General Anatomy of the Skull and Central Nervous.pptx
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The skull contains 22 bones that form the cranium and protect the brain, sensory organs, and entrances to the respiratory and digestive systems. The cranium contains flat bones that form the calvaria and irregular bones that form the cranial base. Several cranial bones contain air spaces that lighten the skull. The brain is divided into five main divisions - the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon. The telencephalon contains the cerebral hemispheres and basal ganglia. Each hemisphere is divided into four main lobes - frontal, parietal, temporal, and occipital.
![References
• Breeland G, Sinkler MA, Menezes RG. Embryology, Bone Ossification. [Updated 2021 May
8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
Available from: https://www.ncbi.nlm.nih.gov/books/NBK539718/
• Greenberg handbook of Neuroanatomy 9th ed.
• Clinically Oriented Anatomy, 5th Edition
• High yield neuroanatomy 5th ed
• https://operativeneurosurgery.com/ - Operative Neurosurgery,
Permanent link:
https://operativeneurosurgery.com/doku.php?id=taylor_haughton_line.](https://image.slidesharecdn.com/generalanatomyoftheskullandcentralnervous-220406104022/85/General-Anatomy-of-the-Skull-and-Central-Nervous-pptx-35-320.jpg)
General Anatomy of the Skull and Central Nervous.pptx
- 1. General Anatomy of the Skull and Central Nervous System Dr. RUTAYISIRE François Xavier PGY2 Basic Neurosciences module University of Rwanda
- 2. Skull • The cranium (skull) is the skeleton of the head. • Most complex bony structure • The skull contains 22 bones • 8 cranial bones (Neurocranium) : • Form the braincase or cranium • 14 facial bones (Viscerocranium) : • The skull protects • The brain • Entrances to respiratory system • Entrance to digestive system
- 4. • The bones forming the calvaria are primarily flat bones (frontal, temporal, and parietal) formed by intramembranous ossification of head mesenchyme from the neural crest. • The bones contributing to the cranial base are primarily irregular bones with substantial flat portions (sphenoidal and temporal) formed by endochondral ossification of cartilage (chondrocranium) or from more than one type of ossification. • The ethmoid bone is an irregular bone that makes a relatively minor midline contribution to the neurocranium but is primarily part of the viscerocranium. • Most calvarial bones are united by fibrous interlocking sutures; however, during childhood, some bones (sphenoid and occipital) are united by hyaline cartilage (synchondroses).
- 5. • Several bones of the cranium (frontal, temporal, sphenoid, and ethmoid bones) are pneumatized bones, which contain air spaces (air cells or larger sinuses), presumably to decrease their weight. • The total volume of the air spaces in these bones increases with age. • In the anatomical position, the cranium is oriented so that the inferior margin of the orbit and the superior margin of the external acoustic opening of the external acoustic meatus of both sides lie in the same horizontal plane. • This standard craniometric reference is the orbitomeatal plane (Frankfort horizontal plane).
- 6. • The spinal cord is continuous with the brain through the foramen magnum, a large opening in the cranial base
- 7. The frontal bone • The frontal bone, specifically its squamous (flat) part, forms the skeleton of the forehead, articulating inferiorly with the nasal and zygomatic bones. • In some adults a remnant of the frontal suture, the metopic suture, is visible in the midline of the glabella, the smooth, slightly depressed area between the superciliary arches. • The intersection of the frontal and nasal bones is the nasion (L. nasus, nose), which in most people is related to a distinctly depressed area (bridge of the nose). • The frontal bone also articulates with the lacrimal, ethmoid, and sphenoids, and a horizontal portion of bone (the orbital part) forms both the roof of the orbit and part of the floor of the anterior part of the cranial cavity.
- 8. The zygomatic bones • The zygomatic bones (cheek bones, malar bones), forming the prominences of the cheeks, lie on the inferolateral sides of the orbits and rest on the maxillae. • The anterolateral rims, walls, floor, and much of the infraorbital margins of the orbits are formed by these quadrilateral bones. • Inferior to the nasal bones is the pear- shaped piriform aperture, the anterior nasal opening in the cranium. • The bony nasal septum can be observed through this aperture, dividing the nasal cavity into right and left parts. • On the lateral wall of each nasal cavity are curved bony plates, the nasal conchae
- 9. Lateral Aspect of the Cranium • The lateral aspect of the cranium (L. norma lateralis) is formed by both the neurocranium and the viscerocranium. • The main features of the neurocranial part include the temporal fossa, the external acoustic opening, and the mastoid process of the temporal bone. • The main features of the viscerocranial part include the infratemporal fossa, zygomatic arch, and lateral aspects of the maxilla and mandible. • The temporal fossa is bounded superiorly and posteriorly by the superior and inferior temporal lines, anteriorly by the frontal and zygomatic bones, and inferiorly by the zygomatic arch. • The superior border of this arch corresponds to the inferior limit of the cerebral hemisphere of the brain. • The zygomatic arch is formed by the union of the temporal process of the zygomatic bone and the zygomatic process of the temporal bone.
- 10. Landmark Shape and Location Pterion (G. wing) Junction of the greater wing of the sphenoid, squamous temporal, frontal, and parietal bones; overlies course of anterior division of middle meningeal artery Lambda (G. the letter L) Point on calvaria at junction of lambdoid and sagittal sutures Bregma (G. forepart of head) Point on calvaria at junction of coronal and sagittal sutures Vertex (L. whirl, whorl) Superior point of neurocranium, in the middle with the cranium oriented in anatomical (orbitomeatal or Frankfort) plane Asterion (G. asterios, starry) Star shaped; located at junction of three sutures: parietomastoid, occipitomastoid, and lambdoid Glabella (L. smooth, hairless) Smooth prominence; most marked in males; on the frontal bones superior to root of nose; most anterior projecting part of forehead Inion (G. back of head) Most prominent point of external occipital protuberance Nasion (L. nose) Point on cranium where frontonasal and internasal sutures meet
- 12. Divisions of the Brain. • The brain consists of five divisions: • Telencephalon, • Diencephalon, • Mesencephalon, • Metencephalon, and • Myelencephalon.
- 13. Telencephalon • Consists of the cerebral hemispheres and the basal nuclei. • The cerebral hemispheres contain the lateral ventricles.
- 14. Cerebral hemispheres Cerebral hemispheres consist of six lobes and the olfactory structures: •Frontal lobe •Parietal lobe •Temporal lobe •Occipital lobe •Insular lobe •Limbic lobe
- 15. Frontal lobe Extends from the central sulcus to the frontal pole and lies superior to the lateral sulcus. It contains: ● Precentral gyrus—consists of the primary motor area (area 4). ● Superior frontal gyrus—contains supplementary motor cortex on the medial surface(area 6). ● Middle frontal gyrus —contains the frontal eye field (area 8). ● Inferior frontal gyrus—contains the Broca speech area in the dominant hemisphere (areas 44 and 45). ● Gyrus rectus and orbital gyri— separated by the olfactory sulcus. ● Anterior paracentral lobule —found on the medial surface between the superior frontal gyrus (paracentral sulcus) and the central sulcus.
- 16. Parietal lobe • Extends from the central sulcus to the occipital lobe and lies superior to the temporal lobe. ● Postcentral gyrus—the primary somatosensory area of the cerebral cortex (areas 3, 1, and 2). ● Superior parietal lobule comprises association areas involved in somatosensory functions (areas 5 and 7). ● Inferior parietal lobule consists of the supramarginal gyrus, which interrelates somatosensory, auditory, and visual inputs (area 40) and the angular gyrus (area 39) that receives impulses from primary visual cortex. ● Precuneus—located between the paracentral lobule and the cuneus. ● Posterior paracentral lobule—located on the medial surface between the central sulcus and the precuneus.
- 18. Temporal lobe • Extends from the temporal pole to the occipital lobe, inferior to the lateral sulcus. • It contains: ● Transverse temporal gyrus (of Heschl)—found within the lateral sulcus. It contains the primary auditory areas of the cerebral cortex (areas 41 and 42). ● Superior temporal gyrus—associated with auditory functions and contains the Wernicke speech area in the dominant hemisphere (area 22). ● Middle temporal gyrus ● Inferior temporal gyrus ● Lateral occipitotemporal gyrus (fusiform gyrus)—lies between the inferior temporal sulcus and the collateral sulcus.
- 19. Occipital lobe • Lies posterior to a line connecting the parieto-occipital sulcus and the preoccipital notch. It contains two structures: ● Cuneus—situated between the parieto-occipital sulcus and the calcarine sulcus and contains the visual cortex (areas 17, 18, and 19). ● Lingual gyrus lies inferior to the calcarine sulcus and contains the visual cortex (areas 17, 18, and 19). Insular lobe (insula) lies within the lateral sulcus.
- 20. Limbic lobe • A C-shaped collection of structures found on the medial hemispheric surface that encircles the corpus callosum and the lateral aspect of the midbrain. • It includes: ● Paraterminal gyrus and subcallosal area—located anterior to the lamina terminalis and inferior to the rostrum of the corpus callosum. ● Cingulate gyrus lies parallel and superior to the corpus callosum and merges with the parahippocampal gyrus. ● Parahippocampal gyrus lies between the hippocampal and collateral sulci and terminates in the uncus. ● Hippocampal formation —connected to the hypothalamus and septal area via the fornix.
- 21. Olfactory structures Found on the orbital (inferior) surface of the brain and include the following: ● Olfactory bulb and tract represent an outpouching of the telencephalon. The olfactory bulb receives the olfactory nerve (CN I). ● Olfactory trigone and striae ● Anterior perforated substance created by penetrating striate arteries. ● Diagonal band of Broca interconnects the amygdaloid nucleus and the septal area.
- 22. Basal nuclei (ganglia) Constitute the subcortical nuclei of the telencephalon and include: • a. Caudate nucleus—part of the striatum, together with the putamen. • b. Putamen—part of the striatum, together with the caudate nucleus and part of the lentiform nucleus along with the globus pallidus. • c. Globus pallidus—part of the lentiform nucleus, together with the putamen. • d. Subthalamic nucleus—part of the diencephalon that functions with the basal nuclei.
- 23. Lateral ventricles • Ependyma-lined cavities of the cerebral hemispheres that contain CSF and choroid plexus. • They communicate with the third ventricle via two interventricular foramina (of Monro) and are separated from each other by the septum pellucidum. Cerebral cortex • Consists of a thin layer or mantle of gray matter that covers the surface of each cerebral hemisphere and is folded into gyri that are separated by sulci.
- 24. White matter Cerebral commissures Interconnect the cerebral hemispheres and include the following structures: ● Corpus callosum—the largest commissure of the brain and it interconnects the two hemispheres. It has four parts, including the rostrum, genu, body, and splenium. ● Anterior commissure—interconnects the olfactory bulbs with the middle and inferior temporal lobes. ● Hippocampal commissure (commissure of the fornix)—located between the fornices and inferior to the splenium of the corpus callosum. Includes the cerebral commissures and the internal capsule.
- 25. Internal capsule Consists of the white matter located between the basal nuclei and the thalamus. It has five parts: ● Anterior limb—located between the caudate nucleus and putamen and contains a mixture of ascending and descending fibers. ● Genu—located between the anterior and posterior limbs and contains primarily the corticonuclear (corticobulbar) fibers. ● Posterior limb—located between the thalamus and lentiform nucleus (comprising the putamen and the globus pallidus) and is primarily made up of corticospinal fibers. ● Retrolenticular portion—located posterior to the lentiform nucleus and contains the optic radiations • Sublenticular portion—located inferior to the lentiform nucleus and contains auditoryradiations
- 26. Diencephalon • Receives the optic nerve (CN II) and consists of the following structures: 1. Epithalamus 2. (Dorsal) Thalamus—separated from the hypothalamus by the hypothalamic sulcus. 3. Hypothalamus 4. Subthalamus (ventral thalamus)—inferior to the thalamus and lateral to the hypothalamus. 5. Third ventricle and associated structures.
- 27. Mesencephalon (Midbrain) 1. Anterior surface a. Cerebral peduncle b. Interpeduncular fossa i. Oculomotor nerve (CN III) ii. Posterior perforated substance—created by the penetrating branches of the posterior cerebral and posterior communicating arteries. 2. Posterior surface a. Superior colliculus (visual system) b. Brachium of the superior colliculus c. Inferior colliculus (auditory system) d. Brachium of the inferior colliculus e. Trochlear nerve (CN IV)—the only cranial nerve to exit the brainstem from the posterior aspect. Located between the diencephalon and the pons and contains the cerebral aqueduct interconnecting the third and fourth ventricles.
- 28. Pons 1. Anterior surface a. Base of the pons b. Cranial nerves, including trigeminal nerve (CN V), abducent nerve (CN VI), facial nerve (CN VII), and vestibulocochlear nerve (CN VIII) 2. Posterior surface (rhomboid fossa) a. Locus ceruleus contains the largest collection of norepinephrinergic neurons in the CNS. b. Facial colliculus contains the abducent nucleus and internal genu of the facial nerve. c. Sulcus limitans separates the alar plate from the basal plate. d. Striae medullares of the rhomboid fossa divides the rhomboid fossa into the superior pontine portion and the inferior medullary portion. Located between the midbrain and the medulla.
- 29. Medulla Oblongata (myelencephalon) 1. Anterior surface a. Pyramid contains descending tracts. b. Olive contains the inferior olivary nucleus. c. Cranial nerves, including glossopharyngeal nerve (CN IX), vagus nerve (CN X), (spinal) accessory nerve (CN XI), and hypoglossal nerve (CN XII) 2. Posterior surface a. Gracile tubercle b. Cuneate tubercle c. Rhomboid fossa i. Vagal trigone ii. Hypoglossal trigone iii. Sulcus limitans iv. Area postrema (vomiting center) Located between the pons and the spinal cord.
- 30. Cerebellum • Located in the posterior cranial fossa, attached to the brainstem by three cerebellar peduncles. • It forms the roof of the fourth ventricle. • It is separated from the occipital and temporal lobes by the tentorium cerebelli and contains the following surface structures/parts: 1. Hemispheres consist of two lateral lobes. 2. Vermis 3. Flocculus and vermal nodulus form the flocculonodular lobule. 4. Tonsil is a rounded lobule on the inferior surface of each cerebellar hemisphere. With increased intracranial pressure, it may herniate through the foramen magnum. 5. Superior cerebellar peduncle connects the cerebellum to the pons and midbrain. 6. Middle cerebellar peduncle connects the cerebellum to the pons. 7. Inferior cerebellar peduncle connects the cerebellum to the pons and medulla. 8. Anterior lobe lies anterior to the primary fissure. 9. Posterior lobe is located between the primary and posterolateral fissures. 10. Flocculonodular lobe lies posterior to the posterolateral fissure.
- 31. Relation of skull markings to cerebral anatomy Taylor-Haughton lines • Taylor-Haughton (T-H) lines can be constructed on an angiogram, CT/MRI scout film, or skull X-ray. • They can be constructed on the patient in the O.R. based on visible external landmarks. 1. Frankfurt plane, AKA baseline: line from inferior margin of orbit through the upper margin of the external auditory meatus (EAM) (as distinguished from Reid’s base line: from inferior orbital margin through the center of the EAM) 2. The distance from the nasion to the inion is measured across the top of the calvaria and is divided into quarters (can be done simply with a piece of tape which is then folded in half twice) 3. Posterior ear line: perpendicular to the baseline through the mastoid process 4. Condylar line: perpendicular to the baseline through the mandibular condyle 5. T-H lines can then be used to approximate the Sylvian fissure (see below) and the motor cortex
- 32. Motor cortex • Numerous methods utilize external landmarks to locate the motor strip (pre-central gyrus) or the central sulcus (Rolandic fissure) which separates motor strip anteriorly from primary sensory cortex posteriorly. 1. method 1: the superior aspect of the motor cortex is almost straight up from the EAM near the midline 2. method 2: the central sulcus is approximated by connecting: a) the point 2cm posterior to the midposition of the arc extending from nasion to inion), to b) the point 5cm straight up from the EAM 3. method 3: using T-H lines, the central sulcus is approximated by connecting: a) the point where the “posterior ear line” intersects the circumference of the skull usually about 1cm behind the vertex, and 3–4cm behind the coronal suture), to b) the point where the “condylar line” intersects the line representing the Sylvian fissure 4. method 4: a line drawn 45° to Reid’s base line starting at the pterion points in the direction of the motor strip
- 33. Sylvian fissure AKA lateral fissure • On the skin surface: approximated by a line connecting the lateral canthus to the point 3/4 of the way posterior along the arc running over convexity from nasion to inion (T- H lines). • On the skull (once it is exposed in surgery): the anterior portion of the Sylvian fissure follows the squamosal suture and then deviates superiorly to terminate at Chater’s point, which is located 6cm above the EAM on a line perpendicular to the orbitomeatal line; it is also ≈
- 34. Thanks
- 35. References • Breeland G, Sinkler MA, Menezes RG. Embryology, Bone Ossification. [Updated 2021 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539718/ • Greenberg handbook of Neuroanatomy 9th ed. • Clinically Oriented Anatomy, 5th Edition • High yield neuroanatomy 5th ed • https://operativeneurosurgery.com/ - Operative Neurosurgery, Permanent link: https://operativeneurosurgery.com/doku.php?id=taylor_haughton_line.
Editor's Notes
- #20: The insulae are believed to be involved in consciousness and play a role in diverse functions usually linked to emotion or the regulation of the body's homeostasis. These functions include compassion, empathy, taste, perception, motor control, self-awareness, cognitive functioning, interpersonal experience, and awareness of homeostatic emotions such as hunger, pain and fatigue. In relation to these, it is involved in psychopathology.
- #21: Emotional life is largely housed in the limbic system, and it critically aids the formation of memories.