Injection (redirected from subarachnoid injection)

injection, introduction of a fluid into the body, usually by means of a needle and syringe. The material injected may be a test substance (as in determining allergic sensitivity or immunity to a disease), an anesthetic, a therapeutic drug, a nutrient (in cases where intravenous feeding is necessary), blood, or blood plasma (see blood transfusion). An intracutaneous injection is the introduction of a small amount of fluid between the skin layers. A subcutaneous injection is directed to the tissues under the skin. When quicker absorption of a drug is required, an intramuscular injection may be used; even more rapid action is obtained by injection into a vein (intravenous). In certain emergencies involving the heart, such as cardiac arrest, an intracardiac injection can penetrate directly into a chamber of the musculature of the heart. Anesthetics are sometimes injected into the spine. In an injection by means of a jet injector gun, fluid penetrates through the skin by means of air pressure and there is no visible puncture mark. Micro-injections can be made into fetuses, even individual cells, with tiny capillary injectors.

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injection [in′jek·shən]

(aerospace engineering)

The process of placing a spacecraft into a specific trajectory, such as an earth orbit or an encounter trajectory to Mars. Also known as insertion.

(electronics)

The method of applying a signal to an electronic circuit or device.

The process of introducing electrons or holes into a semiconductor so that their total number exceeds the number present at thermal equilibrium.

(geology)

Also known as intrusion; sedimentary injection.

A process by which sedimentary material is forced under abnormal pressure into a preexisting rock or deposit.

A structure formed by an injection process.

(mathematics)

A mapping ƒ from a setAinto a setBwhich has the property that for any elementbofBthere is at most one elementaofAfor which ƒ(a) =b. Also known as injective mapping; one-to-one mapping; univalent function.

(mechanical engineering)

The introduction of fuel, fuel and air, fuel and oxidizer, water, or other substance into an engine induction system or combustion chamber.

(medicine)

Introduction of a fluid into the skin, vessels, muscle, subcutaneous tissue, or any cavity of the body.

The substance injected.

(mining engineering)

The introduction under pressure of a liquid or plastic material into cracks, cavities, or pores in a rock formation.

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1.	(mathematics)	injection - A function, f : A -> B, is injective or one-one, or is an injection, if and only if for all a,b in A, f(a) = f(b) => a = b. I.e. no two different inputs give the same output (contrast many-to-one). This is sometimes called an embedding. Only injective functions have left inverses f' where f'(f(x)) = x, since if f were not an injection, there would be elements of B for which the value of f' was not unique. If an injective function is also a surjection then is it a bijection.
2.	(reduction)	injection - An injection function is one which takes objects of type T and returns objects of type C(T) where C is some type constructor. An example is f x = (x, 0). The opposite of an injection function is a projection function which extracts a component of a constructed object, e.g. fst (x,y) = x. We say that f injects its argument into the data type and fst projects it out.

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Injection 

the introduction of small quantities of medicine in solution or emulsion into subcutaneous tissue, intramuscularly, or intravenously with syringe and needle. With injection a more rapid effect is achieved than with ingestion, as well as precise dosage and reliability of effect. With injection, medication may be introduced regardless of the condition of the patient, such as unconsciousness and inability to swallow. For localized effect medicinal solutions are injected into the pleural cavity or joints; intradermal injections are used for analgesia and for diagnostic purposes, for example, the Mantoux reaction for diagnosing tuberculosis. Intracardiac injection is resorted to when there is a sudden heart stoppage (injury from electric shock, gas poisoning, and narcosis). Injection into the cerebrospinal canal is done for analgesia and treatment of certain diseases. The rules of asepsis must be observed without fail in injection.