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5 The Skeletal System 1
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Describe the purpose and components of the skeletal system
OBJECTIVES Describe the purpose and components of the skeletal system Describe bone development Cartilage model Ossification Describe the types of joints Describe selected diseases and disorders
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The Skeletal System bone cell tissue organ skeletal system
Organism (human) bone cell bone cell: nist.gov tissue organ skeletal system
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Made up of connective tissue Bones
The Skeletal System Made up of connective tissue Bones Ligaments Cartilage hard elements (calcium phosphate) contains living cell collagen fibers binds bones together strengthen joints cell: chondroblast fibers of collagen/elastin flexible; reduced friction withstands pressure
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The Skeleton Protects, Supports, and Permits Movement
Provides support for soft organs Protection of many organs Joints provide flexible movement of many parts of the body Mineral storage (calcium, phosphorus) Bone marrow: synthesis of blood cells
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Bone Contains Living Cells
In a typical long bone: Compact bone: forms shaft and ends shaft contains yellow fatty bone marrow Spongy bone: trabeculae with spaces in between Spaces contain red bone marrow- prodeces blood cells Bone cells: Osteoblast (young bone-forming cells) Osteocytes (mature bone-maintaining cells) Osteoclasts (bone crunching cells/dissolve bones) Periosteum: connective tissue covering
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lacuna. Osteocytes remain in contact with each other by
Figure 5.1 Central canal Osteon Osteocytes A photograph of an osteon of compact bone showing osteocytes embeded within the solid structure. Osteocyte Lacuna Osteon Spongy bone (spaces contain red bone marrow) Epiphysis Canalicula A single osteocyte in a lacuna. Osteocytes remain in contact with each other by cytoplasmic extensions into the canaliculi between cells. Compact bone Yellow bone marrow Blood vessel Diaphysis Figure 5.1 Structure of bone. Periosteum Central cavity (contains yellow bone marrow) Spongy bone Compact bone Epiphysis Blood vessels and nerve in central canal Osteoblasts A closer view of a section of bone. Compact bone is a nearly solid structure with central canals for the blood vessels and nerves. A partial cut through a long bone. 7
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Structure of Bone (Ends) (Shaft) Figure 5.1
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Bone Development Begins in the Embryo
Early fetal development: cartilage model forms Formed by chondroblasts (cartilage-forming cells) Later fetal development: osteoblasts replace cartilage with bone Childhood: primary and secondary ossification sites formed Adolescence: elongation at growth plates
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long bones move farther apart and osteoblast activity continues just
Figure 5.2 Adolescence Cartilage growth plate Childhood Fetus: At 2–3 months Fetus: First 2 months Developing periosteum Compact bone containing osteocytes Blood vessel Chondroblasts form hyaline cartilage, creating a rudimentary model of future bone. The periosteum begins to develop and cartilage starts to dissolve. Newly developing blood vessels transport osteoblasts into the area from the periosteum. Osteoblasts secrete osteoid and enzymes, facilitating the deposition of hard hydroxyapatite crystals. Figure 5.2 How bone develops. Cartilage growth plate The growth plates in long bones move farther apart and osteoblast activity continues just below the periosteum. The bone lengthens and widens. 10
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How long bones increase in length
Figure 5.3 How long bones increase in length Osteoblasts convert cartilage to bone at the inner surface Chondroblasts deposit new cartilage at the outer surface Joint cartilage Figure 5.3 How long bones increase in length. Growth plate 11
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Animation: Bone Growth Right-click and select Play
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Mature Bone Undergoes Remodeling and Repair
Remodeling: changes in shape, size, strength Dependent on diet, exercise, age Weight-bearing exercise increases overall bone mass and strength Bone homeostasis depends upon balance of osteoblast and osteoclast activity Bone cells regulated by hormones Parathyroid hormone. (PTH): removes calcium from bones Calcitonin: adds calcium to bones Osteoporosis: loss of bone mass due to prolonged imbalance of osteoblast and osteoclast activity
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The Skeletal System Skeleton Axial Appendicular Skull ribs sternum
Cranium Maxilla Mandible Clavicle Sternum Ribs Humerus Vertebrae Ulna Radius Coxal bone Sacrum Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges Carpals Metacarpals Scapula Axial Appendicular Skull ribs sternum vertebral column pectoral girdle pelvic girdle upper limb lower limb Figure 5.5
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The Skeleton Protects, Supports, and Permits Movement
206 bones Four types of bones Long (bones of limbs and fingers) Short (wrist bones) Flat (cranial bones, sternum, ribs) Irregular (hip bone, verterbrae)
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Skull Cranial bones protect brain facial bones
Temporal bone Parietal bone Skull Cranial bones protect brain facial bones Include maxilla & mandible (Jaw bones) Frontal bone Sphenoid bone Ethmoid bone Lacrimal bone Nasal bone Zygomatic bone Maxilla Occipital bone Mandible External auditory meatus Q: What is the purpose of the foramen magnum? Maxilla Zygomatic bone Palatine bone Sphenoid bone Vomer bone Foramen magnum Occipital bone Figure 5.6
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Vertebral Column 5 regions (vertebrae) protects spinal cord
intervertebral disks cushion flexibility movement 1 2 Cervical vertebrae (7) 3 4 5 6 7 1 2 3 4 5 6 Thoracic vertebrae (12) Intervertebral disks 7 8 9 10 11 12 1 2 Lumbar vertebrae (5) 3 4 5 Sacrum (5 fused) Coccyx (4 fused) Figure 5.7
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Vertebrae
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Ribs (12 pairs) Sternum (breastbone) Protect lungs, heart C7 T1
Figure 5.10 Ribs (12 pairs) Sternum (breastbone) Protect lungs, heart C7 T1 1 2 Sternum (breastbone) 3 4 Figure 5.10 Ribs. Ribs 5 6 T11 Cartilage 7 T12 8 9 Vertebral column L1 12 10 L2 11 Floating ribs 19
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Appendicular Skeleton
Pectoral girdle:shoulder clavicle & scapula humerus (upper limb) radius ulna (lower limb)
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Appendicular Skeleton
Pelvic girdle: pelvis supports upper body protects pelvic organs attachment for legs femur (thigh) tibia fibula • Pelvic girdle in women is broader, shallower (lower limb)
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Joints (Articulations) Form Connections Between Bones
Fibrous joint: Immovable Example: sutures between flat bones of skull Cartilaginous joint: Slightly movable, cartilage connection Example: joints between adjacent vertebrae Synovial joint: Freely movable Bones separated by fluid-filled cavity Hinge joint, ball and socket joint Examples???
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A cutaway anterior view of the right
Figure 5.14 Femur Thigh muscles Hyaline cartilage Tendon Posterior cruciate ligament Ligament Anterior cruciate ligament Patella Meniscus Joint capsule Meniscus Fibula Ligaments Tibia Ligament Ligaments Figure 5.14 The knee joint is a hinged synovial joint. Patella Tendon A cutaway anterior view of the right knee with muscles, tendons, and the joint capsule removed and the bones pulled slightly apart so that the two menisci are visible. A view of the knee with muscles, tendons, and ligaments in their normal position surrounding the intact joint capsule. The combination of ligaments, tendons, and muscles holds the knee tightly together. 23
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Diseases and Disorders of the Skeletal System
Sprains: Stretched or torn ligaments Heal slowly (few cells and poor blood supply) Bursitis and tendinitis: Inflammation of bursae or tendons Arthritis: inflammation of joints Osteoarthritis Rheumatoid arthritis Osteoporosis: excessive bone loss
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