The Skeletal System
Functions of Bones support - hard framework that supports organs protection - cranium, vertebral column, thoracic cage movement - place for attachment of skeletal muscles by tendons
adults - mostly in flat bones 3. storage - fat in marrow, calcium, phosphorus, and other minerals (K, Na, S, Mg, Cu) 4. blood cell formation - hematopoiesis - occurs in red marrow of certain bones adults - mostly in flat bones ex: ribs, pelvis, femur (flat and long bones)
Bone Classification by Shape and Size 1. long - longer than wide shaft and 2 ends ex: humerus, femur, metatarsals
2. short - cube like ex: carpals, tarsals
3. flat - thin, flat, usually curved ex: ribs, most cranial, scapula, sternum
4. irregular - no other category describes them ex: vertebrae, pelvic bones
Gross Anatomy of a Long Bone
Gross Anatomy of a Long Bone diaphysis - shaft epiphysis - end medullary cavity - canal periosteum - covering endosteum - canal lining articular cartilage - on ends of bones for smooth movement marrow - yellow - fat storage - red - blood cell formation
Epiphyseal plate or cartilage is between diaphysis and epiphysis - and is an area of growth. After growth has stopped (cartilage turned to bone) the epiphyseal line marks the area.
osteoclasts - bone destroying cells The endosteum contains: osteoclasts - bone destroying cells osteoblasts - bone forming cells
The bone around the diaphysis is compact. The epiphysis have thin layer of compact inside is spongy.
Flat bones are 2 thin plates of compact bone with spongy bone between. Red marrow is located in spongy area.
Histology of Compact Bone
Harversion System = Osteon Lamellae Haversion Canal Osteocyte in lacunae
osteocyte in lacunae canaliculi
Osteocyte Lacunae Canaliculi
Histology of Compact Bone very dense to naked eye structural unit is Haversian system or osteon lamellae - concentric rings of hard matrix around a central canal - Haversian canal osteocytes are between lamella in cavities called lacunae hair-like canaliculi connect lacunae to each other and Harversian canal allows nutrients, wastes, and gases to travel from blood vessels in Haversian canal to cells = diffusion
Spongy Bone Tissue bone is arranged in trabeculae - partitions in an organ arranged so stress points are well supported contain irregular lamellae, osteocytes, and canaliculi lack Haversian systems nutrients diffuse through canaliculi from marrow spaces between trabeculae
Chemical Composition of Bone organic - 1/3 of mass - cells (blast, cytes, clasts) - organic matrix - tensile strength inorganic - 2/3 of mass - inorganic mineral salts calcium phosphate calcium hydroxide calcium carbonate - provides hardness - bone is extremely strong but not brittle
If mineral removed, bone is too bendable If collagen removed, bone is too brittle