Specialized Tissues, Stem Cells And Tissue Renewal I

Question 1

Asymmetric Division

Answer 1

• Creates 2 cells
• One with stem cell Characteristics
• One with the ability to DIFFERENTIATE

Question 2

TGF-Beta on Epidermis Renewal

Answer 2

• Plays a key role on REPAIR of Skin wounds

- Promotes. The formation of COLLAGEN rich SCAR tissue

Question 3

Regulation of Epidermal Stem Cells

Answer 3

• CONTACT with Basal Lamina Controls number of Stem cells
• Maintenance of contact preserves Stem Cell Potential
• Loss of contact triggers terminal differentiation

Question 4

Characteristics of the Prickle Cell Layer

Answer 4

• Has DESMOSOMES

- Attaches to Keratin filaments

Question 5

Characteristics of Founder stem cells

Answer 5

• Proportion of the parts of a body are determined EARLY in development
• Each organ/tissue has a FIXED number of Founder cells
• Programmed to have fixed number of divisions

Question 6

Layers of the Epidermis from Outermost to Innermost

Answer 6

1. Basal Cell layer
2. Prickle Cell
3. Granular Cell
4. Squame

Question 7

Factors governing Renewal of Epidermis

Answer 7

1. Rate of Stem cell Division
2. % that one daughter will remain a Stem cell
3. Rate of Division of Transit Amplifying Cells
4. Timing of Exit from Basal Layer and the time the cell takes to differentiate and be sloughed away

Question 8

Characteristics of Stem cells

Answer 8

• Not terminally differentiated
• Can divide w/o limit
• Ability to renew themselves
• Undergo Slow Division

Question 9

Characteristics of Multipotent stem cells

Answer 9

• Ability to give rise to different cell types of a given LINEAGE
• Adult stem cells

Question 10

Characteristics of the Basal Cell Layer

Answer 10

• Attached to Basal Lamina
• The Only DIVIDING cells in the Epidermis
• Has STEM cells

Question 11

Characteristics of the Squame Cell Layer

Answer 11

• Flattened Dead cells
• Densely packed with Keratin
• NO ORGANELLES

Question 12

A steady pool of Stem cells are maintained by what?

Answer 12

• Asymmetric Division

- Independent Choice

Question 13

Characteristics of Adult stem cells

Answer 13

• Tissue Specific
• Serves an internal REPAIR system in many tissues
• Replace cells with rapid turnover
• Needs specialized environment

Question 14

Overactive Hedgehog Pathway in Epidermis Renewal

Answer 14

• Makes cells continue to divide

- Even after exit from the Basal Layer

Question 15

The Ectoderm lineage gives rise to what systems?

Answer 15

• Skin

- Neurons (CNS)

Question 16

Characteristics of Pluripotent cells

Answer 16

• Ability to give rise to ALL cells of the Embryo
  (NOT Extra Embryonic)
• Gives rise to adult tissues
• Ex: Embryonic stem cells

Question 17

Characteristics of the Granular Cell Layer

Answer 17

• Sealed together to form a WATERPROOF Barrier

- Forms boundary b/w INNER (active) strata and OUTER (dead) cells

Question 18

Fibroblast on skin composition

Answer 18

• Secrete ECM

- Provide Mechanical support

Question 19

Architecture of the Skin

Answer 19

1. Epidermis
   - Continuously repaired and renewed
2. Dermis
   - Rich in collagen and provides toughness
3. Hypodermis
   - FATTY subcutaneous layer

Question 20

Upregulation vs Loss of Wnt on Epidermis Renewal

Answer 20

Upregulation

• Causes extra HAIR follicles to develop
• Gives rise to tumors

Loss of Fxn
- Leads to failure of HAIR follicle development

Question 21

The Mesoderm lineage gives rise to what systems?

Answer 21

• Muscles

- Blood

Question 22

Developmental Capacity of stem cells: Most to Least

Answer 22

1. TOTI-Potent
2. PLURI-Potent
3. MULTI-Potent

Question 23

Characteristics of Transit Amplifying cells

Answer 23

• Transit from a Stem cell to a Differentiated cell
• Programmed to divide a LIMITED # of times
• Part of growth control

Question 24

Deficit in Hedgehog in Epidermis Renewal

Answer 24

Leads to loss of SEBACEOUS gland

Question 25

Which is more flexible? Asymmetric Division or Ind. Choice?

Answer 25

Independent Choice | - Explains the SHARP increase in Stem Cell # when needed for REPAIR

Question 26

Examples of Adult stem cells

Answer 26

1. Skin 2. Intestinal 3. Blood 4. Neurons

Question 27

Renewal Process of Epidermis

Answer 27

- Some Basal Cells divide and maintain that layer - Others move up to other layers - Change GENE EXPRESSION at each step of differentiation - Cells will eventually lose organelles

Question 28

Time of Birth of a Basal Cell Layer to Shedding from Surface?

Answer 28

1 month

Question 29

The Endoderm lineage gives rise to what systems?

Answer 29

- Lung | - Pancreas

Question 30

The Epidermis is a ________ layer made of ________.

Answer 30

1. Stratified | 2. Keratinocytes

Question 31

Proliferative potential of stem cells are directly correlated with expression of what?

Answer 31

- Beta 1 Subunit of INTEGRIN | - Helps mediate Adhesion to Basal Lamina

Question 32

Drawback of Asymmetric Division

Answer 32

Cannot explain how existing stem cells rapidly increase their numbers

Question 33

3 lineages of Pluripotent stem cells

Answer 33

1. Endoderm 2. Mesoderm 3. Ectoderm

Question 34

What happens to a founder cell when an adult organ needs to be renewed?

Answer 34

- Founder cells divides to make 1. One daughter stem cell 2. Differentiated cell Differentiated cells have a SET number of transit amplifying divisions

Question 35

Independent Choice

Answer 35

- Division makes 2 IDENTICAL cells - The outcome is Randomly Determined Or - Influenced by environment (Does not have to be 50:50 for every division)

Question 36

Notch Signaling on Epidermis Renewal

Answer 36

Restricts the SIZE of Stem cell population

Question 37

Characteristics of Totipotent cells

Answer 37

- Ability to give rise to ALL cells of an organism (Can produce a new being) - Embryonic and Extra embryonic - Ex: Zygote

Question 38

What are the two fates of stem cell division?

Answer 38

1. Can remain a stem cell Or 2. Become a DIFFERENTIATED cell type