Human Anatomy Chapter 6: Skeletal System

Study Notes

Consists of 206 named bones, divided into two principal divisions: axial skeleton and appendicular skeleton
Axial skeleton: skull bones, auditory ossicles, hyoid bone, ribs, sternum, and bones of the vertebral column
Appendicular skeleton: bones of upper and lower limbs, plus bones forming the girdles that connect limbs to axial skeleton

Support: provides hard framework that supports and anchors soft organs of the body
Protection: surrounds organs such as brain and spinal cord
Movement: allows for muscle attachment, using bones as levers
Storage: stores minerals and lipids within bone material
Blood cell formation: bone marrow is responsible for blood cell production

Two types of bone tissue: compact and spongy, differing in density
Three types of cells contributing to bone homeostasis: osteoblasts, osteoclasts, and osteocytes
Bone tissue is a specialized form of connective tissue characterized by a mineralized extracellular matrix
Mineral composition: calcium phosphate (hydroxyapatite crystals), calcium carbonate, magnesium hydroxide, fluoride, and sulfate
Matrix composition: mainly collagen (type I, VI) along with other matrix proteins, with collagen molecules making up ~90% of total weight of bone matrix

Composed of two types of osseous tissue, making up the outer cortex of all bones
In immediate contact with periosteum
Solid, strong bone located along diaphysis of long bones, providing solid structure to skeletal frame
Forms a hollow tube called the medullary cavity

Structural unit is the osteon (haversian system), an elongated cylinder oriented parallel to the long axis of the bone

Sponge-like meshwork consisting of trabeculae, with spaces occupied by marrow and blood vessels
Does not contain osteons, consisting of trabeculae surrounding many red marrow-filled spaces
Forms most of the structure of short, flat, and irregular bones, and the epiphyses of long bones
Light and supports and protects red bone marrow, reducing weight of the bone and providing strength against forces of compression

Long bones: longer in one dimension, with an elongated shaft (diaphysis) and two expanded ends (epiphyses)
Short bones: nearly equal in length and diameter, can be of any shape