Microscopic Anatomy of Respiratory System — MCQs
In a preterm baby with respiratory distress syndrome, which of the following lipids would be deficient?
The activation of muscarinic receptors in bronchiolar smooth muscle is associated with:
All of the following are features of Lymph node histology except:
Bifurcation of the trachea is at which level?
Which of the following is a stain for heart failure cells?
Investigation of choice for Posterior urethral valves?
Granuloma is a pathological feature of all, except which of the following?
Which of the following diseases is NOT associated with Anti-Neutrophil Cytoplasmic Antibodies (ANCA)?
The nasopharynx is primarily lined by which type of epithelium?
All cartilage is covered by perichondrium, except
Microscopic Anatomy of Respiratory System Indian Medical PG Practice Questions and MCQs
Question 1: In a preterm baby with respiratory distress syndrome, which of the following lipids would be deficient?
- A. Cardiolipin
- B. Sphingomyelin
- C. Phosphatidylinositol
- D. Lecithin (Correct Answer)
Explanation: ***Lecithin*** - **Lecithin** (also known as **phosphatidylcholine**) is the primary component of **surfactant** in the lungs, which reduces surface tension and prevents alveolar collapse. - In **preterm babies**, insufficient production of lecithin due to immature lung development leads to **respiratory distress syndrome (RDS)**. *Cardiolipin* - **Cardiolipin** is a major phospholipid found in the **inner mitochondrial membrane**, crucial for oxidative phosphorylation. - Deficiency is associated with mitochondrial disorders like **Barth syndrome**, not primary respiratory distress. *Sphingomyelin* - **Sphingomyelin** is a significant component of **cell membranes** and **myelin sheaths**, important for nerve insulation. - While present in the lungs, its primary role is not in surface tension reduction, and its deficiency is not directly linked to RDS. *Phosphatidylinositol* - **Phosphatidylinositol** is a precursor for various **signaling molecules** and plays a role in cell membrane structure. - While involved in cellular processes, it is not the critical surfactant component whose deficiency causes RDS.
Question 2: The activation of muscarinic receptors in bronchiolar smooth muscle is associated with:
- A. Increase in IP3 and DAG (Correct Answer)
- B. Inhibition of protein kinase C
- C. Activation of adenylyl cyclase
- D. Opening of Na+/K+ cation channels
Explanation: ***Increase in IP3 and DAG*** - **Muscarinic receptors** on bronchial smooth muscle (M3 receptors) are **Gq protein-coupled receptors** [1]. - Activation of **Gq proteins** leads to the activation of **phospholipase C**, which hydrolyzes **PIP2** into **IP3** and **DAG** [1, 3]. *Inhibition of protein kinase C* - **DAG** (diacylglycerol), produced from the breakdown of PIP2, **activates protein kinase C (PKC)**, rather than inhibiting it [2]. - This activation of PKC contributes to downstream cellular responses, including smooth muscle contraction [1]. *Activation of adenylyl cyclase* - **Adenylyl cyclase** is typically activated by **Gs protein-coupled receptors**, leading to an increase in **cAMP**. - **Muscarinic (M3) receptors** are **Gq-coupled**, so they do not activate adenylyl cyclase; instead, they operate through the phospholipase C pathway [1, 3]. *Opening of Na+/K+ cation channels* - While some neurotransmitter receptors are **ligand-gated ion channels** (e.g., nicotinic receptors), muscarinic receptors are **G protein-coupled receptors** [1]. - Their activation does not directly lead to the opening of **Na+/K+ cation channels**; rather, they initiate intracellular signaling cascades.
Question 3: All of the following are features of Lymph node histology except:
- A. Both Efferent and Afferent are present
- B. Subcapsular sinus present
- C. Cortex and Medulla are present
- D. Red pulp and White pulp are present (Correct Answer)
Explanation: ***Red pulp and White pulp are present*** - **Red pulp** and **white pulp** are characteristic histological features of the **spleen**, not lymph nodes [1]. - The white pulp contains lymphoid follicles (PALS - periarteriolar lymphoid sheaths), while the red pulp is involved in filtering blood and destroying old red blood cells [1]. - This is the feature that does NOT belong to lymph node histology. *Both Efferent and Afferent are present* - Lymph nodes have multiple **afferent lymphatic vessels** that bring lymph into the node and usually one or two **efferent lymphatic vessels** that carry lymph away [2]. - This arrangement allows for efficient filtering of lymph and immune surveillance [2]. - This IS a feature of lymph nodes. *Subcapsular sinus present* - The **subcapsular sinus** is a space located directly beneath the capsule of the lymph node, which receives lymph from the afferent lymphatic vessels. - It contains a network of reticular fibers and macrophages, acting as the initial filtering area. - This IS a feature of lymph nodes. *Cortex and Medulla are present* - Lymph nodes are histologically divided into an outer **cortex** and an inner **medulla**. - The cortex contains lymphoid follicles (B-cell areas) and paracortical areas (T-cell areas), while the medulla consists of medullary cords and sinuses. - This IS a feature of lymph nodes.
Question 4: Bifurcation of the trachea is at which level?
- A. Opposite the disc between the T3-T4 vertebrae
- B. Opposite the disc between the T5-T6 vertebrae
- C. Opposite the disc between the T4-T5 vertebrae (Correct Answer)
- D. Opposite the disc between the T7-T8 vertebrae
Explanation: ***Opposite the disc between the T4-T5 vertebrae*** - The **trachea** bifurcates into the right and left main bronchi at the level of the **carina**. - In adults, this anatomical landmark consistently corresponds to the intervertebral disc between the **fourth and fifth thoracic vertebrae (T4-T5)**. *Opposite the disc between the T3-T4 vertebrae* - This level is generally **above the tracheal bifurcation** in most individuals. - The superior margin of the **manubrium sterni** is typically at the level of the T3 vertebral body, which is too high for the tracheal carina. *Opposite the disc between the T5-T6 vertebrae* - This level is generally **below the tracheal bifurcation**. - The **inferior mediastinum** begins roughly at the T5 level, which is after the carina. *Opposite the disc between the T7-T8 vertebrae* - This level is significantly **below the carina** and corresponds to the approximate level of the inferior aspect of the **heart** or the **diaphragmatic domes**. - No major tracheal branching occurs at this lower thoracic vertebral level.
Question 5: Which of the following is a stain for heart failure cells?
- A. PAS
- B. Prussian blue (Correct Answer)
- C. Sudan black
- D. Oil red O
Explanation: ***Prussian blue*** - Heart failure cells are **alveolar macrophages** that have phagocytosed **hemosiderin** (iron-laden pigment) from extravasated red blood cells due to **pulmonary congestion** in heart failure. - The **Prussian blue stain** specifically detects the ferric iron (Fe3+) within hemosiderin, making it the appropriate stain for identifying heart failure cells. *PAS* - **Periodic Acid-Schiff (PAS)** stain detects **carbohydrates** such as glycogen, mucins, and glycoproteins, and is used for conditions like **glycogen storage diseases** or certain fungal infections. - It does not specifically identify iron or hemosiderin, hence it is not used for heart failure cells. *Sudan black* - **Sudan black** is a **lipid stain** used to identify intracellular **lipids** and distinguish between different types of leukemia based on the presence of myeloperoxidase. - It is not designed to detect iron or hemosiderin and thus is not used for heart failure cells. *Oil red O* - **Oil Red O** is another common stain for demonstrating neutral **lipids** and triglycerides in frozen tissue sections. - Like Sudan black, it is a lipid stain and therefore would not be helpful in identifying the iron-laden hemosiderin characteristic of heart failure cells.
Question 6: Investigation of choice for Posterior urethral valves?
- A. Ultrasound
- B. Retrograde urethrography
- C. Micturating Cystourethrography (MCU) (Correct Answer)
- D. Intravenous Pyelography
Explanation: ***Micturating Cystourethrography (MCU)*** - The **Micturating Cystourethrography (MCU)** is the gold standard for diagnosing posterior urethral valves (PUV) as it directly visualizes the posterior urethra during voiding. - It classically shows a **dilated posterior urethra** with a narrow opening at the level of the valves, often accompanied by **vesicoureteral reflux** and bladder wall abnormalities. *Ultrasound* - **Antenatal ultrasound** can suggest PUV by showing bilateral **hydronephrosis**, a dilated bladder, and thick-walled bladder with a "keyhole sign" (dilated posterior urethra). - However, ultrasound alone **cannot definitively diagnose** the valves or rule out other causes of obstruction. *Retrograde urethrography* - **Retrograde urethrography (RGU)** involves injecting contrast against the flow of urine, which can mask the presence of posterior urethral valves, as they are typically obstructive to antegrade flow. - While RGU can highlight urethral strictures and other anterior urethral pathologies, it is **not ideal** for visualizing posterior urethral valves. *Intravenous Pyelography* - **Intravenous Pyelography (IVP)** assesses kidney function and the collecting system, but it provides **limited detailed visualization** of the urethra itself. - While it might show features of obstructive uropathy like **hydronephrosis** or delayed excretion, it cannot directly confirm the presence or location of posterior urethral valves.
Question 7: Granuloma is a pathological feature of all, except which of the following?
- A. Giant cell arteritis
- B. Granulomatosis with polyangiitis
- C. Eosinophilic granulomatosis with polyangiitis
- D. Microscopic polyangiitis (Correct Answer)
Explanation: ***Microscopic polyangitis*** - This condition is associated with **necrotizing vasculitis** without significant **granulomatous inflammation** [1]. - Primarily affects small vessels and typically features **pauci-immune** glomerulonephritis [1]. *Giant cell arteritis* - Characterized by **granulomatous inflammation** in the temporal arteries, leading to headaches and vision loss [2]. - It often shows **multinucleated giant cells** in biopsy specimens, confirming the diagnosis [2]. *Churg strauss disease* - Also known as **Eosinophilic Granulomatosis with Polyangiitis**, it features **granulomas** and affects small to medium vessels. - Typically presents with asthma, nasal polyps, and significant **eosinophilia**. *Wegner's granulomatosis* - Now referred to as **Granulomatosis with Polyangiitis**, it prominently features **necrotizing granulomas** in the respiratory tract and kidneys [3]. - Associated with **c-ANCA** (anti-neutrophil cytoplasmic antibodies), confirming its granulomatous nature [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 518-519. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 516-517. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 519-520.
Question 8: Which of the following diseases is NOT associated with Anti-Neutrophil Cytoplasmic Antibodies (ANCA)?
- A. Wegener's granulomatosis
- B. Henoch schonlein purpura (Correct Answer)
- C. Microscopic PAN
- D. Churg Strauss syndrome
Explanation: ***Henoch schonlein purpura*** - **Henoch-Schönlein purpura (HSP)** is not associated with **ANCA**; it primarily involves IgA deposition [1]. - Commonly presents with **purpura**, **abdominal pain**, and **glomerulonephritis**, differentiating it from ANCA-associated vasculitides [1]. *Wegener's granulomatosis* - **Wegener's granulomatosis**, now known as **Granulomatosis with polyangiitis**, is strongly associated with **c-ANCA** and anti-PR3 antibodies. - It typically presents with **respiratory** and **renal symptoms** due to vasculitis [2]. *Microscopic PAN* - **Microscopic polyangiitis (PAN)** is associated with **p-ANCA** and myeloperoxidase (MPO) antibodies. - It leads to **glomerulonephritis** and **pulmonary hemorrhage**, indicating its vasculitic nature. *Churg Strauss syndrome* - **Churg-Strauss syndrome**, or **Eosinophilic Granulomatosis with Polyangiitis**, is associated with **p-ANCA** and perinuclear staining [1]. - Often presents with **asthma**, **eosinophilia**, and systemic vasculitis affecting multiple organs [1].
Question 9: The nasopharynx is primarily lined by which type of epithelium?
- A. Stratified squamous keratinized
- B. Ciliated columnar (Correct Answer)
- C. Cuboidal
- D. Stratified squamous nonkeratinized
Explanation: ***Ciliated columnar*** - The **nasopharynx** is lined by **pseudostratified ciliated columnar epithelium** with goblet cells, also known as respiratory epithelium [2]. - This specialized epithelium is crucial for **warming**, **humidifying**, and **filtering** inhaled air before it reaches the lungs [1]. *Stratified squamous nonkeratinized* - This type of epithelium is found in areas subject to **abrasion** and needing protection, such as the **oral cavity**, pharynx (oropharynx and laryngopharynx), and esophagus. - It is not primary in the nasopharynx, which requires ciliary action for particle removal. *Stratified squamous keratinized* - This robust epithelium is characteristic of areas that require significant **protection against friction** and **drying**, such as the **epidermis of the skin**. - It is not found in the nasopharynx due to its lack of flexibility and ciliary function. *Cuboidal* - **Cuboidal epithelium** is typically found in glands and kidney tubules, where its function includes **secretion** and **absorption**. - It lacks the specialized cilia and goblet cells necessary for the respiratory function of the nasopharynx [2].
Question 10: All cartilage is covered by perichondrium, except
- A. Hyaline
- B. Elastic
- C. Fibrocartilage (Correct Answer)
- D. All types of cartilage are covered by perichondrium.
Explanation: ***Fibrocartilage*** - **Fibrocartilage** completely lacks a perichondrium as a defining characteristic of this cartilage type. - This type of cartilage is found in structures like **intervertebral discs**, **pubic symphysis**, and **menisci**, where it provides strong support and shock absorption. - It merges imperceptibly with surrounding dense connective tissue without a distinct perichondrial covering. - Among all cartilage types, **fibrocartilage is the only type that NEVER has perichondrium**. *Hyaline* - Most **hyaline cartilage** (such as in the **trachea, bronchi, nose, larynx, and ribs**) is covered by a **perichondrium** that provides growth and nutrition. - **Important exception:** **Articular cartilage** (covering joint surfaces) lacks perichondrium because it receives nutrition from synovial fluid, but this is a specific exception within the hyaline category [1]. - Since hyaline cartilage CAN have perichondrium in most locations, it is not the best answer to this "except" question. *Elastic* - **Elastic cartilage**, found in structures such as the **external ear (auricle)** and **epiglottis**, is always surrounded by a **perichondrium**. - The perichondrium supports growth, provides nutrition, and aids in repair after injury. *All types of cartilage are covered by perichondrium* - This statement is **incorrect** because fibrocartilage never has a perichondrium. - Additionally, articular hyaline cartilage also lacks perichondrium, making this statement doubly false [1].
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