Epithelial Tissue I & II

Question 1

Epithelium

Answer 1

Main Functions:
1. Protection
2. Transcellular transport
3. Secretion
4. Absorption
5. Sensory detection

*Its the main way we feel the world and sense what we’re doing

Question 2

Epithelium Basic Structure:

Answer 2

Avascular
Covers body surfaces
Lines internal, closed body cavities
Constitutes glands

Question 3

Polarity of Epithelium

Answer 3

Cells are closely apposed and attached to one another

Attached basally to a basement membrane
Apically faces into a lumen or the outside world

Question 4

Epithelium Domains

Answer 4

1. Apical Domain
2. Lateral Domain
3. Basal Domain

Question 5

Apical Domain

Answer 5

Specializations of the plasma membrane often define the function of that epithelial

Question 6

Microvilli

Answer 6

Used for absorption

Extends into lumen to increase surface area; often called striated or “brush border”

Has an actin core which is kept stiff by VILLIN

Question 7

Glycocalyx

Answer 7

“Cell coat”

Associated with microvilli and aids in absorption

Carbohydrate chains linked to membrane proteins or lipids

Question 8

Cilia

Answer 8

Movement along surfaces; very mobile hair-like structures that extend from dark basal bodies

Core of microtubules called basal bodies

Question 9

Basal bodies

Answer 9

Part of cilia microtubules

Develop from procentriole organziers as “9 triplets”. As they extend into the cilium, they rearrange into a 9+2 arrangement (9 peripheral doublets and 2 central singlets)

Question 10

Lateral Domain

Answer 10

Borders on neighboring cells and forms a selective barrier, adheres, and communicates

Interdigitations: Lateral surfaces show infolding that increases surface area

3 Complexes:
1. Zonula occludens (Tight Junction)
2. Zonula adherens ( Intermediate Junction)
3. Macula adherentes (Desmosomes/ “Spot” Junction)

Question 11

Zonula Occludents/Tight Junction

Answer 11

Most apical part that separates the luminal space from the intercellular space

First line of defense; forms protective barrier between epithelial cells

Can be SUPER tight or kind of leaky depending on where they are in the body

Question 12

Zonula adherens/Intermediate junction

Answer 12

Cells do NOT touch

Main function: cell to cell adhesion joined by linking proteins
Always affiliated with actin

Question 13

Macula adherentes/Desmosomes

Answer 13

Most inferior of the complex but still very apical on the cell

Main function: cell to cell adhesion via attachment plaques which give stability and link through linking proteins

Always associated with intermediate filaments

Question 14

Gap junction

Answer 14

Specialized lateral domain; “communicating juctions”/”nexus”

Main function: exchange or signaling between adjacent cells; direct passage of signaling molecules from one cell to another

Two way street between cells, but nothing can “leak” out

Question 15

Basal domain

Answer 15

-Borders basement membrane, related to underlying tissues
-Specialized for cell-to-ECM adhesion; also exhibits infoldings

Question 16

How does epithelial attache to the basal lamina?

Answer 16

“Spot Welds” aka Hemidesmosomes: 1/2 demisome that connects to basement membrane (intermediate filaments)
Associated w/ attachment plaques

Also via focal adhesions made of actin

Question 17

Simple epithelium

Answer 17

One-layer thick; every cell touches the basement membrane

Question 18

Pseudostratified columnar epithelium

Answer 18

Looks stratified but its actually simple b/c every cell touches basement membrane

Usually found in respiratory tract

Question 19

Stratified epithelium

Answer 19

more than one layer; named for shape of cells in the apical layer

Question 20

Non-keratanized epithelium

Answer 20

toughest covering for most things w/in the body

Question 21

Keratanized epithelium

Answer 21

“not alive”; layer of protective epithelium

toughest layer (makes up most of the skin)

Question 22

Transitional epithelium

Answer 22

the apical cells have a rounded shape

Most commonly found in the bladder

Question 23

Shape of Epithelial cells

Answer 23

1. Squamous (looks flat)
2. Cuboidal
3. Columnar

Question 24

Two types of tissue to make glands from epithelial cells

Answer 24

1. Parenchyma (general word for working part): epithelial cells
2. Stroma: Connective tissue (supporting tissue)

Question 25

2 major types of glands

Answer 25

1. Endocrine
2. Exocrine

Question 26

Endocrine Glands

Answer 26

Secrete hormones into blood or lymphatic vessels located in CT

Polarized toward the basement membrane (REVERSE polarity)
Ductless (no lumen); produces hormones; secretion can be constitutive or regulated

Question 27

Exocrine Glands

Answer 27

Secretes into ducts

Structure: often named for branching of ducts
1. simple (little or no branching)
2. Compound (multiple layers of branching)
3. Tubular
4. Acinar: “berry” or “flask-shaped”

Question 28

Types of Exocrine Gland Secretion:

Answer 28

1. Serous (watery): pyramida-shaped cells at light-level; basally located, round nuclei; basophilic basal cytoplasm
2. Mucous: pale apical cytoplasm, darkly stained nuclei basally; lumen tend to be larger; mucous is heavy so its darker