L17. Tissues and Stem Cells Flashcards

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1
Q

explain the building blocks of multicellular organisms

A

cells -> tissue -> organ -> organ system -> organism

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2
Q

define tissue

A
  • how multicellular organisms organize their cells
  • they are composed of the extracellular matrix
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3
Q

tissue - extracellular matrix

A
  • the tissue’s internal framework of cytoskeletal filaments
  • gives supportive tissue’s their strength and provides one way to bind cells together
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4
Q

explain connective tissues

A
  • extracellular matrix is plentiful in there cells
  • different tissues have different types and quantities of collagen
  • other molecules are interwoven with collagen
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5
Q

connective tissues - what is collagen

A
  • a fibrous protein that is present in bone, tendon, and skin
  • provides tensile strength to animal connective tissue
  • most abundant extracellular protein in vertebrates
  • 20 different collagens
  • it is long, stiff, and triple-stranded
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6
Q

connective tissues - what molecules are interconnected with collagen

A
  • elastin - a rubbery protein
  • polysaccharide molecules
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7
Q

explain collagen production

A
  • produced by a fibroblast cell
  • synthesized intracellularly via exocytosis secretion
  • outside of the cell, they assemble into aggregates
  • the cell secretes collagen in its precursor form procollagen
  • procollagen proteinase cuts off the terminal extensions to allow assembly of collagen fibril
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8
Q

what happens when there is a genetic defect in procollagen proteinase or procollagen

A

results in improper collagen assembly and lower tensile strength

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9
Q

how is collagen organized

A

they are organized by the cells that excrete it

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10
Q

collagen organization - skin

A
  • they are woven in a wickerwork pattern or alternating layers
  • this provides the skin with tensile strength in multiple directions
  • fibroblasts can draw out the collagen into cables
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11
Q

collagen organization - in cell cultrure

A
  • if you put pieces of embryonic tissue on a collagen gel along with fibroblasts, the fibroblasts will tug on the collagen and compact it
  • this is important for wound healing
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12
Q

what are glycosaminoglycans (GAGs)

A
  • they are negatively charged polysaccharides
  • they are covalently linked to core proteins to form proteoglycans
  • many GAG chains are attached to a single core protein
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13
Q

glycosaminoglycans (GAGs) - what areas have a lot/less

A
  • tendon and bone: less GAGs and mostly collagen
  • eye: lots of GAGs and less collagen
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14
Q

glycosaminoglycans - explain its properties

A
  • GAGs are strongly hydrophilic and take up large amount of large volume relative to their mass
  • they form hydrophilic gels by attracting cations (Na+) and water
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15
Q

polarized epithelia - define epithelia

A
  • multicellular sheets in which the cells are joined together side to side
  • the joined cells then create a barrier
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16
Q

polarized epithelia - define apical surface

A

free and exposed to air or watery fluids

17
Q

polarized epithelia - define basal surface

A

attached to a sheet of connective tissue called the basal lamina

18
Q

polarized epithelia - define basal lamina

A

a thin, tough sheet of extracellular matrix, composed of type IV collagen and lamin

19
Q

explain tight junctions

A
  • makes epithelia leak-proof by sealing neighboring cells together
  • composed of claudins and occludins
  • plays a key role in maintaining the polarity of individual epithelial
20
Q

explain cytoskeleton-linked junctions

A
  • 3 main types: adherens junctions, desmosomes, and hemidesmosome
  • provides mechanical strength
  • proteins that form the cell adhesion are linked to cytoskeletal filaments
  • adherens junctions and desmosomes are both composed of the cadherin family
21
Q

cytoskeletal-linked junctions - adherens junctions

A
  • cadherins are tethered to actin filaments
  • they often form a belt
22
Q

cytoskeletal-linked junctions - desmosomes

A
  • a different set of cadherins connect to keratin filaments (intermediate filaments in epithelial cells)
  • the filaments are “spot-welded” via desmosome junctions
  • this creates great tensile strength
  • example: epidermis of the skin
23
Q

cytoskeletal-linked junctions - hemidesmosomes

A
  • looks like half a desmosome
  • has integrin linked to the lamin in the basal membrane
  • the integrin tails are linked to keratin filaments
24
Q

gap junctions

A
  • present on most epithelia
  • composed of connexons (forms water-filled channels on the membrane)
  • creates an electrical and a metabolic coupling between the cells
  • ex: electrical coupling of the heart
25
Q

what happens when a stem cell divides

A
  • each daughter cell can either remain as a stem cell or to on to be terminally differentiated
  • stem cell division is what renews the basal layer of the epidermis