Lab #4 TTK (Skull)

Axial Skeleton Overview

Introduction to the Axial Skeleton

The axial skeleton consists of the bones of the spine, rib cage, and skull. It forms the central axis of the body and provides support and protection for the brain, spinal cord, and thoracic organs. In this section, we focus on the skull, its bones, and key anatomical landmarks.

• Axial Skeleton: Includes the skull, vertebral column, and thoracic cage.

• Function: Protects vital organs and provides structural support.

• Clinical Relevance: Knowledge of skull landmarks is essential for medical imaging, surgery, and physical assessment.

Skull Anatomy

Main Divisions of the Skull

The skull is divided into two main parts: the cranium and the facial bones. The cranium encases the brain, while the facial bones form the structure of the face.

• Cranial Bones (8): Frontal, Parietal (2), Temporal (2), Occipital, Sphenoid, Ethmoid.

• Facial Bones (14): Nasal (2), Lacrimal (2), Maxillary (2), Zygomatic (2), Palatine (2), Inferior Nasal Conchae (2), Vomer (1), Mandible (1).

• Hyoid Bone: A unique bone in the neck that does not articulate directly with other bones.

Cranial Sutures

Sutures are immovable joints that connect the bones of the skull. They are important anatomical landmarks.

• Frontal (Coronal) Suture: Between frontal and parietal bones.

• Sagittal Suture: Between the two parietal bones.

• Squamous Suture: Between parietal and temporal bones.

• Lambdoid Suture: Between parietal and occipital bones.

Cranial Fossae

The cranial floor is divided into three fossae, which house different parts of the brain.

• Anterior Cranial Fossa: Supports the frontal lobes.

• Middle Cranial Fossa: Supports the temporal lobes.

• Posterior Cranial Fossa: Supports the cerebellum.

Detailed Bone Landmarks

Frontal Bone

• Sinuses: Air-filled cavities that reduce skull weight and contribute to voice resonance.

Parietal Bones (2)

• Form the superior and lateral aspects of the cranium.

Temporal Bones (2)

• Mandibular Fossa: Articulates with the mandible.

• External Acoustic Meatus: Ear canal opening.

• Zygomatic Process: Forms part of the zygomatic arch.

• Mastoid Process: Attachment for neck muscles.

• Styloid Process: Attachment for tongue and neck muscles.

• Internal Acoustic Meatus: Passage for cranial nerves.

Occipital Bone

• Occipital Condyles: Articulate with the first cervical vertebra (atlas).

• External Occipital Protuberance: Prominent midline projection.

• Foramen Magnum: Large opening for the spinal cord.

Sphenoid Bone

• Sella Turcica: Houses the pituitary gland.

Ethmoid Bone

• Perpendicular Plate: Forms part of the nasal septum.

• Crista Galli: Attachment for the brain's meninges.

• Sinus: Air-filled cavity.

Cranial Foramina and Canals

Major Openings in the Skull

Foramina and canals allow the passage of nerves and blood vessels.

• Foramen Magnum: Passage for spinal cord.

• Superior Orbital Fissure: Passage for cranial nerves to the eye.

• Inferior Orbital Fissure: Passage for nerves and vessels.

• Optic Canal: Passage for optic nerve.

• Foramen Rotundum, Ovale, Spinosum, Lacerum: Passage for cranial nerves and vessels.

• Carotid Canal: Passage for internal carotid artery.

• Jugular Foramen: Passage for jugular vein and cranial nerves.

Facial Bones

Key Facial Bones and Landmarks

• Nasal Bones (2): Form the bridge of the nose.

• Lacrimal Bones (2): Contain the lacrimal fossa for tear drainage.

• Maxillary Bones (2): Form the upper jaw; contain the palatine process and sinuses.

• Zygomatic Bones (2): Form the cheekbones; include the temporal process.

• Palatine Bones (2): Form part of the hard palate.

• Vomer (1): Forms part of the nasal septum.

• Inferior Nasal Conchae (2): Increase surface area in the nasal cavity.

• Mandible (1): Lower jaw; includes angle, condyle, and coronoid process.

Composite Structures of the Skull

Structures Formed by Multiple Bones

• Zygomatic Arch: Formed by the temporal process of the zygomatic bone and the zygomatic process of the temporal bone.

• Nasal Septum: Formed by the perpendicular plate of the ethmoid bone and the vomer.

• Orbit of Eye: Composed of several bones including frontal, sphenoid, zygomatic, maxillary, palatine, lacrimal, and ethmoid.

Summary Table: Major Skull Bones and Landmarks

Bone	Key Landmarks	Function/Notes
Frontal	Sinuses	Forehead, roof of orbits
Parietal (2)	-	Superior/lateral cranium
Temporal (2)	Mandibular fossa, external acoustic meatus, zygomatic process, mastoid process, styloid process	Side of skull, ear region
Occipital	Occipital condyles, external occipital protuberance, foramen magnum	Back/base of skull
Sphenoid	Sella turcica	Central skull, pituitary gland
Ethmoid	Perpendicular plate, crista galli, sinus	Nasal cavity, septum
Mandible	Angle, condyle, coronoid process	Lower jaw, only movable skull bone
Maxilla (2)	Palatine process, sinus	Upper jaw, hard palate
Zygomatic (2)	Temporal process	Cheekbone
Palatine (2)	-	Hard palate
Vomer	-	Nasal septum
Inferior Nasal Conchae (2)	-	Nasal cavity
Lacrimal (2)	Fossa	Tear drainage
Nasal (2)	-	Bridge of nose
Hyoid	-	Supports tongue, not attached to other bones

Clinical and Imaging Relevance

Application in Medicine

• CT and X-ray: Used to visualize bones and identify fractures or abnormalities.

• Physical Assessment: Palpation of landmarks aids in diagnosis.

• Medical Imaging: Knowledge of foramina and canals is essential for interpreting scans.

Key Terms and Definitions

• Foramen: An opening in bone for nerves and blood vessels.

• Process: A projection or outgrowth of bone for muscle attachment.

• Fossa: A depression or hollow in bone.

• Suture: An immovable joint between skull bones.

• Sinus: Air-filled cavity within bone.

Example: Identifying the Foramen Magnum

The foramen magnum is a large opening in the occipital bone through which the spinal cord passes to connect with the brain. It is a key landmark in both anatomy and medical imaging.

Additional info:

• Some content was inferred and expanded for clarity and completeness, such as the functions of bones and clinical relevance.

• Definitions and examples were added to ensure the notes are self-contained and suitable for exam preparation.