Anatomy Unit Lecture 3 - Bones

Skeleton Definition

• Skeleton: A hard form of calcified connective tissue.

Types of Skeleton

• Axial Skeleton: Includes skull, vertebral column, hyoid bone, ribs, sternum.
• Appendicular Skeleton: Upper and lower limb bones, girdles.

Bone Composition

• Consists of osteocytes (bone cells), collagenous matrix (organic), and mineral contents (inorganic).

Bone Cells

• Osteoblasts: Responsible for bone building and repair (osteogenesis).
• Osteocytes: Mature bone cells that maintain bone tissue.
• Osteoclasts: Cells that absorb and dissolve bone matrix (osteolysis).

Functions of Bones

• Shape and support the body.
• Protect vital organs (e.g., skull protects the brain).
• Muscle attachment aids locomotion.
• Store minerals like calcium and phosphate.
• Facilitate weight transmission.
• Contribute to respiration.
• Form blood cells in red bone marrow, located in ends of long bones, vertebrae bodies, and flat bones.

Structure of a Long Bone

• Epiphysis: Ends of long bones.
• Diaphysis: Shaft composed of compact bone surrounding the medullary cavity.
• Metaphysis: Area adjacent to epiphyseal cartilage; site of growth in length.
• Endosteum: Membrane lining the medullary cavity.
• Periosteum: Fibrous membrane covering the shaft; responsible for growth in width.

Blood Supply

• Nutrient artery, epiphyseal artery, periosteal artery, and metaphyseal artery supply mature long bones.

Classification of Bones

• According to Position:

  • Axial Skeleton: Skull, vertebral column (32-33 vertebrae), hyoid bone, ribs, sternum.
  • Appendicular Skeleton: Shoulder girdle (clavicle, scapula), arm (humerus), forearm (radius, ulna), hand (carpals, metacarpals, phalanges).

• According to Shape:

  • Long Bones: Arm, forearm, thigh, and leg bones.
  • Short Bones: Tarsal and carpal bones.
  • Irregular Bones: Vertebrae, base of skull, mandible, hyoid.
  • Flat Bones: Scapula, skull cap, ribs, sternum.
  • Sesamoid Bones: Patella, pisiform.
  • Pneumatic Bones: Contain air spaces (skull bones).

Bone Structure

• Compact Bone: Dense bone present in long bone cortex.
• Spongy Bone: Contains trabeculae and spaces located in epiphysis of long bones.

Types of Ossification

• Intramembranous Ossification: Occurs in the shaft of the clavicle and facial bones.
• Intracartilaginous Ossification: Involves a cartilaginous model; found in ribs, vertebrae, upper and lower limb bones.

Types of Cartilage

• Hyaline Cartilage: Found in articular surfaces, costal, and trachea.
• Elastic Cartilage: Located in ear pinna and epiglottis.
• Fibrocartilage: Present in intervertebral discs and menisci.

Clinical Case

• A 28-year-old man presents with shoulder pain after a bicycling accident; he may have a fracture.
• Possible fractured bones: Humerus, radius, ulna, clavicle (to be diagnosed).

This quiz covers the key concepts of bones, including the definitions of the skeleton and its components, functions of bones, and types of cartilage. Students will differentiate between the axial and appendicular skeleton and understand the classification of bones. Prepare to delve into the histological and gross aspects of bone structure.