6.1 & 6.2

Bones and Fossils

• Bones as Fossils:

  • Bones can create good fossils due to their ability to undergo mineralization, turning them into stone over time.

  • Unlike fossils, living bones are made of living tissue that can grow, repair, and renew itself.

  • A well-preserved fossil skeleton helps to determine size and shape of extinct organisms.

Functions of the Skeletal System

• Overview of Skeletal System:

  • Composed of bones and cartilage.

  • Performs various critical functions for the human body including:

  • Support

  • Facilitating movement

  • Protection of internal organs

  • Blood cell production (hematopoiesis)

  • Storage and release of minerals and fat

Definitions

• Bone:

  • Osseous tissue that forms most of the adult skeleton; a hard, dense connective tissue.

• Cartilage:

  • A semi-rigid form of connective tissue providing flexibility and smooth surfaces for movement.

Major Functions

Support

• Provides a scaffold for the body similar to steel beams in buildings.

• Without it, the body would collapse into a mass of organs, muscle, and skin.

Movement

• Bones serve as points of attachment for muscles.

• Act as levers; joints serve as fulcrums.

  • Movement occurs when muscles contract and span a joint.

• For further details on the interaction between skeletal and muscular systems, additional content should be reviewed.

Protection

• Protects internal organs by surrounding or covering them.

  • Example:

  • Ribs protect lungs and heart.

  • Vertebral column protects the spinal cord.

  • Cranium protects the brain.

Orthopedics

• Orthopedist:

  • A physician who specializes in diagnosing and treating disorders related to the musculoskeletal system.

  • Treatments may include medications, exercises, braces, or surgery.

  • Sports medicine specialization addresses both simple and complex injuries.

Metabolic Functions

• Mineral Storage:

  • Bone tissue serves as a reservoir for essential minerals, particularly calcium and phosphorus.

  • Minerals can be released into the bloodstream to maintain physiological processes.

  • Calcium ions are essential for muscle contractions and nerve impulse transmission.

• Energy Storage:

  • Bone marrow (yellow marrow) stores fat; triglycerides can be utilized for energy.

• Hematopoiesis:

  • Process of blood cell production occurs in red marrow, producing:

  • Red blood cells

  • White blood cells

  • Platelets

Bone Classification

• Overview:

  • The adult human skeleton consists of 206 bones that are classified into five categories based on shape:

Long Bones

• Shape:

  • Cylindrical, longer than wide.

• Examples:

  • Humerus, ulna, radius (arms), femur, tibia, fibula (legs), metacarpals, phalanges (fingers and toes).

• Function:

  • Act as levers for movement.

Short Bones

• Shape:

  • Cube-like, approximately equal in length, width, and thickness.

• Examples:

  • Carpals (wrists), tarsals (ankles).

• Function:

  • Provide stability and support with limited motion.

Flat Bones

• Shape:

  • Thin and often curved.

• Examples:

  • Cranial bones, scapulae (shoulder blades), sternum (breastbone), ribs.

• Function:

  • Attach muscles and protect internal organs.

Irregular Bones

• Shape:

  • Complex, do not fit into other classifications.

• Examples:

  • Vertebrae, many facial bones.

• Function:

  • Protect internal organs.

Sesamoid Bones

• Shape:

  • Small and round, resembling sesame seeds.

• Examples:

  • Patellae (kneecaps).

• Function:

  • Protect tendons from compressive forces, found in areas with high joint pressure.

Summary of Bone Classifications