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MC Bio 204 Ch 6

introduction to the skeletal system

QuestionAnswer
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