- published: 25 Aug 2008
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The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina. This adjustment of the lens is known as accommodation (see also Accommodation, below). It is similar to the focusing of a photographic camera via movement of its lenses. The lens is flatter on its anterior side.
The lens is also known as the aquula (Latin, a little stream, dim. of aqua, water) or crystalline lens. In humans, the refractive power of the lens in its natural environment is approximately 18 dioptres, roughly one-third of the eye's total power.
The lens is part of the anterior segment of the eye. Anterior to the lens is the iris, which regulates the amount of light entering into the eye. The lens is suspended in place by the suspensory ligament of the lens, a ring of fibrous tissue that attaches to the lens at its equator and connects it to the ciliary body. Posterior to the lens is the vitreous body, which, along with the aqueous humor on the anterior surface, bathes the lens. The lens has an ellipsoid, biconvex shape. The anterior surface is less curved than the posterior. In the adult, the lens is typically circa 10 mm in diameter and has an axial length of about 4 mm, though it is important to note that the size and shape can change due to accommodation and because the lens continues to grow throughout a person’s lifetime.
Lens or Lense may refer to:
Anatomy (from the Ancient Greek ἀνατέμνειν, anatemnein: ana, "separate, apart from", and temnein, "to cut up, cut open") is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy (zootomy), and plant anatomy (phytotomy). In some of its facets anatomy is closely related to embryology, comparative anatomy and comparative embryology, through common roots in evolution.
Anatomy is subdivided into gross anatomy (or macroscopic anatomy) and microscopic anatomy.Gross anatomy is the study of anatomical structures that can, when suitably presented or dissected, be seen by unaided vision with the naked eye.Microscopic anatomy is the study of minute anatomical structures on a microscopic scale. It includes histology (the study of tissues), and cytology (the study of cells). The terms microanatomy and histology are also sometimes used synonymously (in which case the distinction between histology and cell biology isn't strictly made as described here).