The Skeletal System. Chapter 7a. Skeletal System Introduction Functions of the skeleton Framework of bones The skeleton through life

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1 The Skeletal System Skeletal System Introduction Functions of the skeleton Framework of bones The skeleton through life Chapter 7a Support Protection Movement Storage areas Minerals Lipids Hemopoiesis Red marrow Functions of the Skeleton Histology of Bones Bone = osseous tissue (connective tissue) Intercellular substance Calcium phosphate crystals Collagenous fibers Diaphysis shaft Epiphysis extremity of bone Articular cartilage covers epiphysis Periosteum covering around surface of bone Medullary cavity marrow cavity in diaphysis Endosteum lines medullary cavity Anatomy of a Long Bone Two layers Outer layer Fibrous connective tissue Inner layer Osteoblasts The Periosteum 1

2 The Endosteum Structure of Bone Tissue Single layer Osteoclasts Osteoblasts Pores Living cells Channels for blood vessels Decrease weight of bone Degree of porosity Spongy bone Compact bone Haversian system (Osteon) Haversian canals Lacunae Canaliculi Compact Bone Spongy Bone Composed of trabeculae Penetrated by blood vessels from periosteum Ossification Embryo skeleton Begins as cartilage & membrane Bone formation begins about 6 weeks after fertilization Ossification 1 st stage embryonic cells migrate into future bone sites Become chondroblasts or Become osteoblasts 2

3 Endochondral Ossification Occurs within a hyaline cartilage model Occurs in most bones of the body Periosteum forms at about week 8 Calcification begins in center of diaphysis Primary ossification center Secondary ossification centers at epiphyses Medullary cavity forms Endochondral Ossification Endochondral Ossification Fetus. 10 weeks Fetus, 16 weeks Remaining Cartilage Articular cartilage Epiphyseal plate Bone grows in length 3

4 Remodeling Homeostasis Different rates in body Balance between osteoclasts and osteoblasts Factors affecting bone growth Calcium & phosphorus in diet Vitamins A, C, & D Hormones Fracture Repair Hematoma formation Formation of fibrocartilagenous callus Formation of bony callus Remodeling of bony callus Fracture Repair Disorders Vitamin deficiencies Scurvy Rickets Osteoporosis Scurvy Scurvy Blood Vessels 4

5 Rickets Osteoporosis Organization of the Skeletal System Axial skeleton Skull Vertebral column Thoracic cage Appendicular skeleton Pectoral girdle Upper limbs Pelvic girdle Lower limbs The Human Skeleton Cranium Protects brain Facial bones Skull Protect sense organs Vertebrae Cervical Thoracic Lumbar Sacral Sacrum Coccyx Function Protect spinal cord and nerves Vertebral Column 5

6 Intervertebral Discs The Atlas and Axis Vertebrae Separated by intervertebral discs A Typical Vertebra The Sacrum and Coccyx Sacrum Several fused vertebrae Coccyx Rudimentary tailbone Ribs (12 pairs) Articulate with vertebrae Sternum (breastbone) Function Protect underlying organs Thoracic Cage Scapula (shoulder blade) Clavicle (collar bone) Attached to posterior ribs and sternum Function Connects bones of arms to axial skeleton Aids in arm movements Pectoral Girdle 6

7 Upper Limbs The Radius and Ulna Humerus Radius Ulna Carpals Metacarpals Phalanges Bones of the Wrist and Hand Pelvic Girdle Coxal (hip) bones Ileum Ischium Pubis Attached to sacrum and coccyx Function Connect bones of legs to axial skeleton The Pelvic Girdle Femur Tibia Fibula Patella Tarsals Metatarsals Phalanges Lower Limbs 7

8 The Femur Bones of the Lower Leg The Patella Bones of the Foot 8