epithelial tissue I B

Question 1

A mucosa is composed of two layers:

Answer 1

1. the outer epithelium and

2. the CT directly underneath, which is typically (unfortunately) called the lamina propria.

Question 2

Lamina propriae contain:

Answer 2

lots of immune system cells and small blood vessels

Question 3

Submucosa are directly continuous with ________ but will often have different properties and house other tissues ______.

Answer 3

lamina propria CT,

bigger vessels and muscles, nerve axon bundles, etc.

Question 4

the epithelium of skin is called the ______, while the directly underlying CT is called the _____; deeper CT is called _____ and like _____ has distinct composition and function

Answer 4

epidermis

dermis

hypodermis

submucosae

Question 5

The outer surface is DIRECTLY contiguous with the _______.

Answer 5

spaces of most of these tube and ducts, and ALL of tube duct surfaces are lined by epithelia

Thus, epithelial sheets exist in all of these layers.

Question 6

Simple epithelia have

Answer 6

have all cells arranged in a single layer or sheet.

Question 7

Stratified epithelia have:

Answer 7

more than one layer of cells in which cells of the outer layers do not directly contact the basal lamina.

Question 8

Pseudostratified epithelia are:

Answer 8

a special case where some cells do not reach the free surface (giving a stratified appearance), but all directly rest on the basal lamina.
Further classification relates to cell shape relative to the apical to basal axis.

Question 9

Squamous cells are:

Answer 9

flattened cells

Question 10

Transitional epithelia:

Answer 10

(found around the bladder) are a special case: these epithelia are stratified, but when stretched change their shape from cuboidal to squamous, and appear to decrease the layering: this is indicative of a tightly adherent epithelium that is very resilient and stretchable.

Question 11

how do epithelia cells communicate and adhere to each other.

Answer 11

cell junctions

Question 12

Various types of cell junctions exist to ______.

Answer 12

mediate and control cell attachments

Question 13

Cell junctions are present on the _____ surfaces of epithelial cells, generally towards the _____ side

Answer 13

lateral

apical

Question 14

Tight junctions function:

Answer 14

(or the zonula occludens):

1. provide a highly selective barrier that limits or prevents diffusion of substances between epithelial cells.
2. limit/control diffusion of membrane proteins through the plasma membrane bilayer.

Question 15

Tight Junctions Key core proteins of tight junctions are:

Answer 15

occludins and claudins: In some epithelia the “tightness” of this barrier is regulated.

Question 16

Tight barriers ensure ______

Answer 16

that substances absorbed or secreted must pass through the epithelial cell by specific transport pathways.

Question 17

Adherence junctions function:

Answer 17

(zonula adherens): Promote attachment, but also polarity, morphological organization and stem cell behavior within the epithelial sheet.

Question 18

Adherence junctions contain

Answer 18

specific cadherins that link to actin filaments and other adapter/signaling proteins in the cytoplasm.

Question 19

Cadherins are:

Answer 19

transmembrane proteins with extracellular domains that interact with each other, and cytoplasmic tails that bind adapters and actin filaments.

Question 20

Some cadherin-associated proteins (e.g.____ and _____) control ____

Answer 20

beta catenin and protein kinases

various aspects of epithelial polarity, development, and function.

Question 21

Desmosomes function:

Answer 21

(macula adherens):

Promote mechanical strength and resist shearing forces and promote the structural organization of the epithelial sheet.

Question 22

Desmosomes core component:

Answer 22

a different class of cadherins that link to intermediate filaments and other adapter proteins.

Question 23

Gap junctions function:

Answer 23

Promote rapid communication between epithelial cells, through diffusion of ions and small molecules

Question 24

Most epithelial cells and tissues are highly ____

Answer 24

polarized, which means they contain distinct plasma membrane and cystoplasmic regions.

Question 25

Polarization leads to formation of an ____ and an _____

Answer 25

outer domain, the apical domain, that faces the free surface, and an “inner” basal or basolateral domain that faces the basal lamina.

Question 26

There are two general aspects to polarity:

Answer 26

1. plasma membrane composition is locally segregated into domains
2. the cytoplasm is polarized

Question 27

The plasma membrane in the apical domain contains:

Answer 27

distinct membrane proteins and a distinct phospholipid content compared to the membrane in the basal domains.

Question 28

Key membrane proteins that localize to specific domains include:

Answer 28

transporter enzymes, ion channels, receptors for exocytosis/endocytosis, signaling receptors and effectors, and proteins that mediate cell-cell and cell-lamina attachments.

Question 29

The tight junction complexes tend to reside near the ______

Answer 29

apical surface in these cells.

Question 30

The cytoskeleton (particularly microtubules) is ______ in orientation.

Answer 30

asymmetric or polar

Question 31

_______ in the apical domain are usually different from those in the basal domain, and they move in ______

Answer 31

secretory vesicles

specific directions.

Question 32

Epithelial cell polarity is crucial to allow ______ .

Answer 32

1. unidirectional secretion and/or absorption of molecules to or from one side of the epithelium.
2. “trans-epithelial” transport of ions and macromolecules from the apical to basal surfaces (or visa versa)
3. localizing and orienting intercellular signaling either among epithelial cells, or between epithelial cells and other cell types.

Question 33

transcytosis:

Answer 33

The endocytosis of substances from one membrane region, followed by trans-cellular transport of the vesicles and their exocytosis from another membrane region