The eye is an important sensory organ for vision which houses a sensitive optical apparatus in a relatively isolated tissue compartment. Eye is essentially made of three layers: (1) sclera, (2) uveal tract, and (3) retina with each of these layers performing intricate duties which ensure proper functioning of the eye.
Sclera is an outer fibrous layer which mainly provides the mechanical stability to protect the eye and its sensitive optical apparatus. Sclera is mainly composed of collagen and elastic fiber and their irregularity gives sclera an opaque appearance. The most important function of sclera is to offer resistance to internal and external forces and to provide attachment for the extraocular muscle insertions. The scleral surface area in humans is
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approximately 16-17 cm2 and largely influences the pharmacokinetics of drug diffusion 10. Uveal tract also called as vascular tunic is middle vascular layer which is composed of an ensemble of iris-ciliary body and choroid.
Each component of this ensemble has a specific function. For example, iris acts as a variable aperture to control the light that enters the eye and ciliary body secretes aqueous humor. The vascular layer is the choroid, which provides blood supply to the retina. The iris arises from the anterior face of the ciliary body and is a forward extension of the choroid. The central aperture in the iris is called the pupil and its size is controlled by the iris to regulate the amount of light that enters the eye. The iris is made up of two types of muscles dilator and sphincter muscles. Sympathetic nervous system innervates dilator muscles and parasympathetic nervous system innervates sphincter muscles. Mydriasis which is dilation of the pupil is a result of increase in dilator muscle activity. Miosis the constriction of the pupil is a result of increase in sphincter muscle activity. The ciliary body consists of smooth muscle, which is innervated by the parasympathetic nervous system. When ciliary muscle contracts, the lens become more convex to accommodate proper vision. The other important function of the ciliary body is the production of aqueous humor, which
provides nutrients for the lens and cornea and is also involved in drainage of waste from these areas. Retina, the innermost layer of the eye is a complex structure comprised of several layers of neurons interconnected by synapses. Photoreceptor cells are neurons that are light sensitive and are comprised of rods and cones.
Glaucoma is a disease of the eye and it is fluid pressure within the eye rises and if the eye is left untreated the patient might lose vision or maybe even blind. But this disease is generally affects both eyes but although one of their eyes may have more severe signs or symptoms then the other eye. When you have glaucoma there are small spaces in the front of the eye and they are called anterior chamber. There is clear liquid that flows in and out of the anterior chamber and the fluid nourishes and bathes nearby the tissues. And if the patient has glaucoma the fluid dose not drain like it should drain but the fluid drains out of the eye. And this may lead to fluid build up and pressure inside the rises of the eye. Unless the pressure is brought down and controlled and the optic nerves and some of the other parts of the eye might become damaged leading to ...
It is made mostly of connective tissue (areolar and dense irregular). Connective tissue provides support to the epidermis because it consists of numerous collagen and elastin fibers. The dermis serves as a first line of protection so that pathogens (bacteria and/or microbes) that have made it through the epidermis cannot move any farther. The dermis produces a gel-like substance within the areolar connective tissue that slows down the movement of microbes. The dermis also supplies blood and nutrients to the epidermis (via blood vessels) and supports sensory reception (nerve fibers). Accessory structures found in the dermis include a portion of the hair follicle, secretory glands (sebaceous and sweat glands), touch receptors (nerve fibers) and blood vessels. There dermis has two layers: the papillary layer and reticular layer. The papillary layer is the outer top portion of the dermis that is below (deep to) the epidermis. It has a sub layer called dermal papillae. Dermal papillae has ridge-like projections that interlock with ridges in the lower portion of the epidermis (epidermal ridges). These ridge-like projections have sensory receptors and capillaries. The sensory receptors are called tactile corpuscles that detect light, delicate touch and capillaries supply blood and nutrients to the epidermis above. The reticular layer is the deeper portion of the dermis and consists mostly of dense irregular connective tissue (ground substance and randomly arranged collagen fibers). The lamellated corpusle is a large, leaflet like sensory receptor located in the reticular layer. This receptor detects pressure, rough touch and
Acquired prosopagnosia refers to when the onset of prosopagnosic symptoms occur after brain trauma, resulting in damage to the cortex of the brain from hitting the inside of the skull (Bodamer, 1947). It can also refer to the initiation of symptoms after brain tissue dies (ischemia) such as from loss of blood supply like from a stroke, or a neurodegenerative disease (Villa et al., 2013, pg. 375).
Wistow, G. J., and J. Piatigorsky. 1988. Lens crystallins: the evolution and expression of proteins for a highly specialized tissue. Annu. Rev. Biochem. 57: 479-504.
The optical lenses of the eyes are used to focus light. The light that penetrates the lens is controlled by the iris, which constricts and dilates in response to varying light conditions. Controlling the amount of light that reaches the lens, and subsequently the photoreceptors in the pigmented retina, is not enough to adequately discern images in three dimensions. The lens is therefore responsible for adjusting to conditions based on how far away or near an object is that is being viewed. To view something relatively close, the lens is bent to form a more spherical shape by the ciliary body muscles. Likewise, to view further distanced objects, the lens must undergo accommodation
The five senses include sight, smell, touch, taste, and hearing. Sight is the power of seeing objects and people. To see we use our eyes, our eye is a sphere with a diameter of about 2.5 cm or 1 inch. Our eyes include the eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles. The eyelids are thin, skin covered folds supported by the connective tissue sheets called tarsal plates and are separated by the palpebral fissure and meet at medial and lateral angles of the eye. The eyelid muscle cause blinking every 3-7 seconds and when the objects get in your eye, the flexibility is activated to protect the eye. The eyelashes also protect the eye. Anything that touches the eyelashes is blown away because it will cause your eye to blink. The conjunctiva in our eyes is a mucous membrane; it helps to line the eyelids. The function of the conjunctiva is to produce a lubricating mucus that prevents the eyes from drying out. A conjunctival sac is where contact lens lies and occurs when the eyes are closed and a slit like space occurs. An inflammation of the conjunctiva is called conjunctivitis and happens when the eye get red and really irritated. The lacrimal apparatus in our eyes drains the lacrimal secretions into the nasal cavity. The lacrimal fluid in the eye cleans and protects eye as it moistens. The fluid contains mucous, antibodies, and lysosome. The extrinsic eye muscles originate and insert into outer surface of the eyeball. The extrinsic eye muscles allow the eye to follow a moving object and provide wires to maintain shape of eyeball and hold it in orbit. When movements of these muscles are not the same, a person cannot focus on images correctly and see two images instead. The eye is called an eyeball and ha...
The crystalline lens is a fibrous, jelly-like material that serves to fine tune the vision process by adjusting its shape and therefore the focal length of the system.
Fluid circulating inside the front portion of the eye is produced by a structure called the ciliary body, which is located behind the iris. This fluid moves through the opening of the pupil, passes into the space between the iris and the cornea, and drains out of the eye through a tissue called the angle. With glaucoma, the passing of fluid through the angle is either reduced or suddenly stops, and amounts of fluid inside the eye increase. This high fluid pressure hurts the nerve fibers and the eye's optic nerve and causes blind spots. It may lead to blindness in some cases.
the cornea and the sclera. The cornea is what covers the iris, and is the
In “The Bluest Eye” by Toni Morrison, the audience is shown the skewed idea of beauty and how whiteness in the 1940s was the standard of beauty. This idea of beauty is still prevalent today which is why the novel is powerful and relevant. Narrated by a nine year old girl, this novel illustrates that this standard of beauty distorts the lives of black people, more specifically, black women and children. Not only was it a time when being white was considered being superior, being a black woman was even worse because even women weren’t appreciated and treated as equal back then. Set in Lorain, Ohio, this novel has a plethora of elements that parallels Toni Morrison’s personal life. The population in Lorain back then was considered to be ethnically asymmetrical, where segregation was still legal but the community was mostly integrated. Black and white children could attend the same schools and neighborhoods by then would be inhabited by a mix of black and white families. The theme of race and beauty is portrayed through the lives of three different families and stories told by the characters: Claudia, Pecola, and Frieda. Through the exploration of the families’ and character’s struggles, Morrison demonstrates the horrid nature of racism as well as the caustic temperament of the suppressed idea of white beauty on the individual, and on the society.
One sub-system under the sensory system is the visual system; the main sense organs of this are the eyes. The eye is the sensory organ that allows us to detect light from external stimuli. When a light ray is detected, the eye converts these rays into electrical signals that can be sent to the brain in order to process the information and giv...
In the world of bionics, the technologies such as the bionic eye sit between the realms of science fiction and reality. Bionic eyes are at this time limited by current technologies, and while they can bring a certain quality of life to people with sight impairments, the bionic eye at this point is falls way short of the organic eye. This essay will endeavour to persuade the reader that organic eyes, due to current technological limitations, are superior to bionic eyes. In order for people to benefit from bionic eyes, they need to have a functional visual pathway from the retina to the brain along the optic nerve as well as some intact retinal cells. This need for intact optical nerves \ intact retinal cells limits the potential recipients for treatment to people with retinitis pigmentosa and age-related macular degeneration and other genetic eye conditions that effect around 1.5 million people worldwide.
Have you ever wondered why the sky is blue. Often times I find myself looking up on a clear day, pondering over that question? Why isn’t it green, or red or pink for even that matter. Every day, the human eye blinks more than 23,00 times. The human eye is a complicated organ that performs one of the most important tasks for our body. There are many questions about the eye however. What function do they perform? What happens if we don’t take care of them? How exactly do they work together to help us form images? Exactly how far can they human eye see?
As further protection, the eyelids automatically close when an object suddenly moves close to the eye.Parts Of the EyeThe eye is made of 3 coats, or tunics. The outermost coat consists of the cornea and the sclera. The middle coat contains the main blood supply to the eye and consists of the choroid, the ciliary body, and the Iris. The innermost layer is the retina.Cornea and ScleraThe Sclera, or the white of the eye, is composed of tough fibrous tissue. On the exposed area of the eye the scleral surface is covered with a mucous membrane called the conjunctiva.