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M2M > Epithelial tissue > Flashcards

Epithelial tissue Flashcards

1
Q

Is epithelial tissue vascularized?

A

no, it’s avascular

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2
Q

What are the functions of epithelia?

A
  • barrier that protects internal tissue
  • selective absorption and transport of various molecules from the environment
  • selective secretion of various molecules and fluids
  • movement of particles, solutions and cell elements
  • large scale biochemical modification/conversion/metabolism (e.g. liver, kidney, intestine)
  • communication
  • reception of sensory stimuli
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3
Q

What is endothelia?

A

linings blood and lymphatic vessels that face blood and lymph

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4
Q

What are the sheets of cells that line enclosed internal spaces of body cavities?

A

mesothelium

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5
Q

What is the epithelial to mesenchymal transition?

A
  • embryonic epithelia disassemble and move into the mesenchymal (connective) tissues
  • then they may migrate to other locations to form new epithelia or may transform into distinct non-epithelial cell lineages that give rise to other tissues
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6
Q

Where is connective tissue?

A

under the basal lamina

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7
Q

What runs through the connective tissue?

A

blood vessels, nerves, lymph, muscles

- each is surrounded by its own basal laminae that attach to their own neighboring connective tissue

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8
Q

What are the two layers of mucosa?

A
  • outer epithelium
  • the connective tissue directly underneath called lamina propria (beneath is submucosa that has bigger vessels and muscles)
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9
Q

What is the general relationship with the layers of epithelia tissue?

A

space(lumen)-epithelia-epithelial basal lamina-CT-other CT embedded tissues (blood vessels, muscles, nerves, each with their own basal laminae that connects them with CT)

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10
Q

What are tight junctions?

A
  • provide highly selective barrier that limits or prevents diffusion of substances between epithelial cells
  • key proteins - occluding and Claudine
  • ensure substances must pass through the epithelial cell by specific transport pathways
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11
Q

What are adherence junctions?

A
  • contain specific cadherins that link to actin filaments and other adapter/signaling proteins in the cytoplasm
  • cadherins extracellular domains interact with each other (cytoplasmic tails that bind to adapters and actin filaments)
  • some cadherin proteins control various aspects of epithelial polarity, development and function
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12
Q

What are desmosomes?

A
  • promote mechanical strength and resist shearing forces and promote structural organization of the epithelial sheet
  • different class of cadherins that link to intermediate filaments and other adapter proteins
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13
Q

What are gap junctions?

A

promote rapid communication between epithelial cells through diffusion of ions and small molecules

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14
Q

Is the cytoskeleton asymmetric or polar in orientation?

A

yes, particularly microtubules

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15
Q

Why is epithelial cell polarity crucial?

A

to allow unidirectional secretion and/or absorption of molecules to or from one side of the epithelium

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16
Q

What is transcytosis?

A
  • endocytosis of substances from one membrane region, followed by trans-cellular transport of the vesicles and their exocytosis from another membrane region
17
Q

What does basal laminae do?

A
  • lines basal surface of epithelial tissue

- surrounds blood vessels, muscle and nerve tissue

18
Q

What is basal laminae made of?

A

network forming collagen interwoven with a variety of glycoproteins (laminin and enactins)

19
Q

What are the functions of basal laminae?

A
  • mediate attachment of epithelia to underlying connective tissue
  • contribute to selective filtration of substances diffusing to or from the epithelia
  • necessary for the establishment and maintenance of epithelial cell polarity
  • serve as highways for the migration of cells through connective tissue
  • provide barrier to movement of invading microbes or cancer cells
  • control the gene expression of cells to affect their proliferation or development
  • critical to repair of epithelial tissue following injury (control development, morphogenesis and organization of epithelial cells)
20
Q

How do epithelial cells directly connect to the basal laminae?

A
  • key class is integrins

- attachment of hemidesmosomes and focal adhesions

21
Q

What do focal adhesions regulate?

A
  • integrins of focal adhesions connect to actin filaments inside the epithelial cell
  • regulate epithelial polarity and function through signaling mechanisms
22
Q

What are the key properties of all stem cells?

A
  • competent for cell division
  • must self renew (one mother stem cell is regenerated with each division)
  • produce anywhere from one to many distinct, differentiated cell types specific to each tissue
23
Q

What are transit amplifying cells?

A

daughter stem cells that proliferate at faster rates

- transitional intermediates

24
Q

Where do most stem cells reside in vivo?

A

stem cell niche - a specific tissue subcompartment

25
Q

What are two important principles to understand about stem cell signaling?

A
  • each pathway controls multiple, different stem cell systems
  • a single signaling pathway will have different developmental outcomes in different stem cell lineages
26
Q

How do epithelial glands secrete their substances?

A
  • exocytosis

- total cell disintegration (secretion of sebum)

27
Q

Where do exocrine glands secrete their materials?

A

apical side of epithelial surfaces

28
Q

What are secretory units (in relation to exocrine glands)?

A
  • clumps of secretory epithelial cells that produce the bulk of the exocrine secretion
  • can be organized into alveoli or acini (bowl shaped lobules) or tubular glands (tubes)
29
Q

What are ducts (in relation to exocrine glands)?

A
  • tubular structures that emanate from the secretory units
  • passageways to conduct secretions to their destination
  • simple glands - one duct
  • compound ducts - multiple, branched ducts
30
Q

What are the three types of exocrine glands of the body tubes (alimentary canal, respiratory, and urogenital system)?

A
  • mucous - produces viscous glycoprotein rich fluids
  • serous - produces low viscosity watery fluids carrying specific enzymes
  • mixed - both kinds, typically from different cell types within the gland’s secretory units
31
Q

Where do endocrine glands secrete substances?

A
  • directly into the blood stream (have no ducts)
  • hormones must cross the basal surface and basal lamina of the epithelium
  • most endocrine cells secrete these molecules from the basolateral membrane
32
Q

What generally regulates secretions from both exocrine and endocrine glands?

A

autonomic nervous system, hormones, or both

33
Q

What are adenocarcinomas?

A

cancers derived from glandular epithelium

M2M (41 decks)

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