Epithelial tissue Flashcards

1
Q

What is epithelia?

A

Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body, and line the internal surfaces

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2
Q

What is the exterior epithelial lining?

A

Skin

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3
Q

What kind of epithelium is skin?

A

Keratinised, stratified, squamous

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4
Q

Is skin living or dead?

A

Outermost layer is dead, living underneath

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5
Q

Give 3 interior epithelial surfaces that open to the exterior

A
  • Gastrointestinal
  • Respiratory tract
  • Genitourinary tract
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6
Q

Where does the GI tract start and end?

A

Mouth to anus

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7
Q

Where does the respiratory tract start and end?

A

Nasal cavity to alveoli

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8
Q

Give 5 epithelial surfaces that don’t open to the exterior

A
  • Pericardial sac
  • Pleural sacs
  • Peritoneum
  • Blood vessels
  • Lymphatic vessels
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9
Q

What is the pericardial sac?

A

Sac that contains heart

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10
Q

What is the pleural sac?

A

Very thin sac that contains the lungs

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11
Q

What does the peritoneum contain?

A

Most of the gut contents

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12
Q

What do the blood vessels constitute?

A

The entire cardiovascular system

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13
Q

What is the epithelium a derivative of?

A

The 3 germ layers of the embryo

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14
Q

Describe the structure of the trilaminar embryonic disc

A

3 layers with motor cord in middle

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15
Q

What are the 3 layers in the trilaminar disc?

A

NAME?

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16
Q

What epithelium is derived from the ectoderm?

A
  • Epidermis of skin

- Corneal epithelium of skin

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17
Q

What epithelium is derived from the mesoderm?

A

NAME?

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18
Q

What epithelium is derived from the ectoderm?

A

NAME?

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19
Q

What are the two main classifications of epithelia?

A

NAME?

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20
Q

What is meant by simple epithelium?

A

One cell layer thick

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21
Q

What is meant by stratified/compound?

A

More than 1 cell layer thick

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22
Q

What does all epithelium have?

A

A basal surface on the basement membrane

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23
Q

What is the basement membrane?

A

A thin, flexible, acellular layer that lies between epithelial cells and subtending connective tissue

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24
Q

What is meant by acellular?

A

Not made up of cells

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25
Q

What is the part of the basement membrane closest to the epithelium

A

Basal lamina

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26
Q

What lies down the basement membrane?

A

Epithelial cells

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27
Q

How is the thickness of the basement membrane augmented?

A

By variably thick layer of reticular fibrils, elaborated by type III connective tissue

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28
Q

what are reticular fibrils?

A

Type III collagen

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29
Q

What is the purpose of the basement membrane?

A
  • Serves as a strong, flexible layer to which the epithelial cells adhere.
  • Cellular and molecular filter
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30
Q

What is basement membrane made up of?

A

Not cells, just fibre type connective tissue

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31
Q

How is the basement membrane clinically relevant in cancer?

A

The degree to which the malignant cells permeate the basement membrane is highly relevant to prognosis- better prognosis if the neoplasm is not through the basement membrane

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32
Q

Describe the structure of simple squamous epithelium

A

NAME?

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33
Q

What is endothelium?

A

Simple squamous lining of all vascular elements (arterial, venous, capillary and lymphatics)

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34
Q

What is the function of endothelium?

A
  • Exchange gases and nutrients
  • Allow certain blood cells to enter tissues
  • Regulate platelet coagulation
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35
Q

Where is simple squamous epithelium located?

A
  • Lining of blood and lymph vessels
  • Lining of body cavities- pericardium, pleura, peritoneum
  • Pulmonary alveoli
  • Bowman’s capsule and Loop of Henle in kidney
  • Inner and middle ear
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36
Q

What is simple squamous epithelium called when it’s lining body cavities?

A

Mesothelium

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37
Q

What are the functions of simple squamous epithelium?

A

NAME?

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38
Q

Where does simple squamous epithelium have a lubricating function?

A

NAME?

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39
Q

Where does simple squamous epithelium have a gas exchange function?

A

Pulmonary alveoli

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40
Q

Where does the simple squamous epithelium have a barrier role?

A

In the Bowman’s capsule

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41
Q

Where does the simple squamous have a role in active transport by pinocytosis?

A

Mesothelium and endothelium

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42
Q

What shape are the cells of simple cuboidal epithelium?

A

Polygonal, but the cells are about as high as they are wide

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43
Q

Where is simple cuboidal epithelium found?

A

NAME?

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44
Q

Are all ducts lined with simple cuboidal epithelium?

A

No, depends on location and size

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45
Q

What is the surface of the ovary called?

A

Germinal epithelium

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46
Q

What are the functions of simple cuboidal epithelium?

A
  • Absorption and conduit
  • Absorption and secretion
  • Barrier/covering
  • Hormone synthesis, storage and metabolism
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47
Q

Where does simple cuboidal epithelium have a absorption and conduit function?

A

Exocrine glands

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48
Q

Where doessimple cuboidal epithelium have an absorption and secretion function?

A

Kidney tubules

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49
Q

Where doessimple cuboidal epithelium have a barrier function?

A

Ovary

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50
Q

Where doessimple cuboidal epithelium have a hormonal function?

A

Thyroid

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51
Q

What shape are simple columnar epithelium?

A

Taller than they are wide

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52
Q

How can simple columnar epithelium sometimes appear under microscopes due to the cut?

A

Stratified

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53
Q

What features can simple columnar epithelium found?

A

NAME?

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54
Q

What is the purpose of simple columnar with microvilli?

A

Increase the surface area

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55
Q

Where are junctional complexes?

A

In apical portion of adjoining cells

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56
Q

What is a junctional complex?

A

A particularly tight junction

57
Q

What is the purpose of junctional complexes?

A

Prevents gut contents penetrating between cells and gaining access to the body

58
Q

What is the advantage of junctional complexes?

A

They give very tight control of what goes into the body

59
Q

What does occludin do?

A

Binds adjacent plasma membranes tightly together is apical portions of some epithelia

60
Q

Can membrane proteins bypass the junctional complex?

A

No

61
Q

What are junctional complexes also known as?

A

Zonula occludens

62
Q

What does the zonula occludens allow the cell to do?

A

Restrict certain proteins to apical (free) surface, and restrict others to the lateral and basal surface.

63
Q

What does the junctional complex separate?

A

The luminal space from the intercellular space

64
Q

Describe the passage of fluid from the intestinal lumen

A

Intestinal lumen → cell → intercellular space → basement membrane → connective tissue

65
Q

What are villi?

A

Projections into the small intestine

66
Q

What are villi lined by?

A

Simple columnar epithelium with microvilli

67
Q

What is the purpose of the villi?

A

Increase SA

68
Q

What do villus do?

A

Absorb nutrients from the small intestine

69
Q

What cells do simple columnar often have?

A

Goblet cells

70
Q

Where do goblet cells run from?

A

Basement membrane → surface

71
Q

What do goblet cells do?

A

Produce mucus

72
Q

Where is simple columnar epithelium found?

A
  • Stomach and gastric glands
  • Small intestine and colon
  • Gall bladder
  • Large ducts of some exocrine cells
  • Oviducts
  • Uterus
  • Ductuli efferents of testis
73
Q

What are the functions of simple columnar epithelium?

A
  • Absorption
  • Secretion
  • Lubrication
  • Transport
74
Q

Where doessimple columnar epithelium have an absorption function?

A
  • Small intestine and colon

- Gall bladder

75
Q

Where doessimple columnar epithelium have a secretion function?

A
  • Stomach lining
  • Gastric glands
  • Small intestine
  • Colon
76
Q

Where doessimple columnar epithelium have a lubrication function?

A

NAME?

77
Q

Where doessimple columnar epithelium have a transport function?

A

Oviduct

78
Q

Why is pseudostratified epithelium so named?

A

Because it looks like its stratified, but simple because every cell makes contact with the basement membrane

79
Q

What happens to nuclei inpseudostratified epithelium?

A

They end up in different places

80
Q

How does the basement membrane differ inpseudostratified epithelium?

A

It is thicker

81
Q

What features canpseudostratified epithelium have?

A
  • Can have cilia and stereocilia

- Can contain goblet cells

82
Q

Where doespseudostratified epithelium have cilia?

A

Trachea

83
Q

Where doespseudostratified epithelium have stereocilia?

A

Testes

84
Q

Where ispseudostratified epithelium found?

A
  • Lining of nasal cavity, trachea and bronchi
  • Epididymis and ductus deferens
  • Auditory tubes and part of lymphatic cavity
  • Lacrimal sac
  • Large excretory ducts
85
Q

What are functions ofpseudostratified epithelium?

A
  • Secretion and conduit
  • Absorption
  • Mucus secretion
  • Particle trapping and removal
86
Q

Where doespseudostratified epithelium have a secretion and conduit function?

A

NAME?

87
Q

Where doespseudostratified epithelium have an absorption function?

A

Epididymis

88
Q

Where doespseudostratified epithelium have a particle trapping and removal function?

A

Respiratory tract

89
Q

In stratified epithelium, what is the name based on?

A

The outermost cell- next to the lumen

90
Q

In stratified epithelium, which cell is attached to the basement membrane?

A

Only basal cell layer

91
Q

What kind of epithelium is found in the vagina?

A

Stratified squamous non-keratinized epithelium

92
Q

What are vagina cells rich in?

A

Glycogen

93
Q

Why is it important that vagina cells are rich in glycogen?

A

Substrate for numerous lactobacilli, which produce lactic acid, maintaining a low vaginal pH

94
Q

What do the vaginal cells cause in absence of hormonal stimulation?

A

Atrophy

95
Q

What kind of epithelium is found in the oesophagus?

A

Stratified squamous non-keratinised epithelium

96
Q

What is the role of the epithelium in the oesophagus?

A

Protects from abrasion

97
Q

How is the oesophagus need protection from abrasion?

A

When eating, the outer cells slough off, but are replaced by mitosis, which is occurring in the basal layer, with cells differentiate as they move upwards.

98
Q

What epithelium lines epiglottis?

A

NAME?

99
Q

What does the epiglottis do?

A

Stops food going into lungs on swallowing, and then springs back to allow for breathing

100
Q

What is the epiglottis adapted for?

A

Protection against abrasion

101
Q

What epithelium is on the outermost layer of the eye?

A

Stratified squamous

102
Q

What is the epithelium on the outermost layer of the eye adapted for?

A

To withstand the constant abrasion of opening and closing the eye

103
Q

In what locations is stratified squamous epithelium found?

A
  • Oral cavity
  • Oesophagus
  • Larynx
  • Vagina
  • Part of anal canal
  • Surface of cornea
  • Inner surface of eyelid
104
Q

What are the functions of stratified squamous epithelium?

A

NAME?

105
Q

What is special about keratinised stratified squamous epithelium?

A

Outermost cells are dead and have lost their nuclei

106
Q

What doeskeratinised stratified squamous epithelium line?

A

Skin

107
Q

Where is the epidermis thicker?

A

Sole of foot and palms of hands

108
Q

What is often true of the margin between connective tissue and epidermis?

A

It’s quite convoluted

109
Q

What is meant by the border being convoluted?

A

Dermal papilla go up

110
Q

What is the purpose of the convoluted border?

A

The skin doesn’t slide off as easily, so less likely to blister

111
Q

Where iskeratinised stratified squamous epithelium located?

A

NAME?

112
Q

When does the oral cavity begin to keratinise?

A

If someone mouth breaths a lot

113
Q

What is the function ofkeratinised stratified squamous epithelium?

A
  • Protection against abrasion and physical trauma
  • Prevents water loss
  • Prevents ingress of microbes
  • Shields against UV light damage
114
Q

How is the skin protected from UV damage?

A

Melanosomes in the skin line up on the outer surface of the nuclei, to try and protect the DNA from UV damage

115
Q

Describe transitional epithelium

A

Surface cells can vary in shape, from columnar/cuboidal to flattened. It looks different depending on wether or not its stretched

116
Q

What is transitional epithelium adapted to do?

A

Stretch

117
Q

Why is transitional epithelium adapted to stretch?

A

Because it lines the urinary system, and so needs to allow for extension of the bladder

118
Q

How can transitional epithelium often be recognised on micrographs?

A

By slightly bowed appearance of outermost cells in stretched state

119
Q

Where is transitional epithelium found?

A

NAME?

120
Q

What is the function of transitional epithelium?

A

NAME?

121
Q

Is a epithelial cells rate of renewal variable or constant?

A

Pretty constant

122
Q

What does the turnover rate for each epithelial cell type depend on?

A
  • Location

- Function

123
Q

When is the renewal time frame for epithelium not constant?

A

When injury leads to acceleration

124
Q

What is the time frame for renewal of epidermis?

A

From cell division in basal layer to being sloughed off, ~28 days

125
Q

What happens to a epidermis cell in its lifetime?

A

Differentiation, migration to exterior, keratinisation and death

126
Q

How often are cells lining the small intestine replaced?

A

Every 4-6 cells

127
Q

What replaces cells in the lining of the small intestine?

A

Regenerative cells in the base of crypts

128
Q

What happens to some epithelial cells once adulthood is reached?

A

They cease to be renewed

129
Q

What can happen to cells that cease to be renewed once they reach adulthood?

A

The triggering of cell proliferation

130
Q

What does cell proliferation do?

A

Replace lost cells

131
Q

Why might cells be lost?

A

NAME?

132
Q

Give 2 epithelial cells that have different types of surface specialisation?

A

NAME?

133
Q

What are microvilli?

A

Cytoplasmic apical extensions

134
Q

What is the purpose of microvilli?

A

They increase the SA for selective absorption of intestinal contents

135
Q

What do microvilli have inside them?

A

Little actin threads going into them

136
Q

What is the purpose of the actin threads?

A

Give them shape

137
Q

What are stereocilia?

A

Very long microvilli

138
Q

Where are sterocilia found?

A

Extending from surface of epididymal