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Long Bones

Are Long and Thin
Upper Extremedies- humerus, ulna, radius, metacarpals
Lower Extremedies- femur, tibia, fibula

Flat Bones

Are thin with parallel surfaces
Scapula, ribs, sternum, skull

Irregular Bones

Have complex shapes
Vertebrae, pelvis

Sutural Bones (Wormiam)

Are small, irregular bones
Found between the flat bones of the skull

Short Bones

Are small and thick with multiple articulations
Carpals, tarsals

Sesamoid Bones

Are small and flat, develop inside tendons near joint of knees, hands, feet


The shaft, a heavy wall of compact bone
The compact bone surrounds a central space called a medullary cavity (location of bone marrow)


Wide part at each end, composed of a thin exterior layer of compact bone and a large portion of spongy bone
Ends are covered with hyaline (articular) cartilage

Medullary Cavity

The space within a bone that contains the marrow


Mature bone cell responsible for the maintenance and turnover of the mineral content of the surrounding bone
-live in lacunae, are between layers of matrix called lamellae
-connect by cytoplasmic extensions called canaliculi in lamellae
i. travel between another lacunae or a central canal
-do not divide
-Functions: to maintain protein and mineral context of matrix, to help repair damaged bones, can sense the stress applied to the bone


A cell that produces the fibers and matrix of bone
-immature bone cells that synthesize and secrete the organic matrix (osteoid, then hardens by mineral deposition)
-osteoblasts surrounded by bone become osteocytes


A cell that dissolves the fibers and matrix of bone
-giant, multinucleate cells secrete acids and protein digesting enzymes to dissolve bone matrix and release stored minerals (osteolysis)
-are derived from the same stem cells that produce macrophages


The basic histological unit of compact bone, consisting of osteocytes organized around a central canal and separated by concentric lamellae
-central canal contains blood vessels and connecting each central canal are perforating canals


The process of replacing other tissue with bone
-intramembranous and endochondral


The process of depositing calcium salts which occurs during bone ossification and in other tissues


Secreted from the thyroid gland
Decreases calcium ion levels by:
-inhibit osteoclast activity
-increase calcium excretion at kidneys
Therefore, less Ca++ ions enter the blood and losses are accelerated


Secreted by the parathyroid glands
Increases calcium ions by 3 ways:
-Stimulating osteoclasts
-Increase intestinal absorption of calcium
-Decrease calcium excretion at kidneys
Therefore, more Ca++ ions enter the blood and losses are restricted and homeostasis is maintained


A crack or break in a bone from sudden impacts, extreme loads, stresses from unusual directions or pathology

Functions of the Skeletal System

Storage of minerals (calcium and phosphate)
Storage of lipids (yellow marrow)
Blood cell production (red marrow, wbc, rbc)
Protection of internal organs
Leverage for skeletal movement (force of motion)

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