Anatomy - Epithelium

Front 1

What are the functions of epithelial tissue?

Back 1

Selective diffusion
Absorption
Secretion
Physical protection
Containment

Front 2

Describe the polarity in epithelial cells:

Back 2

In simple epithelia, intracellular organelles, membrane proteins and cell surface specializations are spatially arranged.
In stratified epithelia, the cells differentiate as they move from the basal layer to the surface layer.

Front 3

All epithelia are supported by a __________________

Back 3

Basement Membrane

Front 4

Epithelium has lots of extracellular stuff. T/F

Back 4

F, very little extra cellular things.

Front 5

Define simple epethelia:

Back 5

One layer of cells

Front 6

What are the subclasses of simple epithelia?

Back 6

Simple squamous (flattened or plate-like)
Simple cuboidal
Simple columnar
Pseudostratified columnar (all cells contact the basement membrane, but not all reach the surface)

Front 7

Define stratified epithelia:

Back 7

Cell type changes. Tissue XtoTHEz exhibits polarity.

Front 8

What are the subclasses of stratified epithelia?

Back 8

Stratified squamous
Stratified cuboidal
Transitional (found only in the urinary tract)

Front 9

What type of tissue is in glands?

Back 9

Epithelial cells

Front 10

Holocrine Glands

Back 10

The entire cell and its contents are released into the lumen.

e.g. sebaceous glands.

"holy" self sacrifice

Front 11

Apocrine Glands

Back 11

A portion of the cell is pinched off,

e.g. lactating mammary glands.

"a piece"

Front 12

Merocrine Glands

Back 12

Secretory granules fuse with the apical plasma membrane and the contents are released (exocytosis),

e.g. salivary glands.

Front 13

What are the functions of epithelia?

Back 13

Selective permeability barrier
Protection from mechanical and chemical insult
Transcellular transport
Absorption
Secretion

Front 14

Describe epithelial cell polarity:

Back 14

Most epithelial cells have distinct biochemical and functional domains, i.e. they demonstrate polarity. For instance, an apical domain faces a lumen and a basolateral domain is oriented toward the basement membrane and the extracellular milieu. As a result of the functional specialization, the cell surface may demonstrate structural specializations that are related to specific functions.

Front 15

What are the (3) junctional complexes between cells?

Back 15

1) the zonula occludens or tight junction,

2) the zonula adherens or adhering junction and the

3) macula adherens or desmosome.

Gap junctions, which allow electrical coupling of cells, may also be present, .

Front 16

Describe the Tight Junction:

Back 16

The tight junction is the uppermost (closest to the surface) component of the complex. At the tight junction, the apposed plasma membranes of neighboring epithelial cells are fused together, obliterating the intercellular space. The lines of fusion form an efficient seal that can block the passage of ions, water, and molecules of all sizes from passing between the cells. The tight junction also act as a barrier to prevent diffusion of plasma membrane components (e.g. ion channels) between the apical and basolateral surfaces of the cell.

Front 17

Describe the adhereing junction:

Back 17

The adhering junction is also continuous around the apex of the cell, but it is permeable.

It provides a strong adhesion between cells. The adherens junction contains cadherins, which are integral membrane proteins that span the membrane and have a large domain that projects out from the cell that binds tightly to an identical domain from an adjacent cell.

The intracellular domain links to several proteins that interact with actin microfilaments inside the cell. Thus, mechanical stress can transmitted across the epithelial monolayer.

Front 18

Describe desmosomes:

Back 18

Desmosomes are "spot welds" between cells.

Unlike tight junctions and adhering junctions, they are not arranged as a continuous seal around the cell, but like adherens junctions, they consist of specialized protein plaques connected to the intermediate filaments of the cytoskeleton, transmembrane linking protein of the cadherin family.

As a result, desmosomes are particularly important in providing mechanical strength to epithelial sheets.

Front 19

Describe a gap junction:

Back 19

Within a gap (communicating) junction, apposed plasma membranes are closely parallel, but not fused, and there is a plaque of closely packed intramembrane particles. Each particle, called a connexon, has a central aqueous channel through the membrane. Connexons of adjacent cell membranes are lined up with one another, forming a channel of communication between the adjacent cells (molecules up to 1,500 daltons in size can pass from one cell to the next). Gap junctions are not limited to epithelial tissues. In the heart, gap junctions couple cardiac muscle cells together electrically so contractions of individual cardiac muscle cells are coordinated.

Front 20

Name (4) types of cell-surface specializations:

Back 20

Microvilli
Cilia
Steriocillia
Flagella

Front 21

Describe microvilli:

Back 21

On adsorptive cells (e.g. intestinal epithelium and proximal tubules of the kidney), these extension of the cell surface vastly increase the surface of the cell.

Front 22

Describe Cilia:

Back 22

These hair-like projection are specialized to function in propelling substances across an epithelium. At the electron microscopic level there is a characteristic 9 + 2 organization of microtubulues present in the core of each cilium.

Front 23

Describe sterocilia:

Back 23

Not to be confused with true cilia, these structures are actually long microvilli.

In the ear, they function in signal generation.

Front 24

Describe flagella:

Back 24

Flagella - In humans, the only cells that have flagella are spermatozoa (to be discussed later).

Front 25

Describe the subdivisions of the basolateral domain:

Back 25

The basolateral domain may be subdivided into two regions; a lateral and a basal plasma membrane.

Each region posses its own junctional specializations, such as tight junctions on the lateral membrane and hemidesmosomes on the basal membrane.

These surfaces are also rich in ion channels and Na+-K+-ATPase.

Front 26

Describe the polarity of stratified epithelium:

Back 26

Within stratified epithelia, the different cells also demostrate differences in fiunction and differentiation. Cells in the basal layer form the basement membrane and are capable of mitotic activity. As cells leave the basal layer they actually differentiate, and this differention continues as the cells move toward the surface. Keratinization of surface layer of skin or gingiva and the desquamation of dead cells, for example, represent terminal differentiation of the epithelial cells in a stratified squamous keratinizing epithelium.

Front 27

What are the different names of the basement membrane?

Back 27

basement membrane (light microscope)

or

basal lamina (electron microscope)

Front 28

Describe the basement membrane:

Back 28

fibrillar layer that underlies all epithelia, and is formed by epithelial cells. It has three major protein components.

Front 29

What are the (3) major protein components of the basement membrane?

Back 29

Type IV collagen

Laminin, a large glycoprotein of 850 kiloDaltons (kD).

Heparan sulfate proteoglycan (HSPG)

Front 30

How do the type IV molecules work in the basement membrane?

Back 30

Type IV collagen molecules bind to one another, end to end, to form a fine mesh.

Front 31

How does the laminin in the basement membrane work?

Back 31

Laminin binds to Type IV collagen, and may cross-link the collagen molecule network and attach it to the base of the epithelium.

Front 32

How do the HSPG molecules in the basement membrane work?

Back 32

The HSPG molecules coat the two surfaces of the basement membrane, giving each surface a strong negative charge due to the sulfate groups.

Front 33

Besides collagin type IV, laminin, and HSPG, what other components are in the basement membrane?

Back 33

Other components of the basement membrane include fibronectin, entactin and collagen Type VII (anchoring fibrils). The anchoring fibrils are formed by fibroblasts in the underlying connective tissue.

Front 34

How do epithelial cells anchor themselves to the basement membrane and other ECM items?

Back 34

hemidesmosomes

integrins

The epithelial cells have specialized anchoring junctions (hemidesmosomes and integrins) that link the intracellular cytoskeleton with the components of the basement membrane and other extracellular matrix macromolecules.

Front 35

In addition to anchoring the epithelial tissue, what are some functions of the basement membrane?

Back 35

It acts as a semi-permeable membrane for the passage of nutrients, etc.
It influences cell polarity and metabolism.
It regulates cell proliferation and differentiation by binding growth factors.
It guides cell migration, and acts as a barrier to tumor cells.

Front 36

What is cystic fibrosis?

Back 36

Genetic defect in the chloride transport.

In airways, this leads to very thick mucous => loss of function.

Front 37

Name a location in the body where selective diffusion in epithelial tissue takes place.

Back 37

Lungs, Capillaries

Front 38

Name a location in the body where absorption in epithelial tissue takes place.

Back 38

Lining of gut

Front 39

Name a location in the body where secretion in epithelial tissue takes place.

Back 39

glands, cells that make things for export

Front 40

Name a location in the body where physical protection in epithelial tissue takes place.

Back 40

skin (thick and cornified)

Front 41

Name a location in the body where containment in epithelial tissue takes place.

Back 41

bladder, thyroid gland

Front 42

What are the three general types of epithelial tissue?

Back 42

Simple
Stratified
Glandular

Front 43

What seperates epithelial cells from the connective tissue?

Back 43

Basement membrane

Front 44

What is endothelium?

Back 44

simple squamous epithelium that lines inside of circulatory system

Front 45

From the surface, what do simple cuboidal cells look like?

Back 45

Polygon shaped

Front 46

In simple cuboidal cells, where is the nucleus and how is it shaped?

Back 46

It is in the center and spherical in general

Front 47

Where are simple cuboidal cells found?

Back 47

Simple cuboidal cells are found lining small ducts and tubes which may have excretory, secretory, or absorptive functions.

Front 48

Within simple columnar cells, where is the nucleus and what shape does it form?

Back 48

Nuclei are elongated and generally located near the base.

Front 49

Where is simple columnar located?

Back 49

. Simple columnar is most often found on highly absorptive surfaces such as in the small intestine, and often have specializations of the surface. Also located in gall bladder.

Front 50

Within epithelial tissue, what type of single cell is capable of secretion as its main function?

Back 50

Goblet cells. It secretes mucous

Front 51

What do goblet cells secret?

Back 51

Mucous

Front 52

Why is pseudostratified unique in comparison to other epithelial tissues?

Back 52

All cells are attached to the basement membrane yet not all of them reach the apical surface of the tissue.

Front 53

Within pseudostratified tissue, where are the nuclei and in what shape are they?

Back 53

The nuclei tend to be elongated like columnar, yet can be found at varying heights giving the impretion of stratified tissue.

Front 54

What is pseudostratified epithelium commenly called?

Back 54

Respiratory epithelium

Front 55

Are cilia present on stratified epithelia?

Back 55

No, never.

Front 56

In stratified tissue, do cells exhibit polarity?

Back 56

In general, the cells do not exhibit polarity themselves. The tissue however, does exhibit polarity.

Front 57

Does pseudostratified epithelium have microvilli?

Back 57

NO!! They only have cilia

Front 58

How is stratified epithelia named?

Back 58

According to the cell type on the most apical layer of the tissue

Front 59

How are cells added to stratified epithelial tissue?

Back 59

The basal cells divide continuously, and the daughter cells are pushed up towards the surface where they are shed

Front 60

Where in the body can stratified epithelial tissue be found?

Back 60

Lines the oral cavity, pharynx, esophagus, anal canal, uterine cervix, and vagina

Front 61

Describe the concept of polarity of stratified epithelium.

Back 61

Within stratified epithelia, the different cells also demonstrate differences in function and differentiation. Cells in the basal layer form the basement membrane and are capable of mitotic activity. As cells leave the basal layer they actually differentiate, and this differentiation continues as the cells move toward the surface. Keratinization of surface layer of skin or gingiva and the desquamation of dead cells, for example, represent terminal differentiation of the epithelial cells in a stratified squamous keratinizing epithelium.

Front 62

When looking at histological slides, what is a characteristic difference between keratinized and non-keratinized stratified squamous epithelia?

Back 62

Non-keratinized will retain their nucleus all the way to the apical surface.

Front 63

What happens to the cell layer that becomes keratinized?

Back 63

As the cells die and the nucleus is extruded, the cells develop strong cytoskeletal elements that link each other together and allow for dissapation of forces.

Front 64

What is the most important characteristic to recognize in transitional epithelial tissue slides?

Back 64

The apical surface looks like pillows or umbrellas.

Front 65

Where in the body is transitional epithelial tissue located?

Back 65

Confined to the urinary tract

Front 66

Is simple epithelial tissue considered to exhibit polarity?

Back 66

Yes, even in simple epithelial tissue such as glands exhibit polarity due to the segregation of certain organelles to specific regions.

Front 67

When descibing the top of a cell (facing into the lumen for example) what is it called?

Back 67

Apical surface

Front 68

When referring to the bottom and lower side of the cells, what is it called?

Back 68

Basolateral

Front 69

What are some specializations of the apical domain on cells?

Back 69

cilia
microvilli
stereocillia

Front 70

What is a tight junction called?

Back 70

Zonula occludens

Front 71

What are adhering junctions called?

Back 71

Zonula adherens

Front 72

What are desmosomes called?

Back 72

Macula adherens

Front 73

Describe the tight junction:

Back 73

The tight junction is the uppermost (closest to the surface) component of the complex. At the tight junction, the apposed plasma membranes of neighboring epithelial cells are fused together, obliterating the intercellular space. The lines of fusion form an efficient seal that can block the passage of ions, water, and molecules of all sizes from passing between the cells. The tight junction also act as a barrier to prevent diffusion of plasma membrane components (e.g. ion channels) between the apical and basolateral surfaces of the cell.

Front 74

Describe the adhering junctions:

Back 74

The adhering junction is also continuous around the apex of the cell, but it is permeable. It provides a strong adhesion between cells. The adherens junction contains cadherins, which are integral membrane proteins that span the membrane and have a large domain that projects out from the cell that binds tightly to an identical domain from an adjacent cell. The intracellular domain links to several proteins that interact with actin microfilaments inside the cell. Thus, mechanical stress can transmitted across the epithelial monolayer.

Front 75

Describe the desmosomes:

Back 75

Desmosomes are "spot welds" between cells. Unlike tight junctions and adhering junctions, they are not arranged as a continuous seal around the cell, but like adherens junctions, they consist of specialized protein plaques connected to the intermediate filaments of the cytoskeleton (cytokeratin in epithelium), transmembrane linking protein of the cadherin family. As a result, desmosomes are particularly important in providing mechanical strength to epithelial sheets.

Front 76

What protein is involved in creating the channels in gap junctions between cells?

Back 76

Connexon. Creates a central aqueous channel.

Front 77

What are sterocillia?

Back 77

- Not to be confused with true cilia, these structures are actually long microvilli. In the ear, they function in signal generation.

Front 78

Where in humans are flagella present?

Back 78

Spermatozoa.

Or a nasty case of vaginal infection.....

Front 79

When the number of microvilli per cell is high, what is the descriptive term used for the surface?

Back 79

Brush border

Front 80

What is at the core of each microvillus?

Back 80

Actin

Front 81

What extends up the center of microvilli to give it support?

Back 81

A core of actin filaments

Front 82

What is a basal body?

Back 82

Basal body, a microtubular arrangement identical to that of a centriole, at the base of cilia

Front 83

What extends up the center of cilia?

Back 83

Each cilia contains a central core called the axoneme consisting of 20 microtubules arranges as a central pair surrounded by nine doublets. At the base the axoneme inserts into a basal body which has a microtubular arrangement identical to that of a centriole

Front 84

On the basal surface of epithelial cells, what type of attachment occurs to the basement membrane?

Back 84

Hemidesmosomes and integrins

Front 85

What is an integrin?

Back 85

Two subunits, part of desmosome, but also found elsewhere along the basal surface of the cell, and interact with extracellular proteins and are linked to actin.

Front 86

What is a selectin?

Back 86

involved in homing mechanisms, such as inflammatory process. Tell neutrophill where to get off. Cells of capillary stick this protein out, and neutrophill sticks to it.

Front 87

Name

Back 87

America!....Fuck Yeah!!

Front 88

Name

Back 88

woot

Front 89

Describe endocytosis and phagocytosis:

Back 89

loot

Front 90

What type of secretion is endocrine secretion?

Back 90

merocrine

Front 91

What are the two distinct layers of the basement membrane?

Back 91

lamina lucida and the lamina densa.