It consists of an outer pigmented retina and an inner sensory retina. Be sure to grab a pen and paper to write down your answers. The optic tract fibers synapse with neurons in the , whose axons form the optic radiation, which runs to the of the brain; there they synapse with the cortical cells, and visual interpretation, or seeing, occurs. In the posterior two-thirds, the vascular tunic consists of the choroid, a layer of nutritive and supporting tissue. The lateral angles are attached to the zygomatic bone by the lateral palpebral raphé. These are branches of the ophthalmic artery, one of the branches of the internal carotid artery.
The lacrimal ducts, one in each eyelid, commence at minute orifices, termed puncta lacrimalia, on the summits of the papillæ lacrimales, seen on the margins of the lids at the lateral extremity of the lacus lacrimalis. The retina is also part of the inner tunic Layers tunics of the eye The tunics of the eye consist of the following three layers: Tunica fibrosa refers to the outer fibrous layer of the eye. Each olfactory tract terminates in an area of the brain called the olfactory cortex, located within the temporal and frontal lobes. It holds the lens in its position, produces aqueous humor and controls the shape of the lens accommodation. Most vertebrate animals have eyes that are essentially the same as the human eye. The iris is a light blue colour at birth in fair people with fair skin because of the absence of pigment.
Nearsightedness myopia is blurred vision caused by light rays being incorrectly focused anterior to the Retina. Eyebrows, located on the brow ridges, also shield the eyes from overhead light and divert sweat from the eyes. Tears are secreted continuously by the lacrimal gland, which is located in the superior, lateral part of each. The locations and functions of these muscles are shown in figure 9. Accessory structures Conjunctiva The refers to the lining of the eye.
The tarsal glands are modified sebaceous glands, each consisting of a single straight tube or follicle, with numerous small lateral diverticula. The inner layer undergoes a complex differentiation into the various layers of the neural retina. If they significantly impair vision, cataracts can be corrected through surgery by removing the lens and replacing it with a plastic lens in the posterior chamber. In the upper eyelid it blends by its peripheral circumference with the tendon of the Levator palpebræ superioris and the superior tarsus, in the lower eyelid with the inferior tarsus. Important Disclaimer: All information given here are for educational purposes. Anatomy of the Ear Anatomically, the ear is divided into three major areas: the external, or outer, ear; the middle ear, and the internal, or inner, ear. Phototransduction Vision occurs through the process of.
Cataract The loss of transparency of the lens or its capsule is known as a , and is commonly associated with ageing. The brighter the light, the greater the response and therefore the greater reduction in neurotransmitter release. Its causes include lens abnormalities and the eye being longer than normal. People often complains of having red eyes when they stopped using redness relief eye drops. The eye can also be divided into its anterior front and posterior back segments. As the cells lose their elasticity, the lens is unable to assume the spherical shape needed to accommodate for near vision.
The Obliquus oculi inferior inferior oblique is a thin, narrow muscle, placed near the anterior margin of the floor of the orbit. Image formed on the retina is transmitted to brain by optic nerve. The ocular muscles are the: Levator palpebræ superioris Rectus medialis. Their ducts open on the free magins of the lids by minute foramina. The transparent inner neural layer of the retina contains millions of receptor cells, the rods and cones, which are called photoreceptors because they respond to light. An artery enters the eye and a vein exits the eye via the optic disc.
The Lacrimal Sac saccus lacrimalis. They are imbedded in grooves in the inner surfaces of the tarsi, and correspond in length with the breadth of these plates; they are, consequently, longer in the upper than in the lower eyelid. Blood is returned from these structures via the hyaloids vein. Other glands, analogous to lymphoid follicles, and called by Henle trachoma glands, are found in the conjunctiva, and, according to Strohmeyer, are chiefly situated near the medial palpebral commissure. Option C: The lens is a flexible, biconvex, transparent disc. The outermost layer, called the fibrous layer, consists of the protective sclera and the transparent cornea. Pupil The , which looks black because of the heavily pigmented back of the eye, changes size to control and regulate the amount of light passing through the lens to reach the retina.
Some nocturnal animals have a reflective Structure of the human eye. Baltimore: Lipponcott Williams and Wilkins; 2006. Because cones require bright light to function, only rods allow us to see in dim light. Tunica vasculosa refers to the middle vascular layer. Depth perception is a result of stereoscopic vision.
The many colors that we can see result from stimulation of combinations of these three types of cones. This entry of Ca 2+ triggers the release of neurotransmitter from the synaptic terminal while in the dark. The anterior portion of the sclera is covered by the conjunctiva. The retina consists of several layers of cells, including the rods and cones, the sensory cells that respond to light. This upper band is sometimes termed the superior tendon of Lockwood.