Microscopic Anatomy — MCQs

Microscopic Anatomy Indian Medical PG Practice Questions and MCQs

Question 201: Schwalbe's ring corresponds to:

A. Corneal endothelium
B. Descemet's membrane (Correct Answer)
C. Schlemm's canal
D. Ciliary body

Explanation: ***Descemet's membrane*** - **Schwalbe's ring** represents the **peripheral termination of Descemet's membrane** at the limbus, forming a prominent ring-like thickening. - It is an important anatomical landmark located at the **anterior limit of the trabecular meshwork** in the iridocorneal angle, marking the transition from cornea to trabecular meshwork. - This structure is clinically significant for gonioscopy and assessment of the anterior chamber angle. *Corneal endothelium* - The **corneal endothelium** is a single layer of cells lining the posterior surface of the cornea that maintains corneal transparency through its pump-leak mechanism. - While it covers the posterior corneal surface and is continuous with Descemet's membrane, it is not the structure that forms Schwalbe's ring. *Schlemm's canal* - **Schlemm's canal** is a circular venous channel in the limbal region that collects aqueous humor from the trabecular meshwork. - Though located in the same general area, it is posterior to Schwalbe's ring and serves as the final drainage pathway for aqueous humor, making it anatomically and functionally distinct. *Ciliary body* - The **ciliary body** is part of the uveal tract, responsible for aqueous humor production and accommodation via the ciliary muscle. - It is located posterior to the iris and forms the posterior boundary of the anterior chamber, having no direct anatomical relationship with Schwalbe's ring.

Question 202: Hering's canals are present in ?

A. Spleen
B. Liver (Correct Answer)
C. Kidney
D. Lung

Explanation: ***Liver*** - **Hering's canals** are terminal ductules found in the liver that connect the **bile canaliculi** to the interlobular bile ducts [1]. - They play a crucial role in **bile flow** and are lined by both hepatocytes and cholangiocytes [1]. *Spleen* - The spleen is primarily involved in **filtering blood**, removing old red blood cells, and immune responses. - It does not contain Hering's canals; its functional units include **red pulp** and **white pulp**. *Kidney* - The kidney's main function is **filtering blood** to produce urine, involving structures like **nephrons** and **collecting ducts**. - It does not contain Hering's canals, which are specific to the biliary system of the liver [1]. *Lung* - The lungs are responsible for **gas exchange** (oxygen and carbon dioxide) through **alveoli** and bronchioles. - They do not possess Hering's canals; these structures are not part of the respiratory system.

Question 203: Respiratory bronchioles are formed from?

A. Principal bronchus
B. Terminal bronchioles (Correct Answer)
C. Tertiary Bronchus
D. Lobar bronchi

Explanation: ***Terminal bronchioles*** - **Terminal bronchioles** branch into several **respiratory bronchioles**, which are the smallest bronchioles involved in both conduction and gas exchange [1]. - They represent the transition zone where the respiratory portion of the lung begins, containing scattered **alveoli** buddings. *Principal bronchus* - The **principal (main) bronchi** are large airways that branch from the trachea and lead into the lungs; they are many generations removed from respiratory bronchioles [1]. - They are primarily involved in **air conduction** and contain cartilage, unlike the smaller, more distal airways. *Tertiary Bronchus* - **Tertiary (segmental) bronchi** branch from lobar bronchi and supply specific bronchopulmonary segments, still serving as **conducting airways**. - These bronchi are several branching generations proximal to the terminal and respiratory bronchioles. *Lobar bronchi* - **Lobar (secondary) bronchi** are formed from the principal bronchi and supply the lobes of the lungs; they are primarily involved in **conduction**. - They are much larger in diameter and structural complexity compared to the microscopic respiratory bronchioles.

Question 204: Which of the following is false about the liver?

A. It is covered by Glisson's capsule
B. Kupffer cells are the defense cells.
C. The lobules in the liver are pentagonal. (Correct Answer)
D. Stellate cells are present in the space of Disse

Explanation: The lobules in the liver are pentagonal. - This statement is false because the classical liver lobules are typically **hexagonal** [1], not pentagonal, in shape when viewed in cross-section. - The hexagonal arrangement is defined by the portal triads at the corners and a central vein in the middle [1]. *It is covered by Glisson's capsule* - The liver is indeed enveloped by **Glisson's capsule**, a thin but strong connective tissue layer. - This capsule provides structural integrity and protection to the liver parenchyma. *Kupffer cells are the defense cells.* - **Kupffer cells** are specialized macrophages located in the liver sinusoids, acting as the primary immune defense cells of the liver [1]. - They are responsible for phagocytosing pathogens, cellular debris, and old red blood cells. *Stellate cells are present in the space of Disse* - **Hepatic stellate cells** (also known as Ito cells) are found in the **space of Disse** [1], which is the perisinusoidal space between the hepatocytes and the sinusoidal endothelial cells [1]. - These cells are involved in vitamin A storage and, when activated, play a critical role in liver fibrosis.

Question 205: Which of the following layers is absent in the esophagus?

A. Muscularis propria
B. Mucosa
C. Adventitia
D. Serosa (Correct Answer)

Explanation: ***Serosa*** - The esophagus is primarily located in the **posterior mediastinum** and is covered by an **adventitia**, which blends with surrounding connective tissues. - A serosa is typically found on organs suspended within the **peritoneal cavity**, providing a smooth, lubricating surface. *Adventitia* - The esophagus is largely covered by an **adventitia**, especially in its thoracic portion, which helps anchor it to surrounding structures. - This fibrous layer is characteristic of organs that are **retroperitoneal** or found outside serous cavities. *Muscularis propria* - The **muscularis propria** forms the main contractile layer of the esophageal wall, crucial for peristalsis. - It consists of an **inner circular** and an **outer longitudinal layer** of muscle, with a transition from skeletal to smooth muscle along its length. *Mucosa* - The **mucosa** is the innermost layer of the esophagus, involved in protection and lubrication. - It is composed of a **non-keratinized stratified squamous epithelium**, lamina propria, and muscularis mucosae.

Question 206: Stereocilia are present in?

A. Taste buds
B. Hair cells (Correct Answer)
C. Retina
D. Nose

Explanation: ***Hair cells*** - **Stereocilia** are specialized **mechanosensing organelles** that extend from the apical surface of hair cells in the inner ear [1]. - They play a crucial role in hearing and balance by bending in response to **sound waves** or **head movements**, leading to the generation of electrical signals [1]. *Taste buds* - **Taste buds** contain **taste receptor cells** that have **microvilli**, not stereocilia, on their apical surfaces. - These **microvilli** are responsible for detecting chemical tastants. *Retina* - The **retina** contains **photoreceptor cells** (rods and cones) that are specialized for light detection. - These cells have **outer segments** filled with membranous discs containing **photopigments**, not stereocilia. *Nose* - The **olfactory epithelium** in the nose contains **olfactory receptor neurons** with **cilia** that project into the mucus layer. - These **cilia** bind to odorant molecules, initiating the sense of smell; they are distinct from stereocilia.

Question 207: Stereocilia are found in?

A. Eye
B. Nose
C. Tongue
D. Epididymis (Correct Answer)

Explanation: ***Epididymis*** - **Stereocilia** are long, non-motile microvilli found on the epithelial cells of the **epididymis** and ductus deferens. - In the epididymis, they play a crucial role in **absorbing excess fluid** and secreting substances that contribute to sperm maturation and storage. - These are true stereocilia (modified microvilli), distinct from the stereocilia found in the inner ear hair cells [1] which are specialized for mechanosensation. *Eye* - The eye contains specialized photoreceptor cells (rods and cones) and various supporting cells, but it **does not contain stereocilia**. - Its sensory structures are designed for light detection, not for fluid absorption or mechanosensation in the way stereocilia function. [3] *Nose* - The nose contains **olfactory receptor neurons** with specialized cilia for detecting odors, and goblet cells, but it **does not contain stereocilia**. [2] - The cilia in the respiratory epithelium of the nose are primarily motile cilia involved in mucus clearance, not the non-motile stereocilia found in the epididymis. *Tongue* - The tongue is covered with **taste buds** for chemical sensation and has papillae that aid in food manipulation. - It contains **taste receptor cells** and various epithelial cells, but **no stereocilia**. [2]

Question 208: What is the lining of the lacrimal gland alveoli?

A. Ciliated columnar cells
B. Pyramidal columnar epithelial cells (Correct Answer)
C. Non-keratinizing squamous epithelium
D. None of the options

Explanation: ***Pyramidal columnar epithelial cells*** - The **lacrimal gland alveoli (acini)** are lined by **pyramidal-shaped columnar epithelial cells**, which are specialized **serous secretory cells**. - These cells have a pyramidal/columnar shape with basally located nuclei and apical secretory granules. - They produce the **aqueous component of tears**, containing water, electrolytes, lysozyme, lactoferrin, and immunoglobulins. - The term refers to their shape and epithelial nature, not to be confused with pyramidal neurons of the CNS. *Ciliated columnar cells* - **Ciliated columnar cells** are typically found in the **respiratory tract** (trachea, bronchi) and parts of the reproductive system (fallopian tubes). - Their primary function is **mucociliary clearance** through coordinated beating of cilia, not glandular secretion. *Non-keratinizing squamous epithelium* - **Non-keratinizing stratified squamous epithelium** lines moist surfaces like the **conjunctiva**, oral cavity, esophagus, and vagina. - This type of epithelium provides **protection against abrasion** and friction, but does not specialize in producing secretions. *None of the options* - This option is incorrect because **pyramidal columnar epithelial cells** are indeed the correct lining of the lacrimal gland alveoli.

Question 209: In which layer of the gastrointestinal tract is Auerbach's plexus located?

A. Muscularis layer of the colon
B. Muscularis layer of the esophagus
C. Muscularis layer of the stomach
D. Muscularis layer of all of the above (Correct Answer)

Explanation: ***Muscularis layer of all of the above*** - **Auerbach's plexus**, also known as the **myenteric plexus**, is located between the **inner circular** and **outer longitudinal muscle layers** of the **muscularis externa** (muscularis propria) throughout the entire gastrointestinal tract [1]. - This plexus is crucial for regulating **gastrointestinal motility**, including peristalsis and segmentation, in all regions from the esophagus to the rectum [2]. - It is present in the colon, esophagus, stomach, and all other parts of the GI tract, making "all of the above" the correct answer. *Muscularis layer of the colon* - While Auerbach's plexus is present in the colon and plays a vital role in its motor functions, it is **not exclusive** to this region. - The regulation of colonic motility, essential for waste propulsion, is dependent on the coordinated action of neurons within this plexus. *Muscularis layer of the esophagus* - Auerbach's plexus is found in the esophageal muscularis externa, where it orchestrates the **peristaltic waves** that propel food towards the stomach. - Its presence here is essential for coordinated swallowing, but it is also found elsewhere in the GI tract. *Muscularis layer of the stomach* - The stomach's muscularis externa also contains Auerbach's plexus, which is responsible for the complex **mixing and emptying movements** of gastric contents [3]. - This plexus helps coordinate the contractions of the stomach's **three muscle layers** (outer longitudinal, middle circular, and inner oblique) to facilitate digestion [3].

Question 210: Cells which surround the oocyte in graafian follicle are called ?

A. Discus proligerus
B. Luteal cells
C. Villus cells
D. Cumulus oophorus (Correct Answer)

Explanation: ***Cumulus oophorus*** - The **cumulus oophorus** is a mound of **granulosa cells** that surrounds the oocyte in the Graafian follicle [2]. - These cells are crucial for the development, maturation, and eventual ovulation of the oocyte. *Discus proligerus* - **Discus proligerus** is an older, less commonly used term for the **cumulus oophorus**. - While it refers to the same structure, **cumulus oophorus** is the more current and preferred terminology. *Luteal cells* - **Luteal cells** are formed from the granulosa and theca cells of the ruptured follicle after ovulation, forming the **corpus luteum** [1]. - They are involved in hormone production (progesterone) after the oocyte has been released, not directly surrounding the oocyte within the intact Graafian follicle [1]. *Villus cells* - **Villus cells** are primarily found in the **placenta** and **intestines**, where they are involved in nutrient exchange and absorption. - They have no role in the structure or function of the ovarian follicle or the oocyte within it.

Practice by Chapter

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