Biology Chapter 5: The Skeletal System

Axial vs. Appendicular Skeleton

• Axial skeleton forms the central axis of the body, including the skull, vertebrae, ribs, and sternum.
• Appendicular skeleton includes the limbs and girdles, enabling mobility and manipulation of the environment.

Functions of Bones

• Provide structural support for the body.
• Protect vital organs such as the heart, lungs, and brain.
• Facilitate movement by serving as levers for muscles.
• Store minerals like calcium and phosphorus for metabolic functions.
• Participate in the formation of blood cells within bone marrow.

Spongy vs. Compact Bone

• Compact bone is dense and forms the outer layer of the bone, providing strength and support.
• Spongy bone is lighter and found at the ends of long bones and in the interiors of others, containing red marrow for blood cell production.

Shapes and Sizes of Bones

• Long bones (e.g., femur) contribute to leverage and movement.
• Short bones (e.g., carpals) provide stability and support.
• Flat bones (e.g., skull) protect internal organs and offer surface for muscle attachment.
• Irregular bones (e.g., vertebrae) fulfill various functions, including protection and support.

Parts of a Long Bone

• Diaphysis (shaft) provides length and structure, containing medullary cavity for fat storage.
• Epiphyses (ends) allow for articulation at joints and house spongy bone.
• Periosteum is a protective layer facilitating attachment of muscles and tendons.

Changes in Skeleton Throughout Life

• Bone density typically increases during growth and peaks in early adulthood.
• Bones can become more brittle with age, resulting in a higher risk of fractures.
• Hormonal changes affect bone remodeling, particularly during menopause in females.

Types of Vertebrae

• Cervical vertebrae support the neck and allow head movement.
• Thoracic vertebrae articulate with ribs, providing stability for the chest.
• Lumbar vertebrae are larger and support the lower back, bearing more weight.

True vs. False Bones

• True bones directly connect to the sternum, such as the first seven pairs of ribs.
• False bones do not attach directly to the sternum and include the remaining ribs.

Male vs. Female Pelvic Girdles

• Male pelvis is narrower and more robust for bipedal locomotion.
• Female pelvis is broader and has a wider pelvic inlet for childbirth.

Common Types of Bone Fractures

• Simple fracture involves a break without skin penetration.
• Compound fracture breaks through the skin, increasing risk of infection.
• Comminuted fracture results in multiple bone fragments, usually due to high-impact trauma.
• Greenstick fracture (common in children) features an incomplete break, bending the bone rather than fully breaking it.