ch15_Summary_Saladin3e

ch15_Summary_Saladin3e - Saladin Human Anatomy 3e Detailed...

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Saladin, Human Anatomy 3e Detailed Chapter Summary Chapter 15, The Brain and Cranial Nerves 15.1 Overview of the Brain (p. 399) 1. The adult brain weighs 1,450 to 1,600 g. It is divided into the cerebrum, cerebellum, and brainstem . 2. In brain anatomy, the directional term rostral refers to structures relatively close to the forehead, or anterior to another structure, whereas caudal refers to more posterior structures, closer to the rear of the head or closer to the spinal cord. 3. The cerebrum is conspicuously divided into right and left cerebral hemispheres separated by a deep groove, the longitudinal fissure. The two hemispheres are joined by a bridge, the corpus callosum, at the bottom of this fissure. The corpus callosum constitutes a prominent C -shaped landmark in median sections of the brain. 4. The cerebellum, the second largest part of the brain, lies inferior to the cerebrum in the posterior cranial fossa. 5. The cerebrum and cerebellum are conspicuously marked by surface gyri (folds), sulci (shallow grooves), and fissures (deeper grooves). 6. The brainstem is a vertical stalk composed of the diencephalon, midbrain, pons, and medulla oblongata, from rostral to caudal; many authorities, however, consider only the last three of these to be the brainstem. The brainstem is continuous caudally with the spinal cord. 7. Like the spinal cord, the brain is composed of two kinds of nervous tissue: gray matter and white matter . Gray matter constitutes the surface cortex and deeper nuclei of the cerebrum and cerebellum, and nuclei of the brainstem. White matter lies deep to the cortex and consists of tracts of myelinated nerve fibers. 8. The brain is surrounded by a the same three meninges as the spinal cord: dura mater, arachnoid mater, and pia mater. The dura mater is divided into two layers, periosteal and meningeal, which in some places are separated by blood-filled dural sinuses . In some places, the dura folds inward to separate major brain regions, such as the falx cerebri that separates the two cerebral hemispheres, the tentorium cerebelli between the cerebrum and cerebellum, and the falx cerebelli between the right and left halves of the cerebellum. A subdural space separates some areas of dura from the arachnoid, and a subarachnoid space separates arachnoid from pia.
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9. The brain has four internal, interconnected chambers: two lateral ventricles in the cerebral hemispheres, a third ventricle between the hemispheres, and a fourth ventricle between the pons and cerebellum. The lateral ventricles are connected to the third by an interventricular foramen on each side, and the third is connected to the fourth by the cerebral aqueduct in the brainstem. 10. The ventricles and canals of the CNS are lined with ependymal cells, and each ventricle contains a
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ch15_Summary_Saladin3e - Saladin Human Anatomy 3e Detailed...

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