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Bone Tissue
Bones
| Question | Answer |
|---|---|
| What are 6 kinds of bones? | long, short, flat, irregular, sutural, sesamoid |
| Long bones? | have an axis; they are longer than wide |
| Example of long bones? | femur, humerus, radius |
| short bones | usually cube shaped |
| example of short bones? | wrist bones & ankle bones |
| flat bones | generally thin. 2 plates of compact bone with spongy bone in between |
| example of flat bones? | cranial bones, sternum, ribs, scapula |
| irregular bone | complex shaped bones |
| example of irregular bones? | vertebrae, all facial bones |
| sutural bones | in between cranial bones |
| explain how a sutural bone occurs | you have two cranial bones divided by a suture. the suture delineates left & right side, however if one side or the other breaks off, it makes a sutural bone |
| sesamoid bone | forms within a tendon in response to stress |
| example of sesamoid bone | patella |
| what does the sesamoid bone actually do? be specific | the presence of a sesamoid bone holds the tendon farther away from center of the joint. Prevents tendon from flattening into the joint & gives more leverage |
| draw a long bone and label its parts | include epiphysis & diaphysis, epiphyseal plate/line, compact bone (thick in diaph. & thin in epiph), spongy bone, medullary cavity, yellow marrow, endosteum, periosteum (inner & outer), red marrow, nutrient foramen, hyaline cartilage |
| epiphysis | expanded head at each end of shaft |
| epiphyseal plate | in children & adolescents, it is an area where long bones grow in length |
| epiphyseal line | in adults, when bones have stopped growing, it marks where epiphyseal plate used to be |
| spongy bone | i.e. "cancellous bone", a more loosely organized form of bone tissue found in central space of epiphyses. (also a narrow zone just inside compact bone of shaft). SB is always enclosed by more durable compact bone. contains red marrow (site of hemopoiesis) |
| compact bone | stronger, more durable bone. much of bone is composed of an outer shell of dense white osseous tissue called compact bone |
| medullary cavity | hollow space enclosed by compact bone. has yellow marrow |
| endosteum | delicate, single layer of cells that lines everything inside bone. lines medullary cavity, covers honeycombed surfaces of spongy bone, lines canal system in compact bone |
| diaphysis | shaft of long bone |
| nutrient foramen | minute holes through which blood vessels penetrate into bone |
| yellow marrow | found in medullary cavity. has adipose cells, which stores triglycerides i.e. stores energy |
| sharpey fibers | perforating collagen fibers of the outer periosteum that are continuous with the tendons that bind muscle to bone. They penetrate into compact bone matrix. help provide strong attachment & continuity from muscle to tendon to bone. |
| periosteum | a sheath that forms external covering of bone. |
| what are two layers of periosteum and what are they important for? | outer layer= tough, fibrous layer of collagen, important for protection of the bone. inner layer = delicate, single layer of bone-forming cells. important for growth/rebuilding of bone/healing of fractures |
| articular cartilage | the joint surface where one bone meets another is covered with a layer of hyaline cartilage called the articular cartilage. |
| spongy bone: what does it provide? | has red marrow where hemopoiesis (hematopoiesis) takes place. |
| hemopoiesis | production of any of the formed elements in the blood. |
| red marrow in infants & fetuses? | in fetuses & infants, they have red bone marrow almost everywhere (they are trying to make lots of blood!). |
| Exceptions to red marrow in infants & fetuses? | exception: they don't make blood in hyoid bone & middle ear bones |
| red marrow in adults? | in adults, there is yellow marrow in the shaft of long bones. Exception: there is red bone marrow (to make formed elements in the blood) in the proximal head of humerus & femur, skull, sternum, ribs, pelvis, vertebrae. |
| yellow marrow converts? | yellow marrow can convert back into red marrow in cases of severe or chronic anemia (need more RBCs) |
| what are four types of bone cells? | osteoprogenitor cell, osteoblast, osteocyte, osteoclast |
| draw an osteoprogenitor cell | just a flattish blob w nuclei. |
| draw an osteoblast | draw two cells: one is slightly cuboidal with nucleus & lots of ER, then turns to a cytoplasmic extension cell , make sure you show it secreting its matrix. |
| draw an osteocyte | draw a cytoplasmic extension cell with nucleus, showing it trapped in matrix it just made (maybe outline its lacuna & its canaliculi)> |
| what is ER of osteoblast for? | lots of ER to synthesize the organic matrix |
| osteoprogenitor cell | stem cells that form bone lining & give rise to most other bone cell types. found in endosteum & inner layer of periosteum. can undergo mitosis & are constantly multiplying to help the delicate linings maintain their cell supply. |
| osteoblast | cells that synthesize & secrete the organic matrix. roughly cuboidal & line up on bone surface as single layer under E & P. can't undergo mitosis, so the only way new ones are generated is through mitosis & differentiation of osteoprogenitor cells |
| how do osteoblasts function & change their shape? | As they begin to secrete collagen & other organic molecules (= matrix), they change shape, sending out cytoplasmic extensions to connect w neighboring cells (B4 they are completly surrounded 3D w matrix) This allows them to b in contact w xtracellular env |
| osteocyte: where does it come from, where does it live | a former osteoblast that has finished secreting the org matrix & having completely surrounded itself it becomes trapped. They live in tiny cavities called lacunae, which are interconnected by slender channels called canaliculi (these house their cyto. ext |
| how do osteocytes exchange materials extracellularly? | so these "cavities" (lacunae) and interconnecting "channels" (canaliculi) provide space for extracellular fluid to bathe the osteocytes & provide routes for 02 & CO2 etc. to reach all osteocytes. |
| how do osteocytes exchange materials intracellularly? | osteocytes from neighboring lacunae form gap junctions with eachother, facilitating easy movement of materials from cell to cell. |
| canaliculi | tiny slender interconnecting "channels" of extracellular fluid that house the cytoplasmic extensions of osteocytes. |
| osteocyte: what is its function | they maintain their daily cellular activities of bone tissue, exchanging nutrients & wastes with other cells and blood. |
| osteoclast | bone dissolving cell that develps from fusing hemopoietic stem cells. multinucleated & very lg reside in depression it has etched into the bone surface (Howship's lacunae). secretes acids & enzymes to break down the bone, releasing mineral salts- b plasma |
| bone resorption | process of dissolving bone. it releases minerals into the blood and makes them available for other uses. carried out by osteoclasts. |
| Howship's lacunae | osteoclasts reside here, it is a depression they etch into the surface of bone as they dissolve it. |
| what do osteoclasts use to dissolve bone? | osteoclasts make citric acid, lactic acid & collagenase, also utilizes hydrogen ion pumps in their ruffled border. this makes very acidic solution to dissolve bone. (pH of Howship's lacuna = 4) |
| ruffled border | side of osteoclast facing the bone surface. has many deep infoldings in plasma membrane, which increases cell's surface area & enhances efficiency of bone resorption |
| two components of bone matrix? | organic component (makes up 1/3 of matrix) & inorganic component (makes up 2/3 of matrix) |
| where does organic component of bone matrix come from? | synthesized by osteoblasts |
| where does the inorganic component of bone matrix come from? | not made by cells. for the most part it is brought in by the blood supply |
| what makes up organic matrix, specifically? | collagen & chondroitin sulfate (for support) |
| what makes up organic matrix, in general? | glycoproteins, proteoglycans, glycosaminoglycans |
| osteoid | the organic matrix of bone |
| how does collagen function in matrix of bone? | like steel bars in concrete, collagen gives flexible strength to the matrix. Allows bone to be somewhat flexible. If you remove collagen, bone becomes brittle. if you remove mineral, bone will bend |
| what makes up the inorganic component of matrix? | 85% hydroxyapatite, 10% calcium carbonate, magnesium, flouride, sodium, potassium, and others. |
| hydroxyapatite | calcium phosphate salt |
| how does bone get hard? | as they drift into the matrix from blood supply, inorganic minerals harden the soft organic matrix. |
| why is normal blood calcium concentration level important? | normal blood Ca concentration level is important for calcium-dependent physiological processes |
| what are calcium-dependent physiological processes? what is calcium important for? | contraction of muscle, nerve transmission, blood clotting, used as a cofactor, plays a part in the "2nd messenger" for some hormones, and it is determines permeability properties of cell membranes. |
| explain how blood calcium concentration level determines permeability properties of cell membranes? excitable neurons lead to muscle tremors, muscle spasms & muscle tetany | the conc. of calcium in the blood can affect which materials go through a cell membrane. if you have low Ca, tends to incr. perm. of Na thru cell membrane. If Na flows in, it changes membrane potential & makes xtra xcitable neurons. |
| xtra excitable neurons caused by low calcium concentration in blood: what can this lead to? | muscle tremors, muscle spasms, muscle tetany |
| muscle tetany | inability of a muscle to relax |
| compact bone histology | contains few spaces & forms outer shell of all bones. forms bulk of diaphy. in long bones, helps them resist the stress that is put on them. consists of onion-like layers of matrix (lam) that R concentrically arranged around a H.C. & connected by canalicu |
| Volkmann's (perforated)canal | along their length, haversian canals are joined by transverse passages called Volkmann's (perforating) canals. (in compact bone) |
| haversian (central) canal | center of an osteon, houses blood vessels & nerves |
| lamellae | onion-like layers of matrix connected w eachother by canaliculi |
| endosteum inside compact bone? | lines central & perforating canals |
| osteon | a haversian canal & its surrounding concentric lamellae constitute an osteon- the basic structural unit of compact bone |
| concentric lamellae | layers of matrix found in osteon |
| circumferential lamellae | 3 or 4 layers of matrix that surround the outside boundary of compact bone; lines inner periosteum. |
| pattern of collagen fibers in compact bone matrix? | collagen fibers "corkscrew" down the matrix of a given lamella in a helical arrangement (like threads of a screw). The helices coil in one direction in one lamella & in the opposite direction in the next. this enhances the bone's strength |
| insterstitial lamellae | irregular regions of compact bone; remains of old osteons that were partially destroyed during previous bone resorption |
| how does blood go into a bone? | blood comes in through nutrient foramen & immediately enters Volkmann's (perforating) canal |
| draw the path of blood through compact bone | start at perforating canal, then draw series of Volkmann's and haversian canals (volkmann, letter H, volkmann, spongy bone) |
| draw an osteon | draw haversian canal w blood vessel inside, two columns of osteocytes (3 rows of "spiders" make sure the legs touch eachother,) draw just two osteocytes to left, label whole thing as osteon |
| another name for spongy bone | cancellous bone |
| spongy bone histology | consists of an irregular latticework of delicate slivers of bone called trabeculae. It is a mesh of trebeculae without "true" osteons. Covered with endosteum & permeated by spaces filled with red marrow. Trab= provides framework of support 4 these tissues |
| blood vessels in spongy bone? | blood vessels here weave around trabeculae. |
| how is trabeculae oriented | trabeculae develop along the lines of mechanical stress applied by the weight of the body, and will realign themselves if such stress on the bone changes. |
| where is spongy bone found? | short bones, flat bones, irregular bones & epiphyses of long bones. |
| trabeculae | thin, delicate slivers of bone tissue arranged in irregular latticework in spongy bone |
| which cells have a ruffled border and secrete citric acid, lactic acid, collagenase | osteoclasts |
| the marrow cavity (medullary cavity) of an adult bone may contain | yellow marrow; adipose tissue |
| the spurt of growth in puberty results from cell proliferation in ____ | the ephiphyseal plate |
| osteoclasts are most closely related, by common descent, to _____ | blood cells |
| which of these is NOT an effect of PTH: -rise in blood phosphate level -reduction of calcium excretion -increased intestinal calcium absorption -increased number of osteoclasts -increased calcitriol synthesis | rise in blood phosphate level |
| a child jumps to the ground from the top of a jungle gym. his leg bones do not shatter mainly because they contain _____ | collagen fibers |
| one long bone meets another at its _____ | epiphysis |
| One sign of osteoporosis is _____ | a bone fracture |
| calcium phosphate crystallizes in bone as a mineral called ______ | hydroxyapatite |
| Osteocytes contact each other through channels called _____ in the bone matrix | canaliculi |
| _____ are cells that secrete collagen and stimulate calcium phosphate deposition | osteoblasts |
| the most active form of vitamin D, produced mainly by kidneys, is ____ | calcitriol |
| the most common bone disease is | osteoporosis |
| a pregnant, poorly nourished woman may suffer a softening of the bones called ______ | osteomalacia |
| calc- | calcium (calcitonin) |
| -clast | destroy (osteoclast) |
| -malacia | softening (osteomalacia) |
| myelo- | marrow (osteomyelitis) |
| ortho- | straight (orthopedics) |
| osse- | bone (osseous) |
| osteo- | bone (osteocyte) |
| -physis | growth (epiphysis) |
| spic- | dart (spicule) |
| topo- | place (ectopic) |
Created by:
kalmetina
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