Tissue Regeneration — MCQs
Fixed post-mitotic cells are:
A 43-year-old window cleaner fell off a scaffold. He sustained an open wound on the right leg. Debridement was carried out in the emergency department, and the edges of the wound were left open. Which factor is least likely to inhibit wound contraction?
Stem cells in skin involved in skin homeostasis are present in the following areas except ______
Healing of bone is affected by:
Which of these is not a part of extracellular matrix:
What is the eponymous term for a full-thickness skin graft?
Which of the following is derived from fibroblast cells?
Regeneration is characterized by:
Which of the following type of collagen is present in healing and granulation tissue?
Granulation tissue is replaced by connective tissue in what stage of wound healing?
Tissue Regeneration Indian Medical PG Practice Questions and MCQs
Question 1: Fixed post-mitotic cells are:
- A. Fibroblasts
- B. Spermatocytes
- C. Endothelial cells
- D. Muscle (Correct Answer)
Explanation: ***Muscle*** - **Mature muscle cells** (both skeletal and cardiac myocytes) are **terminally differentiated** and are **fixed post-mitotic cells**. - These cells **cannot undergo mitosis** after reaching maturity and are permanently in the G0 phase of the cell cycle. - They primarily function in contraction and tissue maintenance rather than proliferation. *Spermatocytes* - **Spermatocytes** are germ cells that undergo **meiosis** to produce haploid spermatids. - They are **actively dividing cells** (through meiotic division, not mitosis) and are not in a fixed post-mitotic state. - These cells are derived from spermatogonia (the actual stem cells) and represent an intermediate stage in spermatogenesis. *Fibroblasts* - **Fibroblasts** are connective tissue cells that are capable of **mitotic division**, especially during wound healing and tissue repair. - They can re-enter the cell cycle from G0 phase when stimulated, making them **labile/stable cells**, not fixed post-mitotic cells. *Endothelial cells* - **Endothelial cells** line blood vessels and are typically quiescent but can be stimulated to **proliferate** during processes like angiogenesis and wound healing. - Their ability to divide and re-enter the cell cycle makes them different from fixed post-mitotic cells.
Question 2: A 43-year-old window cleaner fell off a scaffold. He sustained an open wound on the right leg. Debridement was carried out in the emergency department, and the edges of the wound were left open. Which factor is least likely to inhibit wound contraction?
- A. Radiation
- B. Transforming growth factor β (Correct Answer)
- C. Full-thickness skin graft
- D. Cytolytic drug
Explanation: ***Transforming growth factor β*** - **TGF-β** is a potent **pro-fibrotic cytokine** that plays a crucial role in promoting wound contraction and fibrosis by stimulating **fibroblast proliferation**, **myofibroblast differentiation**, and **collagen synthesis**. - Its presence and activity would *enhance* rather than inhibit wound contraction, making it the **least likely factor to inhibit** this process. - In wound healing, TGF-β is essential for the contraction phase and tissue remodeling. *Radiation* - **Ionizing radiation** can damage cells, including **fibroblasts** and **myofibroblasts**, which are essential for wound contraction. - This cellular damage and reduction in viable cells can significantly **impair** the contractile forces within the wound. - Radiation therapy is a known factor that inhibits wound healing and contraction. *Full-thickness skin graft* - A **full-thickness skin graft** introduces a complete layer of skin, including the dermis, into the wound. - The presence of the **dermis** within the graft provides a structural barrier and helps to **anchor the wound edges**, thereby reducing the tendency for contraction. - In contrast, **split-thickness grafts** allow more wound contraction due to less dermal tissue. *Cytolytic drug* - **Cytolytic drugs** are designed to kill cells, and if applied to a wound, they would destroy **fibroblasts** and **myofibroblasts**. - The destruction of these critical cells would directly **inhibit** the cellular machinery responsible for pulling the wound edges together, hence preventing contraction. - These drugs impair the proliferative phase of wound healing.
Question 3: Stem cells in skin involved in skin homeostasis are present in the following areas except ______
- A. Basal layer of interfollicular epidermis
- B. Base of apocrine glands (Correct Answer)
- C. Base of sebaceous glands
- D. Bulge of Hair follicle
Explanation: ***Base of apocrine glands*** - **Apocrine glands** do not typically house multipotent stem cells responsible for skin homeostasis and regeneration in the same manner as other skin adnexal structures [1] - These glands are primarily involved in secreting a specific type of sweat and have **limited regenerative capacity** from intrinsic stem cells compared to other areas - Unlike other skin appendages, apocrine glands lack the well-characterized stem cell niches that contribute to continuous skin renewal *Basal layer of interfollicular epidermis* - The basal layer contains **keratinocyte stem cells** that are crucial for continuous replenishment of epidermal layers [1] - These stem cells ensure constant turnover and repair of the skin's outermost protective barrier [1] - This is a major site of stem cells involved in skin homeostasis *Base of sebaceous glands* - Contains stem cell populations that contribute to regeneration of sebaceous glands and can differentiate to contribute to epidermal repair, especially after injury - These stem cells maintain the integrity and function of sebaceous glands, which produce sebum - Plays an active role in skin homeostasis and wound healing *Bulge of hair follicle* - The **bulge region** is a well-established niche for multipotent **hair follicle stem cells (HFSCs)** [1] - These HFSCs are responsible for cyclical regeneration of the hair follicle and can contribute to repair of the interfollicular epidermis and sebaceous glands after injury [1] - One of the most important stem cell reservoirs in the skin
Question 4: Healing of bone is affected by:
- A. Hypoxia
- B. Micromovement
- C. Muscle interposition
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Hypoxia**, **micromovement**, and **muscle interposition** are all factors known to impede or negatively affect the normal healing process of a bone fracture. - The successful healing of a bone fracture relies on a series of biological events that can be disrupted by these adverse conditions, leading to delayed union or non-union. *Hypoxia* - **Hypoxia**, or insufficient oxygen supply, impairs the metabolic activity of cells essential for bone healing, such as osteoblasts and chondrocytes. - It interferes with **angiogenesis**, the formation of new blood vessels, which is critical for delivering nutrients and oxygen to the healing bone. *Micromovement* - Excessive **micromovement** at the fracture site prevents the formation of a stable callus and can stimulate the development of fibrous tissue or cartilage instead of bone. - While some motion is beneficial, uncontrolled or excessive micromotion can lead to a **non-union** or pseudarthrosis, as it constantly disrupts the delicate tissue bridges attempting to form. *Muscle interposition* - **Muscle interposition** refers to muscle tissue becoming trapped between the bone fragments, physically separating them and preventing direct bone-to-bone contact. - This physical barrier inhibits the formation of the **fracture hematoma** and subsequent callus, thus mechanically hindering the healing process.
Question 5: Which of these is not a part of extracellular matrix:
- A. Collagen
- B. Laminin
- C. Fibronectin
- D. Integrins (Correct Answer)
Explanation: ***Integrins*** - Integrins are **transmembrane receptors** on the cell surface that facilitate cell-extracellular matrix (ECM) adhesion and cell-cell adhesion. - They are part of the cell membrane, **not** an extracellular component. *Laminin* - **Laminin** is a major protein component of the **basal lamina**, a specialized extracellular matrix that underlies epithelial cells. - It plays a crucial role in cell adhesion, differentiation, and migration within the ECM. *Fibronectin* - **Fibronectin** is a large glycoprotein present in the **extracellular matrix** and in soluble form in blood plasma. - It mediates cell adhesion to the ECM by binding to integrins and various ECM components like collagen and proteoglycans. *Collagen* - **Collagen** is the most abundant protein in the human body and a primary structural component of the **extracellular matrix**. - It provides tensile strength and structural integrity to tissues like skin, bone, tendons, and cartilage.
Question 6: What is the eponymous term for a full-thickness skin graft?
- A. Wolfe's graft (Correct Answer)
- B. Thiersch graft
- C. Fernandez graft
- D. Reverdin graft
Explanation: ***Wolfe's graft*** - A **Wolfe's graft** is the eponymous term for a **full-thickness skin graft**, which includes the epidermis and entire dermis. - This type of graft provides superior cosmetic results and contracts less than split-thickness grafts, making it ideal for facial reconstruction. *Thiersch graft* - A **Thiersch graft** refers to a **split-thickness skin graft**, which only includes the epidermis and a portion of the dermis. - These grafts are easier to harvest and take better in less vascularized beds but are prone to greater contraction and can have a less aesthetic outcome. *Fernandez graft* - **Fernandez graft** is not a recognized eponymous term for a type of skin graft in common medical literature. - This term does not correspond to a standard full-thickness or split-thickness skin grafting technique. *Reverdin graft* - A **Reverdin graft** refers to very small, partial-thickness pieces of skin, essentially tiny bits of epithelium transplanted to promote epithelialization. - This is a **split-thickness** technique, not a full-thickness graft, and is used primarily for small granulating wounds.
Question 7: Which of the following is derived from fibroblast cells?
- A. MMP2
- B. Collagen (Correct Answer)
- C. Angiopoietin
- D. TGF-β
Explanation: ***Collagen*** - Collagen is a structural protein that is predominantly produced by **fibroblast cells** in the extracellular matrix [1][2]. - It provides tensile strength and structural support to various tissues, playing a crucial role in wound healing and tissue repair [2]. *TGF-13* - Transforming Growth Factor-beta 1 (TGF-β1) is primarily produced by **immune cells** and is involved in cell growth and differentiation, not primarily by fibroblasts. - It plays a role in **fibrosis** and inflammation, but is not directly synthesized by fibroblast cells themselves. *MMP2* - Matrix Metalloproteinase-2 (MMP-2) is produced by various cell types, including **endothelial and epithelial cells**, but not predominantly by fibroblasts. - It is involved in the degradation of **extracellular matrix** components rather than being a product of fibroblast synthesis. *Angiopoietin* - Angiopoietin is primarily secreted by **endothelial cells** and plays a significant role in blood vessel formation and maturation. - It is not derived from fibroblast cells and is unrelated to their primary function of producing the extracellular matrix. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 31-32. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 34-35.
Question 8: Regeneration is characterized by:
- A. Granulation tissue
- B. Repairing by different type of tissue
- C. Cellular proliferation is largely regulated by biochemical factors
- D. Repairing by same type of tissue (Correct Answer)
Explanation: ***Repairing by same type of tissue*** - **Regeneration** involves the replacement of damaged cells and tissues with cells of the **same type**, leading to a complete restoration of normal structure and function [1]. - This process is seen in tissues with high proliferative capacity, like the **epidermis** or the **liver**, following injury [2]. *Granulation tissue* - **Granulation tissue** is characteristic of **repair by fibrosis** (scar formation), not regeneration [1]. - It consists of proliferating fibroblasts, new blood vessels (angiogenesis), and inflammatory cells, which eventually mature into a fibrous scar. *Repairing by different type of tissue* - The replacement of damaged tissue with a **different type of tissue** (typically fibrous connective tissue) is known as **repair by fibrosis** or **scar formation** [1]. - This occurs when the tissue's regenerative capacity is limited or when the injury is severe, resulting in the loss of normal tissue architecture and function [3]. *Cellular proliferation is largely regulated by biochemical factors* - While **cellular proliferation** is indeed regulated by **biochemical factors** (growth factors, cytokines) in both regeneration and repair, this statement describes a mechanism common to cellular growth and healing in general, not a defining characteristic unique to regeneration [1]. - This regulation guides both the replacement with original tissue (regeneration) and scar formation, so it's not specific enough to define regeneration alone. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 113-115. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 112-113. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 113.
Question 9: Which of the following type of collagen is present in healing and granulation tissue?
- A. Type II
- B. Type I
- C. Type III (Correct Answer)
- D. Type IV
Explanation: ***Type III*** - **Type III collagen** is prominently found in **granulation tissue** during the early stages of wound healing [1]. - It provides a **scaffold** for cellular migration and proliferation [2], contributing to the initial strength of the healing tissue. *Type II* - **Type II collagen** is the primary collagen type found in **cartilage**, particularly **hyaline cartilage**. - It is crucial for the **structural integrity** and resilience of articular surfaces, not typically in granulation tissue. *Type I* - **Type I collagen** is the most abundant collagen in the body, providing **tensile strength** to tissues like bone, skin, tendons, and ligaments. - While ultimately replacing type III collagen in mature scar tissue, it is **less prevalent in initial granulation tissue** compared to type III [1]. *Type IV* - **Type IV collagen** is a major component of **basement membranes**, forming a mesh-like network [3]. - It provides **structural support** and acts as a selective filter in tissues such as the kidneys and lungs, but not in healing granulation tissue. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 105-106. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 117-119. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 32-34.
Question 10: Granulation tissue is replaced by connective tissue in what stage of wound healing?
- A. 7 days (Correct Answer)
- B. 14 days
- C. 21 days
- D. 1 month
Explanation: ***21 days*** - Granulation tissue formation is prominent until about **21 days**, after which it starts to reorganize into fibrous connective tissue [1][2]. - In this stage, collagen deposition increases, contributing to **wound strength** and integrity [2]. *1 month* - By this time, connective tissue maturation continues but the primary transition from granulation tissue typically completes by **21 days** [2]. - It may lead to overestimation of healing progression as remodeling may still be ongoing. *14 days* - At **14 days**, granulation tissue is still present and not yet fully replaced by connective tissue [1]. - This stage primarily involves **vascularization** and **inflammatory responses**, not complete fibrous change [1]. *7 days* - This early phase is characterized by **hemostasis** and **inflammation**, with granulation tissue just beginning to form [1]. - Significant connective tissue replacement has not yet occurred, as the wound healing process is still at the initial stages. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 117-119. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 119-121.
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