Skeletal System Components and Functions
Made of bones, cartilage, ligaments. Each bone is an organ because it contains blood, bone connective tissue, nerves, lymph vessels, etc.
- Support
- Protection
- Mineral storage
- Triglyceride/lipid storage (yellow marrow)
- Red and white blood cell formation called hemopoiesis (red marrow)
- Leverage (assistance in movement)
Components of axial skeleton
Skull, thoracic cage, vertebral column
Components of appendicular skeleton
Upper limbs, lower limbs, pelvic girdle, pectoral girdle
Long bone examples
Longer than they are wide
-femur, tibula, fibula, humerus, ulna, radius, metacarpals, metatarsals
Short bones
Almost equal in length and width
-Carpals (ankle), tarsals (wrist)
Flat bones
Relatively flat but may be curved
-sternum, ribs
Irregular bones
Complex shape
-vertebra
Sesamoid bones
Forms where there is friction, tension, or stress
-patella
Sutural bones
Bones found between sutures of the skull
Endosteum (anatomy of long bone)
Lines the inner surfaces of bone, including medullary cavity, trabecullae of spongy bone, and canals of compact bone
Contains osteogenic cells (important for bone regrowth/ remodeling)
Periosteum
Connective tissue membrane that covers the external surface of bone. It is attached to the bone matrix via perforating fibers.
Contains outer fibrous layer + inner osteogenic layer (important for bone growth/ remodeling)
Bone composition
Bone is made up of connective tissue, which makes up the ECM (ground substance/ minerals and collagen fibers) and cells (osteogenic cells, osteoblasts, osteocytes, osteoclasts)
Osteogenic cells
Made from stem cells (Mesenchymal)
Goes through mitosis nd differentiates into osteoblasts
Osteoblast
Differentiated from osteogenic cell
- forms bone by synthesizing organic components of bone matrix: collagen fibers and glycoproteins in the ground substance
- initiates calcification: takes calcium from blood and deposit it within matrix
Osteocyte
Derived from osteoblasts
- maintains bone tissue. Mature bone cells
- senses bone microdamage (wear and tear) and mechanical forces. It sends signals to repair
Osteoclast
Derived from myloid stem cells
- Breaks down bone (bone resorption)
- releases enzymes and acids that degrade collagen
Spongy bone composition
Trabeculae: Irregular lattice of thin plates
Osteocytes housed in lacunae
Spongy bone location/ function
Location:
- epiphyses of long bone
- surrounding marrow cavities
- flat/short/irregular bones
Function:
- withstand forces (trabeculae arranged along lines of stress)
- lighten skeleton
- contain red marrow for hemopoiesis
Compact bone composition
Solid network of bone organized in concentric ring structures called osteons
Concentric lamellae (around central canal) and circumferential lamellae and interstitial lamellae
*Osteons are straws, while the spaces are filled in with interstitial lamellae
Osteocytes sit within lacunae, and its dendrites sit within canaliculi
Compact bone location/function
Location:
- external layer of ALL bones
- diaphysis of long bones
Function:
-gives long bones ability to withstand forces along longitudinal axis
