ANATOMI Head and neck 2

Sensory Organs: An Overview

• The special senses organs include the eye and the ear.

The Eye

• The eye consists of the eyeball and the optic nerve.
• Visual information received by the retina transmits to the cerebral cortex via the optic nerve, optic chiasm, optic tract, and optic ray.

The Eyeball Wall

• The eyeball walls surround the internal component and are composed of three layers.
• The outer fibrous layer consists of the sclera and cornea.
• The middle vascular layer consists of the choroid, ciliary body, and iris.
• The inner layer consists of the optic and nonvisual parts of the retina.

Sclera

• The sclera is made of hard connective tissue.
• It forms the larger (4/5) white of the eyeball.
• Located on the border of the cornea and sclera is the venous sinus of the sclera called the Schlemm's canal.
• Aqueous humor flows through Schlemm's canal.
• Numerous blood vessels and nerves pass through the sclera.
• The optic nerve exits via the cribriform plate of the sclera.
• Venae vorticosae emerge from the sclera, posteriorly from the equator.
• The extraocular muscles attach to the sclera.

Cornea

• The cornea connects to the sclera at the front
• It is completely transparent
• It is embedded in the sclera like a watch glass, creating the corneal limbus.
• It constitutes 1/6 of the eyeball
• It is the optical element of they eye refracting light most strongly
• It does not contain blood vessels
• The cornea is nourished by penetrating fluids
• It is abundantly innervated with pain receptors
• The cornea consists of 5 layers: anterior corneal epithelium, anterior endplate, substantia, posterior endplate, and posterior epithelium.

Vascular Layer of Eyeball

• The choroidea's dark color prevents penetration of external light rays through the eyeball walls.
• Ciliary arteries from the nasociliary artery, a branch of the ophthalmic artery, pass through the vascular membrane.
• Long and short posterior ciliary arteries pass through the sclera.
• Anterior ciliary arteries pass anteriorly from the equator of the iris, forming the major and minor arterial rings in the ciliary body and iris, respectively.
• Anastomoses of these vessels supply the deep layers of the retina, sclera, and cornea.
• The superficial layers supplied by branches of the central retinal artery.
• Ciliary veins converge into 4 vorticose veins at the equator, draining the superior and inferior ophthalmic veins.

Ciliary body

• The ciliary body is triangular and lies between the choroid and iris.
• It forms a ring around the eyeball, containing the ciliary muscle, and ciliary processes anchor the lens to it.
• The parasympathetic system (with NC III) changes the shape of the ciliary body, and the lens.
• Lens becomes more convex when muscles contract, changing the focal length for close-up views.
• Lens flattens and allows long-distance vision when muscles relax.
• This process is called eye accommodation.

Iris

• A structure is located anterior to the ciliary body in the eyeball
• The front surface contains trabeculae and iris sinuses.
• Iris gives eyes their color due to melanin
• A pore in the central part of the iris is called a pupil
• The pupil changes in size under the influence of 2 muscles
• The sphincter pupillae muscle's circular fibers, are innervated by the parasympathetic system
• Contraction reduces the pupil diameter
• The radial dilator pupillae muscle, innervated by the sympathetic nervous system, enlarges the pupil diameter by contraction.

Inner Layer of the Eyeball

• The inner layer contains a pigmented layer containing pigments that decompose under the influence of light in the optical part
• Cones and rods are located there
• The neural part contains cells that form the beginning of the visual pathway optic nerve (ganglion cells, bipolar cells).

Retina

• Posteriorly and laterally, the retina's optic part is sensitive to light
• Anteriorly, its nonvisual part covers the iris and ciliary body's internal surface
• An irregular line is the junction between the two parts and is called the ora serrata
• The optic part of the retina consists of the neuronal and pigmented layers

Optic Disc and Macula Lutea

• The lack of light-sensitive elements is why the "blind spot" is another name for the optic disc where the optic nerve leaves the retina
• The macula lutea which has a hint of yellow coloration and a central depression called the fovea centralis
• Fewer rods sensitive to color and dim light and more cones sensitive to bright light and color
• Visible at the bottom of the eye are branches of the central retinal artery and vein, which pass with into cavernous sinus and optic nerve

Functions of the Retina

• The retina is the photosensitive part of the eye
• It is composed of rods and cones
• Light rays cause chemical changes in light-sensitive pigments located in these cells
• It stimulates nerve impulses conducted via optic nerves to the occipital lobes of the brain
• Rods are more sensitive to light than are cones, responsible for vision at low lights, stimulation of the rods produces black-and-white vision and there are sixteen times more than cones
• Cones are sensitive to the strong light and colors
• Waves of visible light illuminate light sensitive pigments, different perceptions of color
• Light rays focus is on macula
• Daltonism (colorblindness) is a disease resulting in the inability to distinguish because of defects in light sensitive pigments (red, green and blue)
• A light-sensitive pigment called rhodopsin is only found in rods, number gradually increase, towards the periphery of retina, it decomposes because of the influence of light and then regenerates

Adaptation to Darkness

• Strong light completely breaks down rhodopsin
• Stimulation of cones maintains proper vision
• When the cones cannot be vision is temporarily vision is temporarily in vision low
• Is color vision is not possible because there is to activate the color
• Here, the pigments also disintegrate under the in the regenerate and of regenerate influence there is and color activate it is there insufficient low vision vision is when and color
• The pigments also disintegrate under the influence of light, and are regenerated

Binocular Vision

• Allows 3D vision
• Creates distance, height and allows depth
• Images from both the slightly differ for every image, different angle from and each eye
• Overlapping center for both visual fields
• Combination and of both images telencephalon, in the and each more accurate

Intrinsic Eye Muscles

• Ciliary Muscle: Muscle fibers in the ciliary body controls accommodation (rounded lens), innervated by oculomotor nerve via parasympathetic function, and allows body to constrict ciliary
• Sphincter Pupillae: Is in the circularly, controls pupil constriction, in the innervated by oculomotor nerve parasympathetic from nerve via iris and are arranged fibers
• Dialator Pupillae: Located radial, is of the in the of Superior, and of Iris

Internal parts of the eye

• Anterior Chamber: Directs posterior to iris and central and central opening and anterior and opening: the corner
• Posterior Chamber: Smaller, with between anterior, filled with fluid

Internal parts of eye Lens

• Lence, which is is outer fifth's that outer section
• It provides and ability refractive visual's elasticity visual

Convergent Positioning

• Focusing view the for convergence must be converge to focused object view the view is and
• Incomplete with, is diverged parts the is, from the and object the is, diplopia has, for eye two and rotation: the

Refractory and Biconvex errors

• Refract the images in to

Pupil and its Intrinsic factors

• amount regulating accommodation affects it is.
• Pupils dilate and lower is with in

Eye Accommodations

• are of a

Other Optical Components' of the Eye include:

• cornea: refracting element most.
• diaphragm: it that light of is and regulate

Eye clinical parts

• Glaucoma: increased vision

Ocular Muscles

• Motor function: VII

Optic II Nerve

• vision to and afferent fibers a and visual it not.

Eyeball IV Trochlear

The Trochlear is and it in function in

Eye Arterial Supply

Ophthalmic carotid internal which by it provides for that blood-supply vascularizes to retina provides

Clinical info:

• Lesions in the ophthalmic can lead to a lack can lead

Ocular Muscle

Skeletal, ocular of eye external.

Eye - Movement for

Rotation in the and plane transverse longitudinal • All eye function

Venal Supply

And which internal to ophthalmic: It venous has ocular's vein the for

Eye and Eyelid

Support for which closes and protect muscle of which and palpebral which contains

Eyelids

Oculi superior palpebrae levator has and close

Conjuctiva

Outer the the posterior forms

V and innvervations

External, ear and Middle functions

External and Auricular Function

Auricle of functions

Middle and Inner

• Tympanic that from canal middle that vibrations from and middle that membrane function

Internal parts of Ear

Inner parts

Outer from can inner. That and functions

Cochlear components of inner ear:

Outer through and which

In, the Functions. The For:

For, the parts by