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Physical Protection:  Bone: Skull and vertebral column  Membranes: Skin/Scalp, Meninges  Watery Cushion: Cerebrospinal fluid (CSF) Chemical Protection:  Blood-brain barrier © 2015 Pearson Education, Inc.

 Thin connective tissue layers (superficial to deep)  Dura Mater: double-layered, toughest ◦ Has inner folds between fissures  Arachnoid Mater: web-like, villi reabsorb CSF  Pia Mater: delicate, attaches directly to brain/cord

Skin of scalp Periosteum Bone of skull Periosteal Meningeal Dura mater Arachnoid mater Pia mater Arachnoid villus Blood vessel Falx cerebri (in longitudinal fissure only) Superior sagittal sinus Subdural space Subarachnoid space (a)

 Similar to blood plasma composition ◦ -Proteins and sugars  Formed by the choroid plexus of lateral and 4 th ventricles ◦ –capillaries in the ventricles of the brain  Circulates in: ◦ -Arachnoid space ◦ -Ventricles ◦ -Central canal of the spinal cord  Arachnoid villi reabsorb CSF into venous blood © 2015 Pearson Education, Inc.

Septum pellucidum Inferior horn Lateral aperture Lateral ventricle Anterior horn Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view

Lateral ventricle Anterior horn Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Central canal Posterior horn Inferior horn Median aperture Lateral aperture (b) Left lateral view

Superior sagittal sinus Choroid plexus Corpus callosum Interventricular foramen Third ventricle Arachnoid villus Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord CSF is produced by the choroid plexus of each ventricle. CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. CSF flows through the subarachnoid space. CSF is absorbed into the dural venous sinuses via the arachnoid villi. (c) CSF circulation

 Inflammation of the meninges  Can be bacterial or viral (most common)  CSF is sampled for presence of pathogen  Bacterial Causes: ◦ Strep ◦ Pneumonia ◦ Listeria  Viral Causes: ◦ Enteroviruses ◦ Mumps/Measles/Influenza ◦ West Nile

 Hydrocephalus ◦ CSF accumulates and exerts pressure on the brain if not allowed to drain ◦ Possible in infants - skull bones have not yet fused ◦ In adults, can result in brain damage © 2015 Pearson Education, Inc.

 The least permeable capillaries of the body  -Bound together by tight junctions  -allows water, glucose, essential amino acids  Keeps out potentially harmful substances:  -metabolic wastes (urea, useless proteins)  -some drugs  -potassium ions  Useless against some substances including:  -Fats/fat-soluble molecules  -Respiratory gases  -Alcohol/Nicotine  -Anesthesia © 2015 Pearson Education, Inc.