Essentials of Human Anatomy and Physiology

Axial Skeleton Overview

  • Division of the Skeleton: The skeleton is divided into two main parts:

    • Axial Skeleton: Forms the longitudinal axis.

    • Appendicular Skeleton: Comprises limbs and girdles.

  • Components of Axial Skeleton:

    • Skull

    • Vertebral Column

    • Thoracic Cage (ribs and sternum)

Skull

  • Purpose: Protects the brain and forms the framework for the face.

  • Learning Objectives: Identify skull bones and major sutures.

Cranium

  • Composition: Eight large flat bones with two paired (parietal and temporal) and six single bones.

  • Key Bones:

    • Frontal Bone: Forms the forehead and upper parts of the eye sockets.

    • Parietal Bones: Form lateral and superior walls.

    • Sutures:

      • Sagittal Suture: Joins the two parietal bones.

      • Coronal Suture: Joins parietal bones to the frontal bone.

    • Temporal Bones:

    • Lie inferior to parietal bones; join them at squamous sutures.

    • Key Features:

      • External Acoustic Meatus: Canal leading to the eardrum.

      • Mastoid Process: Attachment site for neck muscles, prone to infection (mastoiditis).

      • Styloid Process: Attachment for neck muscles.

      • Zygomatic Process: Joins with cheekbone.

Occipital Bone

  • Description: Most posterior bone, forms base and back wall of the skull.

  • Key Features:

    • Foramen Magnum: Large opening for spinal cord.

    • Occipital Condyles: Rest on the first vertebra.

Sphenoid Bone

  • Description: Butterfly-shaped bone forming part of the floor of the cranial cavity.

  • Key Features:

    • Sella Turcica: Supports pituitary gland.

    • Optic Canal: Passage for optic nerve.

Ethmoid Bone

  • Description: Irregularly shaped, forming the roof of the nasal cavity and medial walls of the orbits.

  • Key Features:

    • Crista Galli: Attachment for the brain's outer covering.

    • Cribriform Plates: Contain holes for olfactory nerve fibers.

    • Nasal Conchae: Help form lateral walls of the nasal cavity.

Facial Bones

  • Total Count: Fourteen facial bones.

    • Pairs: Twelve (nasal, zygomatic, etc.).

    • Singles: Mandible and vomer.

Key Facial Bones

  • Maxillae:

    • Forms upper jaw and carries upper teeth.

    • Contains sinuses that drain into nasal passages.

  • Palatine Bones:

    • Form posterior hard palate.

    • Failure results in cleft palate.

  • Zygomatic Bones:

    • Known as cheekbones.

  • Nasal Bones:

    • Form the bridge of the nose.

  • Mandible:

    • Largest and strongest facial bone, forms the lower jaw.

    • Articulates with temporal bones, allowing movement.

Hyoid Bone

  • Description:

    • Unique bone in the neck region; does not articulate with any other bone.

    • Horseshoe-shaped, serves as base for the tongue and attachment point for muscles.

Conclusion

  • Review the section questions to reinforce learning and understanding.

  • Suggested inquiries:

    • Identifying axial skeleton components.

    • Function and structure of key skull features and bones.