Cranial and Vertebral Anatomy Study Notes

Cranial Bones and Sutures

  • Paragon bones: Two bones that form the roof of the cranium.
    • Sagittal suture: The suture located between the two paragon bones.
    • Coronal suture: The suture located between the frontal and parietal bones.
    • Occipital bone: One of the bones forming the back of the skull.

Key Features in the Exam

  • Foramen magnum: An essential structure in the exam.
  • Condyles: Notable structures that will be addressed in the exam.
  • Holes and blood vessels: Important anatomical features located in the skull.

Temporal Bones

  • Lambdoidal suture: Shaped like the letter lambda.
  • Temporal bones: Two bones located at the sides and base of the cranium.
    • Form the lower inside of the orbits.
    • Divided from the parietal bones by the squamous suture.
    • Contains the external acoustic meatus (ear canal).
    • Features two processes:
    • Mastoid process: The rounded structure behind the ear.
    • Styloid process: The pointy structure behind the ear.
  • Psychomatic bone/arch: The bridge formed at the junction of temporal and other bones.

Sphenoid Bone

  • Unique butterfly-shaped bone located within the skull.
    • Key references include:
    • Sella turcica: Holds the pituitary gland.
    • Optic canal: Transmits the optic nerve, connecting the eyes to the brain.

Ethmoid Bone

  • Forms the septum of the nose with its perpendicular plate.
  • Crista galli: Central structure for membrane attachment in the brain (meninges).
  • Cribriform plate: Features holes around the crista galli that allow for the olfactory nerves to pass through (responsible for smell).

Maxillary and Other Facial Bones

  • Maxillary bones: Form the upper jaw and anterior roof of the mouth.
    • Alveolar fossa: Spaces for holding teeth (32 teeth in adults).
  • Palatine bones: Form part of the roof of the mouth.
  • Lacrimal bones: Form part of the internal wall of the orbit.
  • Nasal bones: Form the bridge of the nose.
  • Bomer bone: Forms the base of the nasal septum alongside the ethmoid bone.

Nasal Septum

  • Comprised of ethmoid bone and bomer bone.
  • Function: Filters, warms, and directs air to the olfactory region for smell detection.

Mandible (Lower Jaw)

  • Important structure examined with focus on:
    • Body, ramus, and processes such as the mandibular condyle and coronoid process.
    • Alveolar fossa: Spaces for teeth, totaling 16 in the mandible.

Fontanels

  • Soft spots on an infant’s skull; composed of cartilage and bone.
    • Will ossify around one year of age.
    • Two main fontanels: Anterior (larger, takes longer to close) and posterior.
    • Anterior fontanel closes around 18-24 months; posterior fontanel by age 1-2 years.

Vertebral Column

  • Part of the skeletal system; consists of:
    • 33 or 34 total vertebrae:
    • Cervical: 7 vertebrae (neck region).
    • Thoracic: 12 vertebrae (upper back region).
    • Lumbar: 5 vertebrae (lower back region).
    • Sacral: 5 fused vertebrae.
    • Coccygeal: 3-4 fused vertebrae (tailbone).
  • Key differences between vertebrae listed:
    • Cervical vs. Thoracic:
    • Cervical vertebrae have smaller bodies; thoracic have larger bodies.
    • Cervical have holes (transverse foramina) for vertebral arteries.
    • Thoracic vs. Lumbar:
    • Thoracic vertebrae have downward-pointing spinous processes; lumbar vertebrae have square-shaped spinous processes.

Spinal Structures

  • Intervertebral foramen: Space between two vertebrae occupied by spinal nerves.
  • Atlas (C1) and Axis (C2): Key cervical vertebrae that allow head movements.
    • Atlas allows nodding (yes), while Axis allows shaking (no).

Human Spinal Curvatures

  • Four curvatures:
    • Primary: Thoracic and Sacral (retained from embryonic stage).
    • Secondary: Cervical (lifting head) and Lumbar (walking).

Thoracic Cage

  • Sternum: Composed of three parts:
    • Manubrium: Upper section of sternum.
    • Body: Main, middle section.
    • Xiphoid process: The pointed lower section.
  • Ribs: 12 pairs total:
    • True ribs: 7 pairs (attached to the sternum).
    • False ribs: 5 pairs (including floating ribs that aren’t attached to the sternum directly).

Upper Limb Skeleton

  • Clavicles: 2 bones.
  • Scapulae: 2 bones.
    • Features:
    • Spine: divides the scapula into supraspinous and infraspinous fossa.
    • Glenoid cavity: Articulates with the humerus.

Lower Limb Skeleton

  • Femur: Longest bone of the body.
  • Tibia and fibula: Tibia is medial and larger; fibula is lateral.

Phalanges

  • Bones of fingers and toes:
    • Fingers: 14 phalanges (3 in each finger, 2 in the thumb).
    • Toes: 14 phalanges (3 in each toe, 2 in the big toe).

Gender Differences in Pelvis

  • The female pelvis is wider and rounder for childbirth, compared to the narrower male pelvis.
  • False pelvis: Space above the true pelvis; true pelvis is the cavity through which a baby travels during delivery.

Common Spinal Conditions

  • Kyphosis: Hunchback; an exaggerated thoracic curvature.
  • Scoliosis: Lateral curvature of the spine.
  • Lordosis: Exaggerated lumbar curvature; common in pregnant women.

Miscellaneous

  • Calcaneus: Heel bone.
  • Talus: Bone connecting the leg to the foot.
  • Bone density decreases with aging, particularly post-menopause leading to increased risk of fractures.