ABSTRACT
Durante el desarrollo embrionario, las células de muchos tejidos se diferencian de acuerdo con la información de posición que se establece por las gradientes de concentración de morfógenos. Estas son moléculas de señalización secretadas en una región restringida de un tejido y se difunden lejos de su fuente para formar una gradiente de concentración. La molécula de un mismo morfógeno actúa generalmente en distintas etapas de desarrollo de un organismo y puede provocar reacciones muy diferentes en las células en función de su historia de diferenciación. Los morfógenos más conocidos son miembros del factor de crecimiento beta (TGF-b), Hedgehog (Hh), familias Wnt y los microRNAs.
During embryonic development, cells in many tissues differ according to the positional information that is set by the concentration of morphogen gradients. These are signaling molecules that are secreted in a restricted region of a tissue and diffuse away from their source forming a concentration gradient. Morphogens generally act at different development stages in an organism and cause different reactions in cells depending on their history of differentiation. The best known example of morphogens are members of growth factor beta (TGF-beta), Hedgehog(Hh), and Wnt families or microRNAs.
Subject(s)
Vertebrates/embryology , Neural Tube/embryology , MorphogenesisABSTRACT
Fifth lumbar vertebra is an atypical vertebra as it has widely separated inferior articular processes and thick transverse processes projecting out from the body and pedicles of the vertebra. On routine examination of osteology specimens we found a fifth lumbar vertebra in two separate parts. One part consisted of body, pedicles, transverse and superior articular processes. The other part consisted of lamina, spinous and inferior articular processes. Knowledge of this variation may be of importance to the clinicians for diagnosis of certain neurological deficits in the lower limb and to orthopaedic surgeons and neurosurgeons during the surgical intervention of that area.