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Chapter 14 The Brain and Cranial Nerves

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Chapter 14 The Brain and Cranial Nerves
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  Chapter 14 The Brain and Cranial Nerves 1.   Major Landmarks a.   Rostral  –  means toward the forehead in human anatomy i.   In the spinal cord and brainstem, which are vertically oriented, rostral means higher b.   Caudal means toward the spinal column.  i.   In the spinal cord and brainstem, which are vertically oriented, caudal means lower. c.   Brain divided into 3 major portions Cerebrum, Cerebellum and Brainstem  i.   Cerebrum 1.   83% of brains’ volume  2.   Consists of a pair of half globes called cerebral hemispheres a.   Each is marked by thick folds called gyri separated by shallow grooves called sulci b.   Longitudinal fissure  –  separates the right and left hemispheres from each other. c.   Corpus callosum  –  located bottom of fissure which is a bundle of nerve fibers that connects the hemispheres. ii.   Cerebellum 1.   Occupies the posterior cranial fossa inferior to the cerebrum. 2.   It is separated from the cerebrum by the transverse cerebral fissure. 3.   Second largest region of the brain. About 10% of the volume of a brain. 4.   Contains about 50% of the brains neurons. iii.   Brainstem    –  all of the brain except the Cerebrum and Cerebellum. 1.   Major components from higher to lower (rostral to caudal) are: a.   Diencephalon b.   Midbrain c.   Pons d.   Medulla oblongata  2.   In a human, brainstem is oriented like a vertical stalk, with the cerebrum perched on top like a mushroom cap. 3.   Caudally, the brainstem ends at the foramen magnum of the skull and the CNS continues below this as the spinal cord 2.   Gray and White Matter a.   Brain composed of gray and white matter. i.   Gray matter forms a surface layer called the cortex over the cerebrum and cerebellum. ii.   Deeper masses surrounded by white matter are called nuclei.  iii.   White matter lies deep to the cortical gray matter 3.   Embryonic Development a.   Mature brain described in terms of forebrain, midbrain and hindbrain i.   The forebrain (prosencephalon)  –  divided into two parts 1.   Telencephalon 2.   Diencephalon ii.   The midbrain is undivided and is named mesencephalon iii.   The hindbrain divides into two vesicles 1.   The metencephalon 2.   The myelencephalon  4.   Meninges a.   Three membranes the surround the brain, called meninges. ( Dura mater, Arachnoid mater, Pia mater)  b.   Lie between the nervous tissue and bone c.   Protect the brain d.   Provide structural framework for brain’s arteries and veins. i.   Names of membranes 1.   Dura mater a.   Consist of two layers i.   Outer periosteal layer ii.   Inner meningeal layer b.   The two layers of dura separated by dural sinuses i.   Dural sinuses  –  spaces that collect blood that circulated through the brain ii.   Two major sinuses 1.   Superior sagittal sinus  –  found under the cranium along the median line 2.   Transvers sinus  –  runs horizontally from the rear of the head toward each ear. 3.   These sinuses meet like upside down T at back of brain and empty into jugular veins of the neck
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