of glands, duct and canals that produce and drain tears in both eyes?
Lacrimal apparatus
Tears flow from lacrimal gland through…..
lacrimal ducts
How many extrinsic muscles work together to move the eyeball from left to right and up and down?
Six
What are the Six extrinsic muscles of the eye
Superior rectus,
inferior rectus,
lateral rectus,
medial rectus,
superior oblique
inferior oblique
The fibrous tunic is divided into what two regions?
The posterior sclera and the anterior
cornea
______ is a nonvascular, transparent, fibrous coat that covers the iris. This bends light rays to help focus them on the retina
The cornea
_____ is also known as the white of the eye and is comprised of dense connective tissue.
The sclera
What part of the eyeball
1) It covers the entire eye except for the cornea.
2) It provides shape and affords protection to the inner parts.
3) Its posterior aspect is pierced by the optic nerve (cranial nerve II).
The sclera
What is composed of three portions: the choroid, ciliary body, and iris.
The vascular tunic, or middle layer
________ is a thin membrane that lines most of the internal surface of the sclera.
It contains blood vessels that nourishes the retina, and contains pigment melanin (causes dark brown in color) that absorbs stray light rays.
The choroid
_____ consists of the ciliary processes and the ciliary muscle.
The ciliary body
What part of the Celery body
_______ consist of folds on the internal surface of the ciliary body whose capillaries secrete aqueous humor.
The ciliary processes
What part of the Celery body
________ is a smooth muscle that alters the shape of the lens for near and far vision (accommodation)
The ciliary muscle
What is the circular colored portion seen through the cornea. It consists of circular and radial smooth muscle fibers.
The iris
The black hole in the center of the iris is the _____ it is the area through which light enters the eyeball.
Pupil
What functions to regulate the amount of light that passes through the lens into the posterior cavity of the eye.
Iris
The ____ focuses light rays onto the retina
lens
What lies in the posterior three-quarters of the eye and functions in image formation?
The retina, or inner layer,
The _______ layer of the retina contains three zones of neurons which are named in the order they conduct nerve impulses. These are the photoreceptor layer, bipolar cell layer, and ganglion cell layer.
neural
The photoreceptors are called what based on shape?
Rods and Cones
The _____ allow us to see shades of gray in dim light
- Rods
- Cones
Rods
The _____ are instrumental in color vision and in visual acuity (color vision in bright light).
- Rods
- Cones
cones
The cones are densely concentrated in a small depression in the posterior portion of the eye called the ________.
fovea centralis
fovea centralis is located where?
The macula lutea, which is the exact center of retina.
What is the area of the sharpest vision because of the high concentration of cones?
Fovea centralis
What layer of the retina is a sheet of melanin located between the choroid and the neural part of the retina?
The pigmented
The melanin in the pigmented layer of the retina does what?
helps to absorb stray light rays just like the choroid
From photoreceptors, information flows through the outer synaptic layer, to bipolar cells, through the inner synaptic layer, to ganglion cells and exit as the…..
optic (II) nerve.
The pressure in the eye is called what?
intra ocular pressure (IOP).
IOP is produced by what?
aqueous humor (mainly) and the vitreous body.
IOP maintains the shape of the eyeball and ……
Keeps the retina in position and nourished
What is normal IOP
16 mmHg
The eye’s interior is divided into the ________ and the ________ by the lens.
anterior cavity
vitreous chamber
_________ attach the lens to the ciliary muscle and hold the lens in position.
Zonular fibers
The anterior cavity lies anterior to the lens and is filled with a watery fluid which is called….
the aqueous humor
The vitreous chamber is the larger of the cavities in the eye and lies between the retina and the lens. It contains a clear, jellylike substance called the……
vitreous body
This jellylike substance helps maintain the eye’s shape and holds the retina in place.
vitreous body
This watery fluid helps maintain the shape of the eye and nourishes the lens and the cornea….
aqueous humor
