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MS1 - Molecules to Medicine > Epithelial Transport > Flashcards

Epithelial Transport Flashcards

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1
Q

What drives the process of epithelial renewal?

A

epithelial stem cells

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2
Q

How do epithelial tissue get metabolite, gases, and secreted ligands?

A
  • avascular

- they must diffuse through connective tissue and basal laminae to reach epithelia or blood

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3
Q

What are some of the functions served by epithelial?

A
  • barrier
  • selective absorption and transport of various molecules from the environment
  • selective secretion
  • movement of particles, solutions, and cell elements through passageways
  • large scale biochemical modification/conversion/metabolism
  • communication to and from other tissues and organs
  • reception of sensory stimuli
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4
Q

What are endothelia?

A

line blood and lymphatic vessels (made of endothelial cells)

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5
Q

What is mesothelium?

A

sheets of cells that line enclosed internal spaces of body cavities

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6
Q

Embryonic epithelia often disassemble and move into the _______________, where they may migrate to other locations to form new __________ or may transform into distinct _____________ cell lineages that give rise to other tissues.

A

Embryonic epithelia often disassemble and move into the mesenchymal (connective) tissues, where 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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7
Q

What are the two layers of mucosae?

A
  • outer epithelium

- the connective tissue directly underneath called the lamina propria

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8
Q

What does the lamina propria contain?

A

(connective tissue directly underneath the epithelial layer of mucosae)
- immune cells, small blood vessels

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9
Q

What is submucosa?

A
  • deeper connective tissue layer under the lamina propria

- contains bigger vessels and muscles, nerve axon bundles, etc.

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10
Q

What are the general layers of epithelial sheets?

A

Space (lumen) - Epithelia - epithelial basal lamina - connective tissue - other connective embedded tissues (blood vessels, muscles, nerves - with their own basal laminae that connect them to the CT)

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11
Q

What is simple epithelia?

A

all cells arranged in a single layer or sheet

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12
Q

What is stratified epithelia?

A

more than one layer of cells in which the cells of the outer layers do not directly contact the basal lamina

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13
Q

What is pseudostratified epithelia?

A

some cells do not reach the free surface but all directly rest on the basal lamina

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14
Q

What is transitional epithelia?

A

(found in the bladder)

- epithelia are stratified but when stretched change shape from cuboidal to squamous

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15
Q

What are tight junctions?

A
  • highly selective barrier that limits or prevents diffusion of substances between epithelial cells
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16
Q

What are the key core proteins of tight junctions?

A

occluding and claudins

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17
Q

What are adherence junctions?

A

promote attachment, morphological organization, and stem cell behavior within the epithelial sheet

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18
Q

What proteins do adherence junctions contain?

A

specific cadherins that link to actin filaments and other adapter/signaling proteins in the cytoplasm

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19
Q

What are desmosomes?

A

promote mechanical strength and resist shearing forces and promote structural organization of the epithelial sheet

20
Q

What proteins do desomosomes contain?

A

different class of cadherins that link to intermediate filaments and other adapter proteins

21
Q

What are gap junctions?

A

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

22
Q

Why is the membrane surrounding the lateral and basal side of an epithelial cell called the basolateral membrane?

A

because the protein and lipid content is similar on both the lateral and basal sides

23
Q

What are the two key aspects of epithelial cell polarity?

A
  • the plasma membrane composition is locally segregated into domains (apical and basal)
  • the organelles and cytoplasm is polarized ( cytoskeleton, especially microtubules, is asymmetric or polar in orientation)
24
Q

What is transcytosis?

A

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

25
Q

Epithelial cell polarity is crucial to allow _____________ to or from one side of the epithelium.

A

unidirectional secretion and/or absorption of molecules

26
Q

What are two apical surface modifications?

A

microvilli and cilia

27
Q

What are microvilli?

A

cell surface extensions that contain actin bundles connected to cytoskeletal elements in the cell interior

28
Q

What is the primary function of microvilli?

A

to increase surface area, which greatly increases the rate/efficiency of membrane transport and secretion

29
Q

What is a basolateral surface modification?

A

infolds and outfolds of the basolateral membrane (lack structural organization of the apical microvilli and cilia)

30
Q

What is the basal lamina?

A
  • thin sheet of extracellular material that underlies the basal surface of each epithelial tissue, blood vessels, muscle, and nerve tissue
  • made of collagen (esp. collagen IV) and extracellular glycoproteins (lamins and entactin)
31
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 establishment and maintenance of epithelial polarity
  • serve as specific highways for migration of cells through connective tissue
  • barrier to movement of invading microbes or cancerous cell into other tissues
  • control the gene expression of cells to affect their proliferation or development
  • control development, organization, repair from injury or disease (tissue scaffolding)
32
Q

How do epithelial cells directly connect to the basal laminae?

A

by attachment of integrins (hemidesmosomes and focal adhesions) on the basal surface of the epithelial cell to components of the basal lamina

33
Q

What do focal adhesions connect to inside the epithelial cell?

A

actin filaments

34
Q

What are the three key properties of stem cells?

A
  • they are competent for cell division
  • stem cells must self renew (at least one mother stem cell is regenerated with each division)
  • stem cells produce anywhere from one to many distinct, differentiated cell types specific to each tissue
35
Q

What are transit amplifying cells?

A
  • daughters of stem cells that proliferate at faster rates
  • middle step - transitional intermediate
  • transit amplifying cells then produce differentiated cells
36
Q

What regulates cell division and differentiation in stem cells?

A
  • in the stem cell niche, neighboring cells secrete regulatory factors that tightly control stem cell division and differentiation programs
  • signals from distant sources (hormones and endocrine glands)
37
Q

What is the typical cell signaling pathway for stem cells?

A
  • extracellular ligand secreted by signaling cells
  • receptor in receiving cells binds and is activated/inactivated by the ligand
  • downstream effector proteins in the cytoplasm and nucleus
  • numerous modulator proteins that promote or suppress pathway components
38
Q

What are two key principles of stem cell signaling pathways?

A
  • each pathway controls multiple, different stem cell systems (some are unique, but many are shared)
  • a single signaling pathway will have different development outcomes in different stem cell lineages
39
Q

What are exocrine glands?

A

secrete material onto epithelia lined surfaces or the outside world

40
Q

How do glands secrete their substances?

A
  • exocytosis

- total cell disintegration (e.g. oily sebum onto hair and skin)

41
Q

What are the main components of multicellular exocrine glands?

A
  • secretory units (clumps of secretory epithelial cells)

- ducts (tubular structures that emanate from the secretory units)

42
Q

What are the three general types of exocrine glands products?

A
  • mucous (viscous glycoprotein-rich fluids)
  • serous (low viscosity watery fluids)
  • mised
43
Q

Do endocrine glands have ducts?

A

no

44
Q

How do endocrine glands secrete hormones when they’re surrounded by basal lamina?

A

hormone molecules must cross the basal surface and basal lamina of the epithelium, so most endocrine cells secrete these molecules from the basolateral membrane

45
Q

What regulates secretions from the exocrine and endocrine glands?

A

autonomic nervous system and/or hormones from the blood

46
Q

What are adenocarcinomas derived from?

A

glandular epithelium

MS1 - Molecules to Medicine (35 decks)

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