All skull bones are joined by sutures, which are immovable joints.
Fontanel: An unossified area in an infant's skull where the bones have not yet fused, allowing for growth and development. Fontanels close as the child matures.
3. Base of the Skull
The cranial bones that form the base of the skull include:
Occipital
Sphenoid
Temporal
4. Skull and Vertebral Column
The skull fits onto the vertebral column via the occipital condyles, which articulate with the first vertebra (C1).
The two bones forming the joint between the skull and the vertebral column are:
Occipital
Atlas (C1)
5. List of Facial Bones
The skull has fourteen facial bones:
Nasal (2)
Maxilla (2)
Zygomatic (2)
Palatine (2)
Lacrimal (2)
Inferior nasal concha (2)
Vomer (1)
Mandible (1)
6. Eye Socket Composition
The bones making up the eye socket include at least five:
Frontal
Zygomatic
Maxilla
Sphenoid
Ethmoid
7. Hard Palate Formation
The hard palate is formed by:
Maxilla (2)
Palatine (2)
B. Hyoid Bone
Unique Features of the Hyoid Bone
The hyoid bone is unique because it does not articulate with any other bone in the body, being isolated.
Purpose: It supports the tongue and aids in swallowing.
Attachment: It is anchored by ligaments and muscles rather than a joint.
C. Vertebral Column
1. Types of Vertebrae
The vertebral column consists of:
Cervical Vertebrae: 7
Thoracic Vertebrae: 12
Lumbar Vertebrae: 5
The two bones at the caudal end of the vertebral column are:
Sacrum
Coccyx
2. Structure of Intervertebral Discs
Intervertebral discs consist of two major parts:
Fibrocartilage Ring: Annulus fibrosis
Nucleus Pulposus: Gel-like center
Blood Vessels in Discs: There are typically no blood vessels in the intervertebral disc, relying on diffusion for nutrition.
Herniated Disc: A condition where the nucleus pulposus protrudes through a tear in the annulus fibrosis, often causing pain.
3. Curves of the Vertebral Column
Primary Curves: Present at birth, shaped like a C and concave anteriorly.
Thoracic Curve
Sacral Curve
Secondary Curves: Develop after birth, convex anteriorly.
Cervical Curve: Develops when the infant begins to hold their head up (approximately 3-4 months).
Lumbar Curve: Develops when the child starts to walk (approximately 12-18 months).
4. Abnormal Curves of the Vertebral Column
Lordosis: An exaggerated inward curvature of the spine (often in the lumbar region).
Kyphosis: An exaggerated outward curvature of the spine (often in the thoracic region).
Scoliosis: Lateral curvature of the spine.
5. Anatomical Features of Vertebrae
Each vertebra has a large hole called the vertebral foramen, which allows the spinal cord to pass through.
When two vertebrae articulate, they create lateral holes known as intervertebral foramina, essential for the passage of spinal nerves.
Differentiating Vertebrae: Cervical vertebrae can be identified by the presence of transverse foramina, which thoracic and lumbar vertebrae lack.
Names of Key Vertebrae:
C1 is referred to as the Atlas.
C2 is referred to as the Axis.
Articulations with C1:
Occipital bone
C2 (Axis)
Articulations with C2:
C1 (Atlas)
The body of the C3 vertebra
6. Ribs and Their Connections
The superior surface of L5 forms a joint with T12, and the inferior surface of T12 articulates with L1.
The os coxae (coxal bones) connect to the vertebral column via the sacrum.
Articulation of Ribs: 12 thoracic vertebrae articulate with the ribs:
True Ribs: 1-7 - attach directly to the sternum via costal cartilage.
False Ribs: 8-10 - attach indirectly to the sternum.
Floating Ribs: 11-12 - do not attach to the sternum at all.
Type of Cartilage: Costal cartilage is made of hyaline cartilage.
7. Components of the Sternum
The sternum has three parts:
Manubrium
Body
Xiphoid process
Connection to Appendicular Skeleton: The sternum attaches to the clavicles and the first pair of ribs, serving as a midline structure that connects to the appendicular skeleton.