| RC | an electronic circuit containing a resistor and capacitor in series; radiocarpal; reaction center; r... |
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| RCT | radiotherapy and chemotherapy; randomized clinical trial; randomized controlled trial; registered ca... |
| RF | radial fiber; radio frequency; receptive field; regurgitant fraction; Reitland-Franklin [unit]; rela... |
| RMS | rectal morphine sulfate [suppository]; red man syndrome; repetitive motion syndrome; respiratory mus... |
| rms | root-mean-square |
| saber-sheath trachea | A type of tracheal collapse seen in chronic obstructive pulmonary disease in which there is an increase in the outer posterior tracheal dimension with side-to-side narrowing involving the lower 2/3 of the trachea. (05 Mar 2000) |
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| Henle's sheath | <anatomy> The delicate bands of connective tissue among nerve fibres. Origin: NL, fr. Gr. Within + a sinew, nerve. Source: Websters Dictionary (01 Mar 1998) |
| prostatic sheath | Loose fibrous, partly vascular enclosure of the prostate and its dense (true) fibrous capsule; it is continuous inferiorly with the superior fascia of the urogenital diaphragm and posteriorly becomes part of the rectovesical septum; it contains the prostatic venous plexus. (05 Mar 2000) |
| Scarpa's sheath | H;one of the coverings of the spermatic cord, formed of delicate connective tissue and of muscular fibres derived from the internal oblique muscle (cremaster muscle). See: aponeurosis of internal abdominal oblique muscle. Synonym: fascia cremasterica, Cooper's fascia, Scarpa's sheath. (05 Mar 2000) |
| Hertwig's sheath | The merged outer and inner epithelial layers of the enamel organ which extends beyond the region of the anatomical crown and initiates formation of dentin in the root of a developing tooth; it atrophies as the root is formed, and any of the cells that persist are called Malassez' epithelial rests. (05 Mar 2000) |
| schwan's sheath | <anatomy> The neurilemma. Origin: So called from Theodor Schwann, a German anatomist of the 19th century. Source: Websters Dictionary (01 Mar 1998) |
| Huxley's sheath | A layer of cells interposed between Henle's layer and the cuticle of the inner root sheath of the hair follicle. Synonym: Huxley's membrane, Huxley's sheath. (05 Mar 2000) |
| sheath | A protective covering. The lower part of leaf enveloping stem or culm. A secreted, tubular structure formed around a chain of cells or around a bundle of filaments, cells within a sheath may or may not subsequently separate from the sheath. A layer of outer membrane covering the bacterial flagella. (09 Oct 1997) |
| sheath ligaments | See: fibrous digital sheaths of hand, fibrous digital sheaths of foot, fibrous tendon sheath. (05 Mar 2000) |
| sheath of eyeball | A condensation of connective tissue on the outer aspect of the sclera from which it is separated by a narrow cleftlike episcleral space; the sheath is attached to the sclera near the sclerocorneal junction and blends with the fascia of the extraocular muscles. Synonym: vagina bulbi, capsula bulbi, eye capsule, fascia bulbi, sheath of eyeball, Tenon's capsule, vagina oculi. (05 Mar 2000) |
| sheath of Key and Retzius | <anatomy> The delicate bands of connective tissue among nerve fibres. Origin: NL, fr. Gr. Within + a sinew, nerve. Source: Websters Dictionary (01 Mar 1998) |
| sheath of Schwann | <anatomy> The delicate outer sheath of a nerve fibre; the primitive sheath. The perineurium. Origin: NL, from gr. Nerve + peel, skin. Source: Websters Dictionary (01 Mar 1998) |
| sheath of Schweigger-Seidel | <geometry> A solid, all plane sections of which are ellipses or circles. See Conoid, 2 . The ellipsoid has three principal plane sections, a, b, and c, each at right angles to the other two, and each dividing the solid into two equal and symmetrical parts. The lines of meeting of these principal sections are the axes, or principal diameters of the ellipsoid. The point where the three planes meet is the center. Ellipsoid of revolution, a spheroid; a solid figure generated by the revolution of an ellipse about one of its axes. It is called a prolate spheroid, or prolatum, when the ellipse is revolved about the major axis, and an oblate spheroid, or oblatum, when it is revolved about the minor axis. Origin: Ellipse: cf. F. Ellipsoide. Source: Websters Dictionary (01 Mar 1998) |
| sheath of styloid process | A crest of bone (edge of the tympanic portion of the temporal bone) running from the front and medial side of the mastoid process to the spine of the sphenoid; it splits to ensheath the base of the styloid process. Synonym: vagina processus styloidei, vaginal process. (05 Mar 2000) |
| sheath of thyroid gland | Covering of the thyroid gland external to its capsule formed by a splitting of the pretracheal layer of deep cervical fascia at the gland's posterior border; the anterior lamina covers the gland anterolaterally, attaching to the arch of the cricoid cartilage superior to the isthmus of the gland (causing it to move with the trachea during elevation/depression of the larynx); the posterior lamina passes posterior to the oesophagus to blend with the buccopharyngeal fascia; inferiorly, the sheath extends along the inferior thyroid veins to open into the superior mediastinum (hence, expansion of the thyroid, as by goiter, can take this direction). (05 Mar 2000) |