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Histology > Epithelia > Flashcards

Epithelia Flashcards

1
Q

Characteristics of epithelia

A

Avascular
Closely attached to each other (with many specialised junctions)
Functionally distinct surfaces

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2
Q

What does the epithelial group consist of

A

Cells that cover the external body surfaces, line the internal closed cavities, and body tubes that communicate with the exterior
They also form secretory units &a ducts of glands

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3
Q

Epithelial fxs

A 
Protection
Absorption
Secretion/excretion
Contractility
Line/cover surfaces of body
Interfaces between diff bio compartment
Form glands and ducts
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4
Q

Types of epithelia

A

Simple

Stratified

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5
Q

What is simple epithelia

A

One cell layer thick
Ideal for secretion diffusion absorption
Range in shape

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6
Q

What are stratified epithelia

A

2+ cell layers thick
Mostly protective fx
Classified according to morphology of surface cells

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7
Q

Types of simple epithelia

A 
Squamous
Cuboidal
Columnar
Columnar ciliated
Paeudostratified columnar ciliated
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8
Q

Types of stratified epithelia

A 
Squamous
Squamous keratinised
Cuboidal
Columnar
Transitional
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9
Q

Eg junctional complexes

A

Hemidesmosome
Desmosome
Tight junction
Zona adherens (adherens jctn)

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10
Q

Simple squamous

A

Found lining surfaces suitable for diffusion eg alveoli capillary walls lining of pleural pericardial peritoneal cavities
One cell layer thick
Look like fried eggs/flat

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11
Q

Simple cuboidal

A

Found lining ducts and tubules with excretory secretory or absorptive fx eg kidney tubule salivary gland pancreas
Round centrally located nucleus

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12
Q

Simple columnar

A

Line highly absorptive or secretory surfaces eg small intestines stomach gall bladder often interspersed with goblet cells
Nucleus oval shaped and basal border

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13
Q

Simple columnar ciliated

A

Found lining the oviduct cilia beat synchronised

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14
Q

Pseudostratified columnar ciliated aka respiratory epithelia

A 
Found in upper respiratory tract
Always ciliated
Interspersed with goblet cells
Nuclei not all situated at basal border
Give appearance of more than one layer
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15
Q

Stratified squamous

A

Found in oral cavity, pharynx, parts of larynx, oesophagus, anal canal, uterine cervix, vagina
Protective fx withstand mech abrasion but no desiccation must be kept moist
Basal layer always cuboidal
Continual new production of cells from basal layer
Variable no of cell layers which change morphology as they move towards the surface and nuclei also become flattened toward the surface

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16
Q

Stratified squamous keratinised

A

In the skin/epidermis
Protective fx withstand mech abrasion and dessication
Process of keratinisation
As they push towards surface they mature then degenerate.
Nuclei become flattened and pyknotic so cell is dead

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17
Q

Stratified cuboidal

A

Found lining ducts eg salivary glands
Usually 2-3 layers
Minimal secretory absorptive fx
Provides more substantial lining compared to simple

18
Q

Stratified cuboidal

A

Both layers tall - conjunctiva
Basal layers cuboidal - distal urethra, lacrimal sac & duct, salivary gland ducts
Protective fx

19
Q

Transitional epithelia

A

Urinary tract, bladder
Highly specialised to accommodate stretch
Outer/luminal cells become flattened in a stretched state
Relaxed state 4-5 layers
Stretched state 2-3 layers

20
Q

Other BM names

A

Basal lamina

External lamina

21
Q

Features of the BM

A

Secreted by the epithelia

Never penetrated by blood vessels

22
Q

What are the layers of the BM

A

Lamina lucida
Lamina densa
Lamina fibroreticularis

23
Q

Lamina lucida

A

Electron Lucent layer next to the epithelial cells

24
Q

Lamina densa

A

Intermediate electron dense layer (visible by light microscopy)

25
Q

Lamina fibroreticularis

A

Relatively electron Lucent layer which merged with the underlying CT

26
Q

BM composition

A

Anchoring filaments
Structural glycoproteins
Proteoglycans

27
Q

Types of anchoring filament in the BM

A 
Collagen 4 (exclusive to BM)
Some C 3 (reticulin) found in the lamina fibroreticularis
28
Q

Types of structural glycoproteins in BM

A

Laminin (bind to C 4 and other BM constituents and laminin receptors (shaped glycoproteins) in basal membrane of epithelial cells)
Entactin (mediates binding of laminin to C4)
Fibronectin (produced by fibroblasts of underlying CT. binds membrane spanning receptor proteins (integrins) and extra cellular components eg collagen, heparin sulphate so play important cell adhesion role)

29
Q

Types of proteoglycans in the BM

A

Heparan sulphate (extensively hydrated and forming most of bulk of BM)

30
Q

BM fxs

A 
Structural (intermediate in attachment of CT to cells
Compartmentalises (isolate CT and cells)
Filters (regulate movement of substances into the kidneys urinary space within renal corpuscle)
Polarity induction ( defines in vivo shape of epithelia (along with mesenchyme below)
Tissue scaffolding (guide during regeneration of damaged epithelial tissue)
31
Q

Specialisations

A

Cilia
Micro villi
Stereo cilia
Keratin

32
Q

What are Cilia

A

Long motile cytoplasmic structures projecting from surface in parallel rows
7-10microm long
Seen with light microscope
Internal structure made of several micro tubule pairs

33
Q

Cilia fx

A

Beat wave like to move surface film of mucus or fluid in consistent direction

34
Q

What are microvilli

A

Relatively short static cytoplasmic projections extending from cell surface forming striated/brush border
0.5-1microm long
Not seen individually with light microscope
At high electron mag can see the core containing several thin actin filaments

35
Q

Microvilli fx

A

Size And density related to cells absorptive capacity

They increase the cell surface area

36
Q

What are stereocilia

A

Microvilli of unusual length
Named before electron microscopy showed they have a different internal structure to cilia
No micro tubules just filament pus actin skeleton like microvilli
Found in epididymis

37
Q

Keratin fx

A

Prevents desiccation and withstand abrasion

38
Q

Origins of epithelia

A

3 germ layers of early embryo
Ectoderm
Endoderm
Mesoderm

39
Q

Ectoderm

A

Give rise to corneal and lens epithelium of eye, epidermis of the skin and its derivatives.
Lining of oral and anal canal cavities and cells that produce tooth enamel

40
Q

Endoderm

A

Give rise to epithelia lining the alimentary tract (- mouth pharynx anus)
Respiratory system
Intestinal glands (liver gall bladder pancreas)
Thyroid, anterior pituitary gland
Parathyroid, thymus

41
Q

Mesoderm

A

Epithelium of urogenital system
Provide continuous layer lining blood and lymph vessels (endothelium) and peritoneal and other serous cavities (mesothelium)

Histology (10 decks)

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