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MBBS > Epithelia > Flashcards

Epithelia Flashcards

1
Q

Identifying features of epithelia

A

Forms dense cellular sheets
Has no blood vessels
Rests on a basal lamina complex
Polarised cells
Stains well with haematoxylin and eosin

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2
Q

How are epithelial cells attached to each other?

A

Via desmosomes and adherens junctions

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3
Q

Different epithelial cell shapes

A

Squamous
Cuboidal
Columnar

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3
Q

How are nutrients delivered to epithelial cells?

A

Diffuse from blood vessels in adjacent connective tissue

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3
Q

Different types of cell arrangement

A

Simple - single layer
Pseudostratified - all cells in contact with basal lamina
Stratified - multiple layers

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3
Q

Simple squamous epithelium

A

Location - Lining surfaces involved in passive transport of gases or fluids
Function - Allows material to pass through by diffusion and filtration, secretes lubricating surfaces

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3
Q

Simple cuboidal epithelium

A

Location - Lines small ducts and tubules eg - collecting tubules of kidney, small excretory ducts of salivary glands and pancreas
Function - Secretes and absorbs

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4
Q

Cell specialisation types

A

Cilia - movement
Microvilli - absorption
Keratinisation - protection

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4
Q

Function of microvilli

A

Increase surface area for absorption, with a brush border

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5
Q

Structure of microvilli

A

Shape maintained by actin filaments anchored to the cell membrane
Base of actin filaments form part of the terminal web which is linked to intermediate filaments of the cell

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6
Q

Simple columnar epithelium

A

Location - Absorptive surfaces such as small intestine and secretory surfaces such as the stomach
Function - Absorbs - also secretes mucus and enzymes

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7
Q

Why do goblet cells appear empty under the micrscope?

A

Mucus is lipid based

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8
Q

Goblet cell

A

Modified columnar epithelial cell that produces and secretes mucus
Found in many simple epithelial linings
Stains poorly with Hematoxylin and eosin

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9
Q

Pseudostratified columnar epithelium

A

Location - In the airways of respiratory system - all cells are still attached to the basal lamina but not all reach the apical surface
Function - Secretes mucus - ciliated tissue moves the mucus

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10
Q

Cilia function

A

Motile structures that move fluid and particles along the epithelia surface

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11
Q

Structure of cilia

A

Core of 20 microtubules arranged as 9 doublets around a central pair (9+2 arrangement)

12
Q

Which is larger - microvilli or cilia?

A

Cilia

13
Q

Squamous stratified epithelium

A

Location - Physical protection in oral cavity, pharynx, oesophagus, anal canal, uterine cervix and vagina
Function - Protects against abrasion

14
Q

Replication of squamous stratified epithelial cells?

A

Only cells along the basement membrane replicate
The replicated cells move from the base to the apical side

15
Q

Where are keratinised stratified epithelium found?

A

On surface layers of keratinised dead cells
Water cannot pass through

16
Q

Where is transitional epithelium found?

A

Location - In the ureter and bladder only
Function - Allows urinary organs to expand and stretch

17
Q

Features of transitional epithelium

A

Able to change shape
Tight junctions between cells to prevent material flowing
Distension - allow bladder to stretch
Protection - from toxic urine
Waterproof - prevents water leaking into concentrated urine

18
Q

Functions of cell junctions in epithelial cells

A

Keep epithelial cells tightly bound
Allow functional integrity of cells

19
Q

Examples of junctions

A

Desmosomes
Hemidesmosomes
Adherens junctions
Tight junctions
Gap junctions

20
Q

Tight junction

A

Seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them
Found where movement along concentration gradient is prevented

21
Q

Adherens junction

A

Joins an actin bundle in one cell to a similar bundle in a neighbouring cell
Provide some mechanical support

22
Q

Desmosome

A

Joins intermediate filaments in one cell to those in a neighbour

23
Q

Gap junction

A

Allows the passage of small water soluble ions and molecules
Channels are closed until connection is established between 2 adjacent cells

24
Q

Hemidesmosomes

A

Anchors intermediate filaments in a cell to the basal lamina

25
Q

Protein components of desmosomes

A

Desmoglein and desmocolin cross the cell membrane
Outside they bind homophobically - to their same kind
Inside the cell, plaque (a dense protein) bind to intermediate filaments and link them to desmoglein and desmocolin

MBBS (16 decks)

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