protective layers of the brain

In this video, I cover the protective membranes of the brain known as the meninges. I discuss the structure and function of the three meningeal layers: the dura mater, arachnoid mater, and pia mater. I also describe two areas that have clinical relevance: the epidural space and lumbar cistern. For an article (on my website) that explains the meninges, click this link: https://neuroscientificallychallenged.com/posts/know-your-brain-meninges TRANSCRIPT: Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the meninges. The term meninges comes from the Greek for membrane and refers to 3 membranes that surround the brain and the spinal cord: the dura mater, the arachnoid mater, and the pia mater. The meninges protect and provide structural support for the brain as well as contain cerebrospinal fluid. The outermost layer of the meninges is the dura mater, which literally means “hard mother.” This thick and tough layer adheres to the skull on one side and the arachnoid mater on the other side. The dura provides the brain and spinal cord with an extra protective layer, attaches the brain to the skull and the spinal cord to the vertebral column to keep them from being jostled around, and provides a system of veinous drainage through which blood can leave the brain. The arachnoid mater gets its name because it has the consistency and appearance of a cobweb. It is much less substantial than the dura. Strands of connective tissue called arachnoid trabeculae stretch between the arachnoid and pia mater. These help to suspend the brain in place. Between the arachnoid and pia mater there is also an area known as the subarachnoid space, which is filled with cerebrospinal fluid. The pia mater is a thin layer that closely follows the contours of the brain. It forms a tight membrane around the brain and spinal cord, acting as an an additional barrier and aiding in the secretion and containment of cerebrospinal fluid. Blood vessels are held against the pia mater by connective tissue before they penetrate the brain. There is a space between the dura of the spinal cord and the bone of the vertebral column known as the epidural space; analgesics and anesthesia are sometimes administered here. Also, the dura and arachnoid mater extend several vertebrae below the end of the spinal cord, creating a cerebrospinal fluid-filled area called the lumbar cistern where there is no spinal cord present. Cerebrospinal fluid can be withdrawn from here because a needle can be inserted with little risk of damaging the spinal cord. Thus, the lumbar cistern is the site where cerebrospinal fluid is aspirated in a lumbar puncture, also known as a spinal tap. This is done, for example, to diagnose meningitis, a potentially life-threatening inflammation of the meninges. Reference: Nolte J. The Human Brain: An Introduction to its Functional Anatomy. 6th ed. Philadelphia, PA. Elsevier; 2009.

(USMLE topics) Structure, functions of the BBB. Physical, transport and metabolic barriers. Non-barrier areas. Strategies to overcome the barrier, to deliver therapeutic drugs into the brain. Purchase a license to download a non-watermarked version of this video on AlilaMedicalMedia(dot)com Check out our new Alila Academy - AlilaAcademy(dot)com - complete video courses with quizzes, PDFs, and downloadable images. ©Alila Medical Media. All rights reserved. Voice by: Ashley Fleming All images/videos by Alila Medical Media are for information purposes ONLY and are NOT intended to replace professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition. The blood-brain barrier refers to the highly selective permeability of blood vessels within the central nervous system. The barrier controls substances that can enter or leave the nervous tissue. It helps maintain the stable state, or homeostasis, of brain tissue, amid the fluctuations of circulating substances in the blood, many of which can act as neurotransmitters and could create chaos in neuronal activities if allowed to diffuse freely into the brain. The barrier also protects the brain from blood-borne pathogens and toxins. The blood-brain barrier is composed of several cell types, including: - Endothelial cells that form the wall of blood vessels; - Mural cells, namely pericytes, partially covering the outside of endothelial cells; - And glial cells astrocytes, whose extended processes, called end-feet, wrap around the vessels. The endothelial cells alone can fulfill the functions of the blood-brain barrier, but their interactions with the adjacent cells seem to be required for its formation, maintenance and regulation. The brain endothelial cells, unlike their counterparts in other tissues, possess unique properties that allow them to tightly control the passage of substances between the blood and brain. These properties can be classified into physical, transport, and metabolic categories: - The brain endothelial cells are held together by tight junctions, which serve as physical barriers, preventing movements of substances through the space between cells. - They have very low rates of vesicle-mediated transcellular transport. - They control the movement of ions and substances with specific transporters, of which there are two major types: efflux transporters and nutrient transporters: + Efflux transporters use cellular energy to move substances against their concentration gradient. These transporters are usually located on the blood side of endothelial cells. They transport lipophilic molecules, which have passively diffused through the cell membrane, back to the blood. + Nutrient transporters, on the other hand, facilitate the movement of nutrients, such as glucose and essential amino acids, into the brain, down their concentration gradient. - The brain endothelial cells also contains a number of enzymes that metabolize, and thus inactivate, certain neurotransmitters, drugs and toxins, preventing them from entering the brain. An intact blood-brain barrier is critical for normal brain functions. Neurological diseases such as encephalitis, multiple sclerosis, brain traumas, Alzheimer's disease, epilepsy, strokes and tumors, can breach the barrier, and this, in turn, contributes to disease pathology and further progression. But not all areas of the brain have the blood-brain barrier. Some brain structures are involved in hormonal control and require better access to systemic blood, so they can detect changes in circulating signals and respond accordingly. These non-barrier areas are located around the midline of the ventricular system, and are known as circumventricular organs. Some of their bordering regions have a leaky barrier. The blood-brain barrier also has its downside. While it protects the brain from unwanted drugs and toxins, it also prevents therapeutic drugs from entering the central nervous system to treat diseases. Several strategies are developed to overcome this obstacle.