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MSK Week 4 > ICL 5.1: Cartilage and Bone > Flashcards

ICL 5.1: Cartilage and Bone Flashcards

1
Q

what are the 3 components found in all connective tissues?

A
  1. cells
  2. extracellular fibers
  3. ground substance
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2
Q

what are the 2 supportive connective tissues in the body?

A
  1. cartilage

2. bone

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3
Q

what are the 3 types of cartilage?

A
  1. hyaline
  2. elastic
  3. fibrocartilage

the types are based on the predominant fiber present in the extracellular matrix (ECM)

it’s found where you need support but also flexibility

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4
Q

what is hyaline cartilage?

A

most abundant cartilage in the body

ex. found in the trachea and keeps the trachea open

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5
Q

what are the common characteristics of hyaline cartilage?

A
  1. large amount of ECM between cells = pale blue, semitransparent appearance
  2. avascular matrix
  3. mostly surrounded by layer of perichondrium (dense irregular CT)
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6
Q

what are the two types of cells in cartilage?

A
  1. chondroblasts

2. chondrocytes

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7
Q

what are chondroblasts?

A

chondroblasts are derived from mesenchymal
cells and chondrogenic cells in perichondrium

they are Immature cartilage cells, basophilic

elliptic shape near periphery

they secrete cartilage matrix and undergo cell division = mitosis

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8
Q

what are chondrocytes?

A

mature cartilage cells that reside in lacunae

they are more rounded deeper in the cartilage

although they’re mature, they are still capable of cell division

chondroblasts are called chondrocytes once they are embedded in ECM

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9
Q

what is an isogenous group?

A

where two or more cells are in single lacunae or are very closely associated with each other

this represents where a cell has recently undergone cell division and begun to lay down new matrix

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10
Q

what are the two methods of cartilage growth?

A
  1. interstitial growth

growth from within –> tissue is added from the inside of the tissue

  1. appositional growth

growth on outside of tissue proper –> tissue is added on the outer surface of the tissue by the perichondrium

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11
Q

what are the 2 layers of the perichondrium?

A
  1. fibrous layer

2. chondrogenic layer

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12
Q

what is the fibrous layer of the perichondrium? what is it composed of?

A

it’s an outer layer of dense irregular fibrous connective tissue containing blood vessels which supply nutrients to all of the cartilage

it’s composed of type I collagen*, vascular, and fibroblasts

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13
Q

what is the chondrogenic layer of the perichondrium? what is it composed of?

A

it’s the inner layer of the perichondrium

composed mainly of chondrogenic cells that undergo division and differentiate into chondroblasts = appositional growth

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14
Q

what is ground substance? what’s it composed of?

A

it’s one of the three components of connective tissue that’s an amorphous gel-like substance in the extracellular space that contains all components of the extracellular matrix (ECM) except for fibrous materials such as collagen and elastin

it’s abundant; there’s a lot of it between cells

it consists of an amorphous gel that’s rich in proteoglycans and lots of sulfated Glycosaminoglycans (GAGs)

it’s relatively low in hyaluronic acid

two portions = territorial matrix and inter territorial matrix

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15
Q

what is the territorial matrix?

A

it’s the portion of the ground substance immediately around the cell

new chondroblastssecrete a lot of territorial matrix because it’s rich in GAGs

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16
Q

what is the interterritorial matrix?

A

it’s the portion of the ground substance between the cells

it stains lighter than the territorial matrix due to a lower sulfur content

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17
Q

what are proteoglycans?

A

it gives the matrix its characteristic structure and is more organized than connective tissue proper

this is the most important component of cartilage

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18
Q

what is the proteoglycan subunit called?

A

aggrecan

aggrecans are covalently linked to main hyaluronic acid chain forming huge proteoglycan aggregate

they are responsible for the gel-like character of the matrix

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19
Q

what are the 3 functions of proteoglycan aggregates?

A
  1. diffusion of nutrients

holds interstitial fluid important for diffusion of nutrients and oxygen from surface of cartilage to interior

all nutrients come from blood vessels in the fibrous layer of the perichondrium

  1. resists compression
  2. slippery (good for joints)
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20
Q

what are the 2 types of adhesion molecules in hyaline cartilage?

A
  1. chondronectin

adherence of cell membrane to extracellular matrix (ECM) (integrin)

  1. chondrocalcin

calcium binding in the ECM (calcify the cartilage)

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21
Q

what are the 2 types of extracellular fibers in hyaline cartilage?

A
  1. collagen type II

2. pericellular capsule

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22
Q

what is the pericellular capsule?

A

a type of extracellular fibers in hyaline cartilage

it’s immediately adjacent to cell and is a fine meshwork of other types of collagen thought to protect cells from mechanical stresses

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23
Q

where is hyaline cartilage found in the body?

A
  1. costal cartilage
  2. trachea, bronchi of lungs
  3. larynx, nasal cartilage
  4. articular cartilage in synovial joints (no perichondrium)
  5. fetal skeleton
  6. epiphyses (no perichondrium)
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24
Q

what is the function of hyaline cartilage?

A
  1. provides structural support

elastic firmness that is resilient yet fairly rigid; due to gel-like form of ground substance from presence of proteoglycans

  1. withstands lots of pressure and shear forces

acts as shock absorber; due to proteoglycans filled with water

  1. slippery

due to large amounts of proteoglycans containing water; 80% of wet weight is water

  1. capable of rapid growth

important to have support during development because bone grows too slowly and would be too rigid during the birth process

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25
what is elastic cartilage composed of?
chondrocytes are principal fixed cell type -- they're widely scattered the principal fiber type is elastic fibers; collagen type II is also present --> both fibers are secreted by the chondrocytes
26
how can you differentiate between elastic and hyaline cartilage in an H&E stain?
you can't; elastic cartilage looks just like hyaline cartilage on an H&E stain you need a special elastic stain to see the elastic fibers and type II collagen verhoeff’s iron hematoxylin (VIH) stain is specific for the elastic fibers and stains them black and blue
27
what is the ground substance of elastic cartilage like?
it's the same structure as hyaline cartilage but just not as abundant due to lots of elastic fibers
28
where is elastic cartilage found in the body?
1. auricle 2. epiglottis 3. auditory canal 4. larynx
29
what is the function of elastic cartilage?
resilient support is needed with greater flexibility & elasticity to return to original position
30
what are the characteristics of fibrocartilage?
1. chrondrocytes are the principal fixed cell type and they are aligned between bundles of collagen 2. there are densely packed type I collagen fibers in bundles 3. not a lot of ground substance due to numerous collagen fibers 4. NO perichondrium
31
where is fibrocartilage located in the body?
1. pubic symphysis 2. intervertebral discs 3. junction of attachment between tendon and bone
32
what is the function of intervetebral discs?
cushion and absorb impact needs to be tough and resistant to stress but not rigid
33
what are the 5 types of cells found in bones?
1. osteoprogenitor cells 2. osteoblasts 3. osteocytes 4. osteoclasts 5. bone lining cells
34
what are osteoprogenitor cells?
they are derived from undifferentiated embryonic mesenchymal cells they are capable of mitosis and proliferation they differentiate into osteoblasts or chondrogenic cells (low O2) in growing bones, they appear as flattened, elongate or ovoid nucleus
35
where are osteoprogenitor cells found in the body?
they are found in the inner cellular layer of the periosteum, lining harversian canals and in the endosperm
36
what are osteoblasts?
immature cells derived from osteoprogenitor cells they are nOT capable of cell division they are found on existing bone surfaces
37
what do osteoblasts look like?
cuboidal in shape, closely packed together they look like an epithelium forming a lining on the outside surface of the bone tissue
38
what is the function of osteoblasts?
they are always actively laying down unmineralized matrix called osteoid on the editing surface and then mineralizing it so all bone growth is appositional!! there is no interstitial growth like with cartilage
39
what are osteocytes?
mature bone cells, derived from OBs the osteocytes are embedded in the calcified bone matrix that is laid down by the osteoblasts they can NOT divide they lie in lacunae
40
what is the function of osteocytes?
maintaining the ECM surrounding the cell they have numerous cytoplasmic processes, which extend to adjacent cells these processes run in small tunnels through calcified matrix called canaliculi
41
how are osteocytes set up/oriented?
they are arranged in concentric circles around BV = bone tissue is very vascular the blood vessel runs in a central canal/harversian canal of the osteon the osteon is the basic structural and functional unit of compact bone then, the cement line is the outermost limit of the osteon --> it's deficient of collagen and lighter staining than surrounding matrix
42
how does nutrient and waste material get between osteocytes?
gap junctions
43
what are osteoclasts?
large, multinucleate cells that re-absorb bone tissue they're derived from granulocyte-macrophage progenitor cells and arise in the bone marrow --> they then fuse together to form multinucleated osteoclast
44
where are osteoclasts located in the body?
they're located in a depression on bone surfaces called Howship's lacunae/Resorption Bay
45
what are ruffled borders?
regions where collagen fibers are exposed by resorption by osteoclasts they signify active bone resorption
46
how are osteoclasts and osteoblasts related?
osteoclasts are ALWAYS found in associated with osteoblasts RANK receptors on OCs are stimulated by RANKL secreted by OBs RANK receptors can be blocked by osteoprotegerin which is a RANKL decoy receptor that leads to decreased osteoclast activity
47
where are bone lining cells found in the body?
they are the cells that line all bone surfaces they're found in 3 places: 1. all vascular channels 2. endosteum 3. periosteum
48
what is the function of bone lining cells?
1. maintains microenvironment in bone tissue 2. forms interconnecting network with other bone lining cells, osteocytes and osteoblasts by cellular processes 3. senses stress in bone and initiates remodeling process
49
what are the 2 components of the extracellular matrix of bones?
1. organic component | 2. inorganic components
50
what is the organic component of the ECM of bone composed of?
it's made of type I collagen, non-collagenous proteins, ground substance and growth factors 1. collagen makes up 90% of the organic matrix and gives bone its toughness and flexibility 2. ground substance is scant and only contains small amounts of proteoglycans
51
which non-collagenous glycoproteins are found in the organic component of bone ECM?
1. osteocalcin that binds to Ca2+ in the matrix 2. osteonectin binds bone mineral to collagen fibers 3. osteopontin is also bind to hydroxyapatite 4. bone sialoprotein has binding sites for matrix components and interns of osteoblasts and osteocytes
52
what is the inorganic component of the ECM of bone?
consists of all mineral salts in the ECM it's approximately 65% of total dry bone weight is due to minerals it provides mechanical rigidity and load bearing strength to bone tissue
53
what is the inorganic component of the ECM of bone composed of?
ions!!! 1. Ca2+, PO43-, CO32-, Mg2+, OH-, Fl- , citrate ions ions are found in the form of hydroxyapatite crystals = Ca10(PO4)6(OH)2 2. traces of Fe, Zn, Cu, Pb, Al, Sr, etc
54
explain how bone is a biphasic material and how that is beneficial
the ECM of bone is made of an inorganic and organic matrix the inorganic matrix has a lot of strength but it brittle the organic matrix on the other hand is really strong from collagen fibers and is really flexible if you remove the organic matrix, then bone is brittle like china but if you remove the inorganic matrix then the bone would be insanely flexible so together they combine to form stronger yet flexible material that can withstand great stress yet still give without shattering
55
what are the extracellular fibers found in bone?
type I collagen primarily that is densely packed bone tissue is classified by the arrangement of collagen fibers
56
how is bone tissue classified?
bone tissue is classified by the arrangement of collagen fibers 1. woven bone = primary, immature it's characterized by bundles of collagen fibers running in all directions 2. lamellar bone = secondary, mature it's characterized by collagen fibers in one layer running parallel to each other which makes them calcified and stronger -- but the direction of fibers is different in each layer each layer of collagen is called a lamellae
57
how are bones classified by shape?
1. long bones humerus, ulna, radius, femur, tibia, fibula, phalanges 2. short bones carpal and tarsal bones 3. irregular bones vertebrae, hip, facial 4. flat bones skull bones 5. sesamoid bones patella, pisiform
58
what is the gross structure terminology of the parts of a bone?
1. epiphysis = enlarged area at each end 2. diaphysis = central shaft area 3. metaphysic = tapered cone region that connects epiphysis to diaphysis 4. epiphyseal plate = band of cartilage found in metaphyseal region that function to increase length of long bones
59
what is cortical bone?
it's the outer layer of dense bone --> aka compact bone/dense bone consists of osteons, interstitial lamella & circumferential lamella has more bone tissue than space per unit volume
60
what is spongy bone?
the small processes inside the bone aka trabecular bone/cancellous bone consists of thin processes of bone called trabecula or spicules with large amount of space between (Marrow Cavity) has more space than bone tissue per unit volume
61
what is the basic structural unit of compact bone?
an osteon = Haversian system the central canal (Haversian canal) contains blood vessels and lies in the center of the osteon then surrounding the blood vessels are concentric layers of collagen fibers and osteocytes
62
what are Volkmann canals?
they're in the cortical bone and they contain diagonally running blood vessels they supply blood to vessels in osteons you can recognize them by their LACK of concentric layers of cells around them
63
what are interstitial lamellae?
remnants of older osteons in the cortical bone layer you can recognize them because they look like an osteon that doesn't have its central canal
64
what are the outer circumferential lamellae?
it's the layers of cortical bone (osteocytes) that run all away around outside of bone the bind bone together and help hold all the osteons in place they're laid down by periosteum
65
what are the inner circumferential lamellae?
it's the layers of cortical bone (osteocytes) that run all the way around the inner surface of the bone next to the marrow cavity they are laid down by the endosteum
66
what are Sharpey's fibers?
bundles of collagen fibers extending from periosteum to be attached in the bone matrix of the cortical bone they're seen where muscle-tendon or ligaments attach to bone
67
what is the endosteum?
a single layer of cells lining the inner layer of the bone adjacent to the marrow cavity its function is to separate bone tissue from marrow cavity and it helps to maintain the proper microenvironment within bone tissue
68
is bone growth interstitial or appositional?
ALL bone growth is appositional
69
what are the 2 functions of bone?
1. structural support | 2. reservoir for mineral ions
70
how does bone act as a structural support?
inorganic salts impregnated in organic matrix give bone its rigidity and great strength bone maintains the shape and form of the body and protects major organs it also supports soft tissues, provides attachment sites for skeletal muscles
71
how does bone act as a reservoir for mineral ions?
bone releases and stores ions as needed --> the mechanism of ion release/storage is the process of remodeling consists of resorption tunnels & forming osteons bones are the storehouse for 99% of body’s calcium, 85% of Phosphorus, 65% of all the sodium and magnesium
72
what is bone remodeling?
replacement of old bone tissue by new bone tissue remodeling is continuous from the time bone is first formed until you die remodeling replaces woven bone with lamellar bone in both cortical and trabecular bone
73
what are the two types of bone remodeling?
1. internal remodeling | 2. trabecular remodeling
74
what is internal remodeling?
aka Haversian remodeling = cortical remodeling = secondary bone formation it occurs in response to new stress on the bone --> the process begins with bone lining cells sensing new stress the first visible sign is the formation of osteoclasts the end result is a new definitive Haversian system that gets formed in the compact bone
75
what is the resorption cone?
part of internal remodeling they're cavities that are formed by the osteoclasts in dense bone that are tapered and look like bullets OCs are actively removing bone matrix resulting the release of Ca2+ and other ions into blood a resorption cavity is characterized by large lumen in the bone matrix with osteoclasts lining it
76
what is the reversal zone?
part of internal remodeling it's when there is no longer any bone resorption but bone deposition has not yet begun macropages scavenge the debris and smooth out the surface
77
what is the closing cone?
aka forming the osteon a blood vessel follows down behind the formation of the respiration tunnel it carries osteoprogenitor cellsthat migrate across the gap between the BV and the outer limit of the resorption cavity --> the OPs attach to the surface of resorption tunnel and differentiate into OBs then the osteoblasts lay down a layer of bone osteoid
78
how long does one remodeling cycle take to complete?
4 months
79
internal remodeling is under the control of which 2 hormones?
1. parathyroid hormone (PTH) | 2. calcitonin
80
how does parathyroid hormone control internal remodeling?
it's secreted where there is low peripheral blood Ca2+ level PTH stimulates the osteoclasts to increase their resorption activity --> increased bone resorption which in turn increases release of Ca2+ this decreases osteoblastic activity and bone matrix isn't being laid down as rapidly the net effect is an increase in the blood Ca+2 level!
81
how does calcitonin control internal remodeling?
it decreases osteoclastic activity this increases osteoblastic activity and pulls more Ca2+ from blood the net effect is to lower blood Ca2+ level
82
what is trabecular remodeling?
1. osteoclasts scoop out a cavity of bone where the new packet will form 2. osteoprogenitor cells migrate in and differentiate into osteoblasts 3. osteoblasts fill in the cavity one layer at a time to create lamellar bone trabecular remodeling is faster than cortical remodeling!
83
how often do you get a new skeleton via the remodeling process?
about 3% of all cortical bone is turned over each year about 26% of all trabecular bone is remodeled each year new skeleton every 12-15 years!!

MSK Week 4 (11 decks)

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