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Histology > Epithelia > Flashcards

Epithelia Flashcards

1
Q

Tissues

A

A layer or group of cells that collectively perform a specific function ex. Smooth muscle, loose connective, nervous tissue, blood, columnar epithelium

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2
Q

Epithelium

A

Sheet of attached cells

Have polarity

No blood vessels

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3
Q

Basal Side

A

The area of the epithelium where it connects to the basement membrane (bottom)

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4
Q

Apical side

A

Side facing the free surface

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5
Q

Classify Epithelium based on # of cell layers

A

Simple Simple pseudo-stratified (1 layer, appears as multi-layered) Stratified (multi-layer) Transitional (urinary tract; large collecting duct of kidney or in the bladder)

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6
Q

Simple Squamous Epithelium

A

Single layer of cells Extremely flat

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7
Q

Mesothelium

A

Body Cavity Simple Squamous epithelium

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8
Q

Endothelium

A

Blood vessels Simple squamous epithelium

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9
Q

Simple Cubodial Epithelium

A

Single layer of cells Look like cubes Almost always found in the collecting duct of the kidney Height and width is the same

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10
Q

Simple Columnar Epithelium

A

Single layer of cells All anchor to the basement membrane Columnar in shape Usually have microvilli or cillia ex. intestine (microvilli) oviduct (cillia)

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11
Q

Simple Pseudo Stratified Epithelium

A

All cells touch the basement membrane but not all cells reach the free surface

Some are shorter and some are much taller

ex. Trachea

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12
Q

Stratified Squamous Epithelium

A

Cells tightly associated cells with eachother

Not all the cells are touching the basement membrane

ex. esophagus
ex. skin

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13
Q

Stratified Cubodial/Columnar Epithelium

A

Nearly always 2 cell layers

Found in larger excretory ducts or glands (salivary)

Based on the morphology of the top layer

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14
Q

Transitional Epithelium

A

Found in the bladder or the large collecting duct of the kidney

Adaptable, but similiar to stratified squamous

Top layer of cells may vary in shape

Shape ranges from a bulge to complete flattening

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15
Q

Basement Membrane (Component of Epithelia)

A
  • Interface between epithelia and connective tissue
  • Site of attachment for connective tissue
  • Basal Lamina (TEM structure)
  • Type IV Collagen + other proteins + carbohydrates (contain sugars)
  • Synthesized- serves as a scaffold and filtration barrier
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16
Q

Stain used to detect Type IV Collagen

A
  • Heidenhain’s Azan Stain
  • Stains Type IV Collagen Blue in the basement membrane
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17
Q

Stain used to locate the basement membrane by light microscopy

A
  • PAS Stain (Periodic Acid Schiff Stain)
  • Carbohydrates (stain purple)
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18
Q

Hemidesmosomes

A
  • Promote the adhesion of epithelial cells to the underlying basement membrane
  • Attachment of cells to the extracellular matrix
  • Maintenance of tissue structure and integrity
  • Intermmediate filaments extend into the intracellular cytoplasm
  • Connect a cell through a plaque to the basement membrane (ECM) via integrins (multi-protein complexes)
  • TEM - dark dense signaling areas dispersed throughout basement membrane
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19
Q

Tight Junctions (Natural Side of the Cell)- Interior

A
  • Closer to the apical surface
  • Seal neighboring epitheal cells via a band of claudulin proteins
  • Limit the passage of molecules and ions through the space
  • Block the movement of integral membrane proteins
20
Q

Adherens Junction

A
  • Strong mechanical attachments between neighboring cells
  • Uses cadherin- specialized transmembrane protein to adjoin neighboring cells
  • Intracellularly contains actin filaments bound to anchoring proteins
  • Connections are made inside the cell

Mutiple types of adherins proteins (ex. cadherin)- tissue specific

21
Q

Desmosomes

A
  • Hemidesmosome of 1 cell + hemidesmosome of a neighboring cell
  • Connects the intermmediate filaments (intracellular cytoplasmic side) of both cells via a plaque and transmembrane proteins
22
Q

Terminal Web

A
  • Composed of Actin filaments
  • Stabilizes a whole set of microvilli
  • Dense network of F-actin
  • HUGE difference between F-actin belts connecting adherens junctions on slides
23
Q

Gap Junctions

A
  • Spot junctions with pores
  • 2 cells connect to eachother via channel proteins
  • Allows for material exchange between neighboring cells
  • ex. Bone tissues rely on these for nutrient exchange
  • Intercellular exchange of ions and other molecules
24
Q

Cell Junctions (Lateral Side of Epithelial Cells)

A
  • Gap Junctions
  • Tight Junctions
  • Hemidesmosomes
  • Desmosomes
  • Adherens Junctions
25
Q

Cell Surface Specializations

A

Microvilli

26
Q

Microvilli (Apical Cell Surface Specialization)

A
  • Cytoplasmic finger extensions - allows them to expand their apical surface
  • Form a “brush border”
  • Easily seen on TEM
  • Each supported by an actin core
  • Role = expand the surface of the cell
  • Coated by glycocalyx (sugar coating)
  • Underneath F-actin core –> terminal web (dense F-actin network)
  • Highly organized in some tissues, but irregular in others
27
Q

Centrioles (Apical Cell Surface Specialization)

A

*

28
Q

Cillia (Apical Cell Surface Specialization)

A
  • Microtubule based structure
  • Can assist in moving things outside of the cell
  • “beat”- wavelike action
  • Found in the lining of the respiratory tract & female reproductive tract
  • Move mucus (secreted by goblet cells) and particles across epithelial cells
29
Q

Specialized Epithelium (Glands)

A
  • Endocrine
  • Exocrine
30
Q

Endocrine Glands (Specialized Epithelium)

A
  • Secrete hormones directly into the bloodstream
  • Glands without ducts
  • Secretory epithelial cells
  • Tightly controlled secretions
  • ex. Insulin secretion
31
Q

Exocrine Glands (Specialized Epithelial Cells)

A
  • All are glands with ducts
  • Unicellular (Goblet cells) or multi-cellular
  • Secretions are delivered into ducts, that end up on the apical epithelial surface
  • Ex. salivary
  • Constant secretion- not tightly controlled
32
Q

Muticellular Gland Structure (Specialized Epithelium)

A
  • Simple tubular
  • Simple coiled tubular
  • Simple branched tubular
  • Simple acinar
  • Simple branched acinar
  • Compound branched tubular
  • Compound acinar
  • Compound tubulo-acinar

Acinus is different from a tubule

Acinus is at the END of a tubulue & is a balooning out, hollow, ball-like structure

33
Q

Organization of Compound Glands

A
  • Lobes and lobules (areas separated by connective tissue)
  • Duct = the tubulue connecting the gland to the epithelial surface
  • Adenomeres (several acini) = functional units
  • Acinus = group of secretory cells

Lobules are inside lobes

Adenomeres are inside lobules- connected by a collecting duct

34
Q

Cells that facilitate the secretions of glands

A

Myoepithelial Cells

  • Cover the acini
  • Contract and expel
  • Squeeze acini
35
Q

Acini Classifications Based on Material Secreted

A
  • Serous Acinus= protein + H2o
  • Mixed Acinus = protein + sugar
  • Mucous Acinus = mucous

Serous Acinus–> darker cytoplasmic staining on an H&E Stain than other secretions

36
Q

Classification of Glands by Mode of Secretion

EXOCRINE GLANDS ONLY

A
  • Apocrine
  • Merocrine
  • Holocrine
37
Q

Apocrine Secretion

A
  • Apical portion of the cell’s cytoplasm + secretory product is pinched off
  • Released into extra-cellular space
  • After secretion = cells lose large chunk of cytoplasm
  • Apical surface before secretion = flat
  • Post-secretion - apical surface of secretory cells have a pyramidal or triangular shape

ex. Sweat glands, Ceruminous glands (ear wax)

38
Q

Merocrine Secretion

A
  • No breakdown of cellular material during secretion
  • Exocytosis mechanism
  • Membrane of secretory vesicles fuses with plasma membrane
  • Contents of vesicles are released into extracellular space
  • ex. Salviary gland
    *
39
Q

Holocrine Secretion

A
  • Entire cell disintegrates to discharge it’s secretion into collecting duct
  • Results in cell death
  • Complete loss of cytoplasm
  • ex. Sebaceous gland releases lipid to hair follicle
40
Q

Serous Gland Secreted Product

A

Protein + Water

Pink dots appear on Eosin staining

41
Q

Mucous Glands (Secreted Product)

A

Secrete viscous solution of glycoproteins & polysaccharides

Washed out appearance on H&E stain

42
Q

Mixed Gland (Secreted Product)

A

Serous & Mucous Secretion

43
Q

Lipid Glands

A

Breast (milk)

Sebaceous Gland

44
Q

What kind of glands does the pancreas have?

A

The pancreas has exocrine regions that make digestive enzymes, and endocrine regions (Islets of Langerhans) that make stuff like insulin, glucagon, etc.

45
Q

Epithelium

A

Histological layer that lines structures and interfaces with the adjacent environment

46
Q

Varying surface of pseudostratified epithelial cells

A

Any cell with a polarity has an apical vs. basolateral surface

In pseudostratified epithelium, the basolateal aspect always contacts the basement membrane. BUT, some cells may also reach the surface, and thus the apical surface will be there.

Other cells may NOT reach the surface, In that case, the apical surface will be “stuck” in the middle of the layer.

All cells might not reach the lumen but each cell would have an apical surface

Histology (5 decks)

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