Chapter 7: The Skeleton

Overview of the Human Skeleton

The human skeleton is a complex framework of bones that provides structure, protection, and support for the body. It is divided into two main parts: the axial skeleton and the appendicular skeleton. This chapter focuses on the axial skeleton, particularly the skull, which houses and protects the brain and sensory organs.

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

• Appendicular Skeleton: Comprises the limbs and girdles (shoulder and pelvic).

• Functions: Protection of vital organs, support for movement, mineral storage, and blood cell formation.

Skull Anatomy

Major Bones of the Skull

The skull consists of 22 bones, most of which are joined by immovable joints called sutures. The main bones include the frontal, parietal, occipital, temporal, sphenoid, and ethmoid bones.

• Frontal Bone: Forms the forehead and the superior part of the eye sockets (orbits).

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

• Occipital Bone: Forms the posterior and base of the skull; contains the foramen magnum.

• Temporal Bones: Located at the sides and base of the skull; house structures of the ears.

• Sphenoid and Ethmoid Bones: Contribute to the floor of the cranium and the orbits.

Frontal Bone

The frontal bone is a single bone that forms the forehead, the roofs of the orbits, and most of the anterior part of the cranial floor.

• Location: Anterior aspect of the skull, above the eyes.

• Features: Contains the frontal sinuses, supraorbital foramen (notch), and forms part of the orbital cavity.

• Function: Protects the frontal lobes of the brain and supports facial structures.

• Example: The green-highlighted area in the provided images represents the frontal bone.

Parietal Bones

The parietal bones are two large, curved bones that form the superior and lateral aspects of the cranium.

• Location: Sides and roof of the cranial cavity.

• Features: Joined at the sagittal suture; articulate with the frontal bone at the coronal suture.

• Function: Protect the parietal lobes of the brain.

• Example: The green-highlighted area in the second provided image represents the parietal bones.

Key Sutures of the Skull

Sutures are immovable joints that connect the bones of the skull. The main sutures include:

• Coronal Suture: Between the frontal and parietal bones.

• Sagittal Suture: Between the two parietal bones.

• Lambdoid Suture: Between the parietal bones and the occipital bone.

• Squamous Suture: Between the parietal and temporal bones.

Foramina and Other Features

The skull contains several openings (foramina) and bony landmarks that allow the passage of nerves and blood vessels.

• Foramen Magnum: Large opening in the occipital bone for the spinal cord.

• Supraorbital Foramen: Opening above the orbit for nerves and vessels.

• Occipital Protuberance: Prominent projection on the posterior aspect of the occipital bone.

Summary Table: Major Cranial Bones and Their Features

Clinical Relevance

• Fractures: Skull fractures can damage underlying brain tissue or cranial nerves.

• Fontanelles: In infants, soft spots (fontanelles) allow for brain growth and ease of birth.

• Sinus Infections: The frontal bone contains sinuses that can become inflamed (sinusitis).

Additional info: The provided images highlight the frontal and parietal bones, which are essential for understanding the anatomy of the cranial vault. The study of these bones is foundational for further exploration of the skeletal system, including facial bones and the vertebral column.