BI 215 The Axial Skeleton

Chapter AXION

Overview

  • Covers key elements of human anatomy and physiology, particularly the skeletal system.

Lateral View of the Human Skull (Figure 7.1)

  • Highlights major skull structures:

    • Frontal

    • Parietal

    • Temporal

    • Zygomatic

    • Mandible

Skeletal Structure (Figures 7.2-3)

Axial Skeleton

  • Supports head, neck, back, and chest.

  • Composed of:

    • Skull

    • Vertebral column (sacrum and coccyx)

    • Thoracic cage (ribs and sternum)

Appendicular Skeleton

  • Includes bones of upper and lower limbs.

Parts of the Skull (Figure 7.4)

  • Comprises:

    • Rounded brain case

    • Facial bones (jaws, nose, orbits)

Anterior View of Skull (Figure 7.5)

  • Shows:

    • Forehead

    • Eye sockets (orbits)

    • Nasal cavity

    • Upper and lower jaws

Lateral View of Skull (Figure 7.6)

  • Features:

    • Zygomatic arch

    • Temporal fossa

    • Infratemporal fossa

Cranial Fossae (Figure 7.7)

  • Brain case protects the brain, includes:

    • Anterior cranial fossa

    • Middle cranial fossa

    • Posterior cranial fossa

Temporal Bone (Figure 7.8)

  • Displays squamous, mastoid, and zygomatic portions.

Base of Skull (Figure 7.9)

  • Hard palate formed by:

    • Maxilla bones

    • Horizontal plate of palatine bones

  • Cranial cavity floor made of multiple bones.

Posterior View of Skull (Figure 7.10)

  • Displays attachment sites for muscles supporting the skull.

Sphenoid Bone (Figure 7.11)

  • Forms anterior walls and floor of the middle cranial fossa, contains:

    • Lesser and greater wings

    • Sella turcica with hypophyseal fossa

    • Openings for nerves and blood vessels.

Ethmoid Bone (Figure 7.13)

  • Unpaired bone, contributes to the nasal cavity and part of orbits.

  • Features:

    • Crista galli

    • Perpendicular plate (upper nasal septum)

    • Cribriform plates and conchae.

Nasal Septum (Figure 7.17)

  • Composed of:

    • Perpendicular plate of ethmoid

    • Vomer

    • Septal cartilage.

Paranasal Sinuses (Figure 7.19)

  • Air-filled spaces in skull bones:

    • Frontal sinus (above eyebrows)

    • Maxillary sinuses (below orbits)

    • Sphenoid and ethmoid sinuses.

Hyoid Bone (Figure 7.20)

  • Located in the neck, aids in tongue and larynx muscle attachments.

Vertebral Column (Figure 7.21)

  • Comprises:

    • 24 vertebrae + sacrum + coccyx

    • Regions: cervical, thoracic, and lumbar.

    • Curved structure with primary and secondary curves.

Typical Vertebra (Figure 7.22)

  • Structure includes:

    • Body, vertebral arch, and processes.

    • Vertebral foramen for spinal cord passage.

Intervertebral Discs (Figure 7.23)

  • Separate bodies of adjacent vertebrae.

  • Structure:

    • Anulus fibrosus (outer)

    • Nucleus pulposus (gel-like center).

Cervical Vertebrae (Figure 7.25)

  • Characterized by small body and bifid spinous process.

  • Atlas (C1) lacks body or spinous process.

  • Axis (C2) features upward dens.

Thoracic Vertebrae (Figure 7.26)

  • Features:

    • Long spinous process

    • Articulation sites for rib attachment.

Lumbar Vertebrae (Figure 7.28)

  • Large, thick body with short spinous process.

Sacrum and Coccyx (Figure 7.29)

  • Sacrum formed from five fused vertebrae; coccyx from four fused vertebrae.

Ligaments of Vertebral Column (Figure 7.31)

  • Anterior longitudinal ligament runs lengthwise.

  • Supraspinous ligament connects thoracic and lumbar spinous processes.

Thoracic Cage (Figure 7.32)

  • Formed by the sternum and ribs (12 pairs).

  • True ribs (1–7) and false ribs (8–12); last two pairs are floating ribs.

Newborn Skull (Figure 7.33)

  • Unossified bones separated by fontanelles to allow growth.