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Histology > Epithelial Tissue > Flashcards

Epithelial Tissue Flashcards

1
Q

Parenchyma

A

cells responsible for the main functions
typical of the organ

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2
Q

Stroma,

A

Supporting tissue

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3
Q

principal functions of epithelial

A
  1. Covering, lining, and protecting surfaces (eg, skin)
  2. Absorption (eg, the intestines)
  3. Secretion (eg, the epithelial cells of glands)
  4. Contractility (eg, myoepithelial cells).
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4
Q

Lamina propria is a

A
  1. Thin layer of loose connective tissue
  2. Or dense irregular connective tissue,
  3. Lies beneath the epithelium
  4. Together with the epithelium constitutes the mucosa
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5
Q

The area of contact between epithelium and lamina propria is increased by

A

irregularities in the connective tissue surface in the form of small
evaginations called papillae

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6
Q

Papillae occur most frequently

A

in epithelial tissues subject to friction, such as the
covering of the skin or tongue

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7
Q

The region of the cell that faces the
connective tissue is called

A

the basal pole

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8
Q

Basement Membranes =

A

basal lamina + Reticular Lamina

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9
Q

macromolecules components of basal laminae

A
  1. Laminin: These are large glycoprotein molecules that self-assemble to form a lace-like sheet immediately below the cells’ basal poles where they are held in place by the transmembrane integrins.
  2. Type IV collagen: Monomers of type IV collagen contain three polypeptide chains and self-assemble further to form a felt-like sheet associated with the laminin layer.
  3. Entactin (nidogen), a glycoprotein
  4. Perlecan, a proteoglycan with heparan sulfate side chains: these glycosylated proteins and others serve to link together the laminin and type IV collagen sheets.
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10
Q

reticular fibers are made of

A

type III collagen

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11
Q

Basal laminae have many functions

A
  1. simple structural and filtering functions
  2. influence cell polarity
  3. regulate cell proliferation an differentiation by binding and concentrating growth factors
  4. influence cell metabolism and survival;
  5. organize the proteins in the adjacent plasma membrane (affecting signal transduction)
  6. serve as pathways for cell migration
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12
Q

lateral membranes of epithelial cells exhibit several specialized intercellular junctions:

A
  1. Seals to prevent the flow of materials between the cells (occluding junctions)
  2. Sites of adhesion (adhesive or anchoring junctions)
  3. Channels for communication between adjacent cells (gap junctions)
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13
Q

The most apical junctions are:

A

Tight junctions, or zonulae occludens

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14
Q

The seal between the Tight junctions are by:

A

claudin + occludin

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15
Q

An example of epithelia with one or very few fusion sites of zonulae occludens

A

proximal renal tubule

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16
Q

Principal function of the tight junction

A

To ensure that molecules crossing an epithelium ,in either direction,do so by going through the cell (transcelluar pathway) rather that between them (Paracelluar pathway)

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17
Q

zonulae occludens in sheets of epithelial cells help form two functional compartments:

A
  1. an apical compartment that is composed of an organ cavity (such as the lumen of a secretory unit or the gut)
  2. a basal compartment that begins at the junctions and encompasses the underlying tissue.
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18
Q

Zonula Adherens cell adhesion by:

A

Cadherins–>Catenin—>Actin binding proteins—->Actin

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19
Q

Cadherins are..

A

Transmembrane glycoproteins that interact in presence of Ca2+

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20
Q

Desmosome or Macula Adherens is a:

A

Single spot weld

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21
Q

Desmosomes contain larger members of cadherin family called

A

Desmoglein an Desmocollin

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22
Q

Desmoglein an Desmocollin bind to:

A

Plakoglobin and desmoplakin that bind to intermediate filaments of cytoplasm

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23
Q

Gap junctions mediate:

A

Communication

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24
Q

Gap junctions proteins called connexins form:

A

hexameric complexes called connexons

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25
Q

Connexons have

A

a central hydrophilic pore about 1.5 nm in
diameter.

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26
Q

Gap junctions permit:

A

the rapid exchange between cells of molecules with small (<1.5 nm) diameters

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27
Q

Substances that move readily through gap junctions

A

molecules mediating signal transduction, such as cyclic AMP, cyclic GMP

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28
Q

When two cells attach, connexins in the adjacent cell membranes move laterally and align to form connexons between the two cells with each
gap junction having

A

dozens or hundreds of aligned pairs of connexons

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29
Q

Bind the cell to the basal lamina

A

hemidesmosomes

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30
Q

In desmosomes the attachment plaques contain

A

Cadherins,

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31
Q

In hemidesmosomes the
plaques contain abundant

A

integrins, transmembrane proteins that are receptor sites for the extracellular macromolecules laminin and collagen type IV.

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32
Q

nutrients for the epithelial cells must pass out of the capillaries in

A

the underlying lamina propria.

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33
Q

Receptors for chemical messengers (eg, hormones,
neurotransmitters) that influence the activity of epithelial cells are localized

A

in the basolateral membranes.

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34
Q

In absorptive epithelial cells, the apical cell membrane contains, as integral membrane proteins:

A

enzymes such as disaccharidases and peptidases, which complete the digestion of molecules to be absorbed.

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35
Q

microvillus dimensions are

(size)

A

1 um high and 0.08um wide

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36
Q

The complex of microvilli and glycocalyx is easily seen in the light microscope and is called

A

the brush or
striated border.

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37
Q

Stereocilia are long apical processes of cells in other absorptive epithelia such as

A

that lining the epididymis and ductus
deferens.

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38
Q

Stereocilia

(vs mmicrovilli)

A

are much longer and less motile than
microvilli, are branched

39
Q

Epithelia can be divided into two main groups according to their
structure and function

A
  1. Covering (or lining) epithelia
  2. Glandular epithelia.
40
Q

Simple epithelia

A

contain only one layer of cells

41
Q

stratified epithelia

A

contain more than one layer of cells

42
Q

Stratified columnar epithelium can be found

A

in the conjunctiva lining
the eyelids

43
Q

Stratified cuboidal epithelium is

A

restricted to large excretory ducts of sweat and
salivary glands, where it apparently provides a lining more robust than that of a simple epithelium.

44
Q

Transitional epithelium found in

A

urinary bladder, the ureter, and the upper part of the urethra, is characterized by a superficial layer of domelike cells that are neither squamous nor columnar. These cells, sometimes called umbrella cells,
are essentially protective against the hypertonic and potentially cytotoxic effects of urine.

45
Q

pseudostratified columnar epithelium found in

A

lining the passages of the upper respiratory tract

46
Q

The classic unicellular gland is

A

the goblet cell in the lining of the small intestine

47
Q

Glands that retain their connection with the surface epithelium

A

Exocrine glands

48
Q

Glands that have lost their connection to the surface from which they originated during
development.

A

Endocrine glands

49
Q

Ducts can be simple ie.

A

unbranched

50
Q

Ducts can compound ie.

A

with two or
more branches

51
Q

Tubular secretory portion can be:

A

either short or long and
coiled

52
Q

Acinar Secretory portions can be:

A

round or globular

53
Q

Merocrine secretion

A

involves typical exocytosis of proteins or glycoproteins. This is the most common mode of secretion.

54
Q

Holocrine secretion

A

involves the cell filling with secretory
product and then the whole cell being disrupted and shed. This is best seen in the sebaceous glands of skin.

55
Q

Apocrine secretion

A

secretory product is typically a large lipid droplet and is discharged together with some of the apical cytoplasm and plasmalemm

56
Q

Exocrine glands with merocrine secretion can be further categorized as either:

A

serous or mucous

57
Q

Serous Cells synthesize

A

proteins that are mostly non glycycosylated, such as digestive enzymes.

58
Q

serous cells basal ends have

A

well-developed RER
and Golgi complexes

59
Q

serous cells have in apical end:

A

secretory granules in different stages of maturation

60
Q

Serous cells therefore stain intensely with

A

any basophilic or acidophilic stain.

61
Q

Mucous cells eg.

A

Goblet cells

62
Q

Mucous cells are filled apically

A

with secretory granules containing
strongly hydrophilic glycoproteins called mucins.

63
Q

When mucins are
released from the cell

A

they become hydrated and form mucus, a viscous, elastic, protective lubricant material.

64
Q

Mucin-containing granules stain well with

A

the periodic acid-Schiff (PAS) method for
glycoproteins but are not intensely acidophilic like
zymogen granules of serous cells

65
Q

salivary glands are

A

mixed seromucous

66
Q

myoepithelial cells are located

A

between the basal lamina and the basal pole of secretory or duct cells

67
Q

Long processes of myoepithelial cells

A

embrace an acinus as an octopus might embrace a rounded boulder

68
Q

Myoepithelial cells are connected to each other and to the epithelial cells by

A

both gap junctions and desmosomes.

69
Q

Myoepithelial cells are specialized for.

A

contraction and contain myosin and a large number of actin filaments

70
Q

myoepithelial cells major function is

A

to contract around the secretory or conducting portion of the gland and thus help propel secretory products into the duct

71
Q

Endocrine glands are the producers

A

of hormones, which are generally
polypeptide or lipid-derived factors that are released into the
interstitial fluid.

72
Q

paracrine

A

receptors may also be on cells very close to the hormone-secreting cells

73
Q

Autocrine,

A

receptors on the secreting cell itself

74
Q

Intestinal epithelium,
which is replaced

A

every week

75
Q

In stratified epithelial tissues, mitosis only occurs

A

within the basal layer in contact with the basal lamina.

76
Q

In some functionally complex
epithelia, stem cells have been identified only in

A

restricted niches some distance from the transit amplifying cells and differentiating
cells.

77
Q

Epithelium lining the small intestine is derived
completely from stem cells found

A

in the simple glands between the intestinal villi.

78
Q

In the epidermis, stem cells are located

A

at a characteristic position along the wall of hair follicles.

79
Q

Malignant tumors
derived from glandular epithelial tissue are usually called

A

adenocarcinomas

80
Q

Metaplasia is the

A

reversible replacement of one differentiated cell type with another mature differentiated cell type.

81
Q

Metaplasia from cigarette smoke

A

mucus-secreting ciliated pseudostratified columnar respiratory epithelial cells that line the airways to be replaced by stratified squamous epithelium

82
Q

Metaplasia in vitamin A deficiency

A

Epithelial tissue of bronchi and urinary bladder are replaced with stratified squamous epithelium

83
Q

Immotile Cilia Syndrome

A

Kartagner Syndrome

84
Q

Clostridium Perfringens enterotoxin binds to

A

Claudin molecules of intestinal cells…—> loss of water by paracellular pathway.

85
Q

Blistering (bullous) diseases eg. Pemphigus vulgaris are due to

A

abnormal desmosome function caused by autoimmune reactions to specific desmogleins

86
Q

Examples Of Simple Squamous Epithelia

A
  1. Endothelium
  2. Serous lining of cavities
  3. Pericardium
  4. Pleura
  5. Peritoneum
87
Q

Examples of Simple Cuboidal epithelia:

A
  1. Covering the ovary
  2. Thyroid
88
Q

Examples Of Simple Columnar epithelia:

A
  1. Lining of intestine
  2. Gallbladder.
89
Q

Examples Of Pseudostratified Epithelia

A
  1. Lining of trachea
  2. Bronchi
  3. Nasal cavity
90
Q

Examples of Stratified Squamous keratinized

A

Epidermis

91
Q

Examples Of Stratified Squamous Non-keratinized

A
  1. Mouth
  2. Esophagus
  3. Larynx
  4. Vagina
  5. Anal canal
92
Q

Example of stratified Cuboidal

A
  1. Sweat glands
  2. Developing ovarian follicles
93
Q

Examples Of Stratified Transitional Epithelia

A
  1. Bladder,
  2. ureters
  3. renal calyces.
94
Q

Examples Of Stratified Columnar Epithelia

A

Conjunctiva

Histology (8 decks)

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