Eyes

Which special senses use chemoreceptors?

Smell and taste

Which type of receptor is used for sight?

Photoreceptors

Hearing and equilibrium rely on which type of receptor?

Mechanoreceptors

What type of receptor detects temperature?

Thermoreceptors

Pain and pressure are detected by what kind of receptor?

Mechanoreceptors

What structure encloses most of the eye for protection?

Bony orbit

Which of these bones does NOT form the bony orbit around the eye?

Mandible

What provides cushioning for the eye within the orbit?

A cushion of fat

At what age does full color vision and depth perception begin to develop?

Around 6 months

By what age can infants track fast-moving objects and recognize objects?

Around 12 months

When are special senses formed during development?

Early in embryonic development

What is the origin of the eyes during development?

They are outgrowths of the brain

Are all special senses functional at birth?

Yes

What is the main function of the eyebrows?

To protect the eyes from sunlight and perspiration

What are the eyelids made of, and what is their primary function?

Skin, subcutaneous tissue, voluntary muscle, and a tarsal plate; they cover the eye and brush away particles

How do eyelashes help protect the eye?

They trap particles and have nerve endings that trigger the blinking reflex

Modified sebaceous and sweat glands between the eyelashes; they secrete acidic sweat to kill bacteria and lubricate the eyelashes

What is the function of the lacrimal gland?

It produces lacrimal fluid (tears).

Which structure drains lacrimal fluid from the eyes?

The lacrimal canals.

What is the role of the lacrimal sac?

It provides a passage for lacrimal fluid toward the nasal cavity.

Where does the nasolacrimal duct empty lacrimal fluid?

Into the nasal cavity.

What are the key components of lacrimal fluid?

A dilute salt solution, mucus, antibodies, and lysozyme.

What is the purpose of lysozyme in lacrimal fluid?

It destroys bacteria.

What are the functions of lacrimal fluid?

To protect, moisten, and lubricate the eye.

What direction does the superior oblique muscle move the eye?

Out and down

What direction does the superior rectus muscle move the eye?

Up

What direction does the lateral rectus muscle move the eye?

To the side

What direction does the medial rectus muscle move the eye?

Inward

What direction does the inferior rectus muscle move the eye?

Down

What direction does the inferior oblique muscle move the eye?

In and up

What are the three tunics that compose the wall of the eye?

Fibrous, Vascular, Sensory

What structure makes up the outer layer of the eye?

Fibrous tunic (Sclera + Cornea)

What structures make up the middle layer of the eye?

Vascular tunic (Choroid + Iris + Ciliary body)

What structures make up the inner layer of the eye?

Sensory tunic (Pigmented layer + Neural layer)

What is the function of the lens in the eye?

Focuses images clearly on the retina

What does the conjunctiva do?

Lines the eyelid, connects to the surface of the eye, and secretes mucus to lubricate the eye

What is the sclera composed of?

White connective tissue

What is the sclera commonly known as?

The white of the eye

What is the characteristic of the cornea?

Transparent and allows light to pass through

What unique property does the cornea have regarding transplantation?

It can be transplanted without rejection

What is the function of the ciliary body?

Adjusts the shape of the lens for accommodation

What is the role of the iris?

Regulates the size of the pupil and controls the amount of light entering the eye

What pigment does the vascular tunic contain to block light?

Melanin

What does the vascular tunic do for the eye?

Provides nourishment and blocks excess light

Where is the aqueous humor found in the eye?

In the chamber between the lens and cornea

What is the aqueous humor similar to?

Blood plasma

What is the primary function of the aqueous humor?

Helps maintain intraocular pressure

How does the aqueous humor provide nutrients to the eye?

It provides nutrients for the lens and cornea

How is the aqueous humor reabsorbed?

Through the channel of Schlemm into venous blood

What is the vitreous humor?

A gel-like substance behind the lens

What function does the vitreous humor serve in the eye?

Keeps the eye from collapsing

Does the vitreous humor get replaced over time?

No, it lasts a lifetime and is not replaced

What condition is caused by an increase in intraocular pressure due to abnormal circulation of aqueous humor?

Glaucoma

What can glaucoma lead to?

Damage to the retina and optic nerve, resulting in loss of vision

What is the typical age group affected by glaucoma?

People aged 50 years and older

What is the function of the retina?

Reacts to light and transmits signals to the brain via the optic nerve

Where is the macula located in the eye?

At the back of the eye

What is the primary function of the macula?

Central vision with fine detail

What is the fovea?

A small depression within the macula that contains only cones

What is the function of the fovea?

Region of most acute color vision

What is the optic disc also known as?

Blind spot

Why is the optic disc called the blind spot?

It contains only optic fibers and no sensory cells

What passes through the optic disc?

The central retinal artery and vein

What is the function of the pigmented layer in the retina?

Absorbs light to prevent scattering

What type of cells does the pigmented layer contain?

Melanocytes

What does the neural layer of the retina contain?

Photoreceptors, bipolar cells, and ganglion cells

What do rods help with?

Dim light and peripheral vision

Where are rods primarily located?

Toward the edges of the retina

What kind of perception do rods provide?

Gray tones

What do cones allow for?

Detailed and color vision

Where are cones most densely concentrated?

In the fovea

What type of light are cones sensitive to?

Bright light

How many types of cones are there?

Three

Which cone type is sensitive to long wavelengths?

Red

What pigment is found in high concentration in rods?

Rhodopsin

What is rhodopsin composed of?

Opsin and retinal (a derivative of vitamin A)