aperture


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aperture

 [ap´er-chur]
inferior aperture of minor pelvis (inferior aperture of pelvis) pelvic outlet.
numerical aperture an expression of the measure of efficiency of a microscope objective.
superior aperture of minor pelvis (superior aperture of pelvis) pelvic inlet.

ap·er·ture

(ap'er-chūr),
1. Opening. An inlet or entrance to a cavity or channel. In anatomy, a gap or hole.
See also: fossa, ostium, orifice, pore. Synonym(s): apertura [TA]
2. The diameter of the objective of a microscope.
Synonym(s): aditus [TA]
[L. apertura, an opening]

aperture

/ap·er·ture/ (ap´er-cher) opening.
piriform aperture  the anterior end of the bony nasal opening, connecting the external nose with the skull.

aperture

[ap′ərchər]
Etymology: L, apertura, an opening
an opening or hole in an object or anatomical structure.

ap·er·ture

(ap'ĕr-chŭr) [TA]
1. An inlet or entrance to a cavity or channel; in anatomy, an open gap or hole.
2. The diameter of the objective of a microscope.
Synonym(s): aditus [TA] , apertura [TA] .
[L. apertura, an opening]

aperture 

An opening, or the area of a lens, through which light can pass. See pupil.
angular aperture Half of the maximum plane subtended by a lens at the axial point of an object or image. (Sometimes the full plane angle is taken as the angular aperture but this is not convenient in optical calculations.) See sine condition.
aperture of a lenticular lens That portion of a lenticular lens which has the prescribed power (British Standard).
numerical aperture An expression designating the light-gathering power of microscope objectives. It is equal to the product of the index of refraction n of the object space and the sine of the angle u subtended by a radius of the entrance pupil at the axial point on the object, i.e. n sin u.
palpebral aperture The gap between the margins of the eyelids when the eye is open. An abnormal increase in the aperture occurs in some conditions, including Graves' disease, buphthalmos, Parinaud's syndrome and retrobulbar tumour. An abnormal decrease in the aperture occurs in some conditions, including ptosis, microphthalmos and ophthalmoplegia (Figs. A15 and A16). Syn. interpalpebral fissure (this term is more accurate although used infrequently); palpebral fissure. See exophthalmos.
aperture plane See aperture plane.
aperture ratio See relative aperture.
relative aperture The reciprocal of the f number. It is therefore equal to the ratio of the diameter of the entrance pupil to the primary focal length of an optical system. Syn. aperture ratio. Note: the definition of this term is not universally accepted; some authors define it as the reverse of the above. See antimongoloid slant; f number.
Fig. A15 Palpebral aperture PA and corneal apex CAenlarge picture
Fig. A15 Palpebral aperture PA and corneal apex CA
Fig. A16 Average dimensions of the normal palpebral aperture of a Caucasian eyeenlarge picture
Fig. A16 Average dimensions of the normal palpebral aperture of a Caucasian eye

ap·er·ture

(ap'ĕr-chŭr) [TA]
1. [TA] Opening. An inlet or entrance to a cavity or channel. In anatomy, a gap or hole.
Synonym(s): apertura.
2. The diameter of the objective of a microscope.
See also: fossa, ostium, orifice
Synonym(s): aditus [TA] .
[L. apertura, an opening]

aperture,

n an opening such as in bone.

aperture

an opening.

nasal aperture
the opening on the skull bounded by the nasal and incisive bones.
nasomaxillary aperture
the connecting aperture between the middle nasal meatus and the maxillary sinuses.
numerical aperture
measure of efficiency of a microscope objective proportional to the square root of the amount of light entering the instrument.
References in classic literature ?
At length, the blanket was slowly raised, and the scout stood in the aperture with a countenance whose firmness evidently began to give way before a mystery that seemed to threaten some danger, against which all his cunning and experience might prove of no avail.
As the door had slipped aside I had noted its great thickness, fully twenty feet, and as it reached its place once more after closing behind us, great cylinders of steel had dropped from the ceiling behind it and fitted their lower ends into apertures countersunk in the floor.
The little pink sloth-creature was still blinking at me when my Ape-man reappeared at the aperture of the nearest of these dens, and beckoned me in.
Glancing upward, I saw the aperture, a small blue disk, in which a star was visible, while little Weena's head showed as a round black projection.
I heard it give a peculiar thick cry, and forthwith another of these creatures appeared darkly in the deep shadow of the aperture.
D'Artagnan remained for a moment motionless, asking himself where he could be; but soon a ray of light which penetrated through the chamber, together with the warm and perfumed air which reached him from the same aperture, the conversation of two of three ladies in language at once respectful and refined, and the word "Majesty" several times repeated, indicated clearly that he was in a closet attached to the queen's apartment.
He kept his word; twice a day he cast out, through the barred aperture, the provisions his jailer brought him -- at first gayly, then with deliberation, and at last with regret.
The closet into which D'Artagnan and Porthos had been ushered was separated from the drawing-room where the queen was by tapestried curtains only, and this thin partition enabled them to hear all that passed in the adjoining room, whilst the aperture between the two hangings, small as it was, permitted them to see.
After the door has closed behind him, she perceives it thrust partly open, and a vision of her husband's face, through the aperture, smiling on her, and gone in a moment.
As he was reconnoitring the fort, he perceived an Indian peeping through an aperture.
A thick canopy of trees hung over the very verge of the fall, leaving an arched aperture for the passage of the waters, which imparted a strange picturesqueness to the scene.
It wandered along the crest of the hill and terminated before a fragment of wall pierced by a rough aperture which had once been a door.