Types of Tissue 8Repair

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Questions and Answers

What primarily characterizes fibrosis in tissue repair?

Increased vascularization

Regeneration of nerve cells

Proliferation of epithelial cells

Extensive collagen deposition (correct)

What is the main function of growth factors in tissue regeneration?

Initiating DNA synthesis

Directing the formation of scar tissue

Stimulating stem cell apoptosis

Maintaining the integrity of the extracellular matrix (correct)

Which phase does the G1 restriction point occur in?

G1 phase (correct)

S phase

G0 phase

M phase

What type of cells produce the majority of collagen in the liver?

Stellate cells Signup and view all the answers

What is the main role of the S cyclins?

Bind to CDKs for DNA replication initiation Signup and view all the answers

What happens during the G2 phase of the cell cycle?

Cells grow and prepare for mitosis Signup and view all the answers

Which of the following statements about cell cycle checkpoints is correct?

Checkpoints ensure proper DNA replication and division. Signup and view all the answers

Which cell cycle phase is characterized by presynthetic growth?

G1 phase Signup and view all the answers

What drives cell proliferation during regeneration?

Growth factors Signup and view all the answers

Which of the following cellular mechanisms can alter cell numbers?

Apoptosis and differentiation rates Signup and view all the answers

What significant changes occur during the second week of healing by first intention?

Continued collagen accumulation and fibroblast proliferation Signup and view all the answers

By the end of the first month of healing by first intention, what is a characteristic feature of the scar?

Composed of mostly cellular connective tissue Signup and view all the answers

What is the role of myofibroblasts in the healing process by second intention?

Mediating wound contraction Signup and view all the answers

In which situation does healing by second intention most commonly occur?

Large wounds or in cases of ischemic necrosis Signup and view all the answers

What characterizes chronic wounds in the healing process?

Associated with consistent inflammatory response Signup and view all the answers

What leads to the formation of contractures in wounds?

Exaggeration of wound contraction Signup and view all the answers

Which of the following chronic wounds can occur as a result of venous insufficiency?

Venous leg ulcers Signup and view all the answers

During the healing by first intention, what process begins after collagen deposition?

Regression of vascular channels Signup and view all the answers

What is expected to be permanently lost in a healing wound that destroys dermal appendages?

Dermal appendages Signup and view all the answers

What is a potential complication associated with abnormal wound healing?

Formation of keloids Signup and view all the answers

What is the primary role of G1 cyclins in the cell cycle?

To help the cell past the restriction point Signup and view all the answers

Which checkpoint ensures that DNA has been accurately replicated before cell division?

G2/M checkpoint Signup and view all the answers

Which type of tissues are characterized as having cells that are continuously lost and replaced from stem cells?

Labile tissues Signup and view all the answers

What is the main characteristic of permanent tissues?

They are terminally differentiated and non-proliferative. Signup and view all the answers

Which growth factor is primarily involved in wound healing and the proliferation of specific cells?

Platelet-derived growth factor Signup and view all the answers

How do growth factors signal in the same cell that produces them?

Autocrine signaling Signup and view all the answers

What is a primary function of the extracellular matrix (ECM)?

Mechanical support and control of cell proliferation Signup and view all the answers

Which constituents are primarily found in the basement membrane of the ECM?

Laminin and type IV collagen Signup and view all the answers

What type of stem cells are derived from embryos and possess the potential to become any cell type?

Totipotent stem cells Signup and view all the answers

What is a common function of growth factors besides stimulating cell growth?

Influencing cell movement and differentiation Signup and view all the answers

What is the primary component of interstitial ECM?

Fibronectin Signup and view all the answers

Which of the following families do adhesion receptors belong to?

Cadherins Signup and view all the answers

What type of tissue forms during the healing process of a wound?

Granulation tissue Signup and view all the answers

Which type of wound healing results in minimal scarring?

Healing by first intention Signup and view all the answers

What is the sequence of tissue appearance during the healing of skin wounds?

Fibrin, granulation, new epithelium Signup and view all the answers

What does the remodeling phase of scarring primarily involve?

Reorganization of connective tissue Signup and view all the answers

During which time frame does the remodeling of connective tissue begin following injury?

2 to 3 weeks after injury Signup and view all the answers

Which condition is characterized by the replacement of injured cells with connective tissue?

Repair by scarring Signup and view all the answers

What is the gross appearance of granulation tissue?

Pink, soft, and granular Signup and view all the answers

What typically happens to a clean surgical incision during healing by first intention?

It primarily relies on epithelial regeneration. Signup and view all the answers

Study Notes

Types of Tissue Repair

Two main reactions for tissue repair: regeneration and scar formation.
Regeneration: Involves proliferation of residual uninjured cells and maturation of tissue stem cells.
Scar Formation: Involves deposition of connective tissue.

Scar Formation (Connective Tissue Deposition)

Fibrosis: Extensive collagen deposition due to chronic inflammation or ischemic necrosis; commonly in lungs, liver, kidney, and myocardium.
Stellate Cells: Major collagen producers in the liver.

Cell and Tissue Regeneration

Cell proliferation is driven by growth factors (GFs) and the integrity of the extracellular matrix (ECM).
Mature cells develop from stem cells.

Mechanisms Regulating Cell Populations

Changes in cell numbers through stem cell input, apoptosis, and alterations in proliferation rates.

Cell Cycle Phases

G1 phase: Pre-synthetic growth.
S phase: DNA synthesis.
G2 phase: Pre-mitotic growth.
M phase: Mitosis.
G0 state: Quiescent cells not actively cycling.

Cell-Cycle Checkpoints

G1/S Checkpoint: Monitors DNA integrity before committing to DNA replication.
G2/M Checkpoint: Ensures accurate DNA replication before cell division.
M/G1 Checkpoint: Verifies attachment of chromosomes to the spindle and checks DNA damage.

Proliferative Capacities of Tissues

Labile Tissues: Continuously dividing tissues (e.g., small and large bowel, skin, bone marrow).
Stable Tissues: Quiescent cells that can re-enter the cell cycle for regeneration (e.g., liver).
Permanent Tissues: Terminally differentiated and non-proliferative cells (e.g., neurons, cardiac muscle).

Stem Cells

Embryonic Stem Cells: Totipotent cells derived from embryos with the potential to become any cell type.
Adult Stem Cells: Derived from adult tissues, yielding a restricted range of cells.

Growth Factors

Stimulate cell survival and proliferation; influence movement, contractility, and differentiation important in wound healing.
Mutations in growth control genes can lead to oncogenesis.
Key families: Epidermal Growth Factor (EGF), Transforming Growth Factor-beta (TGF-beta), Fibroblast Growth Factor (FGF), Vascular Endothelial Growth Factor (VEGF), Platelet-Derived Growth Factor.

Extracellular Matrix (ECM)

Composite of proteins forming a network surrounding cells, essential for development and repair.
Major components include collagen, elastin, and fibroblasts.
Functions: Water sequestration, mechanical support, controlling cell proliferation, and serving as a reservoir for growth factors.

Role of ECM in Tissue Repair

ECM exists as interstitial matrix and basement membrane.
Interstitial Matrix: Composed of fibrillar and nonfibrillar collagens, fibronectin, elastin, and proteoglycans.
Basement Membrane: Mainly made up of type IV collagen and laminin.

Adhesive Glycoproteins and Adhesion Receptors

Fibronectin: Major component of interstitial ECM.
Laminin: Key constituent of basement membrane.
Cell Adhesion Molecules (CAMs): Includes immunoglobulins, cadherins, selectins, and integrins.

Wound Healing

If regeneration is insufficient, repair involves scar formation replacing injured cells with connective tissue.
Granulation Tissue: Proliferating fibroblasts, loose connective tissue, and new blood vessels typical for healing wounds.

Healing Processes

Primary Intention: Healing with minimal scarring, mainly through epithelial regeneration (e.g., surgical incisions).
Secondary Intention: More complex healing with significant regeneration and scarring (e.g., large wounds, abscesses).

Healing By First Intention

Surgical incision with minimal tissue loss and rapid epithelial regeneration, forming a small scar.
Involves fibrin-clotted blood transitioning to granulation tissue and new epithelium.

Healing By Second Intention

Occurs in extensive tissue losses involving significant inflammation and granulation tissue formation.
Wound contraction mediated by myofibroblasts leads to a larger scar.

Chronic Wounds

Commonly observed in conditions such as venous leg ulcers, arterial ulcers, pressure sores, and diabetic ulcers.

Contractures

Exaggerated wound contraction that can occur after burns, resulting in restricted movement and deformities.

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Description

Explore the two main mechanisms of tissue repair: regeneration and scar formation. Understand how damaged tissues recover through the proliferation of uninjured cells and connective tissue deposition. This quiz covers essential concepts related to fibrosis and its implications in various organs.