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If the analogy of the eye's retina working as a sensor is drawn upon, the corresponding concept in human (and much of animal vision) is the visual field. [2] It is defined as "the number of degrees of visual angle during stable fixation of the eyes". [3] Note that eye movements are excluded in the visual field's definition.
The head is a source for many metaphors and metonymies in human language, including referring to things typically near the human head ( "the head of the bed"), things physically similar to the way a head is arranged spatially to a body ("the head of the table"), metaphorically ("the head of the class"), and things that represent some ...
A human skull and measurement device from 1902. Craniometry is measurement of the cranium (the main part of the skull), usually the human cranium.It is a subset of cephalometry, measurement of the head, which in humans is a subset of anthropometry, measurement of the human body.
The latter flexure mainly appears in mammals and sauropsids (reptiles and birds), whereas the other two, and principally the cephalic flexure, appear in all vertebrates (the sum of the cervical and cephalic ventral flexures is the cause of the 90-degree angle mentioned above in humans between body axis and brain axis).
The head rests on the top part of the vertebral column, with the skull joining at C1 (the first cervical vertebra known as the atlas). The skeletal section of the head and neck forms the top part of the axial skeleton and is made up of the skull, hyoid bone, auditory ossicles, and cervical spine. The skull can be further subdivided into:
Angular size illusions are most obvious as relative angular size illusions, in which two objects that subtend the same visual angle appear to have different angular sizes; it is as if their equal-sized images on the retina were of different sizes. Angular size illusions are contrasted with linear size illusions, in which two objects that are ...
The transponder is moved until a pair of echos are strong and equal. This indicates that the parietals are perpendicular to the transmitting beam. The distance of the reflections equal the biparietal diameter. From this, the size of the head and the fetal weight can be determined with incredible accuracy.
Visual angle is the angle a viewed object subtends at the eye, usually stated in degrees of arc. It also is called the object's angular size . The diagram on the right shows an observer's eye looking at a frontal extent (the vertical arrow) that has a linear size S {\displaystyle S} , located in the distance D {\displaystyle D} from point O ...