| PAD | pain and distress; patient surface axis depth; percutaneous abscess drainage; percutaneous automated... |
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| PAH | para-aminohippurate; phenylalanine hydrolase; polycyclic aromatic hydrocarbon; predicted adult heigh... |
| PCA | para-chloramphetamine; parietal cell antibody; passive cutaneous anaphylaxis; patient care assistant... |
| PICA | percutaneous transluminal coronary angioplasty; Porch Index of Communicative Abilities; posterior in... |
| PPA | palpation, percussion, auscultation; pepsin A; phenylpropanolamine; phenylpyruvic acid; Pittsburgh p... |
| spinal lemniscus | A large ascending fibre bundle in the ventral half of the lateral funiculus of the spinal cord, arising from cells in the posterior horn at all levels of the cord, which cross within their segments of origin in the white commissure. In their contralateral ascent, the bundle is intermingled with numerous intersegmental fibres. The spinothalamic tract continues from the spinal cord into the brainstem, occupying a ventrolateral position and issuing numerous fibres to the rhombencephalic and mesencephalic reticular formation, to the lateral part of the central gray substance of the mesencephalon, and to the deep and intermediate layers of the superior colliculus; the relatively few fibres (10 to 20%) that remain form the true spinothalamic tract which enters the diencephalon and ends in the nucleus ventralis posterior (caudal part) and intralaminar nuclei of the thalamus. In its ascent in the spinal cord the tract is composed of a dorsal part, the lateral spinothalamic tract, which conveys impulses associated with pain and temperature sensation, and a more ventral part, the anterior spinsothalamic tract, involved in tactile sensation. Synonym: lemniscus spinalis, spinal lemniscus, tractus spinothalamicus. (05 Mar 2000) |
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| spinal length | A measurement from the distal surface of the embryo where the plane passes through the developing eye (this is the cranial limit of the spinal cord) down to the rump. (05 Mar 2000) |
| spinal marrow | <anatomy> Elongated, approximately cylindrical part of the central nervous system of vertebrates that lies in the vertebral canal and from which the spinal nerves emerge. (18 Nov 1997) |
| spinal muscle | <anatomy> The medial component of the erector spinae muscle; it is comprised of the spinalis capitis, spinalis cervicis, and spinalis thoracis muscles. Synonym: musculus spinalis, spinal muscle. (05 Mar 2000) |
| spinal muscle of head | <anatomy> An inconstant extension of spinalis cervicis to the occipital bone, sometimes fusing with semispinalis capitis. Synonym: musculus spinalis capitis, biventer cervicis, spinal muscle of head. (05 Mar 2000) |
| spinal muscle of neck | <anatomy> An inconstant or rudimentary muscle; origin, spinous processes of sixth and seventh cervical vertebrae; insertion, spinous processes of axis and third cervical vertebra; action, extends cervical spine; nerve supply, dorsal primary rami of cervical. Synonym: musculus spinalis cervicis, musculus spinalis colli, spinal muscle of neck. (05 Mar 2000) |
| spinal muscle of thorax | <anatomy, muscle> Origin, spinous processes of upper lumbar and two lower thoracic vertebrae; insertion, spinous processes of middle and upper thoracic vertebrae; action, supports and extends vertebral column; nerve supply, dorsal primary rami of thoracic and upper lumbar. Synonym: musculus spinalis thoracis, musculus spinalis dorsi, spinal muscle of thorax. (05 Mar 2000) |
| spinal muscular atrophy | <radiology> 2nd most common autosomal recessive disease in Caucasians, pathology, degeneration of the spinal anterior horn cells, atrophy and wasting of skeletal muscles, types, SMA I = Werdnig-Hoffman disease: rapidly progressive, SMA II = intermediate form, SMA III = Kugelberg-Welander disease: slowly progressive, uncommon adult forms, usual presentations, floppy baby, arthrogryposis, muscle weakness in infancy, diagnosis, weakness and wasting with areflexia, electrophysiology shows anterior horm cell disease, genetics, linked to chromosome 5q., neuronal apoptosis inhibitory protein (NAIP) gene, survival motor neuron (SMN) gene (12 Dec 1998) |
| spinal nerve roots | The paired bundles of nerve fibres entering and leaving the spinal cord at each segment. The dorsal and ventral nerve roots join to form the mixed segmental spinal nerves. The dorsal roots are generally afferent, formed by the central projections of the spinal (dorsal root) ganglia sensory cells, and the ventral roots efferent, comprising the axons of spinal motor and autonomic preganglionic neurons. There are, however, some exceptions to this afferent/efferent rule. (12 Dec 1998) |
| spinal nerves | The 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included. (12 Dec 1998) |
| spinal nucleus of the trigeminus | The long sensory nucleus extending from the caudal border of the pontine sensory nucleus of the trigeminus down through the lateral region of the rhombencephalon into the upper three segments of the spinal cord's dorsal horn; it receives the fibres of the sensory root of the trigeminal nerve which descend along its lateral border as the spinal tract of trigeminal nerve. Synonym: nucleus tractus spinalis nervi trigemini, descending nucleus of the trigeminus, spinal nucleus of the trigeminus. (05 Mar 2000) |
| spinal osteophytosis | Outgrowth of immature bony processes from the vertebrae, reflecting the presence of degenerative disease and calcification. It includes cervical and lumbar spondylosis. (12 Dec 1998) |
| spinal paralysis | Loss of motor power due to a lesion of the spinal cord. Synonym: myeloparalysis, myeloplegia, rachioplegia. (05 Mar 2000) |
| spinal part of accessory nerve | <anatomy, nerve> Originates from the upper five or six cervical spinal segments, emerges from the lateral surface of the spinal cord and ascends through the foramen magnum to join the cranial root. Synonym: radices spinales nervi accessorii, ramus externus nervi accessorii, pars spinalis nervi accessorii, spinal part of accessory nerve. (05 Mar 2000) |
| spinal part of arachnoid | That portion of the arachnoid which lies within the vertebral canal and surrounds the spinal cord and the vertebral portion of the subarachnoid space. It extends from the foramen magnum above to the S-2 vertebral level. Since the spinal cord ends at the L-2 vertebral level, a wide separation occurs between the arachnoid and pia mater, the lumbar cistern, filled with cerebrospinal fluid in which the cauda equina is suspended. Synonym: arachnoidea mater spinalis, spinal part of arachnoid. (05 Mar 2000) |