Special Senses: The Eye and The Vision

Question 1

Includes the eyes and other accessory structures that aid in sight. These include muscles, glands, and protective layers

Answer 1

The visual system

Question 2

Size and shape of the eye

Answer 2

2.5 cm in diameter and has a spherical shape

Question 3

→ Positioned anterior to the eye
→ Together with eyelashes, they protect the eyes from foreign objects

Answer 3

Eyelids (palpebrae)

Question 4

The space between the eyelids

Answer 4

Palpebral fissure

Question 5

Where the eyelids meet at the corners

Answer 5

Lateral commissure (lateral canthus) & Medial commissure (medial canthus)

Question 6

a reddish-pink mound found within the medial canthus, containing sebaceous and sweat glands

Answer 6

Lacrimal caruncle

Question 7

→ Located in the tarsal plate, a crescent-shaped connective tissue that helps maintain eyelid shape.
→ Produces oily secretions that lubricate the eyes and prevent tears from overflowing.

Answer 7

Tarsal (Meibomian) Glands

Question 8

• Located between the eyelashes and act as sweat glands.
• Their ducts open near the base of the eyelashes.

Answer 8

Ciliary glands (glands of moll)

Question 9

→ A mucous membrane that lines the eyelids and covers the outer surface of the eyeball.
→ Secreted mucus to keep the eyes lubricated and moist.

Answer 9

Conjunctiva

Question 10

Covers the anterior white surface of the eye, connecting to the transparent cornea

Answer 10

Bulbar conjunctiva

Question 11

Lines the inner surface of the eyelids

Answer 11

palpebral conjunctiva

Question 12

→ is the white part of the eye, a tough, fibrous outer layer that provides
structure and protection.
→ It helps maintain the shape of the eye and serves as an attachment point for the extrinsic eye muscles.

Answer 12

Sclera

Question 13

Includes the lacrimal glands and ducts, which produce and drain lacrimal fluid (tears).

Answer 13

Lacrimal apparatus

Question 14

Cleanse, protect, moisten, and lubricate the eyes.
Contains: Dilute salt solution, mucus, antibodies, lysozymes

Answer 14

Tears (lacrimal fluid)

Question 15

Pathway of tears

Answer 15

Lacrimal gland → Lacrimal canaliculus → Lacrimal sac → Nasolacrimal duct → Empties into the inferior meatus of the nasal cavity.

Question 16

These six muscles control the movement of the eyes

Answer 16

Extrinsic eye muscles

Question 17

Moves the eye laterally

Answer 17

Lateral rectus

Question 18

Moves the eye medially

Answer 18

Medial rectus

Question 19

Elevates the eye and turns it medially

Answer 19

Superior rectus

Question 20

Depresses the eye and turns it medially

Answer 20

Inferior rectus

Question 21

Elevates the eye and turns it laterally

Answer 21

Inferior oblique

Question 22

Depresses the eye and turns it laterally

Answer 22

Superior oblique

Question 23

Three layers that form the wall of the eyeball

Answer 23

Tunic

Question 24

3 layers of tunic

Answer 24

Fibrous, vascular, sensory

Question 25

Are fluids that fill the interior of the eyeball

Answer 25

Humors

Question 26

Divides the eye into two chambers

Answer 26

Lens

Question 27

Consists of the sclera and cornea

Answer 27

Fibrous layer

Question 28

→ Thick, white connective tissue layer and anteriorly we see this as the white part of the eye → To help maintain the shape of the eyeball and to help protect the internal structures of the eyeball and to provide an attachment point for the muscles that moves the eyeball

Answer 28

Sclera

Question 29

→ The transparent central anterior region of the eyeball → It is the area that is exposed and prone to damage but it can repair itself easily → It allows the light to pass through it → It is the only human tissue that can be transplanted without the fear of rejection. This is because it is less immunologically active.

Answer 29

Cornea

Question 30

→ The term means "membrane." → It is a relatively thin layer located at the posterior part of the vascular layer. → The choroid is a blood-rich layer containing dark pigment, which prevents light from scattering within the eye

Answer 30

Choroid

Question 30

→ contains most of the blood vessels of the eyeball. → It consists of three main structures: the choroid, ciliary body, and iris.

Answer 30

Vascular layer

Question 31

→ It is located in the anterior part of the vascular layer and is modified from the choroid into two smooth muscle structures. → It is attached to the lens via the zonules (zonular fibers). → The function of this is to change the shape of the lens when focusing on objects.

Answer 31

Ciliary body

Question 32

Ciliary bodies are attached to the lens via

Answer 32

Zonules (zonular fibers)

Question 33

It is the pigmented layer that gives the eye its color, which varies among individuals. → It is composed of circular and radial smooth muscle fibers. → At the center of the iris is the pupil, the opening through which light passes. → It acts as a diaphragm that regulates the amount of light entering the eye by controlling the size of the pupil

Answer 33

Iris

Question 34

In bright light or when focusing on close objects: The_______ contract, causing the pupil to constrict (get smaller).

Answer 34

Circular muscles

Question 35

In dim light or when focusing on distant objects: The _______ contract, causing the pupil to dilate (get larger).

Answer 35

radial fibers

Question 36

Composed of the retina.

Answer 36

Sensory layer

Question 37

The retina consists of two main layers:

Answer 37

1. Outer pigmented layer 2. Inner neural layer

Question 38

→ Composed of pigmented simple cuboidal epithelial cells → Absorbs light: Prevents light from scattering inside the eye. → Phagocytic activity: Acts as phagocytes to remove dead and damaged receptor cells. → Storage of Vitamin A: Essential for vision

Answer 38

Outer pigmented layer

Question 39

Contains different receptor cells known as photoreceptors

Answer 39

Inner neural layer

Question 40

2 types of photoreceptors

Answer 40

Rods and cones

Question 41

How many cones do we have?

Answer 41

Approx. 6 to 7 million

Question 41

Respond to light, enabling vision

Answer 41

Photoreceptors

Question 41

→ Location: Primarily found on the edges of the retina → Function: ○ Enable vision in dim light ○ Provide peripheral vision → do not perceive color; they are more sensitive to light.

Answer 41

Rods

Question 42

How many rods do we have?

Answer 42

Approx. 12 million

Question 43

→ Location: Densely concentrated in the center of the retina, particularly in the fovea centralis → Function: ○ Allow for detailed color vision → There are three types, each sensitive to different wavelength of light (red, green, and blue)

Answer 43

Cones

Question 44

Electric signals generated by photoreceptors are transmitted via a two-neuron pathway, which includes:

Answer 44

Bipolar cells and Ganglion cells

Question 45

The signals from these cells (bipolar and ganglion) converge and travel through the ______ to reach the brain.

Answer 45

optic nerve

Question 46

where the neural layer of the retina meets and optic nerves

Answer 46

Optic disc

Question 46

It is a crucial structure in the retina where: ○ The central retinal artery enters ○ The central retinal vein exits ○ Optic nerve exits the eye

Answer 46

optic disc

Question 47

Images focused on the optic disc cannot be seen because it lacks photoreceptors, creating a

Answer 47

blind spot

Question 48

→ Location: Lateral to the blind spot in the retina. → It is the area where light is most focused when looking directly at an object. → It contains only cone cells, which are more densely packed than in other areas of the retina. → This high concentration of photoreceptors results in the greatest visual acuity or sharpest vision.

Answer 48

Fovea centralis

Question 49

→ Sensitive to short wavelengths of light. → Responds best to light around 420 nm (nanometers), which appears as blue.

Answer 49

blue cones

Question 50

→ Sensitive to medium wavelengths of light. → Most responsive to light around 530 nm, corresponding to green light.

Answer 50

Green cones

Question 51

→ Sensitive to long wavelengths of light. → Responds strongly to light around 560 nm, which is perceived as red. → Can also detect some yellow and orange hues due to overlapping wavelengths with green cones

Answer 51

Red cones

Question 52

○ This is a flexible, crystal-like structure.

Answer 52

Lens

Question 53

What is the anterior side of the lens made of?

Answer 53

Layer of cuboidal epithelial

Question 54

What is the posterior side of the lens made of?

Answer 54

Long columnar epithelial cells known as lens fibers

Question 55

The lens is held in place by _______ attached to the ciliary body.

Answer 55

suspensory ligaments

Question 56

→ Located anterior to the lens → Contains aqueous humor, a clear, watery fluid.

Answer 56

Anterior segment (aqueous segment)

Question 57

→ Located posterior to the lens. → Contains vitreous humor, a gel-like substance.

Answer 57

Posterior segment (Vitreous segment)

Question 58

Location: Found in the anterior segment of the eye (aqueous segment). Watery fluid found between lens and cornea Similar to blood plasma Composition:99.9% water (similar to blood plasma). Helps maintain intraocular pressure (the pressure inside the eye). Provides nutrients for the lens and cornea , which are avascular (lack blood supply). Drains into the venous blood through the scleral venous sinus (canal of Schlemm) to prevent pressure buildup, which can lead to vision loss. Should be supplied at and drained at an equal rate to prevent build up of pressure that can cause vision loss

Answer 58

Aqueous humor

Question 59

Location: Found in the posterior segment of the eye (vitreous segment). Gel-like substance posterior to the lens → Prevents the eye from collapsing → Helps maintain intraocular pressure → Cannot be regenerated or actively replenished.

Answer 59

Vitreous humor

Question 60

→ Instrument used to illuminate the interior of the eyeball → Can detect diabetes, arteriosclerosis, degeneration of the optic nerve and retina → Allows visualization of the retina, optic disc, and internal blood vessels at the fundus (posterior wall of the eye).

Answer 60

Ophthalmoscope

Question 61

Bundle of axons that exit the back of the eye carrying impulses from the retina to the brain

Answer 61

Optic nerve

Question 62

→ The location where optic nerves cross. → Fibers from the medial side of each eye cross over to the opposite side of the brain

Answer 62

Optic chiasma

Question 63

→ Fibers from the medial side ofeach eye cross over to the opposite side of the brain. → These tracts synapse with neurons in the thalamus.

Answer 63

Optic tracts

Question 64

Axons from the thalamus run to the occipital lobe, synapsing with cortical cells where visual interpretation occurs (seeing).

Answer 64

Optic radiation

Question 65

→ Each eye perceives a slightly different view. → The field of viewoverlaps for both eyes, enabling binocular vision.

Answer 65

Visual field

Question 66

Two-eyed vision provides depth perception (three-dimensional vision) by fusing the two slightly different images into one.

Answer 66

Binocular vision

Question 67

A reflexive movement where the eyes move medially when focusing on a close object

Answer 67

Convergence

Question 68

The pupils constrict in response to bright light to protect photoreceptors.

Answer 68

Photopupillary reflex

Question 69

The pupils also constrict when viewing close objects to improve focus.

Answer 69

Accomodation pupillary reflex