skeleton system 2

Adult Skeletal System Overview

• The adult skeletal bones are divided into two divisions:
  • Axial Skeleton
  • Appendicular Skeleton

Division of the Skeleton

• The skeletal system is composed of:
  • Bones
  • Cartilages
  • Joints
  • Ligaments
• The skeleton accounts for 20% of body mass.

Axial Skeleton

• Structure:
  • Includes 80 bones total.
  • Specific bones in the axial skeleton:
  • Skull:
    • Cranial cavity bones: 8
    • Facial bones: 14
  • Hyoid bone: 1
  • Auditory ossicles: 6 (see Figure 7.5)
  • Vertebral column: 26
  • Thorax:
    • Sternum: 1
    • Ribs: 24
• Total bones in the axial skeleton: 80

Axial Skeleton Functions

• Contributes to homeostasis by protecting many organs:
  • The cranium surrounds the brain.
  • The vertebrae surround the spinal cord.
  • The ribs protect the heart and lungs.
• Provides support by forming the longitudinal axis of the body:
  • Supports head, neck, and trunk.
  • Protects the brain, spinal cord, and thoracic organs.

Appendicular Skeleton

• Structure:
  • Composed of 126 bones.
  • Specific components of the appendicular skeleton:
  • Pectoral girdle:
    • Clavicle
    • Scapula
  • Upper limbs:
    • Humerus
    • Ulna
    • Radius
    • Carpals
    • Metacarpals
    • Phalanges
  • Pelvic girdle:
    • Hip, pelvic, or coxal bone
  • Lower limbs:
    • Femur
    • Patella
    • Fibula
    • Tibia
    • Tarsals
    • Metatarsals
    • Phalanges
• Total bones in appendicular skeleton: 126

Summary of Total Bones in Adult Skeleton

• Total number of bones in an adult skeleton: 206

Classification of Bones

• Bones are classified into 5 main types based on shape:
  • Long Bones: Greater length than width.
  • Example: Humerus
  • Short Bones: Cube-shaped.
  • Example: Trapezoid bone (wrist bone)
  • Flat Bones: Thin layers of parallel plates.
  • Example: Sternum
  • Irregular Bones: Complex shapes.
  • Example: Vertebra.
  • Sesamoid Bones: Shaped like a sesame seed.
  • Example: Patella.

Sutural Bones

• Some bones are characterized by location rather than shape:
  • Sutural bones: Small, extra bone plates located within the sutures of cranial bones.
  • Sutures: Jointed areas where flat bones come together.
  • Noted sutures and associated bones:
  • Coronal suture
  • Sagittal suture
  • Lambdoid suture
  • Squamous suture
• Associated skull bones and structures:
  • Frontal bone
  • Parietal bones
  • Temporal bones
  • Occipital bone
  • Zygomatic bone
  • Mandible

Visual Representation of the Skull

• Anterior and posterior views of the skull highlighting:
  • Major bones involved, including:
  • Frontal bone
  • Parietal bone
  • Temporal bone
  • Occipital bone
  • Zygomatic process
  • Mastoid process
  • Styloid process
  • External acoustic meatus
  • Occipital condyle