Skeletal System. The skeletal System... Components

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1 Skeletal System The skeletal System... What are the general components of the skeletal system? What does the skeletal system do for you & how does it achieve these functions? Components The skeletal system includes: s s Mainly hyaline & fibrocartilage Joints Ligaments Other connective tissues Such as adipose, areolar 1

2 General Functions Functions of the Skeletal System Support against gravity Protection of soft internal organs Leverage for muscle action Insertions & origins Storage Calcium, phosphorous, other inorganic salts Fat - energy Blood cell production Structure - Macroscopic Shapes: Long Short Flat Irregular Other: Wormian (sutural) & Sesamoid s Structure: The generic The shaft of a = diaphysis The ends of a = epiphyses Covered with articular cartilage The of a = marrow Loose connective tissue Outer covering = periosteum Point of attachment for? Also location of many blood vessels & nerves Inner lining = endosteum Lines marrow Active during growth & remodeling tissue present Spongy (cancellous) in epiphyses & marrow Compact in shaft and lining periphery of 2

3 Composition of s: Microscopic Tissues Present in Dense connective tissue the periosteum An outer fibrous layer An inner cellular (osteogenic layer) Loose connective tissue marrow osseous compact & spongy cartilage hyaline Blood nervous Composition of : Microscopic Osseous or tissue has: Specialized cells 2% of weight Strong flexible matrix Calcium phosphate crystals Two-thirds of weight Collagen fibers Cells of Osseous Tissue Osteoblasts Responsible for deposition (laying down new ) = osteogenesis Osteocytes Responsible for maintenance of tissue in the lacunae of the osteon Recycle the mineral components Osteoclasts These cells are derived from white blood cells multi-nucleate cells Involved with resorption (osteolysis) by secreting enzymes that dissolve bony matrix 3

4 Organization of Tissue that is highly organized is called compact Organized units are called osteons that is not in a highly compacted structure is spongy plates are called trabeculae Trabeculae in large help to increase the strength of The Osteon Basic functional unit of compact ; columnar & cylindrical in shape Strong in long axis of Concentric layers of osteocytes Concentric layers of matrix (lamellae) Central (Haversian) canal Axial tunnel for blood vessels Perforating canal (Volkmann s) Radial tunnel for blood vessels Osteocytes communicate via small canals through the lamallae called canliculi Formation & Growth Two methods of forming s 1. Intramembranous Ossification Ossification Process of converting other tissues to Forms flat s Stem cells differentiate to osteoblasts Produces spongy, then compact 2. Endochondral Ossification Formation in 16 Week Old Fetus 4

5 Formation and Growth Endochondral Ossification Most s formed this way model replaced by Replacement begins in middle (diaphysis) Replacement follows in ends (epiphyses) Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies. Enlarging chondrocytes within calcifying matrix model Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies. Enlarging chondrocytes within calcifying matrix Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of. Epiphysis Diaphysis formation model 5

6 Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies. Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of. Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center. Enlarging chondrocytes within calcifying matrix Epiphysis Diaphysis Marrow formation Primary ossification center Blood vessel model Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies. Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of. Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center. The of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of. Enlarging chondrocytes within calcifying matrix Epiphysis Diaphysis Marrow Marrow formation Primary ossification center Blood vessel Blood vessel model Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calicifies. Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of. Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center. The of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of. Blood vessels invade the epiphyses and osteoblasts form secondary centers of ossification. Articular cartilage Enlarging chondrocytes within calcifying matrix Epiphysis Diaphysis Marrow Marrow Epiphyseal cartilage formation Primary ossification center Blood vessel Blood vessel Secondary ossification center model PLAY Endochondral Ossification 6

7 Growth Appositional vs. Transitional Growth Formation and Growth Requirements for Normal Growth Minerals Calcium, phosphate Vitamins Vitamin D 3 Vitamin C Vitamin A Hormones Growth Hormone Sex hormones, thyroid hormone, others Remodeling/Homeostasis Role of Remodeling in Support Remodeling Continuous breakdown and reforming of tissue Shapes reflect applied loads Mineral turnover enables adapting to new stresses 7

8 Remodeling/Homeostasis Homeostasis and Mineral Storage s store calcium Contain 99% of body calcium Store up to two kg calcium Hormones control storage/release PTH, calcitriol release calcium Calcitonin stores calcium Blood levels kept constant Remodeling/Homeostasis Injury and Repair Fracture A crack or break in a Steps in fracture repair Fracture hematoma Mitoses in periosteum, endosteum Internal External remodeling Immediately after the fracture, extensive bleeding occurs. Over a period of several hours, a large blood clot, or fracture hematoma, develops. fragments Fracture hematoma Dead 8

9 Immediately after the fracture, extensive bleeding occurs. Over a period of several hours, a large blood clot, or fracture hematoma, develops. fragments An internal forms as a network of spongy unites the inner edges, and an external of cartilage and stabilizes the outer edges. Spongy of internal of external Fracture hematoma Dead New Periosteum Immediately after the fracture, extensive bleeding occurs. Over a period of several hours, a large blood clot, or fracture hematoma, develops. fragments An internal forms as a network of spongy unites the inner edges, and an external of cartilage and stabilizes the outer edges. Spongy of internal of external The cartilage of the external has been replaced by, and struts of spongy now unite the broken ends. Fragments of dead and the areas of closest to the break have been removed and replaced. Fracture hematoma Dead New Periosteum Internal External Copyright 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure of 5 Immediately after the fracture, extensive bleeding occurs. Over a period of several hours, a large blood clot, or fracture hematoma, develops. fragments An internal forms as a network of spongy unites the inner edges, and an external of cartilage and stabilizes the outer edges. Spongy of internal of external The cartilage of the external has been replaced by, and struts of spongy now unite the broken ends. Fragments of dead and the areas of closest to the break have been removed and replaced. A swelling initially marks the location of the fracture. Over time, this region will be remodeled, and little evidence of the fracture will remain. Fracture hematoma External Dead New Periosteum Internal External PLAY Steps in the Repair of a Fracture 9

10 Aging and the Skeletal System Osteopenia Less than normal ossification (mineral content) in Osteopenia starts before age 40 Women lose 8% per decade Men lose 3% per decade Spongy most affected Epiphyses Vertebrae Jaws The Skeleton - Terms 10

11 The Skeleton Divisions Axial Creates the support basis for the arms and legs Provides protection for the brain & spinal cord, as well as the heart & lungs Appendicular The arms & legs Provide movement of the body Higgins - control yourself & sit down! 11