<p> Ali Hosin Anatomy of Head, Neck & Spine CRANIUM AND BRAIN Definitions Skull – skeleton of head Cranium – bones which enclose the brain Vault (calvarium) – part of cranium which covers the superior and lateral aspects of the brain Base of skull – part of cranium which holds the base of the brain</p><p>Bones of the skull - Cranium (further subdivided into vault and base) - Facial skeleton</p><p>Bones of the cranium Bones of the facial skeleton - 2x temporal bones - 2x nasal bones - 2x parietal bones - 2x palatine bones - Frontal bone - 2x lacrimal bones - Sphenoid bone - 2x zygomatic bones - Ethmoid bone - 2x maxillae - Occipital bone - 2x inferior nasal conchae - 1x vomer</p><p>- Mandible (strictly not part of the f.s.)</p><p>Anterior view of the skull Lateral view of the skull</p><p>Bones of cranial base superior view Meninges 3 layers of meninges: CSF: - Dura mater flows through the - Arachnoid membrane subarachnoid space - Pia mater</p><p>Dura mater - The outer layer of the dura mater is adherent to the inside of the cranium - The inner layer forms double folds, which: o Divide the cranial cavity into compartments o Stabilise the brain within the cranium</p><p>- Falx cerebri – crescent-shaped; separates the cerebral hemispheres - Tentorium cerebelli separates occipital lobes and posterior temporal lobes from cerebellum - The brainstem (midbrain) passes through the tentorial notch (incisura) in the midline - Diaphragma sellae – surrounds the pituitary stalk in the sella turcica of the sphenoid bone. </p><p>Herniation A space-occupying lesion (e.g. blood, tumour, oedema, cyst) in any compartment may lead to increased intracranial pressure and lead to herniation of part of the brain. 3 main types: 1. Subfalcine herniation – not usually clinically significant 2. Uncal herniation – affects midbrain (pushed against edge of tentorium) – unconsciousness 3. Tonsilar herniation – affects medulla (pushed against foramen magnum) – cardiorespiratory failure</p><p>Dural folds Dural sinuses – note relations with dural folds</p><p>- Dural sinuses are like veins but without valves</p><p>- Superior sagittal sinus – upper margin of falx cerebri</p><p>- Inferior saggital sinus – lower margin of falx cerebri</p><p>- Straight sinus – at junction of falx / tentorium</p><p>- They anastomose with extracranial veins via emissary veins</p><p>- Straight sinus  transverse sinuses sigmoid sinuses  internal jugular vein – key drainage</p><p>Cavernous sinuses - two pairs of cavernous sinuses</p><p>- Located against lateral aspect of body of sphenoid bone; either side of sella turcica</p><p>- Of clinical significance due to the structures passing through them</p><p>- Receive blood from:</p><p> o cerebral veins</p><p> o ophthalmic veins</p><p> o emissary veins</p><p>- pathway for infection to pass from extracranial sites into intracranial locations.</p><p>- As structures pass through the cavernous sinuses, and are located in the walls of these sinuses, they are particularly vulnerable to injury due to inflammation - Structures passing through each cavernous sinus:</p><p> o Internal carotid artery</p><p> o Abducens nerve (VI)</p><p>- Structures in lateral wall of each cavernous sinus – superior to inferior:</p><p> o Oculomotor nerve (III)</p><p> o Trochlear nerve (IV)</p><p> o Ophthalmic nerve (V1)</p><p> o Maxillary nerve (V2)</p><p>- The intercavernous sinuses connect the right and left cavernous sinuses – around the pituitary stalk</p><p>Internal organisation of the forebrain</p><p>- Coronal and horizontal sections through the middle of the forebrain show a very similar relationship of the internal structures. </p><p>- This is because there are two structures at the core, surrounded by several structures, forming an arc:</p><p> o Thalamus on either side of the 3rd ventricle</p><p> o lentiform nucleus (putamen and globus pallidus) lateral to the thalamus.</p><p>- The encircling structures are:</p><p> o Lateral ventricles</p><p> o Associated structures e.g. caudate nucleus; limbic structures</p><p>Coronal section through hypothalamus Horizontal section</p>