Temporal bone structure

The vestibular system in each ear consists of the otolith and saccule (coUectively by caUed the otolithic organs), which are the Hnear motion sensors, and the three semicircular canals (SCCs), which sense rotational motion. The SCCs are oriented in three nearly mutually perpendicular planes so that angular motion about any axis may be sensed. The otoliths and SCCs consist of membranous structures that are situated in hollowed-out sections and passageways in the vestibule of the temporal bone. This hollowed-out... 

CT is an important diagnostic tool in temporal bone imaging. Despite all of these advances, numerous small and important anatomic structures in the temporal bone... 

According to Wolffs law, alteration of function results in a change in the structure of bone. The mastoid processes are barely existent in a newborn infant but become larger, knob-like projections from the temporal bone by adnlt-hood. Hypertrophy of the inion most likely indicates chronic tension introdnced by the trapezius and splenii muscles. Asyimnetric or even symmetric stressors on bone or other bodily components bring abont long-term changes in structure. 

FIG. 103-15 Structure of the temporal bone. (A) External view. (B) Internal view. (C) Inferior view. 

The structures of the inner ear lies within the temporal bone. They function both in hearing and in maintaining body balance. Any condition affecting the inner ear may result in hearing loss, hyperacusis, tinnitus, or vertigo. 

The nose and throat showed no inflammation, swelling of the turbinates, or enlargement of the tonsils. The heart and lungs were normal. Hearing did not appear to be affected —the child responded to his name when it was whispered behind him. On structural examination, he was found to have C2 FS.Rii, T4FSlRl, an internally rotated temporal bone on the right, and external rotation of the left. There was mild condylar compression of the occiput. 

The cerebral cortex is conventionally subdivided into four main regions that may be delineated by the sulci, or large clefts, termed the frontal, temporal, parietal and occipital lobes. These names are derived from the bones of the skull which overlay them. Each lobe may be further subdivided according to its cellular structure and composition. Thus Brodmarm has divided the cortex into approximately 50 discrete areas according to the specific cellular structure and function. For example, electrical stimulation of the strip of cerebral cortex in front of the central sulcus (see Figure 1.3) is responsible for motor commands to the muscles. This is termed the primary motor cortex and can be further subdivided according to which muscles are controlled in different parts of the body. 

The divisions of the cranial central nervous system include the cerebral hemispheres, the diencephalon (thalamus and hypothalamus), the brainstem (midbrain, pons and medulla oblongata) and the cerebellum (Fig. 1.2). Each cerebral hemisphere occupies one half of the cranial vault and can be subdivided into four lobes (frontal, parietal, temporal, occipital), the insula and the limbic lobe. The first four lobes are named for the cranial bones that overlie them. With respect to the floor of the cranial cavity, the frontal lobes lie in the anterior cranial fossa the brainstem and cerebellum occupy the posterior cranial fossa the remaining structures are found either in the middle fossa or within the portion of the cranial vault above the tentorium cerebelli. The insula is covered by the temporal lobe and is not observable unless the temporal lobe is retracted. The hmbic system is a continuous interior... 

---