Surface Epithelium Flashcards

1
Q

What is epithelial tissue?

A

Composed of contiguous (close) cells which form sheaths that cover or line most body surfaces, cavities and tubes

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2
Q

What is the function of epithelial tissue?

A

Protection, transcellular transport, secretion, absorption, sensation, immune defence

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3
Q

What are characteristics of epithelial tissue?

A

-Specialised contacts - junctional complexes bind cells together
-Supported by connective tissue
-Polarity and surface specialisations -apical base polarity
-Regeneration

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4
Q

What is the basement membrane and what is it composed of?

A

Basement membrane is the interface between epithelium and connective tissue
Composed of the basal lamina and lamina reticularis

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5
Q

What is the basal lamina?

A

Constituent of basement membrane
-thin supporting sheet of basement membrane
-avascular
-composed of lamina lucinda and lamina densa

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6
Q

What is the lamina reticularis?

A

Constituent of basement membrane
-responsible for fixing lamina densa to the underlying connective tissue
-thickness varies depending on frictional force on overlying epithelium.

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7
Q

Lamina Lucinda vs Lamina densa

A

Part of basal lamina
-Lamina lucinda - consists of extracellular glycoproteins, lamin and entactin
-Lamina densa - comprised of meshwork of type 4 collagen

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8
Q

What is epithelial tissue classified based on?

A
  1. No. of cell layers - simple (areas of secretion or trasport) or stratified (high abrasion)
  2. Morphology - squamous, cuboidal, columnar
  3. Polarity and Surface Specialisation
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9
Q

What do polarised cells have?

A

-an apical domain that faces the luman
-a basolateral domain that is in contact with the basal lamina

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10
Q

What is simple squamous epithelium and where is this found?

A

-Single layer of flat cells
-Adapted for rapid diffusion
-Found lining air sacs of lung, specific segments of kidney tubules and lining blood vessels.

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11
Q

What is simple cuboidal epithelium and where is it found?

A

-Single layer cube shaped cells large central nucleus
-rapid substance diffusion
-found in parts of renal tubules, respiratory passages, ducts of many glands, thyroid gland

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12
Q

What is simple columnar epithelium and where is it found?

A

-Single layer of rectangular-shaped cells w ovoid nucleus in basal portion of cell
-has microvilli on apical plasma membrane or cilia (propel substances through hollow organs)
-cells w microvilli found in small intestine and ciliated cells found in uterine tubes and parts of respiratory tract

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12
Q

What does stratified squamous epithelium branch into?

A
  1. Keratinized Stratified squamous - apical layers are dead, lack nuclei, filled w keratin, tissue tough, resistant to friction, impermeable to water, outer layers of skin, protection
  2. Non-keratinized stratified squamous - apical (superficial) cellular layers retain nuclei, still alive, found in regions subjected to mechanical stress where surface must remain moist, lining mouth, throat, esophagus, anus, vagina, protection and secretion
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13
Q

What is stratified cuboidal epithelium and where is it found?

A

-Consists of 2 layers of cells
-lines ducts of sweat glands
-absorption and secretion

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14
Q

What is stratified columnar epithelium and where is it found?

A

-only few cell layers
-apical layer is columnar
-basal cell layer is cuboidal
-found in male urethra, cornea of eye, ducts of certain glands-salivary
-secretion, absorption, protection

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15
Q

What is transitional epithelium?

A

-only found in urinary system
-lines interior of kidney, ureters, urinary bladder, urethra
-basal cell layers are cuboidal while apical layers are dome shaped when tissue is relaxed
-ability of apical cells to flatten contributes to ability of urinary tissue to stretch

16
Q

What is pseudostratified columnar epithelium and where is it found?

A

-appears to be layered because nuclei are found at various heights but only one cell layer thick with basal plasma membranes firmly in contact with basal plasma membrane.
-found in segments of respiratory tract and nasal cavity, ciliated

17
Q

What are neighbouring cells plasma membranes linked via?

A

integral proteins

18
Q

What are the 3 types of cell junctions?

A

-Tight junctions
-Desmosomes
-Gap junctions

19
Q

What are tight (occluding) junctions?

A

Hold cells together so that the space between is impermeable to movement of macromolecules - can be tight or leaky
-cytoskeleton connections are actin microfilaments
-protein is claudins, occulins, tricellulin

20
Q

What are adherent junctions?

A

-found just below tight junctions
-attached to microfilaments of cell
-mainatin cell to cell or cell to basal lamina adherence
-protein components are clasic cadherins, catenins

21
Q

What are desmosomes?

A

-Composed of linking integral proteins
-Allow materials in ecf to pass between cells
-Increase strength of tissues by holding cells together
-Integral linking proteins ae attached to intermediate filaments of cytoskeleton
-disk shape
-Found in tissues subject to high mechanical stress e.g skin
-Protein components - cadherins

22
Q

What are gap junctions?

A

-Small pores formed by protein channels between adjacent cells
-Allows ions and small substances to flow freely between each cells cytoplasm
-Found in cells that communicate with electrical signals such as cardiac muscle cells
-main protein components is connexins

23
Q

Basal Surface Specialisations

A

-Basal lamina
-Hemidesmosomes - attach basal cell membrane to underlying basal lamina and have strong adhesive properties
—2 types - both require calcium ions to maintain attachment

24
Q

What are the 2 routes of transport in simple epithelial tissues?

A
  1. Paracellular transport
  2. Transcellular transport
25
Q

What happens in paracellular transport?

A

-Substances leak between cells in an epithelial membrane
-Limited due to tight junctions that make spaces between cells nearly impermeable

26
Q

What happens in transcellular transport?

A

-Substance enters a cell by crossing plasma membrane
-Diffuses across cytosol
-Exiting cell through plasma membrane at opposite side