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Optic Cup (embryology)
During embryonic development of the eye, the outer wall of the bulb of the optic vesicles becomes thickened and invaginated, and the bulb is thus converted into a cup, the optic cup (or ophthalmic cup), consisting of two strata of cells. These two strata are continuous with each other at the cup margin, which ultimately overlaps the front of the lens and reaches as far forward as the future aperture of the pupil. The optic cup is part of the diencephalon and gives rise to the retina The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ... of the eye. References External links Overview at temple.edu Embryology of nervous system Eye {{eye-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optic Vesicles
The eyes begin to develop as a pair of diverticula (pouches) from the lateral aspects of the forebrain. These diverticula make their appearance before the closure of the anterior end of the neural tube; after the closure of the tube around the 4th week of development, they are known as the optic vesicles. Previous studies of optic vesicles suggest that the surrounding extraocular tissues – the surface ectoderm and extraocular mesenchyme – are necessary for normal eye growth and differentiation. They project toward the sides of the head, and the peripheral part of each expands to form a hollow bulb, while the proximal part remains narrow and constitutes the optic stalk, which goes on to form the optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i .... Additional images ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryonic Development
In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm, sperm cell (spermatozoon). Once fertilized, the ovum becomes a single diploid cell known as a zygote. The zygote undergoes mitosis, mitotic cell division, divisions with no significant growth (a process known as cleavage (embryo), cleavage) and cellular differentiation, leading to development of a multicellular embryo after passing through an organizational checkpoint during mid-embryogenesis. In mammals, the term refers chiefly to the early stages of prenatal development, whereas the terms fetus and fetal development describe later stages. The main stages of animal embryonic development are as follows: * The zygote undergoes a series of cell divisions (called cleavage) to form a structure called a morula. * The morula develops into a structure called a bla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optic Vesicles
The eyes begin to develop as a pair of diverticula (pouches) from the lateral aspects of the forebrain. These diverticula make their appearance before the closure of the anterior end of the neural tube; after the closure of the tube around the 4th week of development, they are known as the optic vesicles. Previous studies of optic vesicles suggest that the surrounding extraocular tissues – the surface ectoderm and extraocular mesenchyme – are necessary for normal eye growth and differentiation. They project toward the sides of the head, and the peripheral part of each expands to form a hollow bulb, while the proximal part remains narrow and constitutes the optic stalk, which goes on to form the optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve i .... Additional images ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lens (anatomy)
The lens, or crystalline lens, is a Transparency and translucency, transparent Biconvex lens, biconvex structure in most land vertebrate eyes. Relatively long, thin fiber cells make up the majority of the lens. These cells vary in architecture and are arranged in concentric layers. New layers of cells are recruited from a thin epithelium at the front of the lens, just below the basement membrane surrounding the lens. As a result the vertebrate lens grows throughout life. The surrounding lens membrane referred to as the lens capsule also grows in a systematic way, ensuring the lens maintains an optically suitable shape in concert with the underlying fiber cells. Thousands of suspensory ligaments are embedded into the capsule at its largest diameter which suspend the lens within the eye. Most of these lens structures are derived from the epithelium of the embryo before birth. Along with the cornea, aqueous humour, aqueous, and vitreous humours, the lens Refraction, refracts light, Fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pupil
The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil. The size of the pupil is controlled by the iris, and varies depending on many factors, the most significant being the amount of light in the environment. The term "pupil" was coined by Gerard of Cremona. In humans, the pupil is circular, but its shape varies between species; some cats, reptiles, and foxes have vertical slit pupils, goats and sheep have horizontally oriented pupils, and some catfish have annular types. In optical terms, the anatomical pupil is the eye's aperture and the iris is the aperture stop. The image of the pupil as seen from o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diencephalon
In the human brain, the diencephalon (or interbrain) is a division of the forebrain (embryonic ''prosencephalon''). It is situated between the telencephalon and the midbrain (embryonic ''mesencephalon''). The diencephalon has also been known as the tweenbrain in older literature. It consists of structures that are on either side of the third ventricle, including the thalamus, the hypothalamus, the epithalamus and the subthalamus. The diencephalon is one of the main brain vesicle, vesicles of the brain formed during human embryonic development, embryonic development. During the third week of development a neural tube is created from the ectoderm, one of the three primary germ layers, and forms three main vesicles: the prosencephalon, the Midbrain, mesencephalon and the Hindbrain, rhombencephalon. The prosencephalon gradually divides into the telencephalon (the cerebrum) and the diencephalon. Structure The diencephalon consists of the following structures: * Thalamus * Hypothalamus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retina
The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception. The retina serves a function which is in many ways analogous to that of the photographic film, film or image sensor in a camera. The neural retina consists of several layers of neurons interconnected by Chemical synapse, synapses and is supported by an outer layer of pigmented epithelial cells. The primary light-sensing cells in the retina are the photoreceptor cells, which are of two types: rod cell, rods and cone cell, cones. Rods function mainly in dim light and provide monochromatic vision. Cones function in well-lit conditions and are responsible fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryology Of Nervous System
Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, ''-logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Additionally, embryology encompasses the study of congenital disorders that occur before birth, known as teratology. Early embryology was proposed by Marcello Malpighi, and known as preformationism, the theory that organisms develop from pre-existing miniature versions of themselves. Aristotle proposed the theory that is now accepted, epigenesis. Epigenesis is the idea that organisms develop from seed or egg in a sequence of steps. Modern embryology developed from the work of Karl Ernst von Baer, though accurate observations had been made in Italy by anatomists such as Aldrovandi and Leonardo da Vinci in the Renaissance. Comparative embryology Preformationism and epigenesis As recently as the 18th century, the prevailing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
