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MC Bio 204 Ch 6
introduction to the skeletal system
| Question | Answer |
|---|---|
| functions of the skeletal system | support, protection, assistance in movement, mineral homeostasis, blood cell production, triglyceride storage |
| hemopoiesis | the process through which red bone marrow produces red blood cells, white blood cells, and platelets |
| yellow bone marrow | C/mostly adipocytes | F/storage of triglycerides |
| five categories of bones | long, short, flat, irregular, sesamoid |
| long bones | S/shaft and two extremities | S/slightly curved for strength | EX/femur, tibia, fibula, humerus, ulna, radius, phalanges |
| short bones | A/cube-shaped | EX/most carpals, tarsals |
| flat bones | SF/provide extensive surfaces for muscle attachment | SA/generally thin | EX/cranial bones, sternum, ribs, scapulae |
| irregular bones | A/complex shapes, not easily categorized | EX/vertebrae, hip bones, certain facial bones, heel bone (calcaneus) |
| sesamoid bones | EX/kneecaps; also, tiny bones only a few mm in diameter that develop in certain tendons, esp in palms and soles | F/protect tendons from excessive wear and tear |
| diaphysis | the shaft of a long bone |
| epiphyses | the proximal and distal ends of a long bone |
| metaphyses | in long bones, the regions between the diaphysis and the epiphyses; these are the regions where bone growth (in length) takes place |
| articular cartilage | thin layer of hyaline cartilage covering the part of the epiphysis where the bone forms an articulation with another bone | F/reduces friction and absorbs shock |
| periosteum | in long bones, a tough sheath of irregular CT that surrounds the bone surface wherever it is not covered by articular cartilage | CF/contains bone-forming cells that help the bone to grow in thickness |
| medullary cavity | in long bones, the hollow, cylindrical space within the diaphysis that contains yellow bone marrow in adults |
| endosteum | a thin connective tissue membrane that lines the medullary cavity; contains bone-forming cells |
| ECM of osseous tissue | C/25% water, 25% collagen [providing flexibility and tensile strength], 50% crystallized mineral salts [providing hardness] |
| osteogenic cells | L/endosteum, inner portion of periosteum, canals within bones that contain blood vessels | F/divide to form osteoblasts |
| osteoblasts | F/synthesize and secrete collagen fibers and other organic components of the ECM of osseous tissue; as osteoblasts surround themselves with ECM, they become trapped in their secretions and become osteocytes |
| osteocytes | the most numerous cells in osseous tissue | F/maintain the daily metabolism of osseous tissue, exchanging nutrients and wastes with the blood |
| osteoclasts | A/very large | C/derived from the fusion of as many as 50 monocytes (a type of WBC) | L/concentrated in the endosteum | F/break down the ECM of osseous tissue -- a process known as resorption, which is part of the normal maintenance and repair of bones |
| two major types of osseous tissue | compact and spongy |
| Volkmann's canals | aka perforating canals | in compact bone tissue, transverse canals that protrude from the periosteum; they contain blood vessels, lymphatic vessels, and nerves |
| haversian canals | aka central canals | in compact bone tissue, canals that run longitudinally -- containing blood vessels, lymphatic vessels, and nerves |
| concentric lamellae | rings of ECM that surround haversian/central canals | A/look like tree rings |
| lacunae | in compact bone tissue, small spaces that contain osteocytes | L/between concentric lamellae |
| osteon | aka haversian system | in compact bone tissue, a repeating structural unit consisting of one central canal and its concentrically arranged lamellae, lacunae, osteocytes, and canaliculi | AL/osteons are aligned in the same direction along lines of stress |
| canaliculi | in compact bone tissue, tiny channels radiating from lamellae, containing extracellular fluid | it is important that there be many of these, because diffusion through lamellae is extremely slow |
| spongy bone tissue | is not softer than compact bone tissue; called "spongy" only because of its appearance | does not contain osteons |
| trabeculae | in spongy bone tissue, these are "little beams" of irregularly arranged lamellae | S/within each trabecula are lacunae that contain osteocytes | the spaces between trabeculae are sometimes filled with red bone marrow |
| nutrient foramen | in long bones, a hole near the center of the diaphysis where the large nutrient artery and nutrient vein enter/exit [note: the femur has several nutrient arteries] |
| the two major types of bone formation | intramembranous ossification and endochondral ossification |
| intramembranous ossification | the skull and jaw form this way | steps: development of the center of ossification, calcification, formation of trabeculae, development of periosteum |
| endochondral ossification | most bones form this way | steps: dev. of the cartilage model, growth of the cartilage model, dev. of the primary ossification center, dev. of the medullary cavity, dev. of the secondary oss. centers, formation of articular cartilage + epiphyseal plate |
| epiphyseal plate | in long bones, an area of hyaline cartilage in the metaphysis; responsible for lengthwise bone growth |
| 4 zones of the epiphyseal plate | zone of resting cartilage [nearest epiphysis], zone of proliferating cartilage [here, chondrocytes are formed to replace those at the diaphyseal end], zone of hypertrophic cartilage, zone of calcified cartilage |
| epiphyseal line | in long bones of adults, a bony structure at the former site of epiphyseal plates (those plates close around age 18 in women, 21 in men) |
| how bones grow in thickness | osteoblasts in the inner layer of the periosteum secrete new ECM, creating new lamellae |
| factors affecting bone growth | adequate calcium and phosphorus in diet | vitamins A, C, B12, D, K in diet | hormones | weight-bearing exercise |
| hormones involved in bone growth | in children, insulinlike growth factors (IGFs) | in adolescents, estrogens and androgens | estrogens tend to stop lengthwise growth of long bones; this is one mechanism that accounts for women's shorter average height |
Created by:
dglenn34
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