Podcast
Questions and Answers
What is the primary function of the lens in the eye?
What is the primary function of the lens in the eye?
Cataracts can cause the lens of the eye to become hard and opaque.
Cataracts can cause the lens of the eye to become hard and opaque.
True
What adjusts the thickness of the lens?
What adjusts the thickness of the lens?
Ciliary muscle
The process of bending light rays is known as ______.
The process of bending light rays is known as ______.
Signup and view all the answers
Which of the following conditions is NOT associated with cataracts?
Which of the following conditions is NOT associated with cataracts?
Signup and view all the answers
Accommodation involves the lens flattening when focusing on objects closer than 20 feet.
Accommodation involves the lens flattening when focusing on objects closer than 20 feet.
Signup and view all the answers
What happens to the ciliary muscle when focusing on nearby objects?
What happens to the ciliary muscle when focusing on nearby objects?
Signup and view all the answers
Match the parts of the eye with their functions:
Match the parts of the eye with their functions:
Signup and view all the answers
What happens during retinal detachment?
What happens during retinal detachment?
Signup and view all the answers
Diabetic retinopathy is a complication of diabetes that can lead to visual impairments.
Diabetic retinopathy is a complication of diabetes that can lead to visual impairments.
Signup and view all the answers
What is a major cause of visual impairment in older adults?
What is a major cause of visual impairment in older adults?
Signup and view all the answers
Glaucoma occurs when the aqueous humor does not flow out of the eye properly, leading to increased ______.
Glaucoma occurs when the aqueous humor does not flow out of the eye properly, leading to increased ______.
Signup and view all the answers
Match the following eye components with their functions:
Match the following eye components with their functions:
Signup and view all the answers
What is the primary function of the vitreous humor?
What is the primary function of the vitreous humor?
Signup and view all the answers
The anterior chamber of the eye is located between the ______ and the iris.
The anterior chamber of the eye is located between the ______ and the iris.
Signup and view all the answers
The vitreous humor is replaced throughout life.
The vitreous humor is replaced throughout life.
Signup and view all the answers
What is myopia?
What is myopia?
Signup and view all the answers
Cones are specialized for black-and-white vision.
Cones are specialized for black-and-white vision.
Signup and view all the answers
What muscle contractions cause the pupil to constrict?
What muscle contractions cause the pupil to constrict?
Signup and view all the answers
The three types of cones are: blue, green, and ______.
The three types of cones are: blue, green, and ______.
Signup and view all the answers
Match the following conditions with their descriptions:
Match the following conditions with their descriptions:
Signup and view all the answers
Which statement is true about rods?
Which statement is true about rods?
Signup and view all the answers
Convergence is the outward movement of the eyes when focusing on close objects.
Convergence is the outward movement of the eyes when focusing on close objects.
Signup and view all the answers
What condition is caused by a prolonged deficiency of vitamin A?
What condition is caused by a prolonged deficiency of vitamin A?
Signup and view all the answers
What is the most common type of color blindness?
What is the most common type of color blindness?
Signup and view all the answers
The optic chiasma is the point where optic nerve fibers cross in the eye.
The optic chiasma is the point where optic nerve fibers cross in the eye.
Signup and view all the answers
What is the function of the optic tract?
What is the function of the optic tract?
Signup and view all the answers
The membrane that covers the white part of the eye is called the ______.
The membrane that covers the white part of the eye is called the ______.
Signup and view all the answers
Match the following structures to their respective tunics in the eyeball:
Match the following structures to their respective tunics in the eyeball:
Signup and view all the answers
Which of the following substances is found in tears?
Which of the following substances is found in tears?
Signup and view all the answers
The vitreous humor is a soft, transparent, jelly-like substance found in the anterior cavity of the eyeball.
The vitreous humor is a soft, transparent, jelly-like substance found in the anterior cavity of the eyeball.
Signup and view all the answers
What shape does the lens take to focus light waves?
What shape does the lens take to focus light waves?
Signup and view all the answers
Which structure protects the eye from foreign objects and directs sweat away?
Which structure protects the eye from foreign objects and directs sweat away?
Signup and view all the answers
The sclera is known as the colored portion of the eyeball.
The sclera is known as the colored portion of the eyeball.
Signup and view all the answers
What is the primary function of the cornea?
What is the primary function of the cornea?
Signup and view all the answers
The _____ produces tears that contain salt, water, and lysozyme.
The _____ produces tears that contain salt, water, and lysozyme.
Signup and view all the answers
Match the following parts of the eye with their functions:
Match the following parts of the eye with their functions:
Signup and view all the answers
Photoreceptors in the retina include both rods and cones.
Photoreceptors in the retina include both rods and cones.
Signup and view all the answers
Which part of the eye is responsible for focusing on near and far objects?
Which part of the eye is responsible for focusing on near and far objects?
Signup and view all the answers
The main purpose of the lacrimal apparatus is to produce and _____ tears.
The main purpose of the lacrimal apparatus is to produce and _____ tears.
Signup and view all the answers
Match the following eye chambers with their contents:
Match the following eye chambers with their contents:
Signup and view all the answers
What is conjunctivitis?
What is conjunctivitis?
Signup and view all the answers
The optic disc is known for having the highest concentration of cones.
The optic disc is known for having the highest concentration of cones.
Signup and view all the answers
What conditions can cause watery eyes in individuals?
What conditions can cause watery eyes in individuals?
Signup and view all the answers
The ________ layer of the eyeball is responsible for nourishing the retina.
The ________ layer of the eyeball is responsible for nourishing the retina.
Signup and view all the answers
Study Notes
Sense of Vision Learning Outcomes
- Students should be able to describe the accessory structures of the eye and their functions.
- Students should be able to describe the anatomy of the eye.
- Students should be able to describe the anatomy of eye cavities and their chambers.
- Students should be able to discuss the refraction of light and image formation.
- Students should be able to describe the stimulation of photoreceptors.
- Students should be able to discuss the visual pathway to the brain.
Introduction
- More than half of the sensory receptors in the human body are located in the eyes.
- A large portion of the cerebral cortex is dedicated to processing visual information.
- The eye is the organ of sight located in the orbital cavity and is supplied by the optic nerve (2nd cranial nerve).
Accessory Organs of the Eyes
- Eyebrows/eyelashes - protect the eyeballs from foreign objects, sweat, and direct sunlight.
- Eyelids - protect the eyes from excessive light, injury, and keep the cornea moist.
- Conjunctiva - a thin mucous membrane that lines the inner aspect of the eyelids and the anterior surface of the eyeball.
- Lacrimal apparatus - produces and drains tears, moisturizing the cornea and conjunctiva.
- Extraocular muscles - six muscles attached to the sclera that move the eyeballs in all directions.
Eyelashes and Eyebrows
- Eyelashes - shield the eyeballs from foreign particles, sweat, and sun glare.
- Eyebrows - redirect sweat away from the eyes and contribute to facial expressions.
Eyelids
- Function:
- Protect the eyes from excessive light.
- Protect from injury.
- Help to keep the cornea moist.
- Orbicularis muscle - closes the lids.
- Levator palpebrae superioris muscle - raises upper eyelids.
Conjunctiva
- A thin mucous membrane lining the inner aspect of the eyelids and reflected onto the anterior surface of the eyeball.
Conjunctivitis
- Inflammation of the conjunctiva.
Lacrimal Apparatus
- A group of structures that produce and drain tears.
- Located in the upper outer corner of each orbit.
- Comprises:
- Lacrimal gland
- Lacrimal canal
- Lacrimal sac
- Nasolacrimal ducts
- Tears contain salt, water, and lysozyme.
Lacrimal Apparatus (Flow of Tears)
- Tears from the lacrimal gland flow into the lacrimal puncta.
- Tears are drained through superior and inferior lacrimal canals into the lacrimal sac.
- The right and left nasolacrimal ducts empty into each side of the nose.
Lacrimal Apparatus (Clinical Application)
- Watery eyes - occur due to blockage of the nasolacrimal ducts.
- Blocked nasolacrimal ducts - caused by nasal mucosa inflammation (e.g., cold).
- Overproduction of lacrimal fluid - occurs during emotional responses (crying) and tears spill over eyelid edges, draining into the nasal cavity.
Extraocular Muscles of the Eye
- The six extrinsic muscles are attached to the sclera and move the eyeballs in various directions.
Anatomy of the Eye
- The walls of the eyeball are made up of three layers of tunics:
- Fibrous Tunic - sclera and cornea
- Vascular Tunic (Uvea) - choroid, ciliary body, and iris
- Nervous Tunic - retina
Anatomy of the Eye (Internal Cavity)
- Filled with fluids called humors.
- Lens separates the internal cavity into anterior and posterior segments.
- Anterior segment contains aqueous humor.
- Posterior segment contains vitreous humor.
Fibrous Tunic
- Outermost layer of the eyeball.
- Composed of sclera and cornea.
- Protects the intraocular contents.
- Scleral venous sinus (canal of Schlemm): an opening at the junction of the sclera and cornea that drains aqueous humor.
Fibrous Tunic (Sclera)
- Known as the "white" of the eye.
- Maintains the shape of the eyeball.
- Provides attachment sites for extrinsic muscles.
Fibrous Tunic (Cornea)
- Continuously from sclera.
- Convex anteriorly, acting as a refracting surface for light rays.
- A common visual corrective procedure, LASIK, is performed on the cornea.
Vascular Tunic
- Middle layer of the eyeball.
- Composed of choroid, ciliary body, and iris.
- Choroid - lines between sclera and retina, contains blood vessels to nourish the retina. Contains melanocytes - producing melanin to absorb light.
- Ciliary body - consists of ciliary processes secreting aqueous humor and ciliary muscles that adjust lens shape for near/far vision.
- Iris - colored portion; adjusts pupil size to control light intake.
Choroid
- Located between sclera & retina.
- Contains blood vessels to nourish the retina.
- Melanocytes produce melanin causing the dark brown color - absorbs light rays, preventing reflection and scattering.
Ciliary Body
- Consists of ciliary processes (secrete aqueous humor) and ciliary muscle (changes the shape of the lens).
Iris
- Colored portion of the eyeball.
- Pupil - black hole; adjusts to regulate the amount of light reaching the retina.
Sensory Tunic (Retina)
- Innermost layer of the eyeball.
- Thin, delicate membrane.
- Receives light, converts it into nerve impulses.
- Optic disc - blind spot where optic nerve exits eyeball
- Macula lutea - area rich in cones, the exact center of the posterior retinal portion.
- Fovea centralis - point of sharpest vision due to high cone concentration.
Retina (Rods)
- Specialized for black-and-white vision in dim light.
- Allow us to discriminate between shades of dark and light.
- More than cones.
- Contains rhodopsin.
Retina (Cones)
- Specialized for color vision and sharpness of vision (high visual acuity) in bright light.
- Three types of cones: blue, green, and red.
- Concentrated in the fovea centralis.
Retina (Clinical Application)
- Retinal detachment - retina peels away from its underlying supporting tissue, resulting in visual distortions or blindness.
- Diabetic retinopathy - blood vessels may block or damage, causing damage to the retina; the main cause of blindness in people under 65.
- Age-Related Macular Degeneration (AMD) - leads to vision loss in the center of the visual field due to damage to the macula.
Interior of the Eyeball
- Contains anterior and posterior chambers that contain aqueous and vitreous humor, respectively.
Anterior & Posterior Chamber
-
Anterior cavity: Space between cornea and lens. Contains 2 chambers:
- anterior - between cornea and iris
- posterior - between iris and lens
-
Contains aqueous humor.
- Secreted by ciliary glands.
- Supplies oxygen, nutrients, and removes waste from the cornea, lens, and lens capsule.
- Maintains eye shape.
- Drains through the scleral venous sinus (canal of Schlemm) into the blood stream.
-
Posterior cavity (vitreous chamber):
- Large region between lens and retina.
- Filled with vitreous humor.
- Formed during embryonic development.
- Not replaced thereafter
- Vitreous humor: soft, colorless, transparent, jelly-like substance maintains eye shape and holds the retina against the choroid.
Aqueous Humor (Clinical Application)
- Glaucoma - aqueous humor does not drain properly, leading to increased intraocular pressure that damages the optic nerve, causing blindness if untreated.
Lens
- Biconvex, avascular, colorless, and transparent.
- Located behind the iris and pupil.
- Its thickness is controlled by the ciliary muscle.
- Function: focus light rays onto the retina (refraction).
Lens (Clinical Application)
- Cataracts - lens becomes hard and opaque.
- Common complication of diabetes mellitus.
- Caused by smoking and UV exposure to sunlight.
- Treated by replacing the natural lens with a plastic one.
Pathway of Light and Refraction
- Normal image formation depends on:
- Refraction of light waves
- Accommodation of the lens
- Constriction of the pupil
- Convergence of the two eyes
Refraction
- Bending of light rays by the refractive media (cornea, aqueous humor, lens, vitreous humor) in the eye to focus light rays onto the retina.
- In a normal eye, the refractive media bends light rays from objects at least 20 feet away to be focused on the retina.
Refraction (cont)
- 75% of total light refraction occurs at the cornea.
- Lens further refracts light rays so they come into exact focus on the retina.
- In order to focus light after bending by cornea, the shape of the lens must adjust.
Accommodation
- Adjustment in the lens shape to focus the image on the retina.
- For objects less than 20 feet away:
- Ciliary muscles contract.
- Suspensory ligaments become loose or relaxed.
- Lens becomes bulged (thicker).
- For objects farther than 20 feet (far vision):
- Ciliary muscles relax.
- Suspensory ligaments become taut.
- Lens becomes flat.
Pupillary Response
- Pupil - opening in the center of the iris to allow light into the eye.
- Composed of a radial muscle (radiating from the center of the iris) and a circular muscle.
- Contraction of circular muscles constrict the pupil, limiting light intake.
- Contraction of radial muscles dilate the pupil, allowing more light intake.
Convergence
- Inward movement of the eyes to direct both eyes at the viewed object.
- The closer the object, the greater the degree of convergence, which is coordinated by extrinsic muscles, helping maintain binocular vision.
Refraction Abnormalities
- Myopia (nearsightedness): image is focused in front of the retina, corrected via concave lens.
- Hyperopia (farsightedness): image is focused behind the retina, corrected via convex lens.
- Astigmatism: irregular curvature of the cornea or lens affecting the sharpness of vision.
Photoreceptors
- Rods and cones: Light-sensitive cells in the retina that convert light energy into neural signals.
Photoreceptors (Rods)
- Thin cells with rod-like projections.
- Specialized for black-and-white vision in dim light.
- More abundant than cones.
Photoreceptors (Cones)
- Specialized for color vision in bright light.
- Three types of cones: blue, green, and red.
- Densely concentrated in the fovea centralis.
- Intermediate colors are perceived by activation of more than one type of cone.
Photoreceptors (Clinical Application)
- Night blindness- reduced rhodopsin, vitamin A deficiency.
- Colorblindness- inherited absence or deficiency of one type of cone photopigment; more common in males. (e.g., red-green colorblindness).
Optic Nerve, Optic Chiasma, and Optic Tract
- Optic nerve - cranial nerve carrying impulses from retina to brain.
- Optic chiasma - point where optic nerve fibers cross in the brain.
- Optic tract - extends from the optic chiasma to the thalamus, for visual awareness.
Visual Pathway
- After light stimulation, rods and cones trigger electrical signals to ganglion cells.
- Impulses are conveyed through the retina to the optic nerve, and then to the optic chiasma.
- From there, impulses travel through the optic tract to the thalamus, and then through optic radiations to the visual cortex in the occipital lobe.
Recap/Quiz Points
- Conjunctiva
- Lacrimal gland
- Tears (mucus, antibodies, lysozyme)
- Eye layers (Fibrous, Vascular, Nervous)
- Structures in Fibrous tunic (Sclera, Cornea)
- Structures in Vascular tunic (Choroid, Ciliary body, Iris)
- Structure in Nervous tunic (Retina)
- Lens; separates anterior and posterior segments
- Biconvex lens shape
- Sclera
- Cornea
- Aqueous humor
- Vitreous humor
- Glaucoma
- Accommodation
- Night blindness
- Rhodopsin
- Rods
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the anatomy and functions of the human eye, including conditions such as cataracts and diabetic retinopathy. This quiz covers essential functions of eye components and common visual impairments. Enhance your understanding of how the eye works and what can affect its performance.
