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139 Cards in this Set
- Front
- Back
- 3rd side (hint)
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functions of bone tissue (2)
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-bear heavy loads and stresses
-calcium reservoir |
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hydroxyapatite
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calcium phosphate crystal in bone matrix
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consequences of mineralized matrix (4)
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-gains hardness
-loses flexibility -reduced diffusion of nutrients -no internal (interstitial) growth |
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macroscopic appearance of immature bone
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cancellous (spongy)
network of bony trabeculae |
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microscopic appearance of immature bone
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woven, disorganized
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immature bone tissue (when does it develop, characteristics)
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-primary bone or woven bone
-initially develops in embryo (replaced by mature bone) -not strong |
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mature bone tissue (characteristics)
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-secondary bone or lamellar bone
-replaces immature bone quickly -stronger |
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mature bone matrix (compared with immature)
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-more mineralized
-has lamellar (layered) structure |
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two varieties of mature bone
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-compact (dense)
-cancellous (honey-comb) |
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diaphysis
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shaft of a long bone
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epiphysis
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ends of long bone
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diaphysis (inside)
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marrow cavity
-contains yellow or red bone marrow |
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epiphysis (inside)
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filled with cancellous bone
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mature bone walls are made of..
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compact bone
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mature bone inside made of..
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cancellous bone/spongy
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histological preparations of bone (2)
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-dried prep
-decalcified prep |
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dried preparation of bone
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-dry, white, unstained
-water and organic material NOT present -only mineral present |
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decalcified preparation of bone
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-purple (collagen still present), acidophillic
-mineral is removed -organic material remains |
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extracellular matrix of mature bone (components, abundance)
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-most abundant
-consists of ground substance and fibers |
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cells of mature bone
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osteocytes
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EC matrix of mature bone: organic component (ground substance)
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-similar to cartilage
-has proteoglycan aggregates |
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EC matrix of mature bone: organic component (fibers)
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-collagen type 1
-they are encrusted with minerals (why bone is "mineralized") -makes up 90% of organic component |
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EC matrix of mature bone: organic component (proteins)
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-osteocalcin
-osteonectin --mediate binding of minerals to collagen type 1 |
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EC matrix of mature bone: inorganic component (components)
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hydroxyapatite
-deposited on surface of collagen type 1 fibers; makes them hard |
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EC matrix of mature bone: inorganic component (weight)
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65% of dry weight
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EC matrix of mature bone: organic component (weight)
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35% of dry weight
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3 types of lamellae
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-concentric
-interstitial -circumferential |
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concentric lamellae
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-most important
-form haversian systems -where stresses are felt -"structural unit" of compact bone |
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Haversian Systems
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-cylinders of compact bone
-formed by concentric lamellae |
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elevated and solid, may or may not be clearly demarcated; deeper in dermis, > 2 cm
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tumor
a big nodule 2nd pict result of a av malformation |
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interstitial lamellae
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-whatever is left between osteons-remnants of old osteons
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haversian canal
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-center of haversian system
-where blood vessels are found |
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volkmann's canal
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-interconnects haversian canals
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mature cancellous bone
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-also lamellar
-not thick enough for osteons-only have interstitial lamellae |
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osteocytes (where)
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-mature bone cells embedded in mineralized matrix
-occupy lacunae |
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osteocytes (function)
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-maintain the extracellular matrix of bone tissue
-secrete the components of matrix for bone maintenance -cannot proliferate |
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osteocytes (structure)
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-elongated
-cytoplasm has filipodia -no basement membrane |
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filipodia
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-extend from osteocytes
-connect with other filipodia=allows communication with surrounding osteocytes |
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lacunae
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spaces in matrix where osteocytes are embedded
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canaliculi
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spaces in matrix where filipodia are embedded
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gap junction (function and location)
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-located between filipodia, connects cytoplasm
-communication junction |
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gap junction (structure)
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-made up of many connexons
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connexon pore
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-transmembrane pore constructed from 6 subunits of the protein connexin
-makes up a gap junction -is permeable |
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periosteum (location and function)
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-connective tissue covering mature bone tissue
-performs appositional growth |
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periosteum (2 layers)
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-fibrous layer
-osteogenic (cellular) layer |
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fibrous layer of periosteum
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-outer layer
-relatively thick -acidophillic-pink -collagen type 1 fibers -fibroblasts |
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osteogenic layer of periosteum
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-inner layer
-thick -contains lots of active osteoprogenitor cells -very few if any collagen type 1 |
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osteoprogenitor cells
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-in osteogenic layer of periosteum
-fusiform shape -no basement membrane -rapidly divide -differentiate into osteoblasts |
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osteoblasts
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-young bone cells
-secrete all organic components of matrix -mineralize the matrix -round/cuboidal -cannot divide |
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appositional growth
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-bone grows in thickness at the periosteum
-new matrix put on old one -single row of osteoblasts |
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osteoblasts produce new bone matrix in two steps
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1. secretion of osteoid
2. mineralization |
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Osteoid (components)
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all organic components of the matrix
-ground substance -collagen type 1 fibers -osteocalcin -osteonectin matrix vesicles |
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osteoid matrix vesicles
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-calcium and phosphate ions
enzymes: -alkaline phosphatase -pyrophosphatase |
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osteoid mineralization
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-begins several days after osteoid production
-hydroxyapatite crystals begin to form in matrix vesicles -crystalization spreads to collagen type 1 fibers -mineralized bone is very acidophillic |
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osteocalcin and osteonectin
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mediate crystalization of collagen type 1 fibers
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osteocyte
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-once osteoblast is embedded in immature bone
-replaces immature bone with mature bone tissue |
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osteoblasts (lay down)
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immature bone tissue in two steps
1. secrete osteoid 2. mineralization |
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types of ossification (2)
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1. intramembranous ossification
2. endochondral ossification |
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endochondral ossification center
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-places where cartilage is replaced by bone tissue
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hypertrophy
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enlargement of cell
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2 places where cartilage remains
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1. articular cartilage
2. epiphyseal plate |
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articular cartliage
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-thin band of cartilage that covers the surface of the epiphysis
-provides smooth surface between bones -always remains as long as bone is healthy |
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epiphyseal plate
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-thick plate of cartilage that remains between the diaphysis and the epiphysis
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periosteal bone collar (where)
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established around the diaphyseal portion of a long bone
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growth of endochondral bone begins..
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during 2nd trimester (12 weeks) of fetal life and into early adulthood
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lengthwise growth of bone
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-through the internal growth of epiphyseal plate cartilage
-begins near the center of the plate and proceeds outward toward the primary ossification center |
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lengthwise bone growth (5 distinct layers)
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1. zone of reserve cartilage
2. zone of proliferation 3. zone of hypertrophy 4. zone of calcified cartilage 5. zone of resorption |
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zone of reserve cartilage
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-population of chondrocytes
-NOT dividing |
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zone of proliferation
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-isogenous groups (division occuring)
-cells actively produce collagen II and XI |
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zone of hypertrophy
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-contains hypertrophic cartilage cells
chondrocytes: -remain active -secrete type I and X collagen -secrete VEGF |
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zone of calcified cartilage
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-hypertrophied cells begin to degenerate
-cartilage matrix becomes calcified -scaffold for new bone -chondrocytes (in more proximal part) undergo apoptosis |
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zone of resorption
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-calcified cartilage in direct contact with connective tissue of marrow cavity
-small blood vessels invade (source of osteoprogenitor cells), then differentiate into osteoblasts -new bone formed -has mixed spicules |
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epiphyseal line
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-remnant of epiphyseal plate
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bone resorption (what is it)
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-cellular breakdown of the bone matrix
-important part of bone remodeling |
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bone resorption (by who)
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-done by osteoclasts
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osteoclasts
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-members of mononuclear phagocytic system
-very large -multinucleated -rich in lysosomes -developed from bone marrow cells |
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resorption bays
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-Howships lacunae
-depressions of bone matrix -where active osteoclasts lie |
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ruffled border
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-resorbing surface of active cell
-highly folded surface (microvillus structures) -surrounded by cytoplasmic ring |
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clear zone
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-cytoplasmic ring that surrounds the ruffled border of osteoclasts
-contains band of actin filaments that seal the resorption bay |
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parathyroid hormone
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-secreted by parathyroid gland
-secretion stimulated by decline in blood calcium -increases osteoclast activity |
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calcitonin
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-secreted by thyroid gland
-secretion stimulated by increase in blood calcium -decreases osteoclast activity (inhibits bone resorption) |
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Rickets
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-children
-inadequate mineralization of osteoid (soft bone) -lack of Ca/P, vitamin D |
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osteomalacia
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adult rickets
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osteoporosis
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-decrease in bone density
-brittle bone -prevalent in post menopausal women (decrease in estrogen-inhibits osteoclasts differentiation) |
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muscle cells also known as
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muscle fibers or myofibers
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sarcoplasm
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cytoplasm of muscle cells
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sarcolemma
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plasma membrane of muscle cells
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external lamina
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basal lamina of the basement membrane of muscle cells
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endomycium
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loose connective tissue that supports the basement membrane
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striated muscle (2 classes)
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-skeletal
-cardiac |
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nonstriated muscle (1 class)
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smooth muscle
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skeletal muscle classified as 3 types of muscle
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1. striated
2. somatic (outer body wall) 3. voluntary |
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characteristics of skeletal muscle fibers
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-cylindrical, linear cells
-unbranched -extend from origin to insertion -each cell is multinucleated -nuclei on periphery of cell -each cell separated from other cells by endomycium -cells do not communicate with each other -each cell has own innervation |
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myoblasts
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-can divide
-fuse and form muscle fiber |
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true syncytium
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each muscle fiber has a "true fusion"
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fascicles
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bundles of muscle fibers
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perimycium
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loose and dense connective tissue that wraps each fascicle
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epimycium
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dense connective tissue that wraps around all of the fascicles
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organ
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bundles of parallel muscle fascicles
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fascicle
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bundles of parallel muscle fibers
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Type I skeletal muscle fiber
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SLOW OXIDATIVE
-small fibers -rich in mitochondria and myoglobin -slow-twitch, fatigue resistant -repetitive contraction |
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Type IIa skeletal muscle fiber
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FAST OXIDATIVE GLYCOLYTIC
-medium fibers -intermediate mitochondria and myoglobin -lots of glycogen storage -fast-twitch, fatigue resistant |
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Type IIb skeletal muscle fiber
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FAST GLYCOLYTIC
-large fibers -poor in mitochondria and myoglobin -fast-twitch, fatigue prone |
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satellite cells
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-stem cell population of skeletal muscle
-found under basement membrane |
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actin and myosin
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contractile proteins
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A band
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dark striations
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I band
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light striations
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sarcomere
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unit of muscle contraction
z line to z line |
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thick filaments
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stacked down the center of each sarcomere
create each A band |
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thin filaments
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interdigitate with the thick filaments
6 thin: 1 thick -only on I band |
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H zone
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region down the center of the A band where there is no overlap of thin and thick filaments
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thick filament component
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consists of many myosin molecules
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thin filament components (3)
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-actin
-tropomyosin -troponin |
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actin
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-contractile protein
-has binding sites for myosin heads |
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tropomyosin
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-actin-binding protein
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troponin
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-tropomyosin regulatory protein
-binding sites for Ca |
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titin
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protein that links thick filaments to Z line
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alpha-actin
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protein that links thin filaments to Z line
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myomesin
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protein that holds thick filaments in register
-creates M line |
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sarcolemma function
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-excitable membrane
-conducts action potential along surface of the cell |
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Transverse tubules (T tubules)-where
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-invaginations of the sarcolemma
-one at each A band/I band junction |
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Transverse tubules (T tubules)-function
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-excitable membrane
-conducts action potential into the interior of the cell |
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sarcoplasmic reticulum (where)
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-extends from t-tubule to t-tubule
-completely covers each myofibril |
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sarcoplasmic reticulum (function)
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-Ca storage (used for contraction)
-stored in the terminal cisternae |
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terminal cisternae
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-end "sacs"
-located at each end of the reticulum |
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neuromuscular junction
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point of innervation of each muscle fiber
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motor end plate
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neural side of the neuromuscular junction
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terminal bouton
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-presynaptic membrane
-neurotransmitter vesicles containing acetylcholine -covered by scwhann cell |
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postsynaptic membrane
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-at sarcolemma
-folded |
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primary cleft
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main cleft that runs along the presynaptic membrane
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secondary synaptic cleft
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spaces within the junctional folds
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external lamina of neuromuscular junction
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-runs along primary cleft and folds into each secondary cleft
-rich in acetylcholinesterase |
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acetylcholine receptors
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embedded within postsynaptic membrane
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cardiac muscle cell characteristics
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-NOT true synctia
-single nucleus, centrally located -fibers are cylindrical and short -branched - |
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cardiac muscle regarded as...
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"functional syncytium"
-cells are branched -specialized intercellular junctions -all contracts at the same time (heart beat) |
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intercalated disks (functions-2)
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1. adhere cells together
2. allows chemical and electrical communication |
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intercalated disks (components-2)
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1. transverse component
2. lateral component |
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transverse component of intercalated disks
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-designed for adhesion
-adherens junctions (zonula and macula adherens) |
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lateral component of intercalated disks
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-gap junctions-permits action potential to jump cells (electrical synapse)
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