1. The Skull

What are the Cranial Fossae?

- The Cranial Fossae are depressions or compartments on the superior/interior aspect of the inferior portion of the Skull revealed on the removal of the Calvaria - The Fossae are: 1. Anterior Cranial Fossa - This contains the Frontal Lobes of the Brain and is formed by the Sphenoid, Ethmoid, and Frontal Bones 2. Middle Cranial Fossa - This contains the Temporal Lobes of the Brain and is formed by the Sphenoid, Temporal, & Parietal Bones 3. Posterior Cranial Fossa - This contains the Cerebellum, Pons, and Medulla Oblongata. The PCF is formed by the Occipital, Temporal, Parietal, and Sphenoid Bones

How does the Infant Skull relate to the Adult Skull?

- The Infant Skull is much more flexible than the Adult Skull, with Sutures of the Adult (relatively fixed), being replaced with Fontanelles (Malleable Connective Tissue) - Fontanelles eventually ossify, forming sutures where the bones meet - The Fontanelles usually close in the 1st-3rd years and are fused by the 4th-6th years

Describe the Mandible

- The Mandible is an L shaped bone whose vertical portion is referred to as the Ramus and whose horizontal portion is referred to as the Body. The curved region of transition between these two portions is known as the Angle - The Mandible is marked by several important features, including: 1. The Alveolar Foramen & Canal - Found on the medial aspect of the Ramus, the foramen allows the passage of the Inferior Alveolar Artery and Nerve into the interior of the bone where they will enervate and supply the teeth 2. The Mental Foramen - On the anterolateral aspect of the Body there is a foramen from which the Mental Artery & Nerve, branches of the Alveolar counterparts, exit the Body in order to 3. The Lingula - Found superoanterior to the Alveolar Foramen on the medial aspect of the Ramus, the Lingula is a raised section of bone from which the Sphenomandibular Ligament runs to the Spine of the Sphenoid to hold the Mandible in Place 4. The Angle - The Angle is not only the transition from the Ramus to the Body, it is also the site, on its medial aspect, for the attachment of the Stylomandibular Ligament, which runs from the Styloid Process of the Temporal Bone to secure the Mandible

What do I need to watch out for especially during this lecture?

- All of the Foramen! There are tons of them and they perform all sorts of roles, allowing various nerves in and out of the Skull as well as vessels

What is the Calvaria?

- An anatomical and clinical term used to refer to that portion of the Neurocranium which is frequently removed in order to give gross access to the Brain. - The Calvaria is produced by making an axial cut lengthwise across the top of the Skull, resulting in a section of bone that includes the most of but no more than: 1. Frontal Bone 2. Parietal Bones 3. Occipital Bone

What is the Sella Turcica?

- Known as the Turkish Saddle, this is an indentation in the middle of the Neurocranium where the Middle Cranial Fossae (L&R) meet. - The Sella Turcica is formed by the Sphenoid Bone almost entirely.

What are the Paranasal Sinuses?

- Pneumatized (cavernous) regions of bones in the Skull that surround the nasal passage way. they are: 1. Ethmoid Sinus 2. Sphenoidal Sinus 3. Frontal Sinus 4. Maxillary Sinus

How many bones compose the Skull? List them

- The 22 bones of the Skull are: 1. Frontal (1) 2. Zygomatic (2) 3. Maxilla/ae (2) 4. Nasal (2) 5. Lacrimal (2) 6. Palatine (1) 7. Ethmoid (1) 8. Inferior Concha (2) 9. Parietal (2) 10. Temporal (2) 11. Sphenoid (1) 12. Occipital (1) 13. Vomer (1) 14. Mandible (1)

What are the divisions of the Skull?

1. Cranium - Also known as the Neurocranium, this region is composed of the vault and the base of the Skull 2. Face - Also known as the Viscerocranium, this division is composed of the bony structures underlying the Face

List the components of the Sella Turcica

1. Hypophyseal Fossa (F) 2. Anterior Clinoid Processes (A) 3. Tuberculum Sellae (T) 4. Chiasmatic Sulcus (S) 5. Posterior Clinoid Processes (P) 6. Dorsum Sellae (D)

List the important basilar foramina of the Skull

1. Incisive Foramen 2. Greater & Lesser Palatine Foramina 3. Infraorbital Foramen 4. Zygomaticotemporal Foramen 5. Foramen Ovale 6. Foramen Spinosum 7. Foramen Lacerum 8. Carotid Canal 9. Jugular Foramen 10. Auditory Tube 11. External Acoustic Meatus 12. Internal Acoustic Meatus 13. Condylar Canal 14. Hypoglossal Canal 15. Pterygoid Canal

List the important anteriorly visible foramina of the Skull

1. Supraorbital Foramen 2. Infraorbital Foramen 3. Mental Foramen 4. Zygomaticofacial Foramen

Describe the Occipital Bone. List its prominent features. What bones does it articulate with?

- The Occipital Bone forms the posterior wall of the Skull and articulate with the Sphenoid, Temporal, and Parietal Bones. The Occipital Bone is separated into the Basilar Portion (Anteroinferior) and the Squamous Portion (Posterosuperior) - The Occipital Bone demonstrates the following important features: 1. Foramen Magnum - This is the major passage through the Skull and permits the exit of the fibers which compose the Spinal Cord 2. The Nuchal Lines - Inferior & Superior, these two line run the left right length of the Occipital Bone and meet to form the External Occipital Protuberance 3. Articular Condyles - These lie on the inferior aspect of the Occipital Bone and engage the C1 Vertebrae, allowing nodding to occur 4. Hypoglossal Canal - This is a passage through the bone for the Hypoglossal Nerve (Medial to the Condyles) 5. Jugular Foramen - This foramen is a passage through the bone near the Occipital's border with the Temporal (Lateral to the Condyles) and permits 4 Cranial Nerves to pass alongside the Internal Jugular Vein

What are the Hiatuses of the Petrous Ridge?

- The Petrous Ridge of the Temporal Bone contains 3 Hiatuses: 1. Hiatus for the Greater Petrosal Nerve (Br. CN 7) - This hiatus also contains a groove and is found on the superior lateral slope of the Petrous Ridge 2. Hiatus for the Lesser Petrosal Nerve (Br. CN 9) - This Hiatus is found on the inferior lateral slope of the Petrous Ridge 3. The Internal Acoustic Meatus - This hiatus is found in the anteromedial slope of the Petrous Ridge and allows for the Vestibulocochlear (CN 8) and the Facial Nerve (CN 7) to pass through it. It contains all the nerves necessary for the proper function of the Ear which pass through the Hiatus to engage the organs of the Ear

Describe the Skull

- The Skull is a semifusiform bone produced by the close articulation/near fusion of many smaller bones that occurs over time as the individual develops

Describe the Sphenoid Bone. List its prominent features. What bones does it articulate with?

- The Sphenoid Bone is the keystone of the base of the Skull, articulating with the Frontal, Parietal, Temporal, Occipital, and Ethmoid Bones. The Sphenoid Bone is subdivided into two, "wings," Greater & Lesser and demonstrates the following major features: 1. The Sella Turcica - This is the location of Pituitary Gland and sits on the superior aspect of the of the midline of the Bone 2. The Foramen Lacerum - This passage lies anterior to the Sella Turcica and allows the passage of multiple structures 3. Foramen Ovale - Lying anterior to the Foramen Spongiosum and lateral to the Lateral Pterygoid Plate on the inferior aspect of the bone, the Foramen Ovale allows the several nerves and arteries to pass through it 4. Foramen Spinosum - Lying posterior to the Foramen Ovale and lateral to the Lateral Pterygoid Plate on the inferior aspect of the bone, the Foramen Spongiosum permits multiple structures to pass through it 5. Pterygoid Processes - Meaning, "winglike processes," these projections extend inferolaterally from the Sphenoid and send out two plates, Lateral & Medial. These Plates serve as attachment points for critical muscles inferior to the Skull. Of note, the Medial Pterygoid Plate has its own projection known as the Hamulus 6. Pterygoid Canal - The Pterygoid Canal lies posterior to the Medial Pterygoid Plate on the inferior aspect of the Sphenoid. It allows the passage of the Pterygoid Nerve, Artery, and Vein.

What are the sutures of the Skull?

- The Sutures of the Skull are semifusiform articulations of bone where two or more bones meet with each other. The names of the sutures and their orientations are: 1. Frontal - Also known as the Coronal, this suture lies just anterior to the peak of the Skull and runs left to right. The Frontal Suture is the meeting site of the Parietal & Frontal Bones 2. Lambdoid - This suture lies on the posterior surface of the Skull and is curved, forming an arch which joins the Occipital Bone with the Parietal Bone and Temporal Bone 3. Sagittal - This suture lies on the posteriomedial aspect of the Skull and runs from the superior aspect of the Occipital Bone to the Posterior aspect of the Frontal Bone. This suture is the meeting point of the two Parietal Bones

Describe the Temporal Bone. List its prominent features. What bones does it articulate with?

- The Temporal Bone forms the inferolateral walls of the Skull and articulates with the Occipital, Parietal, Sphenoid, and Zygomatic Bones. Beyond its structural function the Temporal Bone also demonstrates several important features which permit additional functions: 1. The Squamous Portion - This is the superior portion of the bone and plays a structural role only. Of note, it contains the Pterion, and the Middle Meningeal Artery runs alongside that point on the inside of the Skull 2. The Mastoid Process - This process projects inferiorly and lies posterior to the Ear 3. The Tympanic Portion - This portion lies anterior to the Mastoid Process and posterior to the Mandible. It forms the bony inner 2/3rd's of the Ear Canal 4. The Styloid Process - This bony projection lies medial to the Tympanic Portion and points inferiorly 5. Zygomatic Process - This process projects anteriorly to connect with the Zygomatic Bone and is just superior to the Tympanic Portion. The Zygomatic Portion is notable in that it contains the Temporomandibular Joint, a moveable synovial joint with the head of the Mandible

What are the Landmarks of the Skull?

- The landmarks of the Skull are points on the exterior surface of it that are important for clinical or anatomical regions. These landmarks are: 1. The Glabella - The anterior crest of the Frontal Bone, also known as the midline of the Brow, is referred to as the Glabella. It lies superior to the articulation between the Frontal Bone and the Nasal Bones 2. The Nasion - The Nasion is the point of articulation between the Frontal Bone and the Nasal Bones at the midline of the two. This landmark is found at the top of the bridge of the Nose 3. The Pterion - The Pterion is the 4 way point of articulation between the Sphenoid, Temporal, Frontal, & Parietal Bones. There are two Pterions, one for each side of the Skull 4. The Asterion - The Asterion is the 3 point of articulation between the Occipital, Temporal, & Parietal Bones. There are 2 Asterions, one for each side of the Skull 5. Bregma - The Bregma is the 3 point articulation between the Parietal Bones & the Frontal Bone. This is also the meeting point of the Frontal & Sagittal Sutures 6. The Vertex - The Vertex is the peak of the Skull and is found on its Superior Aspect. The Vertex lies just posterior to the Frontal/Coronal Suture, the articulation between the Parietal Bones & The Frontal Bone 7. Lambda -Lambda is the point of articulation between the Parietal Bones and the Occipital Bone and happens also to be the meeting point of the Sagittal & Lambdoid Sutures. It is found on the posterior aspect of the Skull at the peak of the Arch that is the Lambdoid Suture, at the dorsal/ventral midline of the Skull 8. The External Occipital Protuberance - Much like the Glabella, this is the crest of the Occipital Bone and is found near the base of the Skull on its posterior aspect

List the components of the Middle Cranial Fossa

1. The Lesser Wing of the Sphenoid Bone - This forms the anterior wall of the Sella Turcica* 2. The Greater Wing of the Sphenoid Bone - This forms the anteromedial wall of the MCF as well as a portion of its base/floor 3. The Squamous Portion of the Temporal Bone - This portion of the Temporal Bone forms the base of middle portion of the MCF's base/floor 4. Petrous Ridge of the Temporal Bone - This portion of the Temporal Bone forms the posterior wall of the MCF, running from the Sella Turcica to the wall of the Neurocranium 5. The Parietal Bone - This forms the lateral wall of the MCF, filling the spaces where the Sphenoid & Temporal Fail to cover - Of note, the Middle Meningeal Artery and the Internal Carotid Artery both form impressions along the base of the MCF

List the components of the Posterior Cranial Fossa

1. The Petrous Ridge of the Temporal Bone 2. The Clivus - This is a combination of the Sphenoid & the Occipital 3. The Foramen Magnus 4. Squamous Portion of the Occipital Bone

List the foramina visible in the MCF

1. The Superior Orbital Fissure 2. Inferior Orbital Fissure 3. Foramen Rotundum 4. Foramen Ovale 5. Foramen Spinosum 6. Foramen Lacerum 7. Carotid Canal 8. Greater Petrosal Hiatus 9. Lesser Petrosal Hiatus

List the components of the Anterior Cranial Fossa

1. The Superior Orbital Plate - This is forms the majority of the Fossa and is a section of the Frontal Bone. On its obverse side this portion of the Frontal Bone serves as the roof of the Orbits, thus the name 2. Frontal Crest - This is the section of the Frontal Bone which runs to the midline of the Skull in an arch to meet with the Ethmoid Bone 3. The Cribriform Plate - Meaning, "sieve-like," this porous bony structure is a component of the Ethmoid Bone and is porous so as to permit the passage of the Olfactory Nerves into the space inferior to the Ethmoid 4. The Christa Galli - Meaning, "The Rooster's Comb," this ridge of bone forms the midline of the Ethmoid and marks the division between the Cribriform plate on either side of it. 5. The Lesser Wing of the Sphenoid Bone - This is the more medial portion of the Sphenoid and forms the posterior wall of the Fossa

List the important laterally visible foramina of the Skull

1. Zygomaticotemporal Foramen 2. Zygomaticofacial Foramen 3. Mental Foramen 4. Mastoid Foramen