Eye Anatomy & Physiology - Chapter 16

good luck brotatochip

Eyeball

u know where the eye is

Bones of the Orbital Cavity:

• Frontal

• Maxilla

• Zygomatic

• Sphenoid

• Lacrimal

• Ethmoid

• Palatine

Palpebral

Superior and inferior palpebral are your eyelids

Bulbar Conjunctiva

Covering that sits atop the surface of your eye.

Palpebral Conjuctiva

Covering that rests on the inner surface of the superior and inferior palpebral.

Medial and Lateral Commissure

Corner of the eyes

Conjunctivitis

Inflammation of the Conjunctiva

Layers of the Eyeball:

• Fibrous

• Vascular

• Inner

What is a Humor?

Sacs of liquid in the eye that help to keep the shape

Segments of the eye:

• Anterior segment is everything in-front of the lens.

• Posterior segment is everything behind the lens

Fibrous Layer Structure:

• Outermost layer, has no blood supply

• Contains the Sclera

• Contains the Cornea

Sclera

• White in color.

• Dense connective tissue

• Shapes the eye and is the point of muscle attatchment.

Cornea

• Transparent

• Dense connective tissue

Vascular Layer

• Contains the choroid

• Contains the cillary

• Contains the pupil

• Contains the Iris

Choroid Region

• Supplies blood to the eyes.

• Contains brown pigment to prevent light from scattering around the eyes.

Cillary Region

• Surrounds the lens of the eye.

• Has suspending ligaments that connect to the lens of the eye.

Pupil Gap

Gap for da pupil

Iris

• Colored part of the eye, contains the pupil.

• Has circular (sphincter) muscles

• Has straight (radial) muscles

Sphincter Muscles

• Controled by the parasympathetic nervous system.

• Contraction constricts the pupils

Radial Muscles

• Controlled by the sympathetic nervous system.

• Contraction dilates the pupils

Inner (Retina) Layer

• Contains an outer layer (pigament and stores vitamin A)

• Contains an innter layer

Inner (neural) layer of the Retina

• Made up of photoreceptors, rods and cones.

• Has a blindspot where the axons of the photoreceptors meet and form the optic nerve.

• Contains the Marcula Lutea, which the contains the Fovea Centrialis

Rods

Rods absorb dim light and specialize in peripheral vision

Cones

Cones absorb bright light and specialize in color vision

Macula Lutea

Area in the back of the eyes that contains a lot of Cones

Fovea Centrialis

Area in the macula lutea that only contains cones

Posterior Segment

• Contains vitreous humor, which is formed during the embryonic stage of life.

• Supports the posterior surface of the lense

• Keeps the neural layer pushed up against the pigmented layer

• Maintains the shape of the eyeball

Anterior Segment

• Contains the Posterior and Anterior Chambers

• Contains Aqueous Humor, which is constantly being made and

Aqueous Humor

Nourishes the fibrous layer of the eye

Posterior Chamber

• Iris to “here”

Anterior Chamber

• iris to cornea

Aqueous Humor Pathway

• Aqueous Humor forms from the filtered blood from the capillaries in the ciliary process

• aqueous humor flows to other parts of the eye

• Aqueous humor is reabosbred into vienous blood via the canal of schlemm

Lens, General Functionality:

• Focus light onto the retina so we can see

Lens for seeing close

• Ciliary body muscles contract and push the ligaments connected to the lens to make it bulge

Lens for seeing far

Ciliary body muscles relax and pull the ligaments connected to the lens to make it flat

What happens to the Lens when u age

basically those ligaments go bad and u cant see close no more

Lacrimal Gland Location:

Lateral side of the eye

Lacrimal Gland Function:

• Produce tears.

• Tears go to lacrimal sac and drain into the nose.

• If too many tears then they roll down da face

What controls the lacrimal gland

• The ANS

• more specifically, the parasympathetic division

Muscles of the Eyelid:

blow yo shi smoooooove off twin

• Orbicularis Oculi

• Levator Palpebrae

• Extrinsic Eye Muscles (Recuts and Oblique)

Orbicularis Oculi

• Innervated by cranial nerve numero seven (Facial nerve)

• Closes the eyelids

Levator Palpebrae

• Occular Motor Nerve cranial nerve number 3

• Elevate and retract the eyelid

Extrinsic Eye Muscles (6)

• Six straplike muscles

• Originate from the bony orbit and insert on eyeball

• four rectus muscles, superior, inferior, lateral, medial

• two oblique muscles, superior and inferior oblique

Rectus Muscles

• Superior Rectus, move eye up, oculomotor (third nerve)

• Inferior Rectus, move eye down, oculomotor (third nerve)

• Lateral Rectus, move eye laterally, abducens (sixth nerve)

• Medial Rectus, move eye medially, oculomotor (third nerve)

Oblique Muscles

• Superior Oblique, depress the eye, trochlear (fourth nerve)

• Inferior Oblique, elevate the eye, oculomotor (third nerve)

Refraction:

Light enters into our eye via the cornea, however the light has to be refracted into the eye ball or else it just wont get inside. The issue with this is that if the light comes at an angle, the image will be received as upside down, so then the nervous system has to turn the image around again.

Macroscale Vision Pathway

• When light hits the Rods, the Rods deactivate.

• Neurotransmitters that normally inhibit the bipolar cells are no longer released.

• Bipolar cells activate ganglion cells and sight occurs.

Important Molecule on the rod Disks that causes this whole thing to happen?

Rhodopsin, and its protein Retinal (which is made of vitamin A)

Microscale Vision Pathway

1. Cyclic GMP (cGMP) keeps Na+ channels open.

2. Light hits the rod.

3. The molecule retinal, within Rhodopsin, loses its bend and becomes straight.

4. Transducin detatches from Rhodopsin, and attatches to phosphodiasterase (PDE)

5. PDE turns cGMP into GMP.

6. cGMP is removed from Na+ channels.

7. Na+ Channels close.

8. K+ continues to leave the cell, and the cell becomes hyperpolarized and can no longer fire action potentials.

9. Bipolar cells are no longer inhibited, and vision occurs.

Pathway pic continued

How many rods and cones do we have?

120 million rods, 6 million cones (60% red, 30% green, 10% blue)

Rods Functional Characteristics:

• Very sensitive to light.

• Best suited for night and peripheral vision

• Contains a single pigment.

• Perceived input in grey tones only

• Pathways converge, causing fuzzy, indistinct images.

Cones Functional Characteristics:

• Needs bright light for activation.

• Reacts more quickly

• Have one of three pigments for colored view.

• Non-converging pathways results in detailed, high-resolution vision

• Color Blindness: Resulting from lack of one or more cone pigments.

The Visual Projection Pathway

• Each eye has two visual fields: One on the temporal side, the other on the nasal side.

• The temporal side remains on the side of the brain, and the nasal side switches over.

• Temporal side handles peripheral vision from the opposing visual field. Nasal side handles direct vision from the correlated visual field.

• An issue with the optic chasm results in loss of direct vision. An issue with the temporal side results in loss of peripheral vision.

Pupillary Light Reflex

Basically, if there is too much light, the pupil will constrict to protect the photo-receptors