| control arm | The group of participants in a clinical trial who receive standard treatment or a placebo, against which those receiving the experimental treatment are compared. (09 Oct 1997) |
|---|---|
| positive focal length | <microscopy> Any lens which converges parallel rays to a focus at the back of the lens is a positive lens and has a positive focal length. The focal length is measured from the second principal point of the lens to the point on the lens axis where the rays from an infinitely distant point are brought to focus. See: negative focal length. (05 Aug 1998) |
| posterior cutaneous nerve of arm | <anatomy, nerve> A branch of the radial nerve supplying the skin of the posterior surface of the arm. Synonym: nervus cutaneus brachii posterior, posterior cutaneous nerve of arm. (05 Mar 2000) |
| crown-heel length | Length of an outstretched embryo or foetus from skull vertex to heel. See: Streeter's developmental horizon(s). (05 Mar 2000) |
| crown-rump length | In utero measurement corresponding to the sitting height (crown to rump) of the foetus. Length is considered a more accurate criterion of the age of the foetus than is the weight. The average crown-rump length of the foetus at term is 36 cm. (12 Dec 1998) |
| posterior region of arm | The back of arm. Synonym: facies brachialis posterior, regio brachialis posterior, posterior brachial region, posterior surface of arm. (05 Mar 2000) |
| posterior surface of arm | The back of arm. Synonym: facies brachialis posterior, regio brachialis posterior, posterior brachial region, posterior surface of arm. (05 Mar 2000) |
| height-length index | The relation of the height to the length of the skull: (height × 100)/length. Synonym: height-length index, length-height index, transversovertical index. (05 Mar 2000) |
| 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) |
| stabilizing circumferential clasp arm | An arm that is relatively rigid and embraces the height of contour of the tooth. (05 Mar 2000) |
| negative focal length | <physics> The focal length of a negative lens. Parallel rays impinging on a negative lens can be traced to a virtual focus which exists on the same side of the lens as the impinging rays. The distance from the second principal point of the lens to this second focal point is measured on the same side of the lens as is the object. See: negative lens, focal length. (05 Aug 1998) |
| deep fascia of arm | The deep fascia of the arm; it is continuous proximally with the pectoral fascia and the fascia covering the deltoid; distally it is continuous with the antebrachial fascia. Synonym: fascia brachii, deep fascia of arm. (05 Mar 2000) |
| dynein arm | A structure extending clockwise from one tubule of each of the 9 doublet microtubules toward the adjacent doublet seen in the axoneme of cilia or flagella (including human sperm tails); congenital absence of dynein, reflected structurally by absence of dynein arm's, can account for symptoms seen in Kartagener's syndrome and in immotile cilia syndromes. (05 Mar 2000) |
| q arm | <cell biology> The long arm of a chromosome. All human chromosomes have 2 arms: the short (p) arm and the long (q) arms. (12 Dec 1998) |
| triceps muscle of arm | <anatomy, muscle> Origin, long or scapular head: lateral border of scapula below glenoid fossa, lateral head: lateral and posterior surface of humerus below greater tubercle, medial head: posterior surface of humerus below radial groove; insertion, olecranon of ulna; action, extends elbow; nerve supply, radial. Synonym: musculus triceps brachii, triceps muscle of arm. (05 Mar 2000) |