Structure and Function of Skin — MCQs

10 questions

A 45-year-old man presents with the following skin changes (as shown in the image). What relevant history should be taken to diagnose this condition?

The main type of collagen in anchoring fibrils (component of dermoepidermal junction) is:

At what age does a child typically know their full name?

In human beings, the least useful physiological response to low environmental temperature is:

Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.

Langerhans cells in skin are :

Rhinophyma is associated with-

Which of the following is the location beyond which fungus does not penetrate in tinea capitis ?

Wound contraction can be most effectively minimized by:

Q10

Which protein is primarily affected by mutations in Marfan's syndrome?

Structure and Function of Skin Indian Medical PG Practice Questions and MCQs

Question 1: A 45-year-old man presents with the following skin changes (as shown in the image). What relevant history should be taken to diagnose this condition?

A. Dementia
B. History of dietary pattern, dementia, and diarrhea (Correct Answer)
C. Dietary history
D. Depression

Explanation: ***History of dietary pattern, dementia, and diarrhea*** - The image displays skin changes consistent with a "Casal's necklace" pattern, characteristic of **pellagra**, a disease caused by **niacin (Vitamin B3) deficiency**. - Pellagra is classically associated with the "3 Ds": **dermatitis** (the observed skin changes), **diarrhea**, and **dementia**. A comprehensive history should therefore include questions about dietary patterns (especially corn-based diets lacking tryptophan and niacin), gastrointestinal symptoms like diarrhea, and neurological/psychiatric symptoms indicative of dementia. *Dementia* - While **dementia** is one of the classic "3 Ds" of pellagra (niacin deficiency), it is only one component of the presentation and insufficient on its own to guide a complete diagnostic history for this condition. - Focusing solely on dementia would miss crucial aspects like dietary intake and gastrointestinal symptoms that are integral to diagnosing pellagra. *Dietary history* - A **dietary history** is indeed very relevant for diagnosing pellagra, as it helps identify potential niacin deficiency, commonly associated with diets heavily reliant on corn without proper preparation. - However, pellagra is not only characterized by dermatological signs and dietary insufficiency but also by gastrointestinal and neurological symptoms. Limiting the history to diet alone would therefore be incomplete. *Depression* - **Depression** can be a symptom of various nutritional deficiencies and other medical conditions, but it is not one of the classic "3 Ds" of pellagra, which are dermatitis, diarrhea, and dementia. - While mood changes might be present in some patients with niacin deficiency, focusing solely on depression would not encompass the full clinical picture of pellagra and could lead to misdiagnosis.

Question 2: The main type of collagen in anchoring fibrils (component of dermoepidermal junction) is:

A. Type II
B. Type IV
C. Type VII (Correct Answer)
D. Type III

Explanation: ***Type VII*** - **Type VII collagen** is the primary component of **anchoring fibrils**, which are essential structures that firmly attach the **dermal epidermal junction** to the underlying dermis. [1] - Mutations in the gene encoding **Type VII collagen** can lead to **dystrophic epidermolysis bullosa**, a condition characterized by fragile skin and blister formation due to poor dermal-epidermal adhesion. *Type II* - **Type II collagen** is predominantly found in **hyaline cartilage** and **elastic cartilage**, providing tensile strength and resilience within these tissues. - It is crucial for maintaining the structural integrity of **joints** and the respiratory tract, rather than dermal-epidermal adhesion. *Type IV* - **Type IV collagen** is a major component of **basement membranes**, forming a mesh-like network that provides structural support and filtration properties. - Although present at the **dermal epidermal junction** as part of the **basement membrane**, it does not primarily form the anchoring fibrils themselves. *Type III* - **Type III collagen** is widely distributed in **reticular fibers** in various tissues, including skin, blood vessels, and internal organs. - It provides elasticity and support to tissues, often co-localizing with **Type I collagen**, but does not form anchoring fibrils at the dermal-epidermal junction.

Question 3: At what age does a child typically know their full name?

A. 15 months
B. 24 months
C. 36 months (Correct Answer)
D. 48 months

Explanation: ***36 months*** - By **36 months old** (3 years), most children can clearly state their **full name** (first and last name) when asked. - This milestone indicates developing **self-awareness** and **language skills**. - This is a standard developmental milestone tested in CDC and AAP guidelines. *15 months* - At **15 months**, children typically know their **first name** and respond to it, but cannot state their full name. - Their language at this age often includes only a few single words with primarily receptive understanding. *24 months* - By **24 months** (2 years), children often use two-to-four-word sentences and can identify familiar objects and people. - While they know their first name and may start recognizing it, they usually cannot articulate their full name yet. *48 months* - At **48 months** (4 years), a child's language skills are much more advanced, and they can typically tell stories and engage in complex conversations. - Knowing their full name is an expected milestone that should have been achieved earlier, typically by 36 months.

Question 4: In human beings, the least useful physiological response to low environmental temperature is:

A. Shivering
B. Vasoconstriction
C. Release of thyroxine
D. Piloerection (Correct Answer)

Explanation: ***Piloerection*** - **Piloerection**, or 'goosebumps,' is a vestigial reflex in humans, meaning it has lost most of its original function. - While it causes hair to stand on end, which would trap an insulating layer of air in furry animals, humans lack sufficient body hair for this to be an **effective heat retention mechanism**. *Shivering* - **Shivering** involves involuntary muscle contractions that generate heat through increased metabolic activity. - This is a highly effective and significant physiological response for **acute heat production** in response to cold. *Vasoconstriction* - **Vasoconstriction** of peripheral blood vessels reduces blood flow to the skin, thereby decreasing heat loss to the environment through conduction, convection, and radiation. - This is a crucial mechanism for **conserving core body heat** in cold conditions. *Release of thyroxine* - The **release of thyroxine** (thyroid hormone) increases the body's basal metabolic rate over a longer term, leading to increased heat production. - This is an important **adaptive response to prolonged cold exposure**, rather than an immediate one.

Question 5: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.

A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
C. Statements 1 and 2 are incorrect
D. Statement 1 is incorrect

Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1*** **Analysis of Statement 1:** - A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris** - The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid - The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic - **Statement 1 is CORRECT** ✓ **Analysis of Statement 2:** - The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris - This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis - The intact basal cells standing upright resemble a row of tombstones - **Statement 2 is CORRECT** ✓ **Does Statement 2 explain Statement 1?** - Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split - However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split - The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis** - Therefore, **Statement 2 does NOT explain Statement 1** ✗ *Incorrect: Statement 2 is the correct explanation for Statement 1* - While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism *Incorrect: Statements 1 and 2 are incorrect* - Both statements are medically accurate descriptions of Pemphigus vulgaris features *Incorrect: Statement 1 is incorrect* - Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris

Question 6: Langerhans cells in skin are :

A. Antigen presenting cells (Correct Answer)
B. Sensory neurons
C. Pigment producing cells
D. Keratin synthesizing cells

Explanation: ***Antigen presenting cells*** - Langerhans cells are specialized **dendritic cells** found in the epidermis, functioning as crucial **antigen-presenting cells (APCs)** [1], [2]. - They **phagocytose antigens** in the skin, process them, and then migrate to lymph nodes to present the antigens to **T lymphocytes**, initiating an immune response [1]. *Keratin synthesizing cells* - **Keratinocytes** are the primary cells responsible for synthesizing **keratin** and forming the protective barrier of the epidermis [2]. - Langerhans cells originate from the bone marrow and are not involved in structural protein synthesis. *Sensory neurons* - **Merkel cells** and **free nerve endings** are the primary sensory structures found in the skin, responsible for touch, pressure, temperature, and pain sensation [2]. - Langerhans cells are immune cells, not nerve cells. *Pigment producing cells* - **Melanocytes** are the cells responsible for producing **melanin**, the pigment that provides skin color and protects against UV radiation [2]. - Langerhans cells do not produce melanin. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 200. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1144.

Question 7: Rhinophyma is associated with-

A. Epithelial cell hyperplasia
B. Endothelial cell hyperplasia
C. Sweat gland hypertrophy
D. Sebaceous gland hypertrophy (Correct Answer)

Explanation: ***Sebaceous gland hypertrophy*** - **Rhinophyma** is a severe form of rosacea characterized by marked thickening and enlargement of the nose, [1] primarily due to **hypertrophy of the sebaceous glands**. - This glandular overgrowth leads to a bulbous, erythematous, and often disfigured appearance of the nose [1]. *Epithelial cell hyperplasia* - While there may be some secondary **epidermal hyperplasia** in rhinophyma, it is not the primary defining feature of the condition. - The dominant histological change is related to the **sebaceous glands** and connective tissue, not mainly the surface epithelium. *Endothelial cell hyperplasia* - **Vascular changes** and **telangiectasias** are common in rosacea, including rhinophyma, indicating some proliferation of endothelial cells [1]. - However, the most prominent and characteristic pathological feature of rhinophyma is the enlargement of the **sebaceous glands**, not the endothelial cells. *Sweat gland hypertrophy* - **Sweat glands** (eccrine or apocrine) are generally not primarily affected or undergo hypertrophy in rhinophyma. - The pathology is specifically centered on the sebaceous glands, which are distinct from sweat glands. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1176.

Question 8: Which of the following is the location beyond which fungus does not penetrate in tinea capitis ?

A. Isthmus
B. Infundibulum
C. Adamson's fringe (Correct Answer)
D. Stem

Explanation: ***Adamson's fringe*** - Adamson's fringe is the **critical anatomical boundary** located at the opening of the sebaceous gland duct into the hair follicle. - It represents the zone where **hair keratinization is complete** and marks the transition between the keratinized (dead) upper portion and the living, pre-keratinized hair matrix below. - In tinea capitis, dermatophyte fungi **cannot penetrate beyond Adamson's fringe** because they are keratinophilic organisms that can only invade fully keratinized tissue [1]—they cannot survive in the living hair bulb below this level. - This is the **deepest point of fungal penetration** in the hair follicle. *Isthmus* - The isthmus is the mid-portion of the hair follicle located **between the insertion of the arrector pili muscle and the opening of the sebaceous gland**. - It is **above/superficial to Adamson's fringe**, meaning fungi can and do penetrate through this region as they invade downward toward Adamson's fringe. - Therefore, the isthmus is **not the limiting boundary** of fungal penetration. *Infundibulum* - The infundibulum is the **uppermost segment** of the hair follicle, extending from the skin surface down to the sebaceous gland opening. - This is the **most superficial region** where fungal infection typically begins in tinea capitis. - Fungi are readily present in the infundibulum but penetrate **deeper than this level**, making it not the limiting boundary. *Stem* - "Stem" refers to the **hair shaft itself** (the visible, keratinized hair fiber) rather than a specific anatomical boundary within the follicle. - While fungi do invade the hair stem/shaft, this term does not define the **anatomical limit of penetration within the follicle architecture**—that limit is specifically Adamson's fringe. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 638-639.

Question 9: Wound contraction can be most effectively minimized by:

A. Allowing secondary granulation
B. Full thickness grafting (Correct Answer)
C. Split skin graft
D. Dressing with placenta

Explanation: ***Full thickness grafting*** - **Full-thickness skin grafts** include the epidermis and full dermis, which contains **fewer myofibroblasts** than split-thickness grafts, thus minimizing contraction. - The greater amount of dermal tissue acts as a **mechanical barrier** to prevent excessive wound contraction, providing a more stable and aesthetically pleasing result. *Allowing secondary granulation* - Healing by **secondary intention** involves substantial granulation tissue formation, which is rich in **myofibroblasts** and leads to significant wound contraction. - This method of healing is often used for infected or contaminated wounds but results in the **most contraction**. *Split skin graft* - **Split-thickness skin grafts** contain only a portion of the dermis, making them prone to **moderate to significant wound contraction**. - While better than secondary intention, the thin dermal layer provides less resistance to the contractile forces of the **myofibroblasts**. *Dressing with placenta* - **Placental tissue dressings** can promote wound healing by providing growth factors and a scaffold for regeneration. - However, they do not inherently prevent or minimize **wound contraction** in the same way that a full-thickness graft mechanically does, as they do not replace the entire dermal layer.

Question 10: Which protein is primarily affected by mutations in Marfan's syndrome?

A. Collagen I
B. Collagen IV
C. Fibrillin I (Correct Answer)
D. Fibrillin II

Explanation: ***Fibrillin I*** - Marfan's syndrome is caused by a mutation in the **FBN1 gene**, which encodes the protein **fibrillin I**, crucial for connective tissue integrity [1]. - Clinical manifestations include **skeletal abnormalities**, **cardiovascular issues**, and **ocular problems**, linking the mutation to its phenotypic features [1]. *Collagen I* - While collagen is important for connective tissue, **collagen I** mutations are associated with disorders like **osteogenesis imperfecta**, not Marfan's syndrome. - This oes not account for the significant **fibrillin deficiency** noted in Marfan's patients. *Fibrillin II* - **Fibrillin II** does exist but is not the causative factor in Marfan's syndrome; mutations in this protein relate to different syndromes like **Congenital Contractural Arachnodactyly**. - The primary influence in Marfan's is due to the defect in **fibrillin I**, not fibrillin II. *Collagen IV* - Mutations in **collagen IV** are linked to diseases such as **Alport syndrome**, primarily affecting renal function and hearing, rather than the hallmark features of Marfan's. - This type of collagen is more critical for **basement membranes**, differentiating it from the connective tissue role of fibrillin I in Marfan's. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 35-36.

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