Skeletal System: Physiology, Functions, and Structure

Introduction to Bone Physiology and Structure

This lecture focuses on the physiology of bone, including how bones are made, how they heal, and their crucial role in anchorage and movement. It is important to remember that bones do not move independently; they are part of a larger system where muscles, anchored to bones, facilitate movement.

Functions of the Skeletal System

• Support: Bones provide a framework for the body and cradle soft tissues. For example, cranial bones (e.g., frontal, parietal, temporal, occipital) form the skull, supporting and protecting the brain. Long leg bones and sturdy attachments also allow for an upright posture and standing.
• Protection: Bones surround and protect delicate soft tissues and allow for passageways for nerves and blood vessels.
  • Vertebrae are bones designed to encircle and protect the spinal cord, featuring a large vertebral foramen for this purpose.
  • Terms like foramen, fissure, or meatus refer to openings in bones that serve as passageways for nerves or blood vessels, protecting them as they traverse the bone.
• Anchorage: Muscles attach to bones, creating a system of levers that enables movement. Each muscle attaches to the skeletal system at two points: an origin and an insertion.
  • Movement occurs as the insertion moves towards the origin, causing the skeletal system to act as a lever. It's the muscle that performs the movement, but its strong anchorage to the bone facilitates the movement of the skeletal system.
• Mineral Storage: Bones store vital minerals, primarily calcium and phosphate, which contribute to bone density.
  • Bone is a unique connective tissue, being strong, hard, yet lightweight.
  • Calcium and phosphate concentrations are constantly regulated between bone and blood. High blood levels can lead to mineral deposition in bone, while low blood levels result in mineral extraction from bone.
  • Bone tissue is dynamic and constantly remodeling, changing based on diet, exercise, age, and health; it is never static.
• Hematopoiesis: This refers to blood cell formation, which occurs in the red bone marrow.
  • The prefix 'hemato' means blood, and 'poiesis' means to make.
  • All blood cells originate in the bones, not heart or vessels.
• Triglyceride Storage: Adipose tissue (fat) is stored in the yellow bone marrow, serving as an energy reserve.

Classification of Bones

Bones can be classified in several ways:

Based on Location

• Axial Skeleton: This includes bones of the central axis of the body:
  • Skull
  • Vertebral column
  • Ribs
  • Sternum
• Appendicular Skeleton: 'Append' means to hang, referring to structures that