Sensory information from the enteric system is carried back to the CNS by visceral sensory fibers.
Nerve plexuses are either somatic or visceral and combine fibers from different sources or levels to form new nerves with specific targets or destinations (Fig. 1.49). Plexuses of the enteric system also generate reflex activity independent of the CNS.
Major somatic plexuses formed from the anterior rami of spinal nerves are the cervical (C1 to C4), brachial (C5 to T1), lumbar (L1 to L4), sacral (L4 to S4), and coccygeal (S5 to Co) plexuses. Except for spinal nerve T1, the anterior rami of thoracic spinal nerves remain independent and do not participate in plexuses.
Visceral nerve plexuses are formed in association with viscera and generally contain efferent (sympathetic and parasympathetic) and afferent components (Fig. 1.49). These plexuses include cardiac and pulmonary plexuses in the thorax and a large prevertebral plexus in the abdomen anterior to the aorta, which extends inferiorly onto the lateral walls of the pelvis. The massive prevertebral plexus supplies input to and receives output from all abdominal and pelvic viscera.
Specific information about the organization and components of the respiratory, gastrointestinal, and urogenital systems will be discussed in each of the succeeding chapters of this text.
Fig. 1.1 The anatomical position, planes, and terms of location and orientation.
Feet togethertoes forwardHands by sidespalms forwardFace looking forwardInferior margin of orbit level withtop of external auditory meatusSagittal planeCoronal planeSuperiorAnteriorPosteriorMedialLateralInferiorTransverse, horizontal,or axial plane
Fig. 1.2 Cathode ray tube for the production of X-rays.
Fig. 1.3 Fluoroscopy unit.
Fig. 1.4 Barium sulfate follow-through.
Fig. 1.5 Digital subtraction angiogram.
Fig. 1.6 Ultrasound examination of the abdomen.
Fig. 1.7 Computed tomography scanner.
Fig. 1.8 Computed tomography scan of the abdomen at vertebral level L2.
Fig. 1.9 A T2-weighted MR image in the sagittal plane of the pelvic viscera in a woman.
Fig. 1.10 T1-weighted (A) and T2-weighted (B) MR images of the brain in the coronal plane.
Fig. 1.11 A gamma camera.
Fig. 1.12 The axial skeleton and the appendicular skeleton.
Fig. 1.13 Accessory and sesamoid bones. A. Radiograph of the ankle region showing an accessory bone (os trigonum).
B. Radiograph of the feet showing numerous sesamoid bones and an accessory bone (os naviculare).
Fig. 1.14 A developmental series of radiographs showing the progressive ossification of carpal (wrist) bones from 3 (A) to 10 (D) years of age.
Fig. 1.15 T1-weighted image in the coronal plane, demonstrating the relatively high signal intensity returned from the femoral heads and proximal femoral necks, consistent with yellow marrow. In this young patient, the vertebral bodies return an intermediate darker signal that represents red marrow. There is relatively little fat in these vertebrae; hence the lower signal return.
Fig. 1.16 Radiograph, lateral view, showing fracture of the ulna at the elbow joint (A) and repair of this fracture (B) using internal fixation with a plate and multiple screws.