Skeletal System Structure, Classification, and Bone Growth (copy) (copy)

Functions of the Skeletal System

• Support:

  • Serves as the structural framework for the body.

  • Provides a rigid structure that holds up the body and maintains shape.

• Protection:

  • Shields internal organs and tissues from physical impact and trauma.

• Movement:

  • Muscles require bone to initiate and execute movement.

  • Bones act as mechanical levers that muscles pull against to produce motion.

• Mineral Storage (Minerals / Calcium):

  • Stores substances that the body has in extra quantities and may require at a later time.

  • Primarily stores minerals such as calcium, releasing them into the bloodstream as physiological demands require.

• Hematopoiesis:

  • Blood cell production (makes blood).

  • Occurs within the marrow cavities of specific bones.

Classification and Types of Bones

• Long Bones:

  • Dimensional Characteristics: Characterized by being longer than they are wide.

  • Primary Functions: Provide leverage for muscles to act upon and support body weight.

  • Examples: Femur, humerus, and tibia.

• Short Bones:

  • Dimensional Characteristics: Shaped sort of like a cube, possessing similar dimensions in width and length.

  • Locations and Examples: Found in the carpals and tarsals (associated with the wrists/fingers and ankles/toes).

• Flat Bones:

  • Structural Characteristics: Can be straight or curved in structure.

  • Primary Functions:

  • Primarily functional for protection by enclosing and shielding vital internal organs.

  • Serves as an expansive point of attachment for skeletal muscles.

  • Examples: Skull, ribs, sternum, and scapula.

• Irregular Bones:

  • Structural Characteristics: Possess a complex, non-uniform shape that does not fit into other morphological categories.

  • Primary Functions: Dedicated to structural integrity and protection.

  • Examples: Vertebrae and the hip (pelvic) bones.

• Sesamoid Bones:

  • Structural Characteristics: Distinctly roundish in shape.

  • Anatomical Placement: Embedded directly within tendons.

  • Primary Functions: Protect tendons from excessive wear, tear, and mechanical stress.

  • Example: Patella (kneecap).

Bone Growth and Hormonal Regulation

• Longitudinal Growth:

  • Refers to the increase in the length of bones.

  • Regulated and stimulated directly by hormones, specifically Human Growth Hormone ($\text{HGH}$).

• Appositional Growth:

  • Refers to the increase in diameter or width of bones.

  • Dependent on external inputs and nutritional intake, heavily based off diet (particularly calcium intake and related nutrients).

• Hormonal Control of Calcium:

  • Calcitonin and Parathyroid Hormone ($\text{PTH}$): Hormones that control the release and regulation of calcium between the bones and the bloodstream to maintain homeostatic balance.