| spontaneous cephalic delivery | Unassisted expulsion of a foetus that presents by the head. (05 Mar 2000) |
|---|---|
| spontaneous combustion | A circumstance where a substance or organism takes fire and burns without an exogenous source. Spontaneous human combustion differs from preternatural human combustibility in that in the latter, some spark or trivial flame sets the fire and the body tissues, which have a greatly enhanced inflammability, continue to undergo incineration without any external heat source or combustible materials. (bergman na. Spontaneous human combustion: its role in literature and science. Pharos 1988;fall;51(4):18-21) (12 Dec 1998) |
| spontaneous correction of placenta previa | The upward "migration" of the placenta away from the internal os by the differential growth rates of upper and lower uterine segments. (05 Mar 2000) |
| spontaneous emission | <radiobiology> Radiation randomly emitted by excited atoms or ions. Contrast with stimulated emission. (09 Oct 1997) |
| spontaneous evolution | The unaided delivery of the foetus from a transverse lie. (05 Mar 2000) |
| spontaneous fracture | A fracture occurring without any external injury. (05 Mar 2000) |
| spontaneous gangrene of newborn | Gangrene due to vascular occlusion of unknown cause, usually in marasmic or dehydrated infants. (05 Mar 2000) |
| spontaneous generation | The obsolete hypothesis that living organisms can originate from nonliving matter. (09 Oct 1997) |
| spontaneous intermittent mandatory ventilation | Intermittent mandatory ventilation spontaneously initiated by the patient, to increase tidal volume, and subsequently synchronised with patient's respiratory cycle. Synonym: synchronised intermittent mandatory ventilation. (05 Mar 2000) |
| spontaneous mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
| spontaneous osteolysis | <radiology> Several syndromes of vanishing bones: (Cf: rapid demineralization), idiopathic hereditary osteolysis, autosomal dominant, manifest in early childhood, carpals and tarsals involved first, autosomal-recessive carpal and tarsal osteolysis, idiopathic osteolysis with nephropathy, carpals, tarsals, adjacent tubular bones involved, azotaemia may lead to death in early adulthood, massive osteolysis of Gorham, angiomatous destruction (12 Dec 1998) |
| spontaneous phagocytosis | Phagocytosis occurring when a culture of bacteria is brought in contact with washed leukocytes in an indifferent medium, such as a physiologic salt solution. (05 Mar 2000) |
| spontaneous pneumothorax | A sudden collapse of the lung that occurs as the result of a tear in the lung tissue. May be seen after strenuous activity, coughing or straining. Thin males are at greatest risk for this disorder. (27 Sep 1997) |
| spontaneous process | <chemistry> A process that occurs without outside intervention. Spontaneity is independent of rate. To be spontaneous a process must increase the entropy of the universe. (09 Jan 1998) |
| spontaneous recovery | The return of the conditioned response, after apparent extinction, in the presence of the conditioned stimulus without the unconditioned stimulus also being present. See: classical conditioning. (05 Mar 2000) |