Lecture Notes: Human Skeleton

Overview

• The human skeleton consists of 206 bones in adults.
• Includes bones, cartilage, joints, and ligaments.
• Makes up about 20% of body mass.
• Divided into two sections: axial skeleton and appendicular skeleton.

Axial Skeleton

Skull

• Composed of 22 bones.
  • Cranial bones (8) protect the brain.
    • Frontal bone, Parietal bones (2), Occipital bone, Temporal bones (2), Sphenoid, Ethmoid.
    • Connected by sutures: coronal, sagittal, lambdoid, squamous, occipitomastoid.
  • Facial bones (14) give structure to the face.
    • Mandible, Maxillary bones, Zygomatic bones, Nasal bones, Lacrimal bones, Palatine bones, Vomer, Inferior nasal conchi.
  • Hyoid bone (below mandible) not part of the skull.
  • Important foramina: foramen magnum for spinal cord.
  • Cavities: cranial, ear, nasal, and orbits.

Vertebral Column (Spinal Column or Spine)

• Made up of 26 irregular bones.
• Sections:
  • Cervical vertebrae (7)
  • Thoracic vertebrae (12)
  • Lumbar vertebrae (5)
  • Sacrum (5 fused vertebrae)
  • Coccyx (tailbone, fused vertebrae)
• Ligaments & Discs:
  • Anterior and posterior longitudinal ligaments.
  • Intervertebral discs: nucleus pulposus (elastic), annulus fibrosus (collagen).

Thoracic Cage

• Consists of the sternum and ribs.
  • Sternum: manubrium, body, xiphoid process.
  • Ribs: 12 pairs.
    • True ribs (7 pairs), attach directly to sternum.
    • False ribs (5 pairs), indirect or no attachment.
    • Floating ribs (last 2 pairs), no sternum attachment.

Appendicular Skeleton

Pectoral Girdle

• Composed of clavicle (collarbone) and scapula (shoulder blade).
• Attaches upper limbs to axial skeleton.

Upper Limb

• Arm: Humerus.
• Forearm: Radius and Ulna (connected by interosseous membrane).
• Hand:
  • Carpals (wrist bones): scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate.
  • Metacarpals: numbered 1-5 (thumb to pinky).
  • Phalanges: 14 bones per hand, 3 per finger (thumb has 2).

Pelvic Girdle

• Composed of the sacrum and two hip bones (ilium, ischium, pubis).

Lower Limb

• Thigh: Femur (largest bone).
• Leg: Tibia and Fibula (connected by interosseous membrane).
• Foot:
  • Tarsals: talus, calcaneus, cuboid, navicular, cuneiforms (medial, intermediate, lateral).
  • Metatarsals: numbered 1-5.
  • Phalanges: 14 bones per foot, 3 per toe (big toe has 2).

Conclusion

• The skeletal system is primarily composed of bones but also includes joints crucial for mobility.