skeleton

Overview of the Skeleton

  • Subdivisions:

    • Axial skeleton: skull, vertebrae, sternum, ribs, sacrum, hyoid
    • Appendicular skeleton: pectoral girdle, upper extremities, pelvic girdle, lower extremities

  • Number of Bones:

    • Adult skeleton typically has 206 bones
    • Variations in bone number due to sesamoid (e.g., patella) and sutural bones
    • Infants have approximately 270 bones which decrease through fusion

  • Bone Markings:

    • Include ridges, spines, bumps, depressions, canals, pores, articular surfaces
    • Important for muscle attachment and vessel/nerves passage

The Skull

  • Components:

    • Divided into cranial and facial bones
    • Cranial bones: protect the brain, consist of 8 bones (1 frontal, 2 parietal, 2 temporal, 1 occipital, 1 sphenoid, 1 ethmoid)
    • Facial bones: 14 bones, shape the face, support oral and nasal cavities

  • Features:

    • Cranial cavity houses the brain; orbits are eye sockets
    • Several foramina for nerve/blood vessel passage: e.g., foramen magnum in occipital bone

The Vertebral Column and Thoracic Cage

  • Structure: 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 4 coccygeal)
  • Function: Protects spinal cord, supports head and trunk, absorbs stresses
  • Vertebral Features: Body (centrum), vertebral arch, spinous processes, articular surfaces
  • Thoracic Cage: Composed of thoracic vertebrae, sternum, and ribs; protects thoracic organs
    • Ribs categorized: True (1-7), False (8-10), Floating (11-12)

The Pectoral Girdle and Upper Limb

  • Pectoral Girdle: Connections between upper limbs and axial skeleton

    • Composed of clavicle and scapula

  • Humerus: Major bone of the upper arm

    • Features proximal head, greater/lesser tubercles, distal condyles for articulation with radius and ulna

  • Forearm Bones: Radius (lateral) and ulna (medial) offer structures for flexion and extension

  • Hand Composition: 8 carpal bones, 5 metacarpals, 14 phalanges

The Pelvic Girdle and Lower Limb

  • Pelvic Girdle Components: Two hip bones, sacrum

  • Features of the Pelvis: Supports lower limbs, surrounds pelvic cavity; includes features like acetabulum, obturator foramen

  • Lower Limb Bones: Femur, patella, tibia (medial, weight-bearing), fibula (lateral, stabilizing)

  • Foot Composition: 7 tarsal bones, 5 metatarsals, 14 phalanges

  • Arches of Foot: Medial longitudinal, lateral longitudinal, and transverse arches for load-bearing and mobility.