Epithelial Tissue Flashcards Preview

Histology I > Epithelial Tissue > Flashcards

Flashcards in Epithelial Tissue Deck (60):
1

Basic tissue types

1.) Epithelial
2.) Connective
3.) Muscle
4.) Nervous

2

Epithelial tissue location

1.) Cover exterior surfaces (barrier
epithelium)
2.) Line internal cavities (barrier epithelium)
3.) Form secretory portions of glands and
their ducts (glandular epithelium)

3

Characteristics of epithelial tissue

- Free surface( ex: skin, lining of intestine)
- no extracellular matrix (packed close
together)
- Avascular

***even though epithelial tissue is avascular it still lines the walls of blood vessels

4

Morphologic polarity of Epithelial cells

- Apical domain
- Lateral domain
- Basal domain

5

Apical domain

- Forms external (luminal) surfaces
- can exhibit surface modifications (cilia, microvilli, stereocilia)

6

Microvilli

Increase surface area where absorption is important (eg: kidney, small intestine)

7

Microvilli structure

- Core formed by actin bound together by actin binding proteins (fimbrin, facin)

-anchored to the membrane by lateral anchor proteins (Myosin I)

*** Individual microvili can not be seen with light microscope

8

Amphorous apex of microvilli

formed by villin into which actin filaments are anchored

9

Stereocilia

- Modified microvilli (not related to cilia)
- sometimes branching
- Core formed by actin

Locations: epididymis ( fluid absorption) inner ear ( sensory receptors)

10

Cilia

- found in areas where transport is important (respiratory, oviduct)
- Structure ( basal body + axoneme) microtubules

11

Primary Ciliary dyskenesia

- genetic defects of ciliary proteins result in absent or uncoordinated cilia

- embryologic pathologies (dextrocardia)
- Impaired development of skull air sinuses
- No mucus removal from lungs
- Infertility

12

Lateral Domain

Characterized by the presence of junctions

13

Classes of cellular junctions within the lateral domain

1.) Occuluding
2.) Anchoring
3.) Communicating (Gap junction)

14

Occluding junctions

Zonula Occludens:
- single strand of transmembrane protein that binds membranes of two
adjacent cells (like a belt)

- Found in cells with secretory or absorptive role ( function to prevent diffusion
by blocking the paracellular pathway)

15

Anchoring junctions

Provide stability and mechanical strength to the tissue and allow it to function as a unit

Connect cytoskeleton of two adjacent cells

Zonula Adherens
Macula Adherens (Desmosome)

16

Zonula adherens

- connects thin filaments (actin) (cell:cell)

Structure:
- Actin binding protein: vinculin, alpha actinin
- Peripheral protein: Catenin
- Transmembrane protein: CADHERIN (ca2+ dependent)

17

Macula Adherens

- connects intermediate filaments (cell:cell)

Structure:
- intracellular plaque: Desmoplakin ( I.F travel through the plaques)
- Transmembrane protein: CADHERIN

18

Pemphigus

Autoimmune disorder in which the body creates antibodies that attack the desmosomes in the skin
- Prevents normal adhesion
- Causes widespread skin and mucous membrane blistering

19

Communicating (Gap Junctions)

-Allow diffusion of small molecules and ions between the cytoplasm of
adjacent cells through intercellular channels
- Occur in patches
- Common in epithelia, cardiac, smooth muscle, embryonic tissue (cells that
need to talk alot) --> cell proliferation and differentiation

20

Intercellular channel structure

Each channel is made of a pair of connexons each made of 6 connexins

21

Basal Domain

- Faces the basement membrane
- Important for interaction with underlying tissue (usually connective)

22

Basement Membranae

-Separates epithelium from underlying connective tissue and is formed of 2 layers

- Basal lamina
-Reticular lamina

23

Basal lamina

- Most external part of the basement membrane
- Belongs to epithelium
- composed of sheets of collagen IV and laminin

24

Reticular Lamina

-Deeper layer of the basement membrane
- Belongs to connective tissue
- Composed of thin collagen fibers

25

How are epithelial cells connected to the basement membrane?

- Focal adhesions
- Hemidesomsomes

(cell:matrix)

26

Focal Adhesions

- Cell: Matrix
- Connect Thin filaments (actin)

Structure:
- Actin binding protein: vinculin, alpha actinin
- Peripheral protein: talin
- Transmembrane protein: INTEGRIN (Ca 2+ INdependent)

27

Hemidesmosome

- Cell:Matrix
- Connect Intermediate filaments

Structure:
- Intracellular plaque: desmoplakin (TERMINATE on the plaque)
- Transmembrane protein: INTEGRIN

28

Ways to classify an epithelial cell

1.) Number of layers
2.) Cell shape at apical most layer
3.) Apical cell modifications

29

Simple epithelium

1 layer

30

Stratified epithelium

More than one layer

31

Pseudostratified
Epithelium

All cells rest on the basement membrane but not all cells reach the surface

32

Squamous

Flat

33

Cuboidal

Cube (round nuclei)

34

Columnar

Column (oval nuclei)

35

Terminal Bar

Found between cell junctions

Duodenum and Epidydimis

36

Simple Squamous Epithelium (appearance and function)

- Single layer
- Flattened nuclei
- Provide barrier and diffusion

37

Where is simple squamous epithelium found

- Lines vascular system and body cavities
- Parietal layer of Bowmans capsule (Kidney)
- Alveoli of the lungs

*** areas that require barrier and diffusion

38

Endothelium

Specialized type of simple squamous epithelium that lines the walls of blood vessels

39

Mesothelium

Specialized type of simple squamous that covers internal organs in the pleural, parietal, and peritoneal cavities

40

Specialized Simple Squamous

1.) Endothelium
2.) Mesothelium

41

Simple Cuboidal epithelium (appearance and function)

- single layer of cuboidal cells
- spherical nuclei
- Barrier (ducts), Secretion (thyroid), Absorption(kidney)

42

Where is simple cuboidal found

- walls of ducts of various glands
- kidney tubules
- geminal epithelium of ovary
- thyroid follicles

43

Simple Columnar (appearance and function)

- single layer of columnar cells
- oval nucleus
- Surface modifications (microvilli and cilia)

- absorption, secretion, lubrication, and transport

44

Where is Non-Ciliated simple columnar found

- lining of GI tract (Microvilli!!)
- walls of bladder

45

Where is Ciliated Simple Columnar found

- Lining the Oviduct

46

Pseudostratified Columnar Epithelium (appearance and function)

- Most cells columnar shape but also appears to be a layer of more rounded cells that do not reach the surface (basal cells)

47

Basal Cells

Progenitor or replacement cells

48

Where are ciliated pseudostratified columnar found

- mainly in respiratory tract

49

Metaplasia

- Under stress ciliated pseudostratified columnar will change shape and lose their cilia to take on a more squamos appearance

- Common in smokers

- Take away the stress and it can shift back

- Can also occur in simple columnar epithelium

50

Epithelial tissues that can undergo metaplasia

- ciliated pseudostratified columnar
- simple columnar

51

Where do you find nonciliated pseudostratified columnar

- Epididymis
- has stereocilia rather than cilia

52

Stratified Squamous (appearance and function)

- several layers with various shapes BUT apical layer will be flat squamous cells

- Can be kereatinized

- Forms a barrier between underlying tissue and environment

53

Keratinized stratified squamous (appearance and location)

- dead layer on the surface (no nuclei)
- found in epidermis of skin

54

Where do you find nonkeratinized stratified squamous

- beginning of the GI tract (oral cavity, esophagus)
- Female reproductive system (vagina)

55

Stratified Cuboidal (appearance and function)

- RARE
- Two cuboidal layers

- Functions as a barrier and a conduit

56

Where do you find stratified cuboidal

- Rare
- Found in ducts of some glands (most common= sweat glands of skin)

57

Stratified columnar (appearance and function)

- cuboidal basal cells columnar surface cells
- functions as barrier and conduit

58

Where do you find stratified columnar

- RARE
- Larger ducts of several glands (parotid and submandibular salivary glands)

59

Transitional Epithelium

- AKA urothelium
- Multiple layers of different cell types
- Presence of Dome cells in the apical layer
(binucleated)
- Ability to stretch

60

Where is transitional Epithelium found

Urinary system:
- urinary bladder
-Ureter
-Pelvis and calyces of the kidney