The Axial Skeleton Name Lab Time/Date The Skull 1 The skull is one of the major components of the axial skeleton. Name the other two and what structures does each of these three components of the axial skeleton protect? Define suture: With one exception, the skull bones are joined by sutures. Name the exception. What are the four major sutures of the skull, and what bones do they connect? Name the bones composing the cranium. Give two possible functions of the sinuses. What is the orbit? Why can the sphenoid bone be called the keystone of the cranial floor?
The Correct Answer and Explanation is :
The axial skeleton comprises three major components: the skull, the vertebral column, and the bony thorax. Each of these structures serves vital protective functions:
- Skull: Protects the brain.
- Vertebral Column: Protects the spinal cord.
- Bony Thorax: Protects the heart and lungs.
Suture Definition and Exception
A suture is a type of fibrous joint found only in the skull, where bones are tightly joined together by a thin layer of dense connective tissue, allowing minimal movement. The exception to this is the mandible, or lower jawbone, which is connected to the skull by the temporomandibular joint (TMJ), a synovial joint that permits movement.
Major Sutures of the Skull
The four major sutures of the skull are:
- Coronal Suture: Connects the frontal bone to the two parietal bones.
- Sagittal Suture: Connects the two parietal bones along the midline of the skull.
- Lambdoid Suture: Connects the occipital bone to the two parietal bones.
- Squamous Suture: Connects the temporal bones to the parietal bones on each side of the skull.
Bones Composing the Cranium
The cranium is composed of eight bones:
- Frontal Bone: Forms the forehead and the upper part of the eye sockets.
- Parietal Bones (2): Form the sides and roof of the cranium.
- Temporal Bones (2): Form the lower sides of the cranium and house the structures of the ears.
- Occipital Bone: Forms the back and base of the cranium.
- Sphenoid Bone: Located at the base of the skull, it forms part of the floor of the cranial cavity.
- Ethmoid Bone: Forms part of the nasal cavity and the orbits of the eyes.
Functions of the Sinuses
Sinuses are air-filled cavities within the bones of the skull that serve several functions:
- Lightening the Skull: By reducing the weight of the skull, sinuses make it easier to hold the head upright.
- Enhancing Voice Resonance: Sinuses contribute to the quality and tone of the voice by acting as resonating chambers.
The Orbit
The orbit is the bony cavity in the skull that houses and protects the eye. It is formed by parts of several bones, including the frontal, zygomatic, sphenoid, ethmoid, lacrimal, maxillary, and palatine bones.
Sphenoid Bone as the Keystone of the Cranial Floor
The sphenoid bone is often called the “keystone” of the cranial floor because it articulates with all other cranial bones, holding them together. Its central location and extensive connections make it a pivotal structure in the cranial anatomy.
Understanding these components and their functions is essential for comprehending the structural integrity and protective mechanisms of the human skull.