Chapter 7 (PART TWO)

Development at Birth:
- Not completely developed.
- Cranial bones are connected by fibrous membranes.
Fontanels (Soft Spots):
- Membranous areas of incomplete intramembranous ossification.
- Function: Allow bone movement during childbirth and accommodate brain growth.
- Closure: Eventually close as cranial bones grow together, typically between 2 months and 2 years after birth.
Characteristics of Infantile Skull:
- Small face.
- Prominent forehead.
- Large orbits.
- Nasal cavity and jaw are small.
- Sinuses are not completely formed yet.

Articulation: Does not articulate with any other bones.
Position: Fixed in position by muscles and ligaments.
Functions:
- Supports the tongue.
- Serves as an attachment for certain muscles that move the tongue during swallowing.

Overall Structure and Function:
- Forms the vertical axis of the skeleton, running from the skull to the pelvis.
- Supports the head and trunk.
- Protects the spinal cord.
- Composed of bony vertebrae, separated by fibrocartilaginous intervertebral discs.
- Vertebrae are connected by ligaments.
Number of Bones:
- Infant: 33 separate bones.
- Adult: 26 bones, due to fusion.
  - 5 vertebrae fuse to form the sacrum.
  - 4 vertebrae fuse to form the coccyx.
Memory Hint for Vertebrae Counts: 7am, 12pm, and 5pm for the number of cervical, thoracic, and lumbar vertebrae, respectively.
Structure of a Typical Vertebra:
- Body.
- Pedicles.
- Laminae.
- Spinous process.
- Vertebral foramen.
- Transverse processes.
- Superior and inferior articular processes.
- Intervertebral foramina.

Specialized Cervical Vertebrae:
- Atlas (C_1):
  - Supports the head.
  - Has two facets that articulate with the occipital condyles of the skull.
  - Unique for having no body or spinous process.
- Axis (C_2):
  - Contains the tooth-like dens (odontoid process) that pivots within the atlas, allowing head rotation.

Count: 12 thoracic vertebrae in the thoracic region.
Characteristics:
- Articulate with the ribs.
- Larger and stronger than the cervical vertebrae.
- Features include a long, pointed spinous process.
- Have costal facets on the side of the body and transverse processes (costal facet) to articulate with the heads and tubercles of the ribs, respectively.