CHAPTER 4 - Cell PROLIF

Question 1

Explain the difference between cell proliferation and cell differentiation

Answer 1

Cell Proliferation
-Process of increasing the number of cells by mitosis

Cell Differentiation

• Process where cell specializes into specific body structure (organ, tissue, etc.) and function
• Different types of cells differentiate into different rates and process

Question 2

Describe the five phases of the cell cycle.

Answer 2

GAP 1

• Cell starts to prepare for DNA replication and mitosis
• Increased size
• Checkpoint here to ensure proper elements available and ready to divide safely.

SYNTHESIS PHASE

• DNA synthesis
• Chromosomes are replicated
• Lasts 10 to 12 hours

GAP 2

• Premitotic phase
• Enzymes & proteins needed for cell division are synthesized and moved into place

MITOSIS PHASE

• Formation of mitotic spindle and cell division
• Takes 1 hour

GAP 0

• Not part of the “cycle”
• Resting phase after mitosis
• Different cell types act differently here
• Blood cells & GI tract lining cells never enter here but continue to cycle
• Hepatocytes rest but can be stimulated to reenter cycle when needed
• Neurons leave cycle permanently

Cyclins

• Proteins that control entry and cell movement through the cycle
• Help to regulate the repair of DNA at checkpoints if errors occur

Checkpoints occur throughout cycle

Question 3

Define and give an example of labile, stable, and permanent cells in regards to their ability to divide and reproduce.

Answer 3

Labile cells divide and replicate throughout our lives to replaced destroy cells
-skin, oral, vaginal, GI, urinary, and bone cells

Stable cells replication stops when growth stops
resting in gap 0, but can be stimulated to regenerate
-liver, kidney cells, smooth muscles, vascular endothelial cells, fibroblast, wound healing

Permanent cells

• terminally differentiated
• nerve, cardiac, skeletal cells

Question 4

Describe three important properties of stem cells.

Answer 4

Properties

Self-renewal
-Can undergo mitosis while still undifferentiated

Asymmetric replication
-Following division, one cell retains stem cells characteristics and other proceeds towards differentiation

Differential potential
-Each generation of cell becomes increasingly differentiated

Question 5

Describe the three phases of tissue repair by connective tissue deposition.

Answer 5

1. Angiogenesis & Ingrowth of Granulation Tissue
   - Red, moist tissue fills injured area
   - New capillaries induced by growth factors
   - -Not well structured; leak causes fluid/edema
   - Inflammatory cells begins to arrive
2. Emigration of Fibroblasts & Deposition of Extracellular Matrix
   - Scar formation on framework of granulation tissue
   - -Pale, largely avascular scar
   - Phase 1: fibroblast proliferate
   - Phase 2: collagen synthesis and deposition
3. Maturation & Remodeling of Fibrous Tissue
   - Extracellular matrix reorganizes scar tissue to relatively permanent state
   - Slow process

Question 6

Describe healing by primary and secondary intention

Answer 6

Primary Intention

• Wound closure and healing by sutured surgical incision
• Well reduced bone fractures

Secondary Intention

• Wound closure by scarring (burns, etc.)
• Burns, abrasions, etc

Question 7

Trace the wound-healing process through the inflammatory, proliferative, and remodeling phases. (cutaneous wound healing)

Answer 7

Inflammatory Phase
Begins at time of injury

Blood clot

• Vasoconstriction, platelet aggregation
• Vasodilation allow WBC to enter

Inflammatory cells
-Phagocytotic WBCs macrophages arrive and ingest bacteria and cellular debris

Proliferative Phase: new tissue to fill wound
-Begins within 2-3 days of injury
1. Granulation
Fibroblasts synthesized and secrete collagen, growth factors, etc. to begin healing process
Angiogenesis, initially very fragile “proud flesh” may form
2. Epithelialization occurs
Formation of new surface layer similar to original

Remodeling Phase

• Begins 3 weeks after injury (dependent on extent)
• Fibrous scar forms
• Vascularization decreases
• Scar shrinks
• Tensile strength seldom as strong as original

Keloid formation
Abnormal scar tissue
Genetic predisposition

Question 8

Explain the effect of malnutrition; ischemia and oxygen deprivation; impaired immune and inflammatory responses; and infection, wound separation, and foreign bodies on wound healing

Answer 8

?