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29 Cards in this Set
- Front
- Back
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Skeletal system consists of: |
-osseous CT -hyaline cartilage- ends of long bones for synovial joints and costochondral joints, epiphyseal plate -fibrous cartilage- pubic symphysis, intervertebral discs, meniscus of knee |
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Functions of Skeletal system: |
-support- scaffold to support body -movement- points of attachment for muscles to use bones as lever system for movement -protection- skull protects brain, rib cage protects heart/lungs -mineral storage- reservoir for calcium, phosphorus, potassium, and magnesium that can be mobilized into blood stream when needed -energy storage- adipose in yellow marrow stores triglycerides that can be used in cellular respiration to make ATP during starvation -hematopoiesis- hematocytoblasts (stem cells) in red marrow produce red blood cells, white blood cells, and platelets to be released into blood stream |
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bone shapes |
long- longer than wide- extremities, humerus short- cube-like- carpal and tarsal flat- thin- cranial bones, ribs, sternum, scapula irregular- complex/odd- facial bones, ethmoid, sphenoid, vertebrae, auditory ossicles, hip bones |
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Osseous CT |
-osteoblasts create matrix then become trapped as osteocytes within the matrix in holes called lacunae -matrix consists of mineralized ground substance embedded in collagen fibers -organic matrix is the collagen & proteoglycans -inorganic matrix is the calcium phosphate crystals as hydroxyapatite -matrix in bone called osteoid |
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Cancellous bone |
-sponge appearance due to trabeculae -osteocytes in lacuna -osteoblasts found on the edges of trabeculae -covered with endosteum -holes filled with red or yellow marrow-very vascular |
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Compact bone |
-solid due to dense layers called lamellae -osteocytes are in lucunae between lamellae -osteocytes send extensions through canaliculi to check on matrix in the lamellae -in diaphysis of long bones- circumferential lamellae around perimeter osteon formation inside |
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osteoblasts |
-create new matrix in the ossifaction process -do not undergo mitosis -get trapped into their matrix and become osteocytes |
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osteocytes |
-trapped in a small hole called lacunae -maintenance workers that monitor the surrounding matrix by cell processes extending through small tunnels called canaliculi |
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osteoclasts |
-derive from macrophages produced in red bone marrow -responsible for bone resorption (dissolving bone using hydrochloric acid to dissolve calcium crystals and lysosomal enzymes to digest collagen) -involved in shaping the outside of bone for joint spaces and muscle/tendon attachments, creating the medullary cavity and holes in the trabeculae in cancellous bone |
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osteogenic cells |
cells that derive from embryonic mesoderm and undergo mitosis then differentiate into osteoblasts
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long bone structure |
Ends- proximal and distal epiphyses- covered with articular cartilage which is made of hyaline cartilage Shaft- diaphysis- covered with periosteum Periosteum- outer fibrous layer made of dense irregular CT inner osteogenic layer with osteogenic cells involved in new bone growth or hibernating in adulthood unless a fracture occurs Epiphyseal line- separates epiphysis from diaphysis Medullary cavity- found in center of diaphysis, edged with cancellous bone, lined with endosteum, filled with red marrow in children and yellow marrow in adults |
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Osteon Structure in Diaphysis of long bone |
-circumferential lamellae surround perimeter of diaphysis, just under the periosteum -osteons extend the length of the diaphysis and appear as a tree trunk w/ growth rings, called concentric lamellae -osteocytes send extensions through canaliculi into the lamellae to monitor the matrix -a central or Haversian canal runs down the center of each osteon containing blood vessels, nerves, and lymphatic vessels -perforating or Volkmann's canals connect between central canals -the canals are lined with endosteum -the blood vessels in the canals are branches from the nutrient artery that enters at mid-diaphysis |
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Ossification |
-the growth of new bone that starts in fetal life -two types: intramembranous for flat bone endochondral for long bone -bone requires a template to grow >template for intramembranous is a flat sheet of dense irregular CT >template for endochondral is a piece of hyaline cartilage |
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Intramembranous ossification
(flat bone) |
-embryonic mesenchyme differentiates into fibroblasts that create a sheet of dense irregular CT made of collagen fibers as template -at the same time osteogenic cells derive from the mesenchyme and start mitosis to create osteoblasts -osteoblasts lay down matrix to become osteocytes -capillaries extend through the matrix to deliver O2 and nutrients as cancellous bone is formed; red bone marrow fills the holes -the osteoblasts end up under the periosteum (collagen fibers get pushed to the edges) |
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Endochondral ossification (long bone) |
-embryonic mesenchyme differentiates into pieces of hyaline cartilage as template -cartilage matrix calcifies and is removed by osteoclasts -the primary ossification center of osteogenic cells is created in mid-diaphysis -the nutrient artery enters at mid-diaphysis -the medullary cavity is created by osteoclasts and fills with red marrow -at birth secondary ossification centers appear in the epiphyses and process repeats to fill the epiphyses with bone -the remaining hyaline cartilage: >creates the articular cartilage at the end of the epiphyses >creates the epiphyseal plate between the ends of the epiphyses and the diaphysis -growth of new bone in length continues at the epiphyseal plate until the end of puberty |
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Linear bone growth |
-the epiphyseal plate lies between the epiphysis and the diaphysis at the ends of growing long bones -the cartilage grows and is replaced by bone for linear growth -linear growth starts in fetal life and continues until the end of puberty -growth hormone triggers the growth at the epiphyseal plate -on the epiphyseal side of the plate, chondroblasts create new cartilage, pushing the epiphysis away from the diaphysis -on the diaphyseal side, old cartilage calcifies and is dissolved by osteoclasts -osteogenic cells move in and undergo mitosis to create osteoblasts which lay down matrix -growth at the epiphyseal plate continues until the end of puberty when the cartilage calcifies and becomes the epiphyseal line, this occurs due to increasing sex hormones |
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Appositional growth (growth in width) |
-bones grow in width in response to weight bearing forces and tension exerted by muscles and tendons -appositional growth occurs under the periosteum throughout childhood and into the mid-twenties -dominant arm use with increased exercise will increase appositional arm growth -increased appositional growth with obesity due to extra weight bearing |
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Bone remodeling |
-as bones grow, remodeling occurs as osteoclasts continually reshape the outside of bones for muscle and tendon attachments and reshape the medullary cavity -all bone undergoes remodeling throughout its lifetime when matrix becomes damaged or worn out -the osteoclasts reabsorb the matrix and osteocytes replace the matrix |
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Bone Fractures |
-a fracture is when a bone is broken -if the bones remain in place a fractured is called closed, and if the bone breaks through the skin it is called an open fracture -with a simple fracture there is a single break and the ends remain opposite of each other -a spiral fracture may occur from twisting -a comminuted fracture is when a bone is broken in pieces -a greenstick fracture occurs in kids because their bones aren't as calcified |
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Fracture Healing |
Hematoma formation-when a bone is fractured, blood vessels in the canals and medullary cavity are torn and the bleeding occurs forming a large blood clot called a hematoma. the bleeding is held in check due to the periosteum being tightly adhered to the underlying bone Internal and External Callus formation- macrophages remove the hematoma; collagen fibers connect the broken ends and the blood vessels follow these to regrow; osteoblasts from under the periosteum morph into chondroblasts and lay down hyaline cartilage in the area of the fracture. this stabilizes the fracture and creates a template to convert to bone Bony Callus formation-the osteoclasts remove dead bone and cartilage while the osteoblasts lay down matrix to rebuild bone Bone remodeling-the osteoclasts continue to model the bone back to its original shape |
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Calcium and bone health |
-calcium is required in bone to form calcium phosphate and calcium carbonate salts in a hydroxyapatite lattice to make bone hard -osteocalcin, synthesized by vit K, is needed for the calcium and phosphate ions to become crystals of hydroxyapatite -vit D is needed for the small intestines to absorb calcium from foods -milk and dairy have the highest content of calcium and greatest absorption capacity -green leafy vegetables have good amounts of calcium but the fiber in them impairs absorption of the calcium |
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Vitamin D and bone health |
-our main source of vit D is from UVR in sunlight activating a precursor in skin -the activated skin precursor goes to the liver for second activation to become 25-OH D3 and a final activation in the kidneys results in 1,25-OH D3 -1,25-OH D3 triggers the small intestines to absorb calcium from food |
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other nutrients and bone health |
fluoride-replaces an hydroxyl on the apatite to create fluorapatite which increases density in bone and tooth enamel magnesium-part of the bone structure vit K-used to synthesize osteocalcin needed for bone mineralization Omega 3 fatty acids-reduce inflammation that may interfere with osteoblast function |
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Hormones affecting bone |
growth hormone-triggers the epiphyseal plate to grow bones in length from fetal life to the end of puberty by triggering chondrocyte proliferation and osteoblast activity thyroid hormone-increases metabolic rate which promotes osteoblast activity in building new bone sex hormones- >increasing sex hormones-during puberty increases the activity of osteoblasts for the final pubertal spurt >adult levels-when sex hormones reach adult levels they fuse the epiphyseal plate into the scar tissue of the epiphyseal line to halt linear growth >adulthood-sex hormones in adulthood inhibit osteoclasts from absorbing too much bone |
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Bone density curve |
-from fetal life until the end of puberty bones are growing in length and width- osteoblast activity exceeds osteoclast activity and bone density increases -from the end of puberty until the mid-20s bones continue to grow in width- osteoblast activity exceeds osteoclast activity and bone density increases -during adulthood bone density remains constant -after 50 years of age menopause occurs, the lack of sex hormones allows the osteoclasts to become more active |
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Osteoporosis |
-menopause is of an abrupt onset in females as complete ovarian failure occurs in a short period of time so there is an abrupt loss of bone density -menopause in males happens slowly as the testis decrease testosterone production by 10% each decade, so bone density decreases slowly over time -as the osteoclasts resorb bone the effects are seen more dramatically in cancellous bone which becomes porous and fragile leading to fractures of the thoracic vertebrae(kyphosis) causing the elderly to become shorter in height and hip fractures which have a high rate of mortality among the elderly |
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Calcium Homeostasis |
-blood levels of calcium must be kept at about 10mg in order to maintain nerve transmission, muscle contraction, and blood clotting -hormones that maintain calcium homeostasis: >calcitonin and parathyroid hormone hyocalcemia- blood levels of calcium less than 10mg hypercalcemia-blood levels of calcium greater than 10mg |
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Calcium Homeostasis- Calcitonin |
-after eating a meal of milk and green leafy vegetables blood calcium levels will rise -the c cells in the thyroid notice the increase and release calcitonin -calcitonin travels via blood to bone to inhibit osteoclasts from resorbing bone and releasing calcium -calcitonin inhibits calcium reabsorption from kidneys -at the same time calcitonin activates osteocytes and osteoblasts to pull in calcium from the blood to increase the bone matrix -subsequently the blood calcium levels with return to normal and the c cells are turned off by negative feedback |
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Calcium Homeostasis-Parathyroid Hormone |
-missing a meal containing calcium will cause blood calcium levels to decrease below 10 mg -the parathyroid gland notices the decrease and releases parathyroid hormone -parathyroid hormone causes 4 responses 1) parathyroid hormone travels via blood to bone and activates osteoclasts to increase blood resorption and release calcium into the bloodstream 2) At the same time, osteoblasts and osteocytes are inhibited 3) parathyroid hormone also triggers kidney to increase calcium reabsorption from urine and send it into the bloodstream 4) lastly, parathyroid hormone triggers the kidney to increase activation of 1,25-OH D3 so that more calcium can be absorbed from the food in the small intestines and sent into the blood stream when blood levels return to normal, the parathyroid hormone turns off by negative feedback |
