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BMS 460 > Tissues and Organs: Pathophysiological Correlates > Flashcards

Tissues and Organs: Pathophysiological Correlates Flashcards

1
Q

general features of epithelium

A
  • tissue that covers external (epithelium) and internal (endothelium) body surfaces
  • most epithelial tissues are derived from embryonic ectoderm or endoderm (except endothelium is from mesodermal (mesenchymal) origin)
  • avascular
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2
Q

what is the basement membrane

A
  • a thin, mesh-like layer between the epithelial cells and the adjacent connective tissue
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3
Q

what are the two domains of epithelium?

A
  1. apical domain: protection of epithelial surface, absorption of substances, has cilia and microvilli
  2. basolateral domain: anchors epithelial tissues to each other and to basement membrane
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4
Q

what three things are present on the basolateral domain of epithelial cells?

A
  1. junctional complexes
  2. cell adhesion molecules
  3. basement membrane
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5
Q

three types of common cell junctions and their functions

A
  1. zonula occludens (tight junctions): act as a diffusion barrier, for example between the extracellular space and the intestinal lumen. they also confine some transport proteins to a particular portion of the cell membrane, facilitating specialized functions
  2. maculae adherens (spot desmosomes): mediate cell-cell adhesion
  3. nexi (gap junctions): permit direct movement of ions and small molecules between the cytosol of adjacent cells
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6
Q

describe the basement membrane under a light microscope

A

after staining with PAS stain, the basement membrane is a pink perimeter around cells, and is PAS positive (glycoproteins!)

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7
Q

what are the two layers within the basement membrane?

A
  • firstly, these can be seen only under an electron microscope
  • closest to the epithelial cells is the basal lamina, which contains type IV collagen made by epithelial cells
  • below the basal lamina is the reticular lamina, which contains type III collagen made by fibroblasts
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8
Q

where is a basement membrane found?

A
  • located in almost every tissue in the body
  • beneath endothelial and epithelial cells
  • separates cells from underlying connective tissue
  • surrounds muscle, adipose, and nerve (schwann) cells
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9
Q

describe the basal lamina as it relates to the urinary system

A
  • the renal corpuscle has a double basal lamina (wrapping around the glomerular capillaries)
  • this consists of the basal lamina and the podocytes that also wrap around the glomerulus
  • this is the most important element in glomerular filtration
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10
Q

goodpasture syndrome

A
  • autoimmune disorder
  • progressive glomerulonephritis and pulmonary hemorrhage caused by anti-COL4A3 (chromosome 2) antibodies binding to glomerular and alveolar basal laminae
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11
Q

benign familial hematuria

A
  • dominant inherited mutation of COL4A4 gene (chromosome 2, so autosomal)
  • does not lead to renal failure
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12
Q

alport’s syndrome

A
  • x-linked recessive trait
  • predominant in males
  • mutations of COL4A5 gene
  • progressive nephropathy, characterized by irregular thinning, thickening, and splitting of glomerular basal lamina, resulting in hematuria
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13
Q

what is embryonic mesenchyme

A

undifferentiated loose connective tissue derived mostly from the mesoderm

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14
Q

define connective tissue proper

A
  • relatively few cells in a large volume of extracellular matrix, major components of which are collagen and elastin (fibrous proteins)
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15
Q

list the components of CT proper

A
  • fibroblasts
  • extracellular fibers: collagen and elastin
  • extracellular matrix (amyloid)
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16
Q

discuss amyloid secretion

A
  • part of extracellular matrix
  • can accumulate and lead to disease processes
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17
Q

define interstitium

A

-accounts for about 20% of all body fluids
- fluid filled space: fluid that is outside of cells, not in the vascular system

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18
Q

what function does CT have other than connecting cells/tissues to each other?

A

provides a “highway” compartment in which cells and macromolecules can travel without having to cross a basal lamina

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19
Q

describe the collagen protein

A
  • three-chain fibrous protein
  • chains coil around each other (“coiled-coil” structure)
  • triple helix = a protein with a lot of tensile strength!!
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20
Q

describe components of type 1 collagen

A
  • two alpha 1 chains, which are coded by the COL1A1 gene on chromosome 17
  • one alpha 2 chain, which is coded by the COL1A2 gene on chromosome 7
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21
Q

intracellular events in collagen synthesis

A

procollagen is synthesized, then procollagen peptidase modifies it to yield tropocollagen (which can bend)

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22
Q

extracellular events in collagen synthesis

A
  • tropocollagen self assembles into collagen fibrils through the enzymes lysyl hydroxylase and oxidase
  • fibrils aggregate to form fibers
  • fibers form bundles (and sheets in muscles/nerves)
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23
Q

strickler syndrome

A
  • mutated COL2A1 gene
  • myopia, hypoplasia of lower jaw, dysplasia of epiphyses
  • type II collagen is abundant in cartilage and vitreous humor in eyes
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24
Q

describe mutation of COL1A1 and COL 1A2 genes

A
  • firstly, these encode the alpha 1 and alpha 2 chains used to make type I collagen
  • interferes with conversion of procollagen to collagen
  • so, get defective cross-linking and reduction in tensile strength of tendons
  • this is seen in some clinical forms of ehler’s danlos syndrome
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25
Q

osteogenesis imperfecta

A
  • mutation in COL1A1
  • autosomal dominant mutation
  • reduction in production of type 1 collagen, which is needed for normal ossification
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26
Q

how must collagen be assembled stucturally?

A

every third amino acid in the polypeptide sequence must be glycine (G). this is the only amino acid small enough to fit in the conformationally restricted triple helical structure

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27
Q

what are the types of osteogeneis imperfecta?

A

type I: mild, non-deforming, premature stop codon in COL1A1, most prevalent
type II: perinatal lethal, glycine substitutions in COL1A1 or 2
type III: severely deforming, glycine substitutions in COL1A1 or 2
type IV: glycine substitutions in COL1A1 or 2

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28
Q

what cells produce elastic fibers?

A
  • fibroblasts
  • chondroblasts
  • chondrocytes
  • smooth muscle cells
29
Q

what are two amino acids that are characteristic of elastin?

A
  • desmosine and isodesmosine
  • these amino acids are responsible for cross-linking mature elastin fibers to enable their stretching and recoil
30
Q

what is fibrillin?

A

fibrillin is a glycoprotein that interacts with tropoelastin (precursor to proelastin) in the ec space to organize immature elastic fibers, which come together to form mature elastic fibers

31
Q

where are the different types of fibrillin present?

A
  • fibrillin is present in the aorta, suspensory ligaments of the lens, and periosteum
  • fibrillin 1 and 2 are needed for skeletal development
  • fibrillin 1 only is important for cardiovascular development
  • mutations sometimes associated with adolescent idiopathic scoliosis
32
Q

marfan syndrome

A
  • mutation of fibrillin 1 gene (FBN1 on chromosome 15) so there is a deficienty of fibrillin 1
  • defects caused by CT abnormalities because it is too elastic with poor recoiling
  • bone defects: lack of tightness/oppositional force from periosteum during bone growth because it is abnormally elastic
  • arachnodactyly, mitral valve prolapse, dilation of root of aorta, aortia dissection
33
Q

discuss the vascular pathology of marfan syndrome

A

FBN1 (fibrillin 1) mutation causes hyperactivity of TGF-beta (FBN1 usually inhibits TGF-beta. the role of this is an area of research - abnormal/reduced fibrillin 1 causes structural weakness and increased TGF-beta signaling, which leads to vascular remodeling. this can lead to degenerative changes (cystic medial necrosis), which can lead to progressive aortic dilation. fibrillin-1 mutations also cause elastolysis because fibrillin 1 is what makes elastin functional/elastic

34
Q

what is amyloid?

A
  • amyloid is an abnormal fibrillar protein composed of peptides or peptide fragments with a B pleated sheet conformation
  • multiple forms of amyloid
  • derived from a normal cellular protein which gets disregulated to form amyloid
35
Q

4 major types of amyloidosis

A
  1. amyloid light chain (AL): derived from immunoglobulin light chains produced by neoplasmic plasma cells
  2. amyloid-associated (AA): derived from serum-associated amyloid (SAA), which is part of the inflammatory process
  3. beta-amyloid (AB): derived from amyloid precursor protein (APP, normal) - inheritance of point mutations in APP gene in some cases of familial Alzheimer’s disease results in a protein that is more likely to be abnormally processed and cleaved by y-secretase to form AB42 plaques (APP is on chromosome 21, so patients with Down Syndrome who have an extra copy of this chromosome are more likely to develop Alzheimer’s at an early age)
  4. Amyloid transthyretin (ATTR): transthyretin is a protein mainy formed in the liver that transports thyroxine and retinol-binding protein. mutant form of the protein is deposited, = genetically determined familial amyloid polyneuropathies.
36
Q

what type of a process is amyloid deposition?

A

an irreversible pathologic process - usually constant accumulation of amyloid fibril leads to progressive organ dysfunction and eventual death

37
Q

types of amyloidosis

A
  • primary and secondary (systemic/reactive): nephrotic syndrome, arrhythmia, carpal tunnel syndrome
  • senile cerebral (localized): dementia (Alzheimer’s type)
38
Q

layers covering external body surfaces

A

epithelium: epidermis
CT: dermis
epithelium and CT: skin

39
Q

layers lining body cavities open to surface (urinary, respiratory, etc.)

A

epithelium: epithelium (with or without glands)
CT: lamina propria
epithelium and CT: mucosa

40
Q

layers lining closed body cavities (peritoneal, pericardial, and pleural)

A

epithelium: mesothelium (no glands)
CT: submesothelium
epithelium and CT: serosa

41
Q

layers lining the cardiovascular cavity

A

epithelium: endothelium
CT: subendothelium
epithelium and CT: intima (vessels, endocardium)

42
Q

systemic lupus erythematosus (SLE)

A
  • paradigm of complex autoimmune CT diseases
  • consists of abnormalities indicative of B-cell hyperactivity
  • overall manifestation: epidermal atrophy (but not life threatening)
43
Q

scleroderma (progressive systemic sclerosis)

A

autoimmune disease of CT characterized by excessive collagen deposition in skin and internal organs

44
Q

where do cartilage and bone originate from?

A
  • they are specialized forms of CT derived from embryonic mesenchyme
  • both consist of cells embedded in an extracellular matrix
45
Q

describe cartilage

A
  • matrix is highly hydrated (mostly water and collagen)
  • avascular, no nerve or lymphatic supply
  • little potential for regeneration
46
Q

describe bone

A
  • calcified component of skeleton
  • matrix consists of collagen embedded in ground substance with hydroxyapatite
  • high metabolic rate, richly vascularized, up to 10% of cardiac output
  • high potential for regeneration
47
Q

describe the two ways that bone can develop

A
  • with cartilage model: endochondral ossification
  • without cartilage intermediate: intramembranous (mesenchymal) ossification
48
Q

what drives the process of making bone and connective tissues?

A

pluripotent mesenchymal cell –> osteoblast: Cbfa1/Runx2
osteoblast –> osteoclast: osterix
pluripotent mesenchymal cell –> chondroblast/chondrocyte: Sox9

49
Q

osteoblasts vs. osteoclasts

A

osteoblasts secreting matrix/contents of osteoid, osteoclasts responsible for bone remodeling/shaping

50
Q

where to osteoblasts and chondroblasts arise from?

A

pluripotent mesenchymal cells, which arise from the mesoderm but are present in all three embryonic layers (endoderm, mesoderm, ectoderm)

51
Q

describe the functions of Cbfa1/Runx2

A
  • differentiation of pluripotent mesenchymal cells to osteoblasts, and osteoblasts to osteocytes
  • inhibits enlargement of chondrocytes to hypertrophic chondrocytes in endochondral ossification
  • on chromosome 6
  • overall, has a role in both chondrocytic (making them hypertrophic) and osteoblastic (into osteoclasts) differentiation!!
52
Q

describe the functions of Sox9

A
  • differentiation of pluripotent mesenchymal cells to chondroblasts and chondroblasts to chondrycytes
  • enlargement of chondrocytes to hypertrophic chondrocytes during endochondral ossification (Cbfa1/Runx2 stimulates this same process)
53
Q

what does osterix do?

A

osterix is a transcription factor that specifies maturation of osteoblasts and the differentiation of osteoblasts to osteocytes

54
Q

what does osteocalcin do?

A
  • noncollagenous hormone
  • secreted solely by osteoblasts
  • pro-osteoblastic, or bone-building
55
Q

describe appositional growth

A
  • from undifferentiated cells at the surface
  • increases diameter of tissue
56
Q

describe interstitial growth

A
  • from differentiated cells within
  • increases density of tissue
57
Q

what is the perichondrium?

A
  • connective tissue layer containing mesenchymal cells that are stimulated to proliferate, differentiate into chondroblasts, and secrete cartilage matrix (the mass of mesenchymal tissue is called the bastema)
  • has a fibrous layer and a chondrogenic layer
58
Q

hyaline cartilage

A
  • type II collagen
  • avascular
  • temporary skeleton of embryo, articular cartilage, and cartilages of respiratory tract
59
Q

elastic cartilage

A
  • type II collagen and elastin
  • avascular
  • external ear, epiglottis, auditory tube
60
Q

fibro cartilage

A
  • type I collagen
  • generally avascular
  • intervertebral disks, articular disks of the knee, mandible, sternoclavicular joints, pubic symphysis
61
Q

what is Sox9 mainly involved in?

A

chondrogenesis! also, is on the Y chromosome and is responsible for differentiation into male fetus

62
Q

what transcription factors are required for the differentiation of osteoblasts to osteocytes? what happens if these are not expressed?

A

Cbfa1/Runx2 - if not expressed, the entire skeleton will be cartilage because they are needed for ossification

63
Q

cleidocranial dysplasia

A
  • Cbfa1/Runx2 mutation
  • autisomal dominant
  • abnormal clavicles, unfinished fusion of skull bones, other skeletal changes
  • basically, ossification does not happen properly/enough
64
Q

campomelic dysplasia

A
  • chondrogenic cells that do not have Sox9 will not differentiate into chondrocytes
  • rare and severe dwarfism because cartilage is not developing normally/enough
  • also frequently causes sex reversal because Sox9 is also responsible for differentiating into male. so fetus with XY genotype would have female phenotype
65
Q

describe endochondral ossification

A
  1. start with cartilage model of bone, covered by perichondrium
  2. chondrocytes in the diaphysis become hypertrophic and start to secrete type X collagen and release growth factors to attract blood vessels. they also direct adjacent perichondrial cells to differentiate into osteoprogenitor cells which will differentiate into osteoblasts, which will ultimately cause a thin layer of bone to form around the diaphyseal region.
  3. now, there is vascularization of the bone collar and hypertrophy of the diaphyseal chondrocytes. this forms the primary ossification center (3rd month gestation)
  4. blood vessels enter the newly formed medullary cavity and grow towards the epiphyseal ends, “pushing” the cartilage up there and forming the epiphyseal growth plates
  5. bone keeps lengthening and a secondary ossification center arises (at the epiphysis)
  6. in an adult bone, it has achieved full length and width and the epiphyseal plates have become ossified (“epiphyseal line”). the articular surfaces are free of perichondrium (now just articular cartilage)
66
Q

describe intramembranous ossification

A
  1. mesenchymal cells aggregate without a cartilage intermediate, a process controlled by patterning signals from polypeptides of Wnt, hedgehog, fibroblast growth factor, and TGF-B families
  2. mesenchymal cells differentiate into osteoblasts, forming a bone blastema. osteocytes in the core of the blastema are interconnected by cell processes forming a functional syncytium, and osteoblasts line the surface of the blastema
  3. osteoblasts deposit bone matrix (osteoid). later, Ca2+ transported by blood vessels is used in the mineralization process and primary bone tissue is formed.
  4. osteoclasts initiate the modeling of bone tissue
67
Q

describe organization of a primary ossification center in intramembranous ossification

A

multiple trabeculae are enlarged by appositional growth, eventually fusing together as a primary ossification center during the first stage of intramembranous ossification (primary bone formation begins interstitial, then becomes appositionsal)

68
Q

what are BMP’s

A
  • originally discovered by their ability to induce formation of bone and cartilage
  • now recognized that dysregulated BMP signaling can result in pathological processes
  • mutations in BMP’s, their inhibitors, or their receptors are associated with many inherited human disorders affecting the skeleton
69
Q

fibrodysplasia ossificans progressive (FOP)

A
  • activating mutation in gene encoding activin receptor type 1A - this is a receptor for a BMP!
  • result is that the receptor is always activated, so CT and muscle tissue is transformed into a secondary skeleton
  • essentially always making bone

BMS 460 (13 decks)

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