Chapter 6: Skeletal System

Chapter 6 Skeletal system: includes the bones of the skeleton and the cartilages, ligaments, and other connective tissues that stabilize or interconnect the bones Osseous Tissue = Bone Tissue Bone Classification Functions of the Skeletal System: 1. Support 2. Storage of minerals and lipids 3. Blood cell production 4. Protection 5. Leverage · sutural bones · flat bones · short bones · sesamoid bones · irregular bones · long bones Long Bones Epiphysis: the very top and bottom ends of the bone ↳ contains spongy bone Diaphysis: the tubular shaft ↳ the walls of the diaphysis is compact bone Metaphysis: a narrow zone between the epiphysis and diaphysis Bone Markings · projections, openings, and depressions · projections form where muscles, tendons, and ligaments attach and where adjacent bones form joints · openings and depressions are sites where blood vessels or nerves lie alongside or penetrate the bone Bone Tissue: a supportive connective tissue containing specialized cells and a matrix containing extracellular protein fibers in a ground substance · The matrix of bone is very dense due to deposits of calcium salts around protein fibers · The matrix contains bone cells (osteocytes) within pockets called lacunae · Canaliculi are narrow passageways between the lacunae and blood vessels that form a branching network to exchange nutrients, wastes, and gases · a periosteum covers the outer surface of bones (except at joints) · Calcium phosphate makes up 2/3 of the weight of bone · 1/3 of the weight of bone is made up by collagen fibers Bone Cells ① Osteogenic cells (stem cells) ↳ also known as mesenchymal/osteoprogenitor cells ↳ Osteogenic cells divide to create Osteoblasts ② Osteoblasts ↳ immature bone cell ↳ osteogenesis/ossification: the process of bone formation ↳ secretes osteoid that becomes calcified bony deposits ③ Osteocytes ↳ mature bone cells ↳ they maintain the protein and mineral content of the surrounding matrix ↳ Osteocytes help repair damaged bone by coming out of lacunae and un-specialize ④ Osteoclasts ↳ osteolysis: the process of breaking down and absorbing the bone matrix ↳ involves the regulation of calcium and phosphate ion concentrations Types of Bone: 1. Compact Bone 2. Spongy Bone Compact Bone · functional unit is the osteon · Dense and hard · tends to make up the shaft in long bones · Found in areas where weight is usually in one direction In compact bone, osteocytes are in concentric layers around a central canal. Within the canal is blood vessels, veins, and nerves. The circles around them are called lacunae. The osteon is the circular unit around the canal. Outside of the lacunae is circular lamellae, and then the periosteum surrounds that. Spongy Bone · functional units are trabeculae · trabeculae form a branching network · found in the center and ends of long bones · found in less stress areas or where stress is multidirectional · gets nutrients through red bone marrow · may also contain yellow bone marrow Periosteum: except when within joint cavities, the periosteum is the superficial layer of all bones · Made of two layers: ↳ outer layer of fibrous connective tissue ↳ inner layer of osteoprogenitor cells · Functions Yellow Bone Marrow: Storage of lipids/fats -separation and protection Red Bone Marrow: Blood cell production -point of attachment for blood vessels and sensory nerves -participates in growth and repair of bones -connects bone to the surrounding connective tissue network Endosteum: a membrane that lines the center of your bones that contains bone marrow · simple flattened layer of osteogenic cells that covers the bone matrix · at exposed sites the osteoblasts and osteoclasts can attach · active during bone growth and remodelling Bone Formation Ossification: the physical process of bone formation through osteoblasts Calcification: the deposition of calcium salts into tissues · 2 Types of Ossification: ↳ Endochondral Ossification (most common) -hyaline cartilage is replaced by bone -occurs mainly in long bones ↳ Intramembranous Ossification -bone develops straight from mesenchymal (embryonic) tissue -occurs in Flat bones and clavicles (all others are endochondral) Interstitial Growth: growth in length Appositional Growth: growth in width/thickness Bone Remodeling and Repair · Bone Remodeling: the process of recycling & renewing the organic & mineral components of the bone matrix ↳coordinated activity of osteocytes, osteoblasts, and osteoclasts ↳ can change bone thickness and strength in response to stress · Bone Repair (not tested) ↳ bone fractures · Nutritional and Hormonal Factors ↳ requires calcium and phosphorus ↳ Vitamin C and D3 ↳ review table 6-1 Calcium · skeletal tissue functions as a calcium reserve · calcium plays roles in many areas of the body so regulation of calcium must be tightly controlled · Figure 6-16 and 6-17 show how the body regulates calcium