Cranial Meninges PDF

B R A I N A N D N E R V O U S S Y S T E M I I C R A N I A L M E N I N G E S DR. KIRAN C. PATEL COLLEGE OF OSTEOPATHIC MEDICINE NICHOLAS LUTFI, MD, MS, DPM 1 OBJECTIVES Objectives 1. Identify the layers of the cranial meninges 2. Locate the dura mater, arachnoid mater and the pia mater 3. Identify th...

B R A I N A N D N E R V O U S S Y S T E M I I C R A N I A L M E N I N G E S DR. KIRAN C. PATEL COLLEGE OF OSTEOPATHIC MEDICINE NICHOLAS LUTFI, MD, MS, DPM 1 OBJECTIVES Objectives 1. Identify the layers of the cranial meninges 2. Locate the dura mater, arachnoid mater and the pia mater 3. Identify the subarachnoid space, epidural space and subdural space 4. Describe the nerve and arterial supply of the dura mater 2 LECTURIO AND READING ASSIGNMENTS Lecturio Videos & Quizzes 1. Structures and Functions of the Cranial Meninges 2. Dura Mater, Arachnoid Mater and Pia Mater 3. Subarachnoid Space, Epidural Space and Subdural Space 4. Arterial Supply and Nerve Supply of Dura Mater Readings 1. Structure, Functions, and Diseases of the Autonomic Nervous System 2. Meninges: An Overview of the Structure of the Individual Layers Visual/Technology Resources 1. Complete Anatomy (3D4Medical) 3 The meninges refer to the membranous coverings of the brain and spinal cord. There are three layers of meninges, known as the dura mater, arachnoid mater and pia mater. These coverings have two major functions: Cranial Meninges Provide a supportive framework for the cerebral and cranial vasculature. Acting with cerebrospinal fluid to protect the CNS from mechanical damage. The meninges are often involved in cerebral pathology, as a common site of infection (meningitis), and intracranial bleeds. In this presentation we shall look at the anatomy of the three layers, and their clinical correlations. https://nova.lecturio.com/ - /lecture/c/7164/24666 4 5 The dura mater is the outermost layer of the meninges, lying directly underneath the bones of the skull and vertebral column. It is thick, tough and inextensible. Within the cranial cavity, the dura contains two connective tissue sheets: Periosteal layer – lines the inner surface of the bones of the cranium. Meningeal layer – deep to the periosteal layer inside the cranial cavity. It is the only layer present in the vertebral column. Between these two layers, the dural venous sinuses are located. They are responsible for the venous vasculature of the cranium, draining into the internal jugular veins. In some areas within the skull, the meningeal layer of the dura mater folds inwards as dural reflections. They partition the brain and divide the cranial cavity into several compartments. For example, the tentorium cerebelli divides the cranial cavity into supratentorial and infratentorial compartments. The dura mater receives its own blood supply – primarily from the middle meningeal artery and vein. It is innervated by the trigeminal nerve (V1, V2 and V3). Dura Mater https://nova.lecturio.com/ - /lecture/c/7164/24668 https://nova.lecturio.com/ - /lecture/c/7164/24672 6 7 Arachnoid Mater The arachnoid mater is the middle layer of the meninges, lying directly underneath the dura mater. It consists of layers of connective tissue, is avascular, and does not receive any innervation. https://nova.lecturio.com/ - /lecture/c/7164/24670 Underneath the arachnoid is a space known as the sub-arachnoid space. It contains cerebrospinal fluid, which acts to cushion the brain. Small projections of arachnoid mater into the dura (known as arachnoid granulations) allow CSF to re-enter the circulation via the dural venous sinuses. 8 9 Pia Mater The pia mater is located underneath the sub-arachnoid space. It is very thin, and tightly adhered to the surface of the brain and spinal cord. It is the only covering to follow the contours of the brain (the gyri and fissures). Like the dura mater, it is highly vascularized, with blood vessels perforating through the membrane to supply the underlying neural tissue. 10 11 Ventricles of the Brain The ventricles are structures that produce cerebrospinal fluid, and transport it around the cranial cavity. They are lined by ependymal cells, which form a structure called the choroid plexus. It is within the choroid plexus that CSF is produced. Embryologically, the ventricular system is derived from the lumen of the neural tube. In total, there are four ventricle: right and left lateral ventricles third ventricle fourth ventricle. 12 V E N T R I C U L A R S Y S T E M A N D C E R E B R O S P I N A L F L U I D ( C S F ) 13 The ventricular system is a set of communicating cavities within the brain. These structures are responsible for the production, transport and removal of cerebrospinal fluid, which bathes the central nervous system. Here we shall look at the functions and production of cerebrospinal fluid, and the anatomy of the ventricles that contains it. Ventricular System and Cerebrospinal Fluid (CSF) 14 Functions of the Cerebrospinal Fluid (CSF) Cerebrospinal fluid is an ultrafiltrate of plasma that surrounds the brain and spinal cord. It serves three main functions: Protection – acts as a cushion for the brain, limiting neural damage in cranial injuries. Buoyancy – by being immersed in CSF, the net weight of the brain is reduced to approximately 25 grams. This prevents excessive pressure on the base of the brain. Chemical stability – the CSF creates an environment to allow for proper functioning of the brain, e. g. maintaining low extracellular K+ for synaptic transmission. 15 16 Lateral Ventricles Ventricles of the Brain The left and right lateral ventricles are located within their respective hemispheres of the cerebrum. They have ‘horns’ which project into the frontal, occipital and temporal lobes. The volume of the lateral ventricles increases with age. 17 18 Third Ventricle The lateral ventricles are connected to the third ventricle by the foramen of Monroe. The third ventricle is situated in between the right and the left thalamus. The anterior surface of the ventricle contains two protrusions: Ventricles of the Brain Supra-optic recess – located above the optic chiasm. Infundibular recess – located above the optic stalk. 19 Ventricles of the Brain The fourth ventricle is the last in the system – it receives CSF from the third ventricle via the cerebral aqueduct. It lies within the brainstem, at the junction between the pons and medulla oblongata. From the 4th ventricle, the fluid drains into two places: Central spinal canal – bathes the spinal cord Subarachnoid cisterns – bathes the brain, between arachnoid mater and pia mater. Here the CSF is reabsorbed back into the circulation. 20 21 22 P R O D U C T I O N A N D R E A B S O R P T I O N O F C S F 23 Production and Reabsorption of CSF Cerebrospinal fluid is produced by the choroid plexus, located in the lining of the ventricles. It consists of capillaries and loose connective tissue, surrounded by cuboidal epithelial cells. Plasma is filtered from the blood by the epithelial cells to produce CSF. In this way, the exact chemical composition of the fluid can be controlled. Drainage of the CSF occurs in the subarachnoid cisterns (or space). Small projections of arachnoid mater (arachnoid granulations) protrude into the dura mater. They allow the fluid to drain into the dural venous sinuses. 24 25 Cerebrospinal Fluid Flow LATERAL VENTRICLES INTERVENTRICULAR FORAMEN OF MONROE THIRD VENTRICLE CEREBRAL AQUEDUCT FOURTH VENTRICLE FORAMEN OF LUSCHKA INTERNAL JUGULAR VEIN SIGMOID SINUS DURAL VENOUS SINUSES ARACHNOID GRANULATIONS FORAMEN OF MAGENDIE CENTRAL CANAL SUBARACHNOID SPACE 26 27 28 DURAL VENOUS SINUSES 29 The dural venous sinuses lie between the periosteal and meningeal layers of the dura mater. They are best thought of as collecting pools of blood, which drain the central nervous system, the face, and the scalp. All the dural venous sinuses ultimately drain into the internal jugular vein. Unlike most veins of the body, the dural venous sinuses do not have valves. There are eleven venous sinuses in total. The straight, superior, and inferior sagittal sinuses are found in the falx cerebri of the dura mater. They converge at the confluence of sinuses (overlying the internal occipital protuberance). The straight sinus is a continuation of the great cerebral vein and the inferior sagittal sinus. From the confluence, the transverse sinus continues bi-laterally and curves into the sigmoid sinus to meet the opening of the internal jugular vein. https://nova.lecturio.com/ /lecture/c/7166/24674 https://nova.lecturio.com/ /lecture/c/7166/24676 Dural Venous Sinuses The cavernous sinus drains the ophthalmic veins and can be found on either side of the sella turcica. From here, the blood returns to the internal jugular vein via the superior or inferior petrosal sinuses. 30 31 32 33 34 35 36 https://nova.lecturio.com/ - /lecture/c/7166/24660 OPTIC CANAL ICA CN III ICA CN VI CN V1 CN V2 37 MIDDLE CEREBRAL VEIN STRAIGHT SINUS FALX CEREBRUM SUPERIOR SAGITTAL SINUS INFERIOR SAGITTAL SINUS OPHTHALMIC VEIN CONFLUENCE OF SINUSES SIGMOID SINUS CAVERNOUS SINUS OCCIPITAL SINUS INFERIOR JUGULAR VEIN SUPERIOR PETROSAL SINUS INFERIOR PETROSAL SINUS 38 THANK YOU!... 39