Flashcards in Chapter 5-Skeletal System Deck (73)
1
2 types of bone tissue
-compact(dense smooth bone)
-spongy(bone with open spaces within)
2
Components of Skeletal system
-cartilage
-bone
-tendons
-ligaments
3
functions of skeletal system
-protection
-support (rigid structure)
-movement (bones as levers)
-storage (ca, P, fat)
-blood cell protection
4
cartilage consists of
-cells
extracellular matrix
5
cells in cartilage
chondrocytes found in compartments called lacunae
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extracellular matrix
-collagen/elastic fibers
-ground substance of chondrotin sulfates
7
types of cartilage
hyaline
elastic
fibrocartilage
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why does cartilage heal slowly?
no arteries, veins or lymphocytes
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hyaline cartilage
-most common
-made up of chondrocytes, chondrotin sulfate, some collagen
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location of hyaline cartilage
embryonic skeleton, articular surfaces, respiratory passages, nasal septum, between ribs and sternum
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elastic cartilage
-flexible
-structure: chondrocytes, chondrotin sulfate, densely packed elastic fibers
-location: auricle, tip and lateral walls of nose, epiglottis
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fibrocartilage
-very strong
-structure: chondrocytes, chondrotin sulfate, densely packed collagen fibers
-location: intervertebral disc, public symphysis, articular cartilage in knee
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perichondrium
-fibrous connective tissue
-surrounds cartilage
-provides support and protection; new chondrocytes
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perichondrium location
hyaline cartilage and elastic cartilage
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absent form perichondrium
articular surfaces and fibrocartilage
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layers of perichondrium
-outer: binds cartilage to adjacent tissues; provides support and protection
-inner: for growth and maintenance
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apposition growth
-starts in perichondrium
-mesenchymal cells at periphery form in inner layer of perichondrium
-mesenchyme move towards matrix to become chondrogenic cells
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how are chondrocytes formed from apposition growth
-chondrogenic cells aggregate and become chondroblasts
-chondroblasts secrete matrix-force cells apart
-chondroblasts become enclosed in matrix and become chondrocytes
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interstitial growth
-chondrocytes enclosed in matrix and divide
-as the move apart, matrix forms between them
-growth of cartilage from within
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osseous tissue
-supportive CT
-contains specialized cells
-solid extracellular matrix
---osteoid (organic portion, protein fibers)
---ground substance (Ca salts)
---water
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osteoprogenitor
-bone cell
-mesenchymal cells
-predecessor to osteroblasts
-play role in initial growth and fracture repair
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osteoblasts
-derived from osteogenic cells
-secrete osteoid
-common in growing bone
-predecessor to osteocytes
-more osteoblasts=stronger bone
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osteocytes
-mature cells
-exist within bone matrix
-maintain Ca and PO4 homeostasis
-found in spaces called lacunae
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osteoclasts
-involved in osteolysis (bone break down)
-increase osteoclast activity=weaker bone
-very large
-formed from fusion of many white blood stem cells
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bone matrix is composed of...
Inorganic material
-65%
-brittle salts
--mostly hydroxyapatite
Osteoid
-orgaic
-35%
-flexible fibers (collagen, glycoproteins, proteoglycans
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2 types of bone
compact bone
-arranged in osteons
spongy bone
-arranged in trabeculae
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compact bone osteocytes communicate how?
osteocytes
-osteocytes communicate through canaliculi that radiate outward and connect one cell to the next cell
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osteons
a unit of compact bone
-concentric lamellae of matrix surrounding acentral canal
-contains blood vessels and nerves
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how are osteons connected to each other
perforating canals
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3 types of lamellae
-concentric
interstitial
circumferential
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concentric lamellae
-layers of bone surrounding the central canal
-make up osteons
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interstitial lamellae
-found between osteons
-represents older osteons partially removed during tissue remodeling
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circumferential lamellae
surround the compact bone
-directly produced from periosteum
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spongy bone contains
trabeculae
-osteocytes in lacunae
-canaliculi
-matrix
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spongy bone does not contain
-osteons
-central canal
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trabeculae
-latticework of thin plates of bone oriented along lines of stress
-spaces are filled with red marrow where blood cells develop
-found in ends of long bones and inside flat bones
-lightens the bones, allows for movement
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periosteum
-encloses bone
-absent at site of attachment of muscles, tendons and ligaments; surfaces covered by articular cartilage
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layers of periosteum
outer fibrous: gives rise to collage
Inner: for growth or new cells and maintenance
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endosteum
-1 cell layer
-covers surfaces of spongy bone and medullary cavity
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cell types of endosteum
osteogenic
osteoblasts
osteoclasts
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anatomy of a long bone
diaphysis: shaft
epiphysis: one end of long bone
metaphysis: growth plate region
articular cartilage: over joint surface; acts as friction and shock absorber
medullary cavity: marrow cavity
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2 types of bone marrow
-yellow marrow
-red marrow
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yellow marrow
-areolar and adipose CT
-in medullary cavity of long bones
-energy storage
-absent in infants
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red marrow
-areolar and myeloid (precursor to red blood cells) tissue
-produces all types of blood cells
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location of red marrow
-medullary cavities of infants
-spongy bones in adults
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blood and nerve supply of bone
-periosteal arteries: supply periosteum
-nutrient arteries
--enter through nutrient foramen, supplies compact bone of diaphysis and yellow marrow
-metaphyseal and epipheyseal arteris
--supply red marrow ad bone tissue of epiphysis and metaphyses
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how does bone growth occur
ossification (replacing CT with bone)
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2 types of ossification
intramembranous
-mesenchymal cells->spongy bone
endochondral
-hyaline cartilage->spongy bone
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intramembranous ossification begins when and forms what
about 8 week in embryo
-mainly finished by week 15
Forms:
-cranial flat bones
-facial bones
-dentary bones
-clavicle
-sesmoid bones
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primary ossification center
-intramembranous oss.
-location where bone growth begins
51
where does bone growth begin plus beginning steps
primary ossification center
-mesenchymal cells arrange around BVs
-bone morphogenic proteins release
-mesenchymal cells divide and become osteoblasts
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what do osteoblasts do after formation
-secrete osteoid
-become isolated->osteocytes
-produce spicules of bone that interconnect
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how does spongy bone form during intramembranous ossification
-mesenchymal cells at surface form inner layer of periosteum
-calcified matrix is degraded by osteoclasts to form spongy bone
-end up with spongy bone covered in thin layer of compact bone
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when does endochondral ossification begin and what forms
-bone relaces cartilage model
-begins at week 7 of embryo
-continues to adulthood
Forms:
-long bones
-most short bones
-non-cranial irregular and flat bones
-middle ear ossicles
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step 1 of endochondral ossification
-hyaline cartilage forms model of future bone
-cartilage enlarges; chondrocytes near center hypertrophy
--matrix reduced to struts
--chondrocytes deprived of nutrients and die
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step 2 of E.O.
BV's grow around and penetrate cartilage
-cells differentiate into osteoblasts
-compact bone forms around diaphysis
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step 3 of E.O.
-spongy bone forms in center of model
--primary ossification center (creates diaphysis)
-nutrient artery in spongy bone forms and penetrates
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step 4 of E.O.
remodeling of the shaft
-formation of the medullary cavity
-length increases
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step 5 of E.O
-BV's penetrate ends of model
-secondary ossification centers form at both epiphyses (created here)
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step 6 of E.O.
-ends with incomplete ossification of epiphysis
-some cartilage remains
--articular cartilage
--epiphyseal plate (growth plate)
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bone growth: elongation
-occurs at epiphyseal plate
growth in length continues until 2 ossification centers meet
-relative thickness of epiphyseal plat does not change until growth almost complete; then:
--cartilage depleted and epiphyseal plate narrows to epiphyseal line
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bone growth: appositional
-compact bone deposited beneath periosteum
-bone thickens
-bone remodeling occurs throughout life
--due to osteoclasts and osteoblasts
63
bone remodeling
-ongoing since osteoclasts carve out small tunnels and osteoblasts rebuild osteons
-continual redistribution of bone matrix along lines of mechanical stress
-4% of compact bone, 20% of spongy bone remodeled per year
-distal femur fully remodeled every 4 months
64
fractures: break in a bone (types)
closed (simple): break that does not penetrate skin
open (compound): broken bone penetrates through skin
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bone repair
-fractures treated by reduction and immobilization
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stages of bone repair
-fracture hematoma
-fibrocartilage callus
-bony callus
-remodel tissue
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fracture hematoma formation
-facture hematoma forms within hours of injury
-mass of blood
-swelling and inflammation occur in response to dead bone cells
-phagocytes and osteoclasts eliminate dead cells/broken matrix
68
fibrocartilaginous callus formation
-consists of mass bridging broken ends of bone
-fibroblasts in periosteum produce collagen
-periosteum cells differentiate into chondrocytes
-results in fibrocartilage
-about 3 weeks
69
bony callus formation
-endochondral ossification
-formation of bony callus occurs as fibrocartilaginous callus is converted to spongy bone trabeculae
-bony callus lasts 3-4 months
70
bone remodeling
-remaining dead bone fragments are resorbed, compact bone replaces spongy bone
-well-healed fracture is virtually undetectable
-process can take weeks to months depending on severity
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factors affecting growth, repair, development
-nutrition=vitamin D
-sunlight (vit D)
-hormones: PTH, calcitonin, GH, thyroid hormone, sex hormones
-physical stress
72
osteoporosis
-abnormal reduction of bone mass
-reasons:
-loss of estrogen at menopause
-deficiency of minerals in youth
-imbalance in activity between osteoblasts and osteoclasts
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