Core 2: Skeletal System Overview

Study Notes

Humans start with approximately 300 bones at birth, but end up with 206 bones after some fuse together during development, such as those in the skull.

Long Bones: Characterized by a long shaft and two ends; consist of compact bone on the exterior and spongy bone inside (e.g., femur, humerus).
Short Bones: Cube-like, primarily composed of spongy bone with a compact bone surface (e.g., carpals, tarsals).
Flat Bones: Thin, flat bones that often protect organs (e.g., skull, sternum).
Irregular Bones: Variably shaped bones that do not fit into other categories (e.g., vertebrae, pelvis).
Sesamoid Bones: Small, round, flat bones found where tendons over joints; protect tendons and improve movement (e.g., patella).

Support: Provide a framework and shape for the body (e.g., vertebrae supporting ribs).
Protection: Shield vital organs (e.g., pelvis protecting reproductive organs).
Movement: Work with muscles as levers (e.g., knee joint flexion aiding in kicking).
Mineral Storage: Store crucial minerals, including calcium.
Blood Cell Production: Occurs in the cavities of certain bones.

Axial Skeleton: Comprises skull, ribs, and vertebral column; provides stability and supports the appendicular skeleton's movements; includes mostly immovable bones.
Appendicular Skeleton: Consists of pelvic girdle, limbs, and shoulder girdle; contains key long bones essential for movement.

Plane Joints: Allow limited gliding movements (e.g., intertarsal joints).
Hinge Joints: Allow movement along one axis, primarily for flexion/extension (e.g., elbow, knee).
Pivot Joints: Enable rotational movements (e.g., C1 to C2 vertebral joint).
Ellipsoid/Condyloid Joints: Permit movement in two planes (e.g., wrist joint).
Saddle Joints: Similar to condyloid but with no axial rotation (e.g., base of the thumb).
Ball-and-Socket Joints: Most mobile; allow movement across three planes (e.g., shoulder, pelvis).

Cartilaginous Joints: Joints joined by cartilage allowing slight movement (e.g., between vertebrae).
Fibrous Joints: Immovable joints connected by fiber (e.g., cranial sutures).

Ligaments: Strong bands connecting bones, providing stability by controlling movement.
Tendons: Tough cords that attach muscles to bones.
Synovial Fluid: Lubricates joints, providing cushioning and nourishing joint surfaces.