Chapter 4 - Epithelial Tissue

Question 1

Epithelial tissue

Answer 1

• aggregated polyhedral cells
• lining of surface of body cavities; glandular secretion (exocrine, sweat glands, etc.)
• barrier tissue, plays a role in signaling, proliferation, and cell migration

Question 2

How are epithelial cells arranged?

Answer 2

maximum cell to cell contact; packed very tightly w/ minimal extracellular material btwn them

Question 3

Where is epithelial tissue located?

Answer 3

• rests on basal lamina/basement membrane

Question 4

What are epithelial cells held together by?

Answer 4

intercellular junctions

Question 5

Is epithelial tissue vascularized?

Answer 5

No

Question 6

Does epithelial tissue/cells have any surface modifications?

Answer 6

Yes, depending on where in the body, it may have cilia or microvilli, etc.

Question 7

Are epithelial cells polarized?

Answer 7

Yes, the top/outer surface has different proteins than the basal surface

Question 8

Intercellular junctions

Answer 8

• barrier movement of molecules btwn adjacent cells
• holds cells together tightly
• allow intercellular communication

Question 9

Zonulae occludens/tight junctions/occluding junctions

Answer 9

• occlude cells, molecules cannot pass btwn cells w/o being transported into the cell first
• encircle apical region of cell (like a belt), always at the top of the cell
• adjacent cell membranes are fused

Question 10

Zonulae adherens

Answer 10

• adhesion of adjacent cells
• web/belt of microfilaments (actin), encircle the cell
• thicker than tight junctions
• cells are held tightly together, but not fused; not as occlusive as tight junctions
• always beneath the tight junctions

Question 11

Maculae (spot) adherens/desmosome

Answer 11

• “spot welds btwn adjacent cells, do not encircle the cell

Question 12

Intermediate filaments

Answer 12

• filament of the cytoskeleton, inserts into the maculae adherens
• can be used in the diagnosis of the origin of a tumor

Question 13

Gap junctions/communicating junctions

Answer 13

• ions and small molecules can pass through (like calcium)
• formed by connexons
• important in intercellular communication (especially in cardiac cells)

Question 14

Connexons

Answer 14

• form gap junctions
• a pore than can open and close; made of a protein called connexin

Question 15

Cilia

Answer 15

• Move in unison to propel material past the cell surface
• covered by the cell/plasma membrane
• mainly found moving mucus in respiratory and reproductive systems in animals
• ATP-dependent movement

Question 16

Structure of cilia

Answer 16

• longer than microvilli
• similar to flagella, but longer
• supported by microtubules arranged in a 9+2 assembly (circle of 9 pairs of microtubules, w/ one pair in the middle)
  
  • insert into the basal body for stability
  • contains the protein dymein, which forms arms on the microtubules to grab adjacent microtubules, causing the cilia to bend, thus allowing it to move
  • dymein cannot function without ATP

Question 17

Microvilli

Answer 17

• fingerlike extensions of the cell that increase cell surface area for absorption
• covered by cell/plasma membrane
• supported by actin filaments
• about 1 micrometer in length
• found on cells whose functions is absorption (intestinal epithelium, renal tubular epithelium)

Question 18

Surface epithelia

Answer 18

• cover and line things
• classified by number of layers (simple and stratified) and shape of cells (squamous, cuboidal, columnar)

Question 19

Simple squamous

Answer 19

• surface epithelia
• single layer of squamous epithelia
• mesothelium (embryonic tissue, forms peritoneum), endothelium of blood vessels, alveoli

Question 20

Simple cuboidal

Answer 20

• surface epithelia
• single layer of cuboidal epithelia
• roughly the same in height and width, nuclei are round and in the middle
• renal tubules

Question 21

Simple columnar

Answer 21

• surface epithelia
• single layer of columnar epithelia
• tall and skinny, nuclei are oval and sometimes towards the bottom
• intestinal epithelium, gall bladder

Question 22

Stratified squamous

Answer 22

• surface epithelia
• multiple layers of squamous epithelia
• underlayers appear cuboidal or columnar, outer layers become thin and squished
• provides protection from abrasion (oral cavity, esophagus, vagina, cervix, skin)

Question 23

What are the two types of stratified squamous epithelia?

Answer 23

• nonkeratinized - covers wet surfaces/surfaces where mucus is present
• keratinized - waterproof, covers dry surfaces, cells become packed with keratin and the outer cells die/slough off when come in contact with abrasion

Question 24

Transitional epithelium

Answer 24

• multilayered epithelia, outermost layer is dome-like when relaxed and become flattened when stretched
• lines things that need to expand
• urinary bladder, ureters, urethra

Question 25

Pseudostratified ciliated columnar epithelium (PSCCE)

Answer 25

• appears to be stratified, but all cells are attached to basal lamina
• respiratory tract ONLY (nasal cavity/sinuses, trachea, bronchi)
• contains many different types of cells - cilia, goblet cells, stem cells, mitotic figures, etc.

Question 26

How are glands derived from epithelial tissue?

Answer 26

• during fetal development, epithelial cells proliferate and penetrate the underlying connective tissue
• cells may or may not maintain a connection with the surface epithelium
• exocrine maintain contact w/ surface epithelia, endocrine do not

Question 27

Glandular epithelium

Answer 27

• function: synthesis, storage, secretion of proteins, or lipids
• derived from epithelial tissue during embryonic development

Question 28

What are the different types of glandular epithelium?

Answer 28

• unicellular - goblet cells in intestinal and respiratory tracts
• multicellular - clusters of cells
• exocrine - secretions released into ducts, which empty into epithelium (goblet cells)
• endocrine - secretions enter circulatory system

Question 29

What cells turn into epithelial cells during mitosis?

Answer 29

stem cells; found in basal layer of stratified epithelia

Question 30

What is the rate of division for epithelial cells?

Answer 30

• have high turnover rate, tend to divide quicker than other types of tissue in the body (intestine = 7 days, skin =10-14 days)
• chemo inhibits the rapid replenishment of epithelial cells, which is why pts. w/ cancer often have intestinal issues

Question 31

Metaplasia

Answer 31

• abnormal conversion of one cell type to another
• in smokers, bronchial PSCCE can convert to stratified squamous

Question 32

Carcinoma

Answer 32

a malignant tumor of epithelial origin

Question 33

Adenocarcinoma

Answer 33

• malignant tumor from glandular epithelium
• Immunocythochemistry used to determine origin of tumors