Accessory Special senses

What are eyelids? Name some parts that help form the eyelids, what is it separated by and where does it unite? What is the function of eyelids?

*Eyelids form the movable anterior that covers over the eye surface. * Eyelids are formed by fibrous for (tarsal plate), the tarsal muscles and tarsal glands, and the palpebral part of orbicularis oculi, palpebral conjunctiva, thin covering of skin, tarsal glands (sebaceous glands that produce secretion to prevent tear overflow ad keep eyelids from adhering) *Separated by central palpebral fissure *United at medial and lateral palpebral commissures

What is the purpose of the lacrimal apparatus? What are the parts that make up lacrimal apparatus?

*Functions to produce, collect, and drain lacrimal fluid from the eye that aids in lubrication of anterior surface of eye. This helps to reduce the friction from eyelid movement and cleanses and moistens the eye surface *The lacrimal apparatus is made up of lacrimal glands, lacrimal punch, and nasolacrimal duct.

How many cavities are found within the eye interior?

2 cavities filled with fluid. There is a lens between them.

What chambers is the anterior cavity separated into?

Anterior (btwn iris and cornea) and posterior chamber (lens and iris)

What fluid is found within the anterior chamber of the eye? What produces this fluid?

Aqueous humor which is a filtrate of blood plasma resembling cerebrospinal fluid. Produced the ciliary processes and secreted into the posterior chamber too.

What are ciliary glands? What is the function of ciliary glands?

Ciliary glands are housed in caruncle and forms the secretory products that help clean your eyes. Contributes to gritty material found around eyelids after waking.

The ciliary body is composed of what structures?

Ciliary muscles (bands of smooth muscles) and ciliary processes (containing capillaries secreting aqueous humor)

What are the lens within the eye composed of?

Composed of precisely arranged layers of cells that have lost their organelles. It is filled completely by crystallin protein.

The ocular conjunctive (lining over external anterior eye) and the palpebral conjunctiva (lining over internal surface of eyelid) are continuous with what tissue?

Conjunctiva

Contraction of the ciliary muscles (smooth muscles) results in what?

Contraction changes tension on ligaments, altering lens shape and contraction of suspensory ligaments extending from muscle to lens.

Which action of the ciliary muscles allows for near sightedness; farsightedness?

Contraction of the ciliary muscle allows for accommodation (near sight) moving the ciliary body anteriorly and suspensory ligaments are relaxed. On the other hand, relaxing of the ciliary muscles moves the ciliary body posteriorly and suspensory ligaments are taut to view far distances.

What kind of tissue is the cornea made up of? What is its function?

Cornea is formed from outer stratified squamous epithelium, corneal epithelium and inner simple squamous epithelium.

What is the dilator pupillae muscle? What CN controls it?

Dilator pupillae muscles are organized in a radial pattern and is controlled by sympathetic division of the ANS to dilate. Contracts when stimulated by low light.

What are eyebrows? What is the function of eyebrows?

Eyebrows are curved rows of thick, short hairs found at the superior edge of orbit along supraorbital ridge. Eyebrows function to prevent sweat from dripping into open eyes

What are some external accessory structure of the eyes?

Eyebrows, eyelashes, lacrimal caruncle, ciliary glands, eyelids, and conjunctiva

What are eyelashes? What is the function of eyelashes?

Eyelashes are hairs that extend from the margins of eyelids. These prevent large objects from coming into contact with the eye.

Name the three principal layers of the eye

Fibrous tunic, the vascular tunic, and retina

Which two types of cells are capable of producing action potential?

Ganglion cells and amercing cells

What are some characteristics of the choroid body?

Houses vast capillaries supporting the retina, the cells are filled with pigment from melanocytes, and pigment absorbing extraneous light.

What is the function of the lacrimal gland?

It continuously produces lacrimal fluid and washes over eyes by blinking eyelids. The fluid is transferred to lacrimal caruncle on medial eye

What are lacrimal caruncle? What is the function of lacrimal caruncle?

Lacrimal caruncle is a small reddish body at medial commissure.

What is the function of optic disc?

Location where ganglion axons exit toward the brain

What is the ora serrata?

Ora serrata is located on the edge of the retina, found not he margin between photosensitive posterior and non photosensitive anterior of the retina. The anterior region of the ora errata covers ciliary body and the posterior side of the iris

What is the function of orbital fat?

Orbital fat cushions posterior and lateral eye and provides the support and protection.

Which three layers are responsible for forming the neural layer?

Outermost neural layer has photoreceptor cells, middle layer is the layer with bipolar cells, the site of convergence of visual signals from multiple photoreceptors, and the innermost neural layer formed by ganglionic cells where axons extend from here through the optic disc.

What is the function of the peripheral retina?

Peripheral retina functions most effectively in low light

What are the cavities of the eyes?

Posterior cavity and anterior cavity.

What is the function of he aqueous humor?

Provides nutrients and oxygen to lens and cornea and helps to maintain the chemical environment within the anterior cavity.

What are the components of the fibrous tunic made of? Which layer of the eye wall is it?

Sclera and Cornea. Outer most layer of eye wall

What kind of tissue is the sclera made up of? What is its function?

Sclera is the "white" of the eye and is composed of dense irregular connective tissue. It provides eye shape and eye's internal components. The attachment site for extrinsic eye muscles and is continuous with dura mater surrounding optic nerve

What are cataracts? What causes them? What is the issue with cataracts?

Small opacities w/in the lens. Result of aging. They make it difficult for the eyes to focus on close objects. Reduced visual clarity and reduced color intensity.

What is the sphincter pupillae muscle? What CN controls it?

Sphincter pupillae muscle resembles concentric circles but it is responsible for constricting the pupil. Under control of parasymph division CN III in response to bright lights

What structures creates tension on the lens that enable it to change shape?

Suspensory ligaments and ciliary muscles.

What is the iris?

The colored portion of the eye composed of 2 layers of pigment-forming cells. it is made up of Two groups of smooth muscle fibers. It's perisperhal edges are continuous with ciliary body.

How does the shape of the cornea affect light rays?

The convex transparent structure of the cornea refracts light rays coming into the eye.

Where does the external epithelium of the cornea obtain nutrients from?

The external epithelium obtains nutrients and oxygen from lacrimal gland fluid

What are some characteristics of the eye?

The eye is an almost spherical organ that is mostly receded into skull orbit.

Describe the inner neural layer

The inner neural layer houses photoreceptors and is associated with neurons. It is responsible for absorbing light rays and converts it into nerve signals that are transmitted to the brain.

Where does the internal epithelium of the cornea obtain nutrients from?

The internal epithelium obtains nutrients and oxygen from nutrients and gases from fluid in anterior chamber.

Describe the pigmented layer of the retina

The pigmented later is internal to choroid and attached to it. It provides vitamin A for photoreceptors (light-detecting cells) Light rays passing through inner layer is absorbed here

What are the components of the retina? which layer of the eye wall is it?

The retina has an outer pigmented layer and an inner neural layer. This is the internal layer of eye wall.

What structure is responsible for continually resorbing the aqueous humor into the vascular space?

The scleral venues sinus located in the limbus.

What is the function of the lacrimal punch?

The structure drains fluid through lacrimal canaliculus into lacrimal sac

What are conjunctiva? What is the function of the conjunctiva?

These are specialized stratified squamous epithelium that serves to form a protective layer over part of the eye (does not cover surface of cornea) so that this highly vascularized and innervated tissue supplying nutrients to avascular sclera does not interfere with passage of light.

What is the function of horizontal cells?

These integrate stimuli sent from photoreceptors of other layers

What is the function of amacrine cells?

These process visual info between bipolar and ganglionic neurons

What is the function of the nasolacrimal duct?

This duct receives fluid from lacrimal sac and aids to drain fluid into lateral side of nasal cavity where it mixes with mucus.

What is trachoma?

This is a chronic contagious form of conjunctivitis caused by chlamydia trachomatis. Results in scarring and thickening of conjunctiva due to inflammatory process. Common cause of neonatal blindness in developing countries, newborn affected as passes through birth canal.

What occurs with clinical disease of macular degeneration? What is the result of this disease? Symptoms?

This is a physical deterioration of macula lutea. This is the leading cause of blindness in developed countries and may be associated with diabetes, ocular infection, HTN, eye trauma. Result is loss of visual acuity in center of visual field. Symptoms are diminished perception and "floaters"

What occurs with clinical disease conjunctivitis? What is common cause of it?

This is the most common non traumatic eye complaint, inflammation and reddening of the conjunctiva. Due to viral infection, bacterial infection, allergens, chemicals, irritants.

What is the function of Macular lutea?

This region contains the fovea centralism, the location with the high proportion of cones and few rods, where the area of sharpest vision is.

What is the function of the lens?

This strong deformable transparent structure focuses incoming light onto the retina. The shape determines the degree of light refection.

What are the components of the vascular tunic? which layer of the eye wall is it?

Vascular layer/ also referred to as uvea/ is made pf choroid, ciliary body, and iris. The vascular tunic is the middle layer of the eye wall

What is the posterior cavity of the eye filled with?

Vitreous humor which is a transparent, gelatinous fluid that fills the space btw lens and retina to help maintain the eye shape and supports the retina.

What occurs with clinical disease of detached retina? What are the results? Symptoms?

this disease occurs when outer pigment and inner neural layers separate. May result from head trauma and is an increased risk in diabetics and nearsighted individuals. Result is nutrient deprivation of the inner neural layers. Symptoms are floaters, curtains in affected eye, symptoms of flashes of light, decreased vision.