The remainder of the tube forms the medulla spinalis or spinal cord; from its ectodermal wall the nervous and neuroglial elements of the medulla spinalis are developed while the cavity persists as the central canal.
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The anterior spinal artery arises bilaterally as two small branches near the termination of the vertebral arteries. One of these vessels is usually larger than the other, but occasionally they are about equal in size. Descending in front of the medulla oblongata, they unite at the level of the foramen magnum. The single trunk descends in the front of the medulla spinalis, extending to the lowest part of the medulla spinalis.
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It extends throughout the entire length of the medulla spinalis, and on transverse section appears as an oval area in front of the posterior column and medial to the posterior spinocerebellar tract.
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The vessel is placed in the pia mater along the anterior median fissure. It supplies that membrane, and the substance of the medulla spinalis, also sending off branches at its lower part to be distributed to the cauda equina.
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On either side of the posterior median sulcus of the spinal cord, and at a short distance from it, the posterior nerve roots are attached along a vertical furrow named the posterolateral sulcus. The portion of the medulla spinalis which lies between this and the posterior median sulcus is named the posterior funiculus.
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Image of a Nissl-stained histological section through the rodent hippocampus showing various classes of cells (neurons and glia). Motor nerve cell from ventral horn of medulla spinalis of rabbit. The angular and spindle-shaped Nissl bodies are well shown. A Nissl body, also known as Nissl substance and Nissl material, is a large granular body found in neurons.
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Medulla spinalis - Substantia grisea Rexed lamina The Rexed laminae comprise a system of ten layers of grey matter (I–X), identified in the early 1950s by Bror Rexed to label portions of the grey columns of the spinal cord. Similar to Brodmann areas, they are defined by their cellular structure rather than by their location, but the location still remains reasonably consistent.
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In the following year he read before the Royal Society a paper On the Inverse Ratio which Subsists between Respiration and Irritability in the Animal Kingdom. His most important work in physiology was concerned with the theory of reflex action, embodied in a paper On the Reflex Function of the Medulla Oblongata and the Medulla Spinalis (1833)Hall M. On the reflex function of the medulla oblongata and medulla spinalis. Philosophical Transactions 1833, 123: 635–665, which was supplemented in 1837 by another On the True Spinal Marrow, and the Excito-motor System of Nerves. In this theory, he stated that the spinal cord is comprised by a chain of units that functions as an independent reflex arcs, and their activity integrates sensory and motor nerves at the segment of the spinal cord from which these nerves originate.
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From the mesoderm surrounding the neural tube and notochord, the skull, vertebral column, and the membranes of the brain and medulla spinalis are developed. A postembryonic vestige of the notochord is found in the nucleus pulposus of the intervertebral discs. Isolated notochordal remnants may escape their lineage-specific destination in the nucleus pulposus and instead attach to the outer surfaces of the vertebral bodies, from which notochordal cells largely regress.
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The branch for the second intercostal space usually joins with one from the highest aortic intercostal artery. This branch is not constant, but is more commonly found on the right side; when absent, its place is supplied by an intercostal branch from the aorta. Each intercostal gives off a posterior branch which goes to the posterior vertebral muscles, and sends a small spinal branch through the corresponding intervertebral foramen to the medulla spinalis and its membranes.
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The spinal root of accessory nerve (or part) is firm in texture, and its fibers arise from the motor cells in the lateral part of the anterior column of the gray substance of the medulla spinalis as low as the fifth cervical nerve. Passing through the lateral funiculus of the medulla spinalis, they emerge on its surface and unite to form a single trunk, which ascends between the ligamentum denticulatum and the posterior roots of the spinal nerves; enters the skull through the foramen magnum, and is then directed to the jugular foramen, through which it passes, lying in the same sheath of dura mater as the vagus, but separated from it by a fold of the arachnoid. In the jugular foramen, it receives one or two filaments from the cranial part of the nerve, or else joins it for a short distance and then separates from it again. As it exits from the jugular foramen, it runs backward in front of the internal jugular vein in 66.6% of cases, and behind it in 33% of cases.
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He was a pioneer in psychiatry and what would be called today psychosomatic medicine. He came to hold, as a major conviction of his professional life, the view that the mind plays a far greater role in health and illness than his contemporaries realized. He had seventy-two professional and scientific medical papers published, a great number of which referred to nervous diseases, such as paralysis agitans, sclerosis of Medulla spinalis, aphasia and others. It can be rightly argued that Dr. Laza Lazarević was the first Serbian neurologist.
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The anterior median fissure of the spinal cord has an average depth of about 3 mm, but this is increased in the lower part of the spinal cord. It contains a double fold of pia mater, and its floor is formed by a transverse band of white substance, the anterior white commissure, which is perforated by blood vessels on their way to or from the central part of the medulla spinalis. The anterior median fissure provides a groove in which the anterior spinal artery sits. From here, it provides the anterior part of the spinal cord.
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Dissection of human embryo The cephalic end of the neural groove exhibits several dilatations that, when the tube is closed, assume the form of the three primary brain vesicles, and correspond, respectively, to the future forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon) (Fig. 18). The walls of the vesicles are developed into the nervous tissue and neuroglia of the brain, and their cavities are modified to form its ventricles. The remainder of the tube forms the spinal cord (medulla spinalis); from its ectodermal wall the nervous and neuroglial elements of the spinal cord are developed, while the cavity persists as the central canal.
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The location of motor neurons in the anterior grey column of the spinal column The anterior grey column, directed forward, is broad and of a rounded or quadrangular shape. Its posterior part is termed the base, and its anterior part the head, but these are not differentiated from each other by any well-defined constriction. It is separated from the surface of the medulla spinalis by a layer of white substance which is traversed by the bundles of the anterior nerve roots. In the thoracic region, the postero-lateral part of the anterior column projects laterally as a triangular field, which is named the lateral grey column.
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It is concave in front, convex behind, broader and thicker in the middle than at the ends, and firmly attached on either side to a small tubercle on the medial surface of the lateral mass of the atlas.Gray's anatomy, 1918 As it crosses the odontoid process, a small fasciculus (crus superius) is prolonged upward, and another (crus inferius) downward, from the superficial or posterior fibers of the ligament. The former is attached to the basilar part of the occipital bone, in close relation with the membrana tectoria; the latter is fixed to the posterior surface of the body of the axis; hence, the whole ligament is named the cruciate ligament of the atlas. The transverse ligament divides the ring of the atlas into two unequal parts: of these, the posterior and larger serves for the transmission of the medulla spinalis and its membranes and the accessory nerves; the anterior and smaller contains the odontoid process.
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