Overview of the Skeletal System

Skeletal System Overview

• The skeletal system, along with the muscular and articular systems, is vital for human movement
• Three organ systems (Skeletal, Muscular & Articular) must be united for movement
• Skeletal system provides support and shape
• Skeletal system consists of bones, cartilages, ligaments, and tendons

Parts of the Skeletal System

• Bones (skeleton): The hard framework of the body
• Cartilage (flexible connective tissue): Flexible support and cushioning between bones
• Ligaments (connective tissues): Connect bones together, particularly at joints
• Tendons (fibrous connective tissue): Attach muscles to bones

The Bone

• Bone is a rigid tissue composed of cells in a hard, intercellular matrix
• The matrix primarily consists of collagen and calcium phosphate
• Bone structures are significantly diverse

Types of Bone

• Compact bone: Forms the hard outer layer of all bones; provides protection and strength
  • Units called Osteons encase a central canal containing blood vessels and nerve fibers
• Spongy bone: Forms the inner layer of all bones; lightweight and porous structure
  • Filled with marrow and blood vessels

Classification of Bones by Shape

• Long bones:
  • Consist of a proximal (upper) end, diaphysis (shaft), and distal (lower) end
  • Examples: humerus, femur, tibia (upper and lower limbs)
• Short bones:
  • Generally cuboidal in shape
  • Examples: Carpals (wrist), tarsals (ankle)
• Irregular bones:
  • Vary in shape and don't fit into other categories
  • Examples: Vertebrae, hip bones, and some skull bones
• Flat bones:
  • Flat shape
  • Examples: Cranium bones (skull), sternum

Bone Development

• Intramembranous ossification: Bone develops from fibrous connective tissue membranes; examples: skull flat bones and clavicles
• Endochondral ossification: Bone initially develops from cartilage, then replaces cartilage with bone; examples: all long bones

Axial Skeleton

• Consists of skull, vertebral column, and thoracic cage
• Skull protects the brain
• Vertebral column comprises vertebrae for support
• Thoracic cage protects vital organs like the heart and lungs

Appendicular Skeleton

• Includes the pectoral girdle, pelvic girdle, upper limbs, and lower limbs

Skull

• Protects the brain
• Provides entrances to respiratory and digestive systems
• Contains 22 bones: 8 cranial bones and 14 facial bones

Vertebral Column

• Consists of a series of vertebrae
• Provides support and flexibility to the body

Thoracic Cage

• Made up of the thoracic vertebrae, ribs, and sternum
• Protects internal organs, such as the heart and lungs

Ribs

• Attached to vertebrae and the sternum (true ribs), others are attached to costal cartilage of the 7th rib (false ribs)
• Several floating ribs that do not connect to the sternum

Sternum

• Consists of three parts: manubrium, body, and xiphoid process

Upper Appendicular

• Consists of the shoulder girdle (clavicle and scapula), humerus, radius, ulna, carpals, metacarpals, and phalanges

Lower Appendicular

• Consists of the pelvic girdle (ilium, ischium, and pubis), femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges