Histology: Bone and Cartilage Flashcards Preview

Skin MS: Week 6 > Histology: Bone and Cartilage > Flashcards

Flashcards in Histology: Bone and Cartilage Deck (86):
1

Cartilage origin

Mesenchyme

 

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Cartilage considered _____ tissue

Considered specialized CT due to supportive properties

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What is this tissue?

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Hyaline Cartilage - shown w/ perichondrium

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Label

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Blue - osteoid

Red cells - osteoblasts

isolated cells - osteocytes

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Differences between Bone and Cartilage

Bone matrix can become mineralized.  If cartilage matrix mineralizes it will degenerate

Cartilage is avascular, bone is highly vascular

Cartilage lacks nerve innervation

Cartilage growth is appositional and interstitial; bone grows only appositionally

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Cartilage cell types

chondroblasts – active

chondrocytes – considered to be inactive

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Cell morphology (Cartilage)

lacunae

few mitochondria – predominantly anaerobic

typical Golgi, RER

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Cartilage matrix is 60-80% _______

Water

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Cartilage matrix contains

Ground substance and fibers 

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Cartilage ground substance contains

proteoglycan (aggrecan - hyaluronate - extremely hydrophilic, binds water to create stiff gel) and glycoproteins (chondronectin - help bind various components of cartilage)

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Cartilage matrix fibers

Collagen (+elastin for elastic cartilage)

Microfibrillar

Difficult to see d/t same refractive index as ground substance

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Cartilage matrix is _________ (blood/lymph)

Avascular

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Cartilage types

Hyaline cartilage

Elastic

Fibrocartilage

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Most common cartilage

Hyaline

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Hyaline cartilage locations

Fetal skeleton, epiphyseal plate in children

nose, larynx, trachea, ribs articular cartilage in adult

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Morphology of Hyaline Cartilage

glossy, collagenous fibers (Type ____) difficult to see

______ with 2 or more chondrocytes = ________

outer layer = ___________

 

glossy, collagenous fibers (Type II) difficult to see

lacunae with 2 or more chondrocytes = isogenous group

perichondrium

 

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Perichondrium of hyaline cartilage (fibrous layer, chondrogenic zone, function, articular cartilage)

fibrous layer – contains fibroblasts and type I collagen

chondrogenic zone – contains chondroblasts

function

protection

continuous supply of chondrocytes

lacking on articular surface of articular cartilage

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Hyaline cartilage nutrition

diffusion – matrix is permeable to nutrients, oxygen and metabolic waste

mineralization prevents diffusion

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Growth of hyaline cartilage (appositional, interstitial, regeneration)

appositional – addition of chondroblasts onto surface

interstitial – mitotic activity of chondroblasts (formation of isogenous nests) and synthesis of matrix - note: not possible in bone

regeneration of damaged cartilage is difficult

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Elastic cartilage location 

pinna of ear, eustachian tube, external auditory canal

epiglottis, some laryngeal cartilages

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Elastic Cartilage morphology

abundance of ______ fibers

______ fibers and ground substance also present

higher density of _________ than hyaline

_______________ (outer layer)

abundance of elastic fibers

collagen (Type II) and ground substance also present

higher density of cells/isogenous nests than hyaline

perichondrium

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Nutrition of elastic cartilage

Same as hyaline cartilage (diffusion)

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Fibrocartilage Locations

Intervertebral discs, pubic symphysis, tendon/ligament attachments

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Fibrocartilage morphology:

large ______ fibers (____)

_______ in ground substance

_____ cells per unit area

Perichondrium?

large collagenous fibers (Type I)

reduction in ground substance

fewer cells per unit area

no perichondrium

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Herniated intervertebral disc

Rupture of annulus fibrosis allowing expulsion of nucleus pulposus

Dislocation of annulus and compression of spinal cord

Fibrocartilage

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General Characteristics of Bone

Dynamic - living tissue, Undergoes continuous remodeling, repair

Structural support

Calcium reservoir

 

 

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Bones contains ____% of body calcium and for what purpose

99%

Mineral metastasis

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3 bone cell types

osteoblasts, osteocytes, osteoclasts

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Bone matrix contains

Ground substance, type I collagen, minerals (ca, MN, FE, SR)

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Bone is _____ vascular/innervated (vs cartilage)

Bone is HIGHLY innervated/vascular - cartilage is not

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Osteoblast function 

synthesis of organic matrix = osteoid prior to mineralization

deposition of inorganic components

alkaline phosphatase secretion → concentrate phosphate ions → organic matrix (calcium added)

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Osteoblast location and appearance

Bone surface

cuboidal to columnar when active

basophilic

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Cell process of osteoblasts

in contact with neighboring osteoblasts

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Osteoblasts have receptors for ____

receptors for parathyroid hormone: binding of parathyroid hormone causes release of osteoclast stimulating factor from the osteoblast

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Osteoblasts --> 

Osteocytes (completely surrounded by matrix)

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Osteocytes have ______ protein synthesis (compared to osteoblasts)

Reduced

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Function of osteocytes

maintenance of matrix and regulation of calcium; death of osteocyte → resorption of the matrix

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Osteocytes are located in __________

lacunae

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Osteocyte cell processes

canaliculi = channels through matrix for osteocyte processes

Used to be “arms” of osteoblasts - now canaliculi

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Osteocyte communicationn

communicate via gap junctions

cell-cell coordination

nutrient transfer

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Describe and function

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Sharpey's fibers: anchor periosteum to bone

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What are black dots?

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Osteocytes - cells that are alive, communicated via caniculi/gap junctions

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label zones of epiphyseal plate

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Resting

Proliferative

Hypertrophic

Calcified Cartilage

Ossification 

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Large multinucleated motile bone cells

osteoclasts

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Osteoclasts are responsible for 

bone resorption

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Osteoclasts are derived from ______ and amitotic/mitotic

derived from circulating monocytes (not “related” to osteoblasts/osteocytes)

amitotic

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Osteoclast ruffled border and process 

"Ruffled border" - where osteoclast lies against bony surface

Membranes pump H+ into sub-osteoclastic compartment

Lower pH and mineral is liberated

Minerals enter osteoclast and are then delivered to nearby capillaries

Osteoclast secretes lysosomal hydrolases, collagenase, and gelatinase into sub-osteoclastic compartment

Degrade organic components of decalcified bone matrix

Degradation products are endocytosed by osteoclast

Broken down into amino acids, monosaccharides, and disaccharides and released into capillaries

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Howship's Lacunae

regions of resorbed matrix containing an osteoclast - looks like a depression in surface of bone w/ osteoclast

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Bone matrix composition

Inorganic (mostly calcium) and organic (type 1 collagen and ground substance)

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Organic part of bone matrix 

type I collagen

ground substance

chondroitin sulfate form proteoglycan

hyaluronate aggregates

glycoproteins: osteonectin; osteocalcin; osteopontin → bind everything to everything else

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Types of bone

 

Cancellous, compact

primary, secondary

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Cancellous bone

spicules or trabeculae of bone united to form network

found in interior of bone (e.g. idploe of skull, ends of long bones)

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Compact bone

found on bone exteriors

dense, thick layers

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Primary bone

first bone tissue to appear during growth or repair

woven bone

irregular array of collagen fibers

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Secondary bone

replaces primary bone

parallel arrays of collagen

lamellar deposition of matrix

production of Haversian systems

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Diaphysis of long bone 

bone shaft between opposing epiphyseal plates

primarily compact bone, but metaphysis is cancellous (spongy)

periosteum

endosteum

marrow cavity

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Metaphysis of long bone

distal end of diaphysis

cancellous/spongy

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Epiphysis of long bone

distal end of long bone

articular hyaline cartilage cap (no perichondrium - just adjacent to synovial fluid)

medullary cavity is cancellous with marrow cavity

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Epiphyseal plate of long bone 

junction between diaphysis and epiphysis

hyaline cartilage in a child

perichondrium continuous with periosteum

Responsible for bone growth

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Periosteum of compact bone

fibrous layer

-fibroblasts, collagen, elastin, protection of bone

Osteogenic layer (can’t normally see, unless fracture/growing)

- Osteoblasts adjacent to bone surface, Osteoclasts if remodeling is underway, Osteoprogenitor cells – precursors to osteoblasts

Blood vessels, nerves

Sharpey's fibers: anchor periosteum to bone

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endosteum of compact bone

between bone marrow and bone matrix

layer of osteoblasts, osteoclasts and few osteogenic cells

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Haversian System (Osteon)

concentric lamellae of bone

usually don't exceed 10/osteon

canaliculi (little processes) of osteocytes

plane of collagen deposition perpendicular to adjacent lamellae - strength

surround vascular passageways running longitudinally

blood vessels, nerves, lymphatics

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Volkmann's Canals

vascular passageways running radially

not surrounded by bone lamellae

blood vessels, nerves, lymphatics → Haversian canals or bone marrow cavity

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Interstitial Lamellae of compact bone 

remnants of partly resorbed osteons (incomplete osteons visible between complete osteons)

no vessels

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Outer Circumfrential Lamellae of compact bone

beneath periosteum

usually do not completely encircle bone shaft

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Inner circumfrential lamellae of compact bone

adjacent to endosteum

incomplete

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Bone development: _______ growth only 

Appositional Growth Only (cannot grow by interstitial growth - mineralized)

osteocytes are amitotic

calcified matrix cannot expand - deposit onto already existing bone

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Types of bone development

intramembranous, endochondral ossification

Note:  both types of ossification result in compact and cancellous bone tissue formation

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Intramembranous ossification 

embryonic CT precursor

CT template is vascular

gives rise to "membrane" bones = Skull, mandible, maxilla, clavicles

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Endochondral ossification

hyaline cartilage precursor/template

cartilage is avascular

calcified cartilage matrix is removed

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Intramembranous ossification: Primary Ossifcation center, Mineralization of Matrix, Spicule Formation, Cancellous and compact bone 

differentiation of mesenchymal cells into osteoblasts, osteoid secretion

encapsulation of osteoblasts --> osteocytes, immature woven bone, mature lamellar bone

small mineralized "fingers" of bone, surrounded by osteoblasts, fusion of adjacent spicules --> trabeculae

depends on degree of lamellar bone deposition and spacing of spicule and trabeculae

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Endochondral ossification: bone collar formation 

intramembranous ossification around diaphysis of cartilage template

prevents diffusion into cartilage matrix

calcification of cartilage matrix

hypertrophy and destruction of chondrocytes

resorption of matrix surrounding chondrocytes

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Endochondral ossification: Primary Ossification Center 

osteogenic bud invasion

penetration of calcified cartilage by capillaries

introduction of osteoprogenitor cells

differentiation of osteoprogenitors into osteoblasts

deposition of bone matrix on remnants of cartilage matrix

first appearance of bone marrow precursors

osteoclast resorption of cartilage matrix and remodeling of bone spicules, formation of medullary cavity

expansion of bone collar

further calcification of cartilage

longitudinal expansion of bone deposition

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Endochondral Ossification: Secondary OC

ossification of epiphysis

no bone collar formation

bone growth is radial

articular cartilage remains

epiphyseal cartilage continues appositional and interstitial growth

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Ossification of Epiphyseal cartilage 

Five zones based on chondrocyte disposition

Closure of epiphyseal plate in young adult

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5 zones based on chondrocyte diposition

resting – normal hyaline cartilage

proliferative – high mitotic activity, columns of isogenous nests formed (stack of pancakes)

hypertrophic – glycogen accumulation, very little matrix

calcified – death of chondrocytes, deposition of hydroxyapatite + calcification

ossification – osteoblasts and bone matrix appear

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Synovial Joint

Synovial membrane, matrix, blood and lymphatic vessels

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Synovial membrane

Fibroblasts (type B cells) - secrete synovial fluid, hyaluronate and GAGs - viscosity, hydrophilic, lubrication of joint, provides nutrients for articular cartilage

macrophages (type A cells)

not an epithelium (epithelioid-like though)

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Synovial joint matrix

collagen

ground substance

adipose cells

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Bone plasticity

stress induced remodeling (i.e. braces)

fracture

disuse

hormone changes, developmental and pathological

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Bone- calcium homeostasis, 2 hormones

99% of body calcium is in bone

Parathyroid hormone – increases Ca resorption

stimulates osteoclast activity (via binding to parathyroid hormone receptors on osteoblasts) and osteoclast numbers

resorption of matrix

Calcitonin – promotes calcium deposition

inhibits osteoclast activity

matrix deposition

Produced by Thyroid gland

82

Scurvy

vitamin C deficiency

improper collagen synthesis (hydroxyproline)

weakness in epiphyseal plate, diaphysis

loosening of teeth

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Rickets

calcium deficiency in children

Incomplete bone matrix calcification

spicules distort under strain → bone deformation

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Osteomalacia

calcium deficiency in adults

deficient calcification of new bone

decalcification of existing bone

no bone distortion

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Osteoporosis

Most common in postmenopausal women

Bone tissue diminished – due to a more rapid destruction of bone by osteoclasts than osteoblast formation of bone

Estrogen therapy helps alleviate this tendency but has many side effects (cancer, heart attacks), bisphosphonates more common now

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