Lecture 8 Flashcards

1
Q

What are the general features of epithelium?

A
  1. Avascular
  2. covers external body surfaces
  3. lines internal closed cavities
  4. lines body tubes
  5. forms secretory portion of ducts of glands (parenchyma)
  6. specialized cells function as receptors for special senses.
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2
Q

What are the three characteristics of epithelium

A
  1. the cells are closely apposed and adhere to each other
  2. exhibit functional and morphological polarity
  3. the basal surface is attached to an underlying basement membrane
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3
Q

What are the three surface domains of epithelial?

A
  1. free space / apical domain
  2. lateral domain
  3. basal domain
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4
Q

What are the junctional complexes of the lateral domain?

A
  1. Occluding junction
  2. anchoring junction
  3. communicating junction
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5
Q

Example of an occluding junction?

A

tight junction or zonula occludens

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6
Q

Example of anchoring junctions?

A
  1. adhering junctions (zona adherens)

2. Desmosomes (macula adherens)

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7
Q

Explain zona occludens?

A

Occluding junctional complex (cell to cell)

It is a tight junction

function:

  1. localized sealing of the PM of adjacent cells
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8
Q

What transmembrane proteins can be found in the zona occludens?

A

caludins- Forms backbone of ZO and forms/regulates aqueous channels

occludins- maintains barrier between apical and lateral cell surface

JAM- mediates interactions between endothelial cells and monocyte adhesions

ZO-1 = important link in transduction of signals

ZO-2- required in epidermal growth factor-receptor signaling

ZO-3 = Interacts with ZO-1. occludin, and actin

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9
Q

What domain separates the luminal space from the intercellular space and connective tissue?

A

zonula occludens

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10
Q

What domain establishes the functional domains: apical and basolateral?

A

zonula occludens

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11
Q

Explain the zonula adherens?

A

anchoring junctional complex (cell to cell)

lateral adhesion between cells
it is a continuous band that surrounds the entire cell. (beneath the tight junction)

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12
Q

What protein is found in the zonula adherens?

A

E-cadherin (calcium dependent)

helps to attach adjacent cells
interacts with actin

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13
Q

Explain the macula adherens?

A

anchoring junctional complex

macula adherens = desmosome
lateral, localized, spot adhesion
focal dense spots (macula)

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14
Q

Where is the macula adherens found?

A

Found below the zonula adherens

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15
Q

What proteins are found in the macula adherens?

A

Transmembrane protein:
desmocollin
desmoglein
(cadherin family, Ca dependent)

Intracellular plaque:
plakoglobins
desmoplakins

interacts with intermediate filaments

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16
Q

What are the functions of gap junctions

A

communicating junctional complex

help coordinate activity of adjacent cells

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17
Q

Where are gap junctions found?

A

epithelium
smooth and cardiac muscle
nerve tissue

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18
Q

What proteins make up the gap junction?

A

connexin- transmembrane protein subunits

connexon- half channel formed by 6 connexins

19
Q

What do connexons do?

A

they align to form a communicating channel connecting the cytoplasm of adjacent cells

20
Q

What are lateral interdigitations?

A

infoldings of cytoplasmic processes of adjoining cells

21
Q

What is the purpose of lateral interdigitations?

A

Increase later cell SA

22
Q

Where are lateral interdigitations common?

A

Common in cells engaged in fluid and electrolyte transport

tight junctions prevent fluid leak

23
Q

What is focal adhesion?

A

Anchoring junction

This junction functions to anchor the actin cytoskeleton to the extracellular matrix.

24
Q

What protein is present for focal adhesion?

A

Integrins

25
Q

The hemidesmosome?

A

anchoring cell junction
helps to anchor epithelial cells to the basement membrane

interaction with intermediate filaments

26
Q

hemidesmosome protein?

A

integrins

27
Q

What is bullous pemphigoid?

A

A disease that is characterized by blister formation at epithelium attachment to basement membrane

28
Q

What are the purpose of basal infoldings?

A
  1. increase cell SA of the basal domain
  2. allow for more transport proteins and channels
  3. well developed in cells that perform active transport
29
Q

Structure of the basement membrane?

A

can be seen with a light microscope

amorphous layer at the basal surface of epithelia
found between epithelial cells and connective tissue

thick in respiratory epithelium

30
Q

What comprises the basal lamina?

A

laminins
type IV collagen
proteoglycans and glycoproteins

31
Q

What are the two layers of the basal lamina?

A
  1. lamina lucida (considered an artifact)

2. lamina densa (electron dense)

32
Q

What is the basal lamina called in non-epithelial cells?

A

external lamina

33
Q

What are the two major types of glands?

A
  1. exocrine- secrete onto a surface directly or through ducts that are connected to a surface
  2. Endocrine- secrete products (hormones) into the connective tissue and then enter bloodstream
34
Q

What are three release mechanisms of glands?

A

merocrine- exocytosis of membrane bound vesicles

apocrine - product released at apical surface surrounded by envelope of PM

Holocrine - programmed cell death releases secretory products and cell debris

35
Q

Explain paracrine vs autocrine?

A

paracrine signals nearby cells

autocrine is the same cell signaling

36
Q

unicellular glands vs multicellular glands?

A

unicellular = 1 cell
Ex: goblet cell (secrets mucus)

multicellular = numerous cells

37
Q

What are the shapes of secretory cells?

A

Tubular- tube

alveolar (acinar) - flask

tubuloalveolar - tube ends in a dilation

38
Q

A duct can be simple or compound.. what does that mean?

A

Simple = no branching

compound = branching

39
Q

Names of simple glands?

A
  1. simple tubular - intestine; straight tube
  2. simple coiled tubular - skin; deep in dermis
  3. simple branched tubular - stomach; secrete mucus
  4. simple acinar - urethra; single layer of secretory cells
  5. branched acinar - stomach/skin; opens directly into lumen
40
Q

Names of compound glands?

A
  1. compound tubular- intestine; located deep in submucosa
  2. compound acinar- pancreas; pyramid shaped
  3. compound tubuloacinar - salivary gland;
41
Q

What are the three classifications of exocrine glands?

A
  1. serous
  2. mucus
  3. mixed
42
Q

Explain serous exocrine glands?

A

watery

nuclei are rounded or oval

43
Q

Explain mucous glands (exocrine)?

A

viscous and slimy
extensive glycoslyation

nuclei are flattened and compressed to the base of the cell

PAS positive

44
Q

Mixed exocrine glands?

A

contains both mucous and serous secretory components