Skull Anatomy

Cranial Bones

The cranial bones form the protective case around the brain and provide attachment points for head and neck muscles. Each bone has distinct features and important bone markings that serve as passageways for nerves and blood vessels or as points of muscle attachment.

• Frontal Bone: Forms the forehead and the superior part of the orbit (eye socket).

• Parietal Bones: Paired bones forming the superior and lateral aspects of the skull.

• Occipital Bone: Forms the posterior part and base of the skull.

• Temporal Bones: Paired bones on the lateral skull, containing structures for hearing and balance.

• Sphenoid Bone: Spans the width of the cranial floor, contributing to the base of the skull and the orbits.

• Ethmoid Bone: Located between the nasal cavity and the orbits, contributing to the medial wall of the orbit and the nasal septum.

Important Cranial Bone Markings

• Supraorbital foramen (notch): Passageway for the supraorbital arteries and nerves.

• Foramen magnum: Large opening for the spinal cord to connect with the brain.

• External occipital protuberance: Prominent midline bump for ligament attachment.

• Zygomatic process: Articulates with the zygomatic bone to form the cheek.

• Mastoid process: Attachment site for neck muscles.

• Carotid canal: Passageway for the internal carotid artery.

• Cribriform plate: Contains olfactory foramina for olfactory nerve fibers.

Facial Bones

The facial bones form the framework of the face, house the special sense organs, and provide openings for air and food passage. They also anchor the facial muscles.

• Nasal Bones: Form the bridge of the nose.

• Lacrimal Bones: Small bones forming part of the medial wall of each orbit; contain the lacrimal fossa for tear drainage.

• Maxillae: Upper jawbones, forming the central part of the facial skeleton and containing the upper teeth.

• Zygomatic Bones: Cheekbones, forming the prominence of the cheeks and part of the orbit.

• Mandible: Lower jawbone, the largest and strongest facial bone.

• Palatine Bones: Form the posterior part of the hard palate and part of the nasal cavity and orbit.

• Vomer: Forms part of the nasal septum.

• Inferior Nasal Conchae: Thin, curved bones in the nasal cavity.

Important Facial Bone Markings

• Alveolar process: Sockets for teeth in the maxillae and mandible.

• Infraorbital foramen: Passageway for infraorbital nerve and vessels to the skin of the face.

• Mental foramen: Passageway for nerves and vessels of the chin.

• Coronoid process: Insertion point for the temporalis muscle (mandible).

• Condylar process: Articulates with the temporal bone to form the temporomandibular joint (mandible).

Vertebral Column Anatomy

Structure and Curvatures

The vertebral column, or spine, is a flexible, curved structure composed of individual vertebrae separated by intervertebral discs. It supports the head, protects the spinal cord, and provides attachment points for ribs and muscles.

• Cervical Curvature: Concave posteriorly; consists of 7 vertebrae (C1–C7).

• Thoracic Curvature: Convex posteriorly; consists of 12 vertebrae (T1–T12).

• Lumbar Curvature: Concave posteriorly; consists of 5 vertebrae (L1–L5).

• Sacral Curvature: Convex posteriorly; formed by the sacrum (5 fused vertebrae).

Key Vertebral Features

• Spinous Process: Posterior projection for muscle and ligament attachment.

• Transverse Processes: Lateral projections for muscle and ligament attachment.

• Intervertebral Discs: Pads of fibrocartilage between vertebrae, providing cushioning and flexibility.

• Intervertebral Foramen: Openings between adjacent vertebrae for spinal nerves to exit the spinal cord.

Example: Vertebral Formula

• Total number of vertebrae in the adult human spine: 26 (7 cervical, 12 thoracic, 5 lumbar, 1 sacrum, 1 coccyx).

Additional info: The normal curvatures of the vertebral column help to absorb shock and maintain balance during movement. Abnormal curvatures include scoliosis (lateral curvature), kyphosis (excessive thoracic curvature), and lordosis (excessive lumbar curvature).