Histology — MCQs

Histology Indian Medical PG Practice Questions and MCQs

Question 371: Which of the following images displays the characteristic histology of the Thymus?

A. Image of Spleen
B. Image of Thymus (Correct Answer)
C. Image of Lymph node
D. Image of Tonsil

Explanation: ***Image of Thymus*** - The image correctly illustrates the key histological features of the thymus, including the division of thymic lobules into a dark outer **cortex** and a lighter inner **medulla**. - A pathognomonic feature shown is the presence of **Hassall's (thymic) corpuscles**, which are whorls of epithelial reticular cells found exclusively in the thymic medulla. *Image of Tonsil* - Tonsillar histology is characterized by deep invaginations called **tonsillar crypts** and numerous **lymphoid follicles** with prominent germinal centers, neither of which are depicted in the image. - Tonsils are covered by **stratified squamous epithelium** (in palatine and lingual tonsils) or pseudostratified columnar epithelium (in pharyngeal tonsils), a feature not seen in the thymus. *Image of Lymph node* - A lymph node has a distinct architecture with a **cortex** containing **lymphoid follicles**, a **paracortex**, and a **medulla** with medullary cords and sinuses, which is structurally different from the image provided. - Lymph nodes are surrounded by a capsule with afferent lymphatic vessels and a **subcapsular sinus**, features that are absent in the thymus. *Image of Spleen* - Splenic histology is organized into **red pulp** and **white pulp**. The white pulp consists of **lymphoid follicles** and **periarteriolar lymphoid sheaths (PALS)** surrounding a central arteriole, which is not shown. - The red pulp, which makes up the majority of the spleen, contains **splenic sinusoids** and the **cords of Billroth**, structures for filtering blood that are absent in the thymus.

Question 372: Identify the lymphatic structure from the histology section given below?

A. Spleen
B. Lymph node
C. Tonsil
D. Thymus (Correct Answer)

Explanation: ***Thymus*** - The histology shows lymphoid tissue organized into **lobules** separated by connective tissue septa, with each lobule having a darkly stained outer **cortex** and a paler inner **medulla**. - The medulla contains **Hassall's corpuscles**, which are pathognomonic for the thymus, and the cortex lacks the germinal centers found in other lymphoid organs. *Tonsil* - Tonsils are characterized by an overlying **stratified squamous epithelium** that invaginates to form deep **tonsillar crypts**, neither of which is present in this image. - They contain numerous lymphoid follicles with prominent germinal centers but lack the distinct lobulated cortico-medullary architecture of the thymus. *Lymph node* - A lymph node has a distinct architecture with a **subcapsular sinus**, a cortex with B-cell follicles, a paracortex, and a medulla with medullary cords and sinuses, which is structurally different from the image provided. - The lobulated pattern with clear cortico-medullary differentiation within each lobule is a key feature of the thymus, not a lymph node. *Spleen* - The spleen's parenchyma is divided into **red pulp** (containing sinusoids) and **white pulp** (lymphoid tissue), an organization not seen in this section. - Splenic white pulp is characterized by a **central arteriole** surrounded by a **periarteriolar lymphoid sheath (PALS)**, a feature absent in the image.

Question 373: A renal biopsy image is shown. Identify the cells marked in the histological section.

A. Podocytes
B. Lacis cells (Correct Answer)
C. Juxtaglomerular (JG) cells
D. Macula densa

Explanation: ***Lacis cells*** - The highlighted cells are **extraglomerular mesangial cells**, also known as Lacis cells, located in the triangular space between the afferent arteriole, efferent arteriole, and macula densa at the vascular pole of the glomerulus. - They are part of the **juxtaglomerular apparatus (JGA)** and are thought to play a role in transmitting signals from the macula densa to the juxtaglomerular cells, contributing to **tubuloglomerular feedback**. *Macula densa* - These are specialized, densely packed epithelial cells in the wall of the **distal convoluted tubule** where it contacts the glomerulus. The highlighted cells are situated outside of any tubule. - Macula densa cells function as **chemoreceptors** that monitor the **sodium chloride** concentration in the tubular fluid, regulating renin release and glomerular filtration rate. *Juxtaglomerular (JG) cells* - These are modified smooth muscle cells located primarily in the wall of the **afferent arteriole**. The cells in the image are not within an arteriolar wall. - JG cells synthesize, store, and secrete **renin**, and they function as **mechanoreceptors** by sensing changes in blood pressure within the afferent arteriole. *Podocytes* - These are specialized cells located **inside Bowman's capsule**, wrapping around the glomerular capillaries. The highlighted cells are distinctly **extraglomerular** (outside the glomerulus). - Podocytes form **filtration slits** with their interdigitating foot processes (**pedicels**), which are a critical component of the glomerular filtration barrier.

Question 374: What is the type of cartilage present in the histology section given below?

A. Articular cartilage
B. Hyaline cartilage (Correct Answer)
C. Fibrocartilage
D. Elastic cartilage

Explanation: ***Hyaline cartilage*** - The image displays a **homogenous, glassy matrix** with **chondrocytes** residing in spaces called **lacunae**. This appearance is due to the presence of fine **Type II collagen** fibrils that are not visible with a standard light microscope. - A **perichondrium**, the layer of dense connective tissue seen on the left, is typically present and provides nourishment. This type of cartilage is found in the **trachea**, **larynx**, and **articular surfaces of bones**. *Elastic cartilage* - This cartilage is characterized by a matrix containing abundant **elastic fibers**, which would appear as dark, branching lines, giving it a less homogenous look. These fibers are not visible in the provided slide. - It is found in structures that require flexibility and the ability to recoil, such as the **epiglottis** and the **external ear** (pinna). *Articular cartilage* - While histologically a type of hyaline cartilage, articular cartilage specifically covers the ends of bones in **synovial joints** and is distinguished by its **lack of a perichondrium**. - The image clearly shows a perichondrium on the left side, making it more likely to be hyaline cartilage from a location like the respiratory tract rather than a joint surface. *Fibrocartilage* - Fibrocartilage has a distinct, fibrous appearance due to thick, parallel bundles of **Type I collagen** within its matrix, which is absent in this image. - It is a transitional tissue between dense connective tissue and hyaline cartilage, found in areas requiring great tensile strength, like the **intervertebral discs** and **pubic symphysis**.

Question 375: Identify the given histology slide:

A. Pancreas (Correct Answer)
B. Lymph node
C. Spleen
D. Glomerulus

Explanation: ***Pancreas*** - The image displays a classic histological feature of the pancreas: a pale-staining cluster of endocrine cells, known as an **Islet of Langerhans**. - This islet is surrounded by more intensely stained, basophilic **acinar cells**, which constitute the exocrine component of the pancreas responsible for producing digestive enzymes. *Lymph node* - A lymph node has a distinct architecture with a **cortex** containing **lymphoid follicles** (often with germinal centers) and a **medulla**, which is not seen in this image. - The predominant cells would be lymphocytes, which appear as small, dark-staining cells, unlike the larger glandular cells shown here. *Glomerulus* - A glomerulus is a capillary tuft surrounded by **Bowman's capsule**, located within the renal cortex of the kidney. - The surrounding tissue would be composed of **renal tubules** (proximal and distal convoluted tubules), not the acinar cells seen in the slide. *Spleen* - The spleen is characterized by its division into **red pulp** (containing sinusoids and erythrocytes) and **white pulp** (lymphoid tissue surrounding a central artery). - The organized structure of islets and acini is distinct from the splenic architecture of lymphoid follicles and blood-filled sinuses.

Question 376: Identify the histological image below.

A. Pseudostratified columnar epithelium
B. Non-keratinized squamous epithelium
C. Stratified squamous epithelium
D. Transitional epithelium (Correct Answer)

Explanation: ***Transitional epithelium***- This is also known as **urothelium** and is specialized to line the urinary tract (ureters, bladder, proximal urethra) due to its unique structure.- It is characterized by large, bulbous surface cells called **dome cells** or **umbrella cells**, which protect subepithelial layers from urine. *Pseudostratified columnar epithelium*- This epithelium appears layered because the nuclei are at different levels, but all cells rest on the **basement membrane**.- It is commonly found lining the respiratory tract (**trachea** and bronchi) where it typically features **cilia** and goblet cells. *Non-keratinized squamous epithelium*- This tissue consists of multiple layers of cells (stratified) where the surface cells are flattened and **nucleated**.- Locations include the lining of the **vagina**, esophagus, and oral cavity, where protection from abrasion is needed. *Stratified squamous epithelium*- This general category includes both keratinized and non-keratinized types, but it lacks the characteristic **dome cells** of urothelium.- Its main function is providing robust protection from **mechanical stress**, and it does not exhibit the high degree of stretchability seen in the bladder lining.

Question 377: Identify the structure labeled in the histology image shown.

A. Alveolar duct
B. Respiratory bronchiole (Correct Answer)
C. Bronchus
D. Terminal bronchiole

Explanation: ***Respiratory bronchiole*** - The key identifying feature is the presence of **alveoli** opening directly from its lumen, which is characteristic of the respiratory zone where gas exchange begins. - It represents the transition from the conducting to the respiratory portion of the airway, lined by a simple **cuboidal epithelium** with scattered cilia and club cells. *Terminal bronchiole* - A terminal bronchiole is the most distal part of the **conducting zone** and has a continuous wall without any associated alveoli. - It is lined by simple cuboidal epithelium, which includes **club cells** (formerly Clara cells), but no gas exchange occurs here. *Alveolar duct* - An alveolar duct is a tube whose walls are almost entirely composed of the openings of alveoli and alveolar sacs. - It lacks the more continuous epithelial wall seen in a respiratory bronchiole and is primarily just a passageway lined by alveolar openings. *Bronchus* - A bronchus is a larger airway characterized by the presence of **cartilage plates** or rings and **submucosal glands** in its wall, both of which are absent in the image. - It is lined by **pseudostratified ciliated columnar epithelium** containing goblet cells, which is different from the simple epithelium seen here.

Question 378: Which of the following organs does this epithelium most likely belong to?

A. Trachea
B. Gallbladder
C. Intestine
D. Ureter (Correct Answer)

Explanation: ***Ureter*** - The image displays **transitional epithelium** (urothelium), which is characterized by multiple cell layers and large, dome-shaped (**umbrella**) cells on the apical surface. - This specialized stratified epithelium is highly stretchable and is exclusively found lining the urinary tract, including the renal pelvis, ureter, and bladder. *Gallbladder* - The gallbladder is lined by **simple columnar epithelium**, which is specialized for water reabsorption and concentration of bile, lacking the stratified layers seen here. - It has a single layer of cells with microvilli but does not possess the unique apical **umbrella cells** of the urothelium. *Trachea* - The trachea is lined by **pseudostratified ciliated columnar epithelium**, which includes numerous **goblet cells** and distinct cilia on the apical surface. - This tissue type appears stratified but all cells contact the basement membrane, unlike the true stratification seen in the image. *Intestine* - The small and large intestines are lined by **simple columnar epithelium** with prominent **microvilli** (forming a striated border) and numerous **goblet cells**. - This is a single-layered epithelium primarily designed for absorption and secretion, which is structurally distinct from the urinary epithelium shown.

Question 379: Out of the following, which statements are correct? 1. Epidermis can regenerate from hair bulbs and sebaceous glands 2. Stratum corneum is the outermost cellular layer 3. Epidermis originates from the ectoderm 4. Dermis and hypodermis originate from the endoderm

A. 3,4
B. 1,2
C. 2,3
D. 1,3 (Correct Answer)

Explanation: ***Correct Option: 1,3*** - **Statement 1 is correct:** Deep injuries or burns destroy the interfollicular epidermis, and regeneration must occur from stem cells found in the **adnexal structures**, primarily the **hair follicle bulge** [1] and sweat/sebaceous glands [2]. - **Statement 3 is correct:** The epidermis, being the outer epithelial layer, is derived embryologically from the **surface ectoderm**. *Incorrect Option: 1,2* - Statement 1 is correct. However, Statement 2 is incorrect because the **stratum corneum** is the outermost layer composed of **dead, anucleated keratinocytes** (corneocytes) [2], making it an acellular/non-cellular barrier, not the outermost cellular layer. - The outermost true cellular (viable) layer is the stratum granulosum. *Incorrect Option: 2,3* - Statement 2 is incorrect because the stratum corneum is composed of **dead cells** forming a protective layer; it is not considered a viable cellular layer [2]. - Statement 3 is correct, confirming the derivation of the epidermis from the **surface ectoderm**. *Incorrect Option: 3,4* - Statement 3 is correct. However, Statement 4 is incorrect because the connective tissue layers—the **dermis** and the **hypodermis**—are derived from the embryonic **mesoderm** (specifically the dermatome component of the somites), not the endoderm.

Question 380: Tight junctions are primarily located at which part of the cell?

A. Apical (Correct Answer)
B. Apicolateral
C. Basal
D. Basolateral

Explanation: ***Apical*** - **Tight junctions** (Zonula Occludens) are the most **apical** component of the junctional complex in many epithelial cells [1]. - Their primary function is to seal adjacent cells, preventing the passage of molecules between them (paracellular route), thus establishing **epithelial polarity** [1], [2]. *Apicolateral* - This term is less precise; the junctional complex includes the tight junction (**apical**), followed by the adherens junction, and then the desmosome (**lateral**). - The tight junction itself is specifically located at the very **apical** edge, not spanning the entire apicolateral domain [1]. *Basal* - The **basal** part of the cell is where the cell attaches to the **basement membrane** via structures like hemidesmosomes [1]. - Tight junctions are not found here, as they are essential for defining the **apical** vs. basolateral domains. *Basolateral* - The **basolateral** domain comprises the sides and base of the cell, where structures like **desmosomes** (lateral) and hemidesmosomes (basal) are found [1]. - This region is separated from the lumen by the function of the **tight junction** located upstream at the apical pole [2].

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Endocrine System Histology

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Respiratory System Histology

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Digestive System Histology

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Urinary and Reproductive System Histology

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Histology — MCQs

Histology — MCQs

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