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S1 Intro To Physio With Pharmacology > L9 Epithelia > Flashcards

L9 Epithelia Flashcards

1
Q

What are junctional complexes?

A

Structures involved in cell adhesion and communication

Junctional complexes include tight junctions, adhering junctions, and gap junctions.

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2
Q

What do tight junctions (TJ) do?

A

Impedes paracellular movement

Tight junctions restrict the passage of substances between cells.

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2
Q

What are the 3 primary germ layers?

A
  • Ectoderm: Outermost layer
  • Mesoderm: Middle layer
  • Endoderm: Innermost layer
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3
Q

What determines the ‘tightness’ of tight junctions?

A

Protein strands called claudins

The ‘tightness’ can vary significantly, influencing permeability.

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4
Q

What is the permeability variation range of tight junctions?

A

10,000 fold

Permeability varies between different tissues, such as small intestine and bladder.

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5
Q

What are adhering junctions?

A

Form a belt around the cell, linked by actin filaments and cadherins

These junctions help maintain tissue organization.

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6
Q

What is epithelial-mesenchymal transition (EMT)?

A

Reversible process of epithelial assembly

EMT allows epithelial cells to disassemble and migrate.

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7
Q

What role do gap junctions play?

A

Allows laterial communication between epithelial cells
Permit small molecule diffusion between neighboring cells

They allow electrical coupling of cells.

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8
Q

What separates epithelial cells from underlying connective tissue?

A

Basement membrane

The basement membrane is composed of ECM proteins like collagen IV.

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9
Q

What are the main functions of epithelial cells?

A

Secretion - gland
Diffusion - lung
Protection - skin
Absorption - small intestine

These functions are essential in various organs.

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10
Q

What are the common properties of epithelial cells? (4)

A
  • Entirely cellular - Composed of tightly packed cells
  • Avascular - Lack their own blood vessels. Receive nutrients via diffusion
  • Lack extracellular fibres
  • Minimal extracellular space
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11
Q

Epithelial cells able to import substances against steep conc gradients. What properties facilitate this?

A
  • Connected via tight junction, decrease free diffusion
  • Distinct apical and basolateral domains with differing membrane properties and functions (polarised)
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12
Q

What do desmosomes do?

A

Form strong adhesion points between cells

They connect intermediate filaments to cadherin proteins.

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13
Q

What are the two main types of epithelial classification for number of cell layers?

A

Simple and stratified

Simple epithelium has a single cell layer (lung), while stratified has multiple layers (skin)
Pseudostratified epithelium is another layer

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14
Q

How are basic types of epithelia classified?

A

Classified based on:
The number of cell layers
The cell shape

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15
Q

What is the appearance of simple squamous epithelium?

A

Thin ‘scales’

This structure facilitates rapid passage of molecules.

16
Q

What is the appearance of stratified squamous epithelium?

A

Apical cells appear squamous, basal cells are cuboidal or columnar

Common in areas of high abrasion, such as the skin.

17
Q

What are goblet cells?

A

Unicellular glands that secrete mucus

Often found interspersed in columnar epithelium.

18
Q

What types of glands are classified as exocrine?

A

Glands with ducts that secrete substances onto epithelial surfaces

Examples include salivary glands and sebaceous glands.

19
Q

What type of epithelium allows for shape change without damage?

A

Transitional epithelium

Found in the bladder, it accommodates distension.

20
Q

What is the role of stem cells in epithelial tissues?

A

Continual cell replacement for tissue homeostasis

This is crucial due to the hostile external environment.

21
Q

What are the two uncommon epithelial types that do not fit into simple or stratified categories?

A

Pseudostratified and transitional epithelia

Pseudostratified epithelium is found in the upper respiratory tract.

22
Q

What type of epithelial cells line the GI tract?

A

Simple columnar epithelium

This type may have cilia or microvilli for absorption and secretion.

23
Q

What is a characteristic feature of stratified cuboidal epithelium?

A

Less common, found in glands

It typically consists of two or more layers of cuboidal cells.

24
Q

True or False: All epithelial tissues are avascular.

A

True

Epithelial tissues lack blood vessels and rely on diffusion for nutrients.

25
Q

What are the common properties of epithelial cells? (6)

A

Polarity
Cellularity
Junctional complexes
Avascular (lacking blood vessels)
Minimal extracellular space
Lack extracellular fibres

26
Q

What does ECM proteins mean? And examples?

A

ECM - Extracellular matrix.
Collagens, Laminin, Proteoglycans

ECM proteins secreted by epithelial cells

27
Q

What are the membranes of an epithelial cell?

A

Apical membrane
Basolateral membrane

Apical - Faces the lumen or external environment
Basolateral - Faces underlying connective tissue

28
Q

What properties facilitate the import or expel of substances in epithelial cells?

A
  1. Polarity
  2. Tight junctions

  1. Distinct apical and basolateral domains with differing membrane properties and functio
  2. Connects the epithelial cells together
29
Q

What are the types of junctions you need to know about?

A

Adhering junctions
Gap junctions
Tight junctions

30
Q

How do epithelial cells regenerate?

A

Through stem cells

31
Q

What four characteristics do all epithelia share despite their differences?

A

Cellularity
Polarity
Avascularity
Regeneration

Epithelial tissues composed of closely pacjed cells with minimal extracellular matrix

32
Q

What is the function of a simple squamous epithelia?

A

Primary function is to facilitate rapid diffusion and absorption of molecules

33
Q

What are the types of epithelia?

A

Based on number of cell layers:
Simple epithelium
Stratified epithelium
Pseudostratified epithelium

Based on the shape of the cells:
Squamous epithelium
Cuboidal epithelium
Columnar epithelium

Pseudostratified - Appears to have multiple layers but all cell touch the basement membrane

34
Q

What type of epithelia is found in the small intestine?

A

The simple columnar epithelia

Apical surface covered with microvilli

35
Q

What is psuedostratified columnar epithelia?

A

Despite having multiple layers of cells, it consists of asingle layer of cells of varying heights so single cell layer attached to the basement membrane.

Cilitated cells often interspersed with goblet cells

36
Q

What is the most common type of stratified epithelium in human body?

A

Stratified squamous epithelia

37
Q

What shape do the transitional epithelia cells look when relaxed?

A

Rounded

38
Q

What are the two types of glands?

A

Exocrine (ducts)
Endocrine (ductless)

Secretes directly onto the epithelial surface
Secretes directly into blood

S1 Intro To Physio With Pharmacology (33 decks)

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