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M1 > Histology - Epithelium > Flashcards

Histology - Epithelium Flashcards

1
Q

What are the basic tissue types?

A

Epithelium, connective tissue, muscle, and nerve

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2
Q

How is epithelium involved in homeostasis?

A

It regulates the content of the internal milieu of organs via selective transport and by forming barriers with variable permeabilities.

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3
Q

What are the three domains of a polar epithelial cell?

A

Apical - free surface

Lateral - cell-to-cell

Basal - attached to basement membrane

In general epithelial cells rest on an underlying layer of connective tissue

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4
Q

When epithelial cells lack a free surface

A

They are considered to constitute epithelioid tissues (i.e. endocrine organs)

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5
Q

What germ layer(s) is(are) epithelial cells derived from?

A

All germ layers give rise to epithelial tissue

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6
Q

What is the only exception of avascular epithelium?

A

The stria vascularis of the inner ear

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7
Q

How do epithelial cells get nutrients?

A

Diffusion from the blood veseels in underlying connective tissue.

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8
Q

Mesothelium

A

Epithelium that lines body cavities: visceral pleura, parietal pleura, pericardium, peritoneal cavity

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9
Q

Endothelium

A

Epithelium that lines the cardiovascular system

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10
Q

What are the basic functions of epithelium?

A
  • Protection of underlying tissues from abrasion or injury
  • Transcellular transport of molecules across epithelial layers
  • Secretion (of mucus, hormones or enzymes)
  • Absorption of material from a lumen (as in the intestinal tract or kidney tubules)
  • Control of movement via selective permeability (of cells or specialized junctional complexes)
  • Detection of sensations (as in taste buds, cells of retina, hair cells of the inner ear)
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11
Q
A

Simple squamos

Endothelium and mesothelium

(i.e. Bowman’s capsule and the alveoli)

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12
Q
A

Simple cuboidal

Small exocrine ducts
Germinal epithelium (ovary)
Kidney tubules
Thyroid follicles

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13
Q
A

Simple columnar

GI tract
Bladder

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14
Q
A

Pseudostratified columnar

Also referred to as respiratory epithelium

Trachea
Bronchial tree
Vas deferens
Epididymis

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15
Q
A

Stratified squamos nonkeratinized

Oral cavity
Esophagus
Vagina

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16
Q
A

Stratified cuboidal

Sweat gland ducts
Large exocrine ducts

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17
Q
A

Transitional (relaxed) epithelium

Urothelium: renal calyces, ureters, bladder, urethra

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18
Q
A

Stratified keratinized

Epidermis

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19
Q
A

Stratified columnar

Largest exocrine ducts

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20
Q
A

Transitional (distended) epithelium

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21
Q

Fuction of simple squamos epithelium

A

Fluid transport

Gas exchange

Lubrication

Reduce friction so viscera move

Lining membrane

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22
Q

Function of simple cuboidal epithelium

A

Secretion
Absorption
Protection

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23
Q

Function of simple columnar epithelium?

A

Transportation
Absorption
Secretion
Protection

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24
Q

Function of pseudostratified epithelium?

A

Secretion
Absorption
Lubrication
Transportation
Protection

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25
Q

Function of stratified squamos (nonkeratinized)?

A

Secretion
Protection

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26
Q

Function of stratified squamos (keratizined)?

A

Protection

Epidermal cells are flat without nuclei

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27
Q

Function of stratified cuboidal?

A

Absorption
Secretion

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28
Q

Function of stratified columnar?

A

Secretion
Absorption
Protection

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29
Q

Function of transitional?

A

Distensible
Protection

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30
Q

Endothelial cells

A

Simples squamos cells that line blood vessels, lymphatic vessels, and chambers of the heart

Contain Weibel-Palade bodies which are storage granules that contain von Willebrand factor

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31
Q
A

Weibel-Palade bodies (contain von Willebrand factor)

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32
Q

What epithelium lines the pericardium?

A

Mesothelium

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33
Q

What is released when endothelium is damaged to induce clot formation?

A

Von Willebrand factor (contained within the Weibel-Palade bodies)

34
Q

How does endothelium take part in the immune system?

A

By interacting with lymphocytes and expression adhesion molecules and secreting several classes of interleukins (IL-1, IL-6, and IL-8)

35
Q

How do endothelial cells take part in hormone synthesis?

A

Growth factors: hemopoietic colony-stimulating factors, fibroblast growth factor, and platelet-derived growth actor

Growth inhibitors: heparin, transforming growth factor b

36
Q

Vasoconstrictors secreted by endothelium

A

Endothelins

Angiotensin-converting enzyme

37
Q

Vasodilators secreted by endothelium

A

Nitric oxide and prostacyclin

38
Q

Antithrombogenic substances produced by endo/subendothelial tissue

A

Tissue plasminogen activator (interferes with platelet aggregation)

Thrombomodulin

39
Q

Anticoagulants that are produced by endo/subendothelial tissue

A

Thrombomodulin

Plasminogen tissue factor

40
Q

Microvilli

A

Contain an actin core, and are covered by a plasma membrane (appear as a brush border in some cells like intestinal epithelial cells)

41
Q

Glycocalyx

A

glycoproteins secreted by goblet cells. The glycocalyx is adsorbed onto the surface of microvilli.

PAS stain

Glycocalyx serves for cell protection and cell recognition; often contains digestive enzymes.

Glycocalyx stain positively with perioidc acid Schiff (PAS)

42
Q

Stereocilia

A

long microvilli (nonmotile)

43
Q

Terminal web

A

Of the cytoskeleton, contains: actin, myosin, and spectrin (along with other cytoskeletal proteins)

44
Q

The cortical cytoskeleton

A

Composed of intermediate filaments (including various cytokeratins) and the terminal web

45
Q

Axoneme

A

the 9+2 arrangement of microtubules in cilia

9 outer doublet microtubules plus two central microtubules

46
Q

Basal bodies

A

Found at the base of every cilium, consisting of 9 triplet microtubules and no central microtubules

46
Q

Where are the dynein of cilia found?

A
47
Q

Tight junctions

A

Forms zonula occlusions

Impermeable (intercellular diffusion barrier)

Do not function to hold epithelial cells together or to an underlaying basal lamina.

But they maintain apical and basolateral membrane domains, thus limiting the movement of proteins with the plane of the lipid bilayer and therefore contributing to the functional polarity of epithelial cells

(Tight junctions are Ca2+ dependent but for as needed with no protein synthesis)

Found at the apical surface of epithelial cells (from proteins occludins and claudins)

48
Q

Adherin junctions

A

Zona adherens and Macula adherens

Provide mechanical stability by linking the cytoskeleton of one cell to another (or to basal lamina)

Also, importgant for cell-to-cell recognition and singal transduction

49
Q

Communicating junctions (gap junctions)

A

Allow for chemical and electrical coupling between cells; coordinating cellular activity related to homeostaasis

Transmembrane proteins call connexons (hexameric protein) that open and close in response to changing pH and Ca2+.

Connexons of neighboring cells line up to form patent channels

50
Q

What cell types contain actin? What cell types contain keratin?

A

Actin - virtually all cell types

Keratin - unique to epithelial cells

51
Q

Zonula

A

belt-like structure that encircles apical portion of the cell

52
Q

Maculae

A

Spot-like or button-like structures

53
Q

Zonula adherens (ZA)

A

Belt desmosomes

A belt-like junction around apical portions of an epithelial the cell, but immediately below the level of tight junctions. ZA interacts with actin in the cortical cytoskeleton.

The membranes of adjacent cells approximate, do not contact ZA

54
Q

Macula Adherens

A

MA is known as a desmosome
(or spot desmosome to contrast with “belt desmosome” – an older term for ZA). Desmosomes are located below the level of the zonula adherens and they interact with intermediate
filaments (keratins in epithelia cells) of the cytoskeleton.

Calcium dependent “spot welds” that bind adjacent cells together

Resist shear forces

The intercalated disc is a highly specialized type of MA

55
Q

Actin molecules of adjacent cells are attached to? By?

(Desmosomes)

A

Attached to E-cadherin-catenin complexes by alpha-actinin and vinculin

E-cadherin and catenin are membrane proteins

alpha-actinin and vinculin are cytoskeletal proteins

56
Q

Pemphigus vulgaris

A

Individuals produce autoantibodies to desmosomal proteins. Those affected can suffer fluid loss through the skin and mucous membranes (this can be fatal)

Disruption of desmosomal proteins causes epithelial cells in the basal layers of the skin to lift off their underlying basal lamina and for cells (keratinocytes) in the middles and upper layers to lose continuity with each other.

57
Q

Where in epithelium can desmosomes be found?

A

Throughout the lateral domains, but below the level of the zonula occludens and zonula adherens

Hemidesmosomes: create static or very stable links between the cytoskeleton and extracellular matrix on the basal membrane domain of epithelial cells. Hemidesmosomes are abundant in mature organs.

58
Q

Focal adhesions

A

Create dynamic links between the cytoskeleton and extracellular matric on the basal membrane domain of epithelial cells. They are abundant during embryonic development when cells are migrating.

59
Q

Hemidesmosomes

A

Robustly anchor epithelial cells to their underlying basal lamina by forming attachements to keratin (very stable protein)

60
Q

Focal adhesions

A

Dynamically anchor epithelial cells to their underlying basal lamina by forming attachments to actin.

61
Q

Basement membrane

A

Composed of basal and reticular lamina

Basal lamina - synthesized by epithelial cells and consists primarly of collagen type IV, laminins, entactin, proteoglycans, and fibronectin. Nidogens function as glue and perlecan (heparan sulfate bound to nidogen)

Reticular lamina - synthesized by connective tissue cells and consists primarily of collagen type III

62
Q

Collagen IV

A

unique to basal lamina (lamina densa) and provides the structural framework for the basal lamina. Collagen IV is heavily glycosylated and is comprised of small fibrils that do not form large fibers typical of many collagens. Collagen IV is highly flexible; its C-terminal
ends (indicated by the dark balls on the drawing)
dimerize while its N-terminal ends form extensive
networks.

63
Q

Laminin

A

A protein found in the basal lamina of the basement membrane. Laminin is a large, cross-shaped glycoprotein that binds components of basal lamina to each other and to epithelial cells. There are three components (alpha, beta, and gamma)

64
Q
A

A - Simple squamos

B - Simple cuboidal

C - Simple columnar

65
Q
A

D - transitional

E - endothelium

66
Q
A

F - stratified squamos

67
Q
A

G - ciliated pseudostratified columnar (respiratory)

I - endothelium

68
Q

Cadherin

A

Calcium dependent adhesion protein

Found in desmosomes

E-cadherin lost in breast cancer cells - metastasis

69
Q

A principal cytoskeletal component associated with the zonual adherens in epithelial cells is

A

Actin

70
Q

What mesothelium is the only example of non-simple structure?

A

The germ mesothelium of the ovary is simple cuboidal

71
Q

Ducts within organs are lined with what type of tissue interiorly?

A

Typically squamous lines interior duct

72
Q

Ducts that exit an organ

Tissue type - Histo

A

Typically stratified cuboidal epithelium lines duct

73
Q

Where can ciliated pseudostratified columnar epithelium be found other than the respiratory tract?

A

Parts of the male reproductive system

74
Q

What is the predominant protein found in cilia?

A

Tubulin

75
Q

What is the predominant protein found in microvilli and stereocilia?

A

Actin

76
Q

Epithelium of the urinary bladder

A

Transitional epithelium (only found in the bladder and the most proximal parts of the ureter)

Transitional epithelium is often binucleated (also can either polyploid or monoploid)

77
Q

What forms the internal glandular tissue?

Hair follicle

A

Stratified squamos epithelium of the hair follicle

78
Q

What cell junction is disrupted in endothelial cells to cause edema (leaking of cellular fluid into extracellular space)?

A

Tight junctions (Zonula occludens)

79
Q

PAS Stain on goblet cell

A

Stains the glycocalyx

80
Q

What cells are within the blue oval?

A

Resident lymphocytes in the intestines

81
Q

Metaplasia

A

A reversible transformation of a mature cell type into another cell type that is not native to that specific region in response to chronic irritation or cell injury (e.g., transformation of squamous epithelium into columnar epithelium in the case of Barrett esophagus).

Abmoss

M1 (53 decks)

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