Skeletal System & Bones

Components of the Skeletal System

  • Composed of more than just bones:

    • Joints

    • Cartilage

    • Tendons

    • Ligaments

  • Definition of tendons and ligaments:

    • Tendons: Connect muscle to bone.

    • Ligaments: Connect bone to bone.

Functions of the Skeletal System

  • Support of the Body:

    • Provides structure; without it, the body would consist of merely skin, muscle, and tissue.

    • Enables posture: standing and sitting.

  • Protection:

    • Protects vital organs:

    • Brain: Enclosed by the skull.

    • Rib Cage: Protects lungs, heart, and parts of the liver.

  • Movement:

    • Facilitate movement through attachment to skeletal muscles (voluntary control).

    • Skeletal muscles are attached to long bones, allowing for movement.

  • Storage of Minerals and Fats:

    • Stores essential minerals (e.g., calcium) and fat.

  • Blood Cell Formation:

    • Occurs within bones, specifically in long bones.

Types of Bone Tissue

  • Compact Bone:

    • Appears like the rings of a tree trunk; dense and structural.

  • Spongy Bone:

    • Less dense, composed of small needle-like pieces called trabeculae, contains bone marrow, and produces blood cells.

Classification of Bones by Shape

  • Long Bones:

    • Longer than they are wide; examples include:

    • Humerus

    • Radius

    • Ulna

    • Femur

    • Tibia

    • Fibula

  • Short Bones:

    • Cube-shaped; generally contain spongy bone.

    • Examples:

    • Bones in the wrists (carpals)

    • Bones in the ankles (tarsals)

  • Flat Bones:

    • Thin, flat, and occasionally curved.

    • Structure: thin layer of compact bone on the outside and spongy bone inside.

    • Examples include:

    • Skull bones

    • Ribs

    • Sternum

  • Irregular Bones:

    • Do not fit into other categories due to unique shapes.

    • Examples: Vertebrae, pelvic bones.

Anatomy of Long Bones

  • Diaphysis:

    • The shaft of the bone, primarily composed of compact bone.

  • Epiphysis:

    • The ends of the long bones, contains spongy bone.

    • Each epiphysis has a proximal end (closest to attachment) and a distal end (farthest from attachment).

  • Medullary Cavity:

    • Found inside the diaphysis, contains yellow bone marrow (fat) in adults; red bone marrow (for blood cell formation) in children.

  • Articular Cartilage:

    • Covers the surfaces of the epiphysis where bones meet (joints).

    • Function: Provides cushioning to reduce friction where bones articulate.

  • Periosteum:

    • Fibrous connective tissue membrane covering the diaphysis.

    • Contains blood vessels supplying the bone.

  • Hyaline Cartilage:

    • Smooth cartilage that decreases friction at the joints.

Microscopic Anatomy of Bone

  • Osteon (Haversian System):

    • Basic unit of compact bone tissue; resembles tree rings.

  • Lacunae:

    • Small cavities in the bone tissue that contain osteocytes (bone cells).

  • Canaliculi:

    • Microscopic channels that connect lacunae and transport nutrients and waste.

Growth and Remodeling

  • Epiphyseal Plate:

    • Growth plate located between diaphysis and epiphysis, allows for lengthening during childhood.

    • Composed of cartilage that changes into bone as growth continues.

  • Process of Bone Remodeling:

    • Osteoblasts: Immature bone cells responsible for forming new bone.

    • Osteoclasts: Bone-resorbing cells that break down old bone tissue.

    • Remodeling occurs as bones are repaired and calcium levels are maintained; affects both length and width of bones.

Types of Bone Cells

  • Osteocytes:

    • Mature bone cells; maintain bone tissue.

  • Osteoblasts:

    • Cells responsible for new bone formation.

  • Osteoclasts:

    • Cells that resorb (break down) bone; crucial for calcium homeostasis and repair of fractured bones.

Bone Fractures

  • Definition and Types of Bone Fractures:

    • Fracture: Painful break in the bone.

    • Simple Fracture (Closed Fracture):

    • A break that does not penetrate the skin.

    • Open Fracture (Compound Fracture): different type of fracture where the broken bone penetrates through the skin.

    • Importance of understanding types of fractures for diagnosis and treatment.

  • The significance of bone fractures in relation to recovery, repair, and potential complications.