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Hypoplasia
Hypoplasia (from Ancient Greek ὑπo- ''hypo-'' 'under' + πλάσις ''plasis'' 'formation'; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a tissue or organ. Dictionary of Cell and Molecular Biology (11 March 2008) Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells.Hypoplasia Stedman's Medical Dictionary. lww.com Hypoplasia is similar to aplasia, but less severe. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turner's Hypoplasia
Enamel hypoplasia is a defect of the teeth in which the enamel is deficient in quantity, caused by defective enamel matrix formation during enamel development, as a result of inherited and acquired systemic condition(s). It can be identified as missing tooth structure and may manifest as pits or grooves in the crown of the affected teeth, and in extreme cases, some portions of the crown of the tooth may have no enamel, exposing the dentin. It may be generalized across the dentition or localized to a few teeth. Defects are categorized by shape or location. Common categories are pit-form, plane-form, linear-form, and localised enamel hypoplasia. Hypoplastic lesions are found in areas of the teeth where the enamel was being actively formed during a systemic or local disturbance. Since the formation of enamel extends over a long period of time, defects may be confined to one well-defined area of the affected teeth. Knowledge of chronological development of deciduous and permanent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optic Nerve Hypoplasia
Optic nerve hypoplasia (ONH) is a medical condition arising from the underdevelopment of the optic nerve(s). This condition is the most common congenital optic nerve anomaly. The optic disc appears abnormally small, because not all the optic nerve axons have developed properly.Sadun, Alfredo A., and Michelle Y. Wang. ''Handbook of Clinical Neurology''. p. 37. In press. It is often associated with endocrinopathies (hormone deficiencies), developmental delay, and brain malformations. The optic nerve, which is responsible for transmitting visual signals from the retina to the brain, has approximately 1.2 million nerve fibers in the average person. In those diagnosed with ONH, however, there are noticeably fewer nerves. Symptoms ONH may be found in isolation or in conjunction with myriad functional and anatomic abnormalities of the central nervous system. Nearly 80% of those affected with ONH will experience hypothalamic dysfunction and/or impaired development of the brain, regardless ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cerebellum
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebellum plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language as well as emotional control such as regulating fear and pleasure responses, but its movement-related functions are the most solidly established. The human cerebellum does not initiate movement, but contributes to coordination, precision, and accurate timing: it receives input from sensory systems of the spinal cord and from other parts of the brain, and integrates these inputs to fine-tune motor activity. Cerebellar damage produces disorders in fine movement, equilibrium, posture, and motor learning in humans. Anatomically, the human cerebellum has the appearance of a separate structure attached to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asymmetric Crying Facies
Asymmetric crying facies (ACF), also called partial unilateral facial paresis and hypoplasia of depressor angula oris muscle, is a minor congenital anomaly caused by agenesis or hypoplasia of the depressor anguli oris muscle, one of the muscles that control the movements of the lower lip. This unilateral facial weakness is first noticed when the infant cries or smiles, affecting only one corner of the mouth and occurs on the left side in nearly 80% of cases. It is only rarely associated with other birth defects. When the hypoplasia of the depressor anguli oris muscle is associated with congenital cardiac defects, the term 'Cayler cardiofacial syndrome' is used. Cayler syndrome is part of 22q11.2 deletion syndrome DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent i .... It was character ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agenesis Of The Corpus Callosum
Agenesis of the corpus callosum (ACC) is a rare birth defect in which there is a complete or partial absence of the corpus callosum. It occurs when the development of the corpus callosum, the band of white matter connecting the two hemispheres in the brain, in the embryo is disrupted. The result of this is that the fibers that would otherwise form the corpus callosum are instead longitudinally oriented along the ipsilateral ventricular wall and form structures called Probst bundles. In addition to agenesis, other degrees of callosal defects exist, including hypoplasia (underdevelopment or thinness), hypogenesis (partial agenesis) or dysgenesis (malformation). ACC is found in many syndromes and can often present alongside hypoplasia of the cerebellar vermis. When this is the case, there can also be an enlarged fourth ventricle or hydrocephalus; this is called Dandy–Walker malformation. Signs and symptoms Signs and symptoms of ACC and other callosal disorders vary greatly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reelin
Reelin, encoded by the ''RELN'' gene, is a large secreted extracellular matrix glycoprotein that helps regulate processes of neuronal migration and positioning in the developing brain by controlling cell–cell interactions. Besides this important role in early development, reelin continues to work in the adult brain. It modulates synaptic plasticity by enhancing the induction and maintenance of long-term potentiation. It also stimulates dendrite and dendritic spine development and regulates the continuing migration of neuroblasts generated in adult neurogenesis sites like the subventricular and subgranular zones. It is found not only in the brain but also in the liver, thyroid gland, adrenal gland, Fallopian tube, breast and in comparatively lower levels across a range of anatomical regions. Reelin has been suggested to be implicated in pathogenesis of several brain diseases. The expression of the protein has been found to be significantly lower in schizophrenia and psychoti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Popliteal Pterygium Syndrome
Popliteal pterygium syndrome (PPS) is an inherited condition affecting the face, limbs, and genitalia. The syndrome goes by a number of names including the ''popliteal web syndrome'' and, more inclusively, the ''facio-genito-popliteal syndrome''. The term PPS was coined by Gorlin '' et al.'' in 1968 on the basis of the most unusual anomaly, the popliteal pterygium (a web behind the knee). Symptoms and signs Clinical expressions of PPS are highly variable, but include the following: * Limb findings: an extensive web running from behind the knee down to the heel (90%), malformed toenails, and webbed toes. * Facial findings: cleft palate with or without cleft lip (75%), pits in the lower lip (40%), fibrous bands in the mouth known as syngnathia (25%), and tissue connecting the upper and lower eyelids * Genital findings (50%): hypoplasia of the labia majora, malformation of the scrotum, and cryptorchidism. Genetics The genetic locus for PPS was localized to chromosome 1 in 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypoplastic Right Heart Syndrome
Hypoplastic right heart syndrome is a congenital heart defect in which the right atrium and right ventricle are underdeveloped. This defect causes inadequate blood flow to the lungs and thus, a blue or cyanotic infant. Symptoms and signs Common symptoms include a grayish-blue (cyanosis) coloration to the skin, lips, fingernails and other parts of the body. Other pronounced symptoms can be rapid/difficulty breathing, poor feeding, cold hands or feet, or being inactive and drowsy. "In a baby with hypoplastic right heart syndrome, if the natural connections between the heart's left and right sides (foramen oval and ductus arteriosus) are allowed to close, he or she may go into shock." Signs of shock can include cool or clammy skin, a weak or rapid pulse, and dilated pupils. Causes The Notch-signaling pathway is involved in multiple processes during heart development, along with Wnt signaling. Cardiomyocyte differentiation, patterning of the different cardiac regions, valve developme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus. Structure The optic nerve has been classified as the second of twelve paired cranial nerves, but it is technically part of the central nervous system, rather than the peripheral nervous system because it is derived from an out-pouching of the diencephalon (optic stalks) during embryonic development. As a consequence, the fibers of the optic nerve are covered with myelin produced by oligodendrocytes, rather than Schwann cells of the peripheral nervous sys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DiGeorge Syndrome
DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent infections, developmental delay, learning problems and cleft palate. Associated conditions include kidney problems, schizophrenia, hearing loss and autoimmune disorders such as rheumatoid arthritis or Graves' disease. DiGeorge syndrome is typically due to the deletion of 30 to 40 genes in the middle of chromosome 22 at a location known as ''22q11.2''. About 90% of cases occur due to a new mutation during early development, while 10% are inherited from a person's parents. It is autosomal dominant, meaning that only one affected chromosome is needed for the condition to occur. Diagnosis is suspected based on the symptoms and confirmed by genetic testing. Although there is no cure, treatment can improve symptoms. This often includes a mul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corpus Callosum
The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mammals. It spans part of the longitudinal fissure, connecting the left and right cerebral hemispheres, enabling communication between them. It is the largest white matter structure in the human brain, about in length and consisting of 200–300 million axonal projections. A number of separate nerve tracts, classed as subregions of the corpus callosum, connect different parts of the hemispheres. The main ones are known as the genu, the rostrum, the trunk or body, and the splenium. Structure The corpus callosum forms the floor of the longitudinal fissure that separates the two cerebral hemispheres. Part of the corpus callosum forms the roof of the lateral ventricles. The corpus callosum has four main parts – individual nerve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Testes
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testosterone. Testosterone release is controlled by the anterior pituitary luteinizing hormone, whereas sperm production is controlled both by the anterior pituitary follicle-stimulating hormone and gonadal testosterone. Structure Appearance Males have two testicles of similar size contained within the scrotum, which is an extension of the abdominal wall. Scrotal asymmetry, in which one testicle extends farther down into the scrotum than the other, is common. This is because of the differences in the vasculature's anatomy. For 85% of men, the right testis hangs lower than the left one. Measurement and volume The volume of the testicle can be estimated by palpating it and comparing it to ellipsoids of known sizes. Another method is to use cal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
