| sphincter muscle of common bile duct | Smooth muscle sphincter of the common bile duct immediately proximal to the hepatopancreatic ampulla; it is this sphincter that controls the flow of bile in the duodenum. Synonym: musculus sphincter ductus choledochi, Boyden's sphincter, choledochal sphincter, sphincter muscle of common bile duct. (05 Mar 2000) |
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| sphincter muscle of pancreatic duct | Smooth muscle sphincter of the main pancreatic duct immediately proximal to the hepatoduodenal, ampulla. Synonym: musculus sphincter ductus pancreatici, pancreatic sphincter, sphincter muscle of pancreatic duct. (05 Mar 2000) |
| sphincter muscle of pupil | A ring of smooth muscle fibres surrounding the pupillary border of the iris. Synonym: musculus sphincter pupillae, sphincter muscle of pupil. (05 Mar 2000) |
| sphincter muscle of pylorus | A thickening of the circular layer of the gastric musculature encircling the gastroduodenal junction. Synonym: musculus sphincter pylori, sphincter muscle of pylorus. (05 Mar 2000) |
| sphincter muscle of urethra | Origin, ramus of pubis; insertion, with fellow in median raphe behind and in front of urethra; action, constricts membranous urethra; nerve supply, pudendal. Synonym: musculus sphincter urethrae, external urethral sphincter, Guthrie's muscle, musculus compressor urethrae, musculus constrictor urethrae, musculus sphincter urethrae membranaceae, sphincter muscle of urethra, Wilson's muscle. (05 Mar 2000) |
| sphincter muscle of urinary bladder | The complete collar of smooth muscle cells of the neck of the urinary bladder which extend distally to surround the preprostatic sportion of the male urethra. There is not a comparable structure in the neck of the femoral bladder; the internal urethral sphincter may exist to prevent reflux of semen into bladder. Synonym: annulus urethralis, internal urethral sphincter, musculus sphincter vesicae, preprostate urethral sphincter, proximal urethral sphincter, sphincter muscle of urinary bladder. (05 Mar 2000) |
| spinalis capitis muscle | <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) |
| spinalis cervicis muscle | <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) |
| spinalis 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 | <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) |
| spindle-shaped muscle | <anatomy> One that has a fleshy belly, tapering at either extremity. Synonym: musculus fusiformis, spindle-shaped muscle. (05 Mar 2000) |
| splenius muscle of head | <anatomy, muscle> Origin, from ligamentum nuchae of last four cervical vertebrae and supraspinous ligament of first and second thoracic vertebrae; insertion, lateral half of superior nuchal line and mastoid process; action, rotates head and extends neck; nerve supply, dorsal primary rami of second to sixth cervical spinal nerves. Synonym: musculus splenius capitis, splenius muscle of head. (05 Mar 2000) |