Human Skeleton Lecture Notes

Overview

• The skeletal system consists of bones, cartilage, joints, and ligaments.
• Adult human skeleton has approximately 206 bones.
• Skeletal system constitutes about 20% of body mass.

Sections of the Human Skeleton

Axial Skeleton

• Components: Skull, vertebral column, thoracic cage

Skull

• Comprised of 22 bones: cranial (protect the brain) and facial bones (structure of the face).
• Cranial Bones (8): frontal, 2 parietal, occipital, 2 temporal, sphenoid, and ethmoid.
• Facial Bones (14): mandible, maxillary, 2 zygomatic, 2 nasal, 2 lacrimal, 2 palatine, vomer, 2 inferior nasal conchae.
• Important Features:
  • Sutures: coronal, sagittal, lambdoid, squamous, occipitomastoid.
  • Foramina: holes for nerves, veins, and arteries, e.g., foramen magnum for the spinal cord.

Vertebral Column (Spine)

• Structure: 26 irregular bones forming a flexible S-shaped structure.
• Sections:
  • Cervical (7 vertebrae)
  • Thoracic (12 vertebrae)
  • Lumbar (5 vertebrae)
  • Sacrum (5 fused vertebrae)
  • Coccyx (tailbone, small fused bones)
• Key Features:
  • Ligaments: anterior and posterior longitudinal ligaments
  • Intervertebral discs: cushiony pads acting as shock absorbers (nucleus pulposus and anulus fibrosus).
  • Vertebra Structure: body, vertebral arch, processes (spinous, transverse, superior and inferior articular).
  • Variations: Cervical (short spinous process, large vertebral foramen), Thoracic (long spinous process, demifacets), Lumbar (larger size, distinctive pedicles and laminae).

Thoracic Cage

• Components: Sternum and ribs.
• Sternum: manubrium, body, xiphoid process.
• Ribs:
  • True Ribs: (first 7 pairs) attach directly to the sternum.
  • False Ribs: (next 5 pairs) attach indirectly or not at all (last 2 called floating ribs).

Appendicular Skeleton

• Components: Limbs and girdles (pectoral and pelvic).

Pectoral Girdle

• Bones: Clavicle (collarbone), scapula (shoulder blade).
• Functions: Attaches upper limbs to axial skeleton.

Upper Limb

• Components: Arm (humerus), forearm (radius and ulna), hand.
• Hand:
  • Carpus (wrist): 8 carpals (scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate).
  • Metacarpals: 5 bones.
  • Phalanges: 14 bones per hand (3 per finger, 2 per thumb).

Pelvic Girdle

• Bones: Sacrum and hip bones (ilium, ischium, pubis).
• Functions: Attaches lower limbs to axial skeleton, provides stability.

Lower Limb

• Components: Thigh (femur), leg (tibia and fibula), foot.
• Foot:
  • Tarsus: 7 tarsals (talus, calcaneus, cuboid, navicular, medial, intermediate, lateral cuneiform).
  • Metatarsus: 5 metatarsals.
  • Phalanges: 14 bones per foot (3 per toe, 2 for big toe).

Next Topic

• Overview of joints, critical for skeleton function and mobility.