Human Skeletal System

Skeletal System

Functions:

• Supports the body
• Protects internal organs
• Facilitates movement
• Produces blood cells
• Stores minerals

Divisions:

• Axial Skeleton (80 bones)
  • Skull
  • Vertebral column
  • Ribs
  • Sternum
• Appendicular Skeleton (126 bones)
  • Upper limbs
  • Pelvis
  • Lower limbs

Bone Types:

• Long bones (e.g., femur, humerus)
• Short bones (e.g., carpals, tarsals)
• Flat bones (e.g., ribs, sternum)
• Irregular bones (e.g., vertebrae, pelvis)
• Sesamoid bones (e.g., patella)

Bone Structure:

• Compact bone (dense, compact tissue)
• Cancellous bone (spongy, porous tissue)
• Bone marrow (produces blood cells)
• Periosteum (outer bone covering)
• Endosteum (inner bone lining)

Joints:

• Synovial joints (freely movable)
  • Hinge joints (e.g., elbow, knee)
  • Ball-and-socket joints (e.g., shoulder, hip)
  • Pivot joints (e.g., neck, forearm)
• Cartilaginous joints (partially movable)
  • Fibrous joints (immovable)
  • Synchondroses (temporary joints in growth plates)

Skeletal System Development:

• Ossification (bone formation) begins in embryonic development
• Endochondral ossification (in cartilage models)
• Intramembranous ossification (direct bone formation)

Skeletal System

Functions

• Provides support to the body
• Protects internal organs such as the heart, lungs, and brain
• Enables movement through the musculoskeletal system
• Produces blood cells in the bone marrow
• Stores minerals such as calcium and phosphorus

Divisions of the Skeletal System

• Axial Skeleton: consists of 80 bones that make up the skull, vertebral column, ribs, and sternum
• Appendicular Skeleton: consists of 126 bones that make up the upper and lower limbs, pelvis, and shoulder girdle

Types of Bones

• Long bones: characterized by their length, examples include the femur and humerus
• Short bones: cube-shaped bones, examples include the carpals and tarsals
• Flat bones: thin and flat bones, examples include the ribs and sternum
• Irregular bones: bones with complex shapes, examples include the vertebrae and pelvis
• Sesamoid bones: small, rounded bones embedded within tendons, example is the patella

Bone Structure

• Compact bone: dense, compact tissue found in the shaft of long bones
• Cancellous bone: spongy, porous tissue found in the ends of long bones and interior of flat bones
• Bone marrow: the spongy tissue inside some bones that produces blood cells
• Periosteum: a double-layered membrane that covers the bone surface
• Endosteum: a thin layer of cells that lines the bone cavity

Joints

• Synovial joints: freely movable joints that have a space between the bones, examples include the elbow and knee
• Hinge joints: joints that allow movement in one plane, example is the elbow
• Ball-and-socket joints: joints that allow movement in multiple planes, example is the shoulder
• Pivot joints: joints that allow rotational movement, example is the neck
• Cartilaginous joints: partially movable joints that have cartilage between the bones
• Fibrous joints: immovable joints that have connective tissue between the bones
• Synchondroses: temporary joints in growth plates that disappear as the bone matures

Development of the Skeletal System

• Ossification: the process of bone formation that begins in embryonic development
• Endochondral ossification: the process of bone formation in cartilage models
• Intramembranous ossification: the process of direct bone formation in the embryo