Zusammengestellt von der im Jahre 1923 gewählten Nomenklatur-Kommission, unter Berücksichtigung der Vorschläge der Mitglieder der Anatomischen Gesellschaft, der Anatomical Society of Great Britain and Ireland, sowie der American Association of Anatomists, überprüft und durch Beschluß der Anatomischen Gesellschaft auf der Tagung in Jena 1935 endgültig angenommen. The posterior Chamber is also referred to as the Vitreous body as indicated in the diagram below - anatomy of the eye. Beginning from the external surface choroid side , the retina consists of the following layers: i Pigment Cell Layer: This layer lies close to the choroid. Neural Coat— The Retina: The retina is the neural and sensory layer of the eye ball. An eye disorder common in older people is cataract.
Conjunctiva: It is a transparent mucous membrane, which covers the internal palpebral surfaces, and folds on to the anterior sclera and comea where it is continuous with the comeal epithelium. Just anterior to the pituitary gland, these nerves give rise to the X-shaped optic chiasma. Cameras do this by altering the distance between the lens and film, but eyes do it by altering the shape and therefore the focal length of the lens. It serves as a soft, shockproof pad. Rods and cones also differ in the sharpness of the perceived images, or visual acuity. Cornea At the front of the eyeball, the sclera becomes the cornea. There are two muscles that affect the iris color of the eye , they are the iris sphincter and iris … dilator muscles.
The cones are responsible for high visual acuity high resolution. How the antagonistic muscles work to constrict and dilate the pupil. The suspensory ligaments are purely passive, but the ciliary muscles are innervated with motor neurones from the autonomic nervous system, and accommodation is controlled automatically by the brain. The more densely-packed the cone cells, the better the visual acuity. The photosensitive compounds photo pigments in the human eyes are composed of opsin a protein and retinal an aldehyde of vitamin A.
Extrinsic Eye Muscles and their Nerve Supply: There are six extrinsic muscles attached to the eyeball. The capsule and ligaments, together with the ciliary body, hold the lens in place. The full Latin expression exhibits three words that each can be traced back to antiquity. Because of this, impulses from a group of rods are conducted to the brain on a single nerve fiber. Mechanism of Vision: The light rays pass through comea, aqueous humour, lens and vitreous humour and focus on retina where they generate potentials impulses in rods and cones. Radial and circular muscle Located in the iris, the radial muscle opens the pupil wider, and the circular muscle reduces it, but only one type can work at any one time, while the other relaxes. Rods give less precise images because axon branches from rods undergo convergence.
Suspensory ligaments and ciliary muscles body medlineplus medical encyclopediadefinition of muscle by dictionary. Rhodopsin consists of a membrane-bound protein called opsin and a covalently-bound prosthetic group called retinal. This sinus is in the wall of the anterior chamber at the junction of the cornea and the sclera. It works in opposition to the pupillary constrictor. The structure of a rod cell is: The detection of light is carried out on the membrane disks in the outer segment. The diagrams below show cross sections of the human eyeball.
Retina The retina is the innermost layer lining the back of the eyeball. Working antagonistically, they contract and relax in turn to push ingested food down the digestive system. Impulses from the sympathetic nerve cause pupil dilation and impulses from the parasympathetic nerve causes pupil constriction. Dim light stimulates the radial cells to contract, which increases the amount of light entering the eye. The epithelium of the ciliary process continuously secretes a watery fluid, the aqueous humour. It connects the lens to the ciliary body and allows the lens to change shape.
The drug atropine inhibits the parasympathetic nerve, causing the pupil to dilate. Six muscles that control movement of the eye and one muscle that controls eyelid elevation. When the ciliary muscles relax, the zonules pull the edges of the lenses so they become flatter and thinner for distance vision. The sclera makes up the posterior five-sixths of the outer layer of the wall of the eye. The melanin that these cells produce absorbs excess light, which helps keep the inside of the eye dark. Conjunctiva Is a thin protective covering of epithelial cells. The color a person perceives depends on which cones the light in a given image stimulates.
In the back of the eye, the optic nerve and certain blood vessels pierce the sclera. The final result of the bleaching of the rhodopsin in a rod cell is a nerve impulse through a sensory neurone in the optic nerve to the brain. Each orbit is lined with the periosteum of various bones, and also contains fat, blood vessels, nerves, and connective tissues. It contracts or relaxes in order for an individual to see at multiple distances. The cornea helps focus entering light rays. The iris constantly regulates the amount of light entering the eye so that there is enough light to stimulate the cones, but not enough to damage them. These action potentials impulses are transmitted by the optic nerves to the visual cortex area in the occipital lobe of the cerebral hemisphere of the brain where the neural impulses are analysed and erect image is recognised.
Rods and cones contribute to different aspects of vision. The total number of rods in the human retina has been estimated at 110 to 125 million and cones at 6. The tears flow downward and medially across the eye. When the radial muscle contracts and the circular muscle relaxes, the pupil opens wider. An artery and a vein also pass through the optic disc.