Ims: Histo Block 1 Lecture 1A

Front 1

What are the basic characteristics of epithelium? Functions?

Back 1

made up of cells closely packed and arranged, in a single layer or in multiple layers, upon a basal lamina

Cover external surfaces, line internal surfaces, form glands

Front 2

Describe the sidedness of epithelial cells.

Back 2

Cells exhibit polarity; apical side faces lumen (hollow interior or external world), lateral (contain inter-cellular junctions), and basal (usually has underlying connective tissue) surfaces

Front 3

What feature dictates epithelial cell subtype?

Back 3

Cell shape at apical layer

Front 4

What three cell junctions occur in epithelial cells? Describe their location relative to one another.

Back 4

Tight (occluding) junctions occur most apical, on lateral surface
Beneath them are adhering junctions (hold cells together)
Beneath them are gap junctions (communicators)

Front 5

Contrast the zonula occludens with the zonula/macula adherens.

Back 5

Zonula (belt) occludens (cellular material can't past through): belt-like junction; ring around apical-lateral area; ~plastic on six pack of beer

Macula (spot) adherens (holds cells together; either belt-like or spot like)

Front 6

What is the main role of zonula occludens?

Back 6

Regulate permeability in epithelial tissues, act as backup to already selective cell membrane

Front 7

What are adhering junctions comprised of? Describe their subatomic structure.

Back 7

Strands of integral membrane proteins that seal off space between adjacent cells.

Cadherin cell-cell adhesion proteins spans two adjacent cells and is anchored on each side by cytpolasmic accessory molecules, the catenins. Actin-based filaments then extend from catenin into apical terminal web to provide support.

Front 8

What are macula adherens? Describe their subatomic structure.

Back 8

Literally: "spot adhesion"; aka desmosomes

Cadherin cell-cell adhesion proteins spans two adjacent cells and is anchored on each side by cytpolasmic accessory molecules, the catenins. Intermediate filaments (KERATIN) then extend from catenin and anchor in terminal web.

Front 9

What is the main role of gap junctions? Describe their subatomic structure.

Back 9

Permit electrical and metabolic coupling between cells

Junctions formed by groups of six proteins (CONNEXINS) arranged in hexagonal doughnut around central pore, forming a CONNEXON (doughnut hole). Adjacent connexons from adjacent cells align to form channel.

Front 10

Contrast zonula adherens with macula adherens.

Back 10

They're both adhering junctions.

Zonula adherens = circumferential belt

Macula adherens = spot adhesion; aka desmosome; occur more basal than belt adhesions

Front 11

What is the role of a brush border? What is it constructed of? AKA?

Back 11

Microvilli (little fingers); increases sell surface area, allow for absorption and secretion

Contains regular membrane infoldings with actin core

Front 12

Describe the subatomic structure of cilia. What roles do they serve?

Back 12

emanate from basal body of microtubule organizing center and feature a 9+2 array of MT's, such that 9 pairs of MT's arrange in a circle and 1 pair of MT's form the pore

Cilia sweep material past apical surface; good for moving debris, mucus, other cells

Front 13

What are the characteristic features of the basal surface of epithelial cells?

Back 13

Infoldings to increase membrane surface area for desmosome, transport processes; hemi-desmosomes to anchor cell to basal lamina (these are adhering junctions but no adj cell for other half of desmosome)

Front 14

What is the basal lamina? Describe some of its roles.

Back 14

network of extracellular molecules that form epithelial-connective tissue interface. Provides mechanical support and acts as sieve to excluse proteins, but allow small molecs to pass through.

Front 15

Contrast simple epithelium with stratified epithelium. Roles?

Back 15

SImple: one cell layer thick; used in filtration, diffusion, absorption, secretion

Stratified: many layers thick; used for protection, renewal

Front 16

Describe simple squamous epithelial cells. Where would they be found?

Back 16

Thin layer of flat, attenuated (broadened) cells. Will be found in areas needing quick diffusion (blood vessel linings, filtration in bowman's capsule in kidney, gas diffusion in alveoli)

SQUISHED nuclei

Front 17

Describe simple cuboidal epithelial cells. Where can they be found?

Back 17

Cells are cube-like, found in glands (thyroid), and tubules (nephron)

Nucleus is rounder, more cytoplasmic real estate

Front 18

Describe simple columnar epithelium. Where can they be found?

Back 18

tall, rectangular in profile, nuclei are more basal region of cytoplasm

Found in lining of GI tract

Front 19

Describe pseudostratified columnar epithelial cells. Where can they be found?

Back 19

all cells contact basal lamina, but not all reach the surface; cells vary in shape
nuclei at different levels

Show up in lining of respriratory tract, vas deferens

Front 20

How would you visually differentiate between cilia and microvilli?

Back 20

Cilia are a lot longer than microvilli

Front 21

Describe the structure of stratified squamous epithlium. Where would it be found?

Back 21

Layers of cells; cells are flattened at surface (may be keratinized if external); base is mitotically active (allows for constant renewal)

Bottom most layer is youngest, oldest, most dx/dy'd cells on top; cells joined by mostly ADHERING jns

Found in areas of friction, but not absorption, e.g, epidermis, esophagus, vagina

Front 22

Describe transitional epihtelium. Where is it found?

Back 22

Unique apical surface cells that are dome-shaped; can change to flat shape (hence the name transition cells); rich in occluding junctions to prevent leakage

Present in urinary bladder and lining of ureters

Front 23

Describe stratified cuboidal epithelium. Where is it found?

Back 23

UNCOMMON. Ovarian follicles.

Front 24

Describe stratified columnar epithelium. Where is it found?

Back 24

UNCOMMON; large excretory ducts of sweat glands

Front 25

What are glands? What are their two main subcategories? How do they differ?

Back 25

Epithelial cells specialized for secretion.

Exocrine: glands which secrete via a duct into a lumen

Endocrine: no duct, secrete basally into a vascular supply

Front 26

Draw the four simple types of exocrine glands.

Back 26

Tubular: upside down cursive l
Branched tubular: chicken foot
Coiled tubular: flaccid penis
Branched alveolar: three leaf clover

Front 27

Draw the two compound types of exocrine glands.

Back 27

Tubular: three, connected four-toed chicken feet
Alveolar: three connected branches of three leaf clovers

Front 28

List all simple epithelial types, their roles (if applicable), and where they can be found.

Back 28

Squamous: quick diffusion; blood vessel lining, Bowman's capsule (kidney), gas diffusion in alveoli

Cuboidal: blank; glands, tubules

Columnar: blank; lining of GI tract

Pseudostratified: black; respiratory tract lining, vas def

Front 29

List all stratified epithelial types, their roles (if applicable), and where they can be found.

Back 29

Squamous: areas of friction NOT absorption (keratinized if external); high in adherens jns; skin, esophagus, vagina

Transition: prevent leakage; dome-shaped or flat shaped on top, lots of occluding jns; bladder, ureters

Cuboidal: uncommon; ovarian follicle

Columnar: uncommon; sweat glands

Front 30

Which class of stratified epithelial cells can be keratinized? Under what circumstances would they be keratinized?

Back 30

Stratified squamous; if exposed to external environment (would see lots of dead cells on top)

Front 31

Which class of stratified epithelial cells exhibit a high number of occluding junctions?

Back 31

Transitional

Front 32

Which class of stratified epithelial cells exhibit a high number of adherens junctions?

Back 32

Stratified squamous