Microscopic Anatomy — MCQs

Microscopic Anatomy Indian Medical PG Practice Questions and MCQs

Question 221: Which plexus in the gastrointestinal tract is located closest to the lumen?

A. Submucosal plexus (Correct Answer)
B. Auerbach's plexus
C. Mucosal plexus
D. Myenteric plexus

Explanation: ***Submucosal plexus*** - The **submucosal plexus** (also known as **Meissner's plexus**) is located in the **submucosa**, just beneath the muscularis mucosae, which positions it **closest to the lumen** among all the major enteric plexuses [1]. - It primarily regulates **glandular secretion**, **local blood flow**, and **contraction of the muscularis mucosae**. *Auerbach's plexus* - **Auerbach's plexus** (also known as the **myenteric plexus**) is located **between the inner circular and outer longitudinal layers** of the muscularis propria [1], [2]. - This position is significantly **farther from the lumen** than the submucosal layer. - It primarily controls the **major peristaltic contractions** of the GI tract [2]. *Myenteric plexus* - **Myenteric plexus** is an alternative name for **Auerbach's plexus** [1]. - Located in the muscularis propria, it is **farther from the lumen** than the submucosal plexus. - It controls **motor function** and coordinated muscular contractions along the GI tract [2]. *Mucosal plexus* - The **mucosal plexus** is not a distinct, well-defined neural plexus recognized in standard anatomical nomenclature. - While nerve fibers do extend into the mucosa, they are part of the network regulated by the submucosal plexus, not a separate named plexus with its own anatomical identity.

Question 222: Intercalated disc is present in:

A. Cardiac muscle (Correct Answer)
B. Smooth muscle
C. Skeletal muscle
D. All of the options

Explanation: ***Cardiac muscle*** - **Intercalated discs** are unique structures found only in cardiac muscle, forming specialized cell-cell junctions [1]. - These discs contain **gap junctions** for electrical coupling and **desmosomes** for strong adhesion, allowing the heart muscle to contract in a coordinated fashion. *Smooth muscle* - **Smooth muscle cells** are spindle-shaped and lack striations and organized sarcomeres. - They do not possess intercalated discs; instead, communication and coordination are often mediated by **gap junctions** scattered along the cell membranes [2]. *Skeletal muscle* - **Skeletal muscle cells** are long, multinucleated, and highly organized with prominent striations [3]. - They do not have intercalated discs as individual muscle fibers are innervated separately and generally do not directly communicate via specialized junctions for coordinated contraction. *All of the options* - As **intercalated discs** are characteristic features *only* of **cardiac muscle**, this option is incorrect. - Their presence in all three muscle types would contradict the specific cellular organization of smooth and skeletal muscle.

Question 223: In the context of blood pressure regulation, where are baroreceptors primarily located?

A. Tunica intima
B. None of the options
C. Tunica media
D. Tunica adventitia (Correct Answer)

Explanation: ***Tunica adventitia*** - **Baroreceptors** are specialized mechanoreceptive nerve endings that detect changes in blood pressure by sensing arterial wall stretch. - These sensory nerve endings are primarily located in the **tunica adventitia** (outermost layer) of the **carotid sinus** and **aortic arch** [1]. - The adventitia contains the **nerve fibers and endings** (including baroreceptors), as well as the vasa vasorum and connective tissue supporting the vessel wall [1]. - The nerve terminals extend from the adventitia toward the adventitial-medial border where they sense wall tension changes. *Tunica media* - The **tunica media** is the middle layer composed of **smooth muscle cells** and elastic fibers. - While this layer responds to stretch and changes thickness with blood pressure variations, it does **not contain nerve endings or baroreceptors** [1]. - The media is responsible for vasoconstriction and vasodilation but lacks the sensory innervation needed for baroreception. *Tunica intima* - The **tunica intima** is the innermost layer lined by **endothelial cells**. - Its primary functions include providing a smooth surface for blood flow and regulating vascular permeability. - This layer does not house baroreceptors or other mechanoreceptive nerve endings. *None of the options* - This option is incorrect because **tunica adventitia** is indeed the correct location of baroreceptors. - The adventitia contains the neural elements necessary for blood pressure sensing in these specialized arterial regions [1].

Question 224: Oxyntic cells are present in -

A. Pylorus
B. Cardia
C. Body (Correct Answer)
D. None of the options

Explanation: ***Body*** - **Oxyntic cells**, also known as **parietal cells**, are predominantly located in the **fundus and body** of the stomach [1], [2]. - These cells are responsible for secreting **hydrochloric acid (HCl)** and **intrinsic factor**, which are crucial for digestion and vitamin B12 absorption [1]. - The gastric glands in the body contain the highest concentration of parietal cells [2]. *Pylorus* - The pylorus is the distal part of the stomach that connects to the duodenum. - It primarily contains **G cells**, which secrete **gastrin**, a hormone that stimulates HCl secretion from parietal cells [3]. - Pyloric glands contain mainly mucus-secreting cells, with few or no parietal cells [2]. *Cardia* - The cardia is the region near the gastroesophageal junction (entrance of the stomach). - This area primarily contains **cardiac glands** with mucus-secreting cells that protect the esophageal lining from gastric acid reflux. - Parietal cells are sparse or absent in the cardia [2]. *None of the options* - This option is incorrect because the **body of the stomach** is the correct location for oxyntic cells.

Question 225: Which layer of the epidermis is known as the dead layer?

A. Stratum basale
B. Stratum corneum (Correct Answer)
C. Stratum granulosum
D. Stratum spinosum

Explanation: ***Stratum corneum*** - This is the **outermost layer** of the epidermis, composed of 15 to 30 layers of dead, flattened **keratinocytes** [1]. - These cells, called **corneocytes**, are anucleated and filled with keratin, providing a protective barrier [1]. *Stratum basale* - This is the **deepest layer** of the epidermis, consisting of a single layer of cuboidal or columnar cells [1]. - It is responsible for **cell proliferation** and regeneration of the epidermis, making it a living, metabolically active layer [1]. *Stratum granulosum* - This layer is characterized by cells containing **keratohyalin granules** and lamellar granules. - These granules are involved in the process of **keratinization** and forming the epidermal water barrier, but the cells here are still living and undergo programmed cell death as they move upwards. *Stratum spinosum* - This layer is composed of several layers of polyhedral cells connected by **desmosomes**, giving them a "spiny" appearance. - It contains **Langerhans cells** and is involved in keratin synthesis, but the cells are still living and metabolically active [1].

Question 226: Blood tissue barrier in testis is formed by?

A. Basal lamina & interstitial cells
B. Basal lamina & spermatogonia
C. Basal lamina & leydig cells
D. Adjacent Sertoli cells with basal lamina (Correct Answer)

Explanation: ***Adjacent Sertoli cells with basal lamina*** - The **blood-testis barrier** is primarily formed by **tight junctions** between adjacent **Sertoli cells**, which divide the seminiferous epithelium into basal and adluminal compartments [1]. - The **basal lamina** of the seminiferous tubule also contributes to this barrier, regulating the passage of substances from the interstitial fluid to the basal compartment [1]. *Basal lamina & interstitial cells* - While the **basal lamina** is part of the barrier, **interstitial cells (Leydig cells)** are located outside the seminiferous tubules and are primarily involved in **testosterone production**, not barrier formation [1]. - **Interstitial cells** are part of the connective tissue between the tubules and do not form tight junctions that would restrict molecular movement into the seminiferous epithelium. *Basal lamina & spermatogonia* - **Spermatogonia** are germ cells located in the **basal compartment** of the seminiferous tubule, *beneath* the Sertoli cell tight junctions [1]. - They are able to cross the barrier as they differentiate and move into the adluminal compartment, but they do not form the barrier itself. *Basal lamina & leydig cells* - As mentioned previously, **Leydig cells** (interstitial cells) are responsible for **androgen synthesis** and are located outside the seminiferous tubule [2]. - They do not form components of the physical blood-testis barrier.

Question 227: Which layer of the skin contains abundant desmosomes?

A. Stratum basale
B. Stratum spinosum (Correct Answer)
C. Stratum corneum
D. Stratum granulosum

Explanation: ***Stratum spinosum*** - This layer is characterized by abundant **desmosomes**, which connect keratinocytes and give them a "spiny" appearance when stained, hence its name. - The desmosomes provide **strong cell-to-cell adhesion**, crucial for the skin's barrier function and mechanical strength [1]. *Stratum corneum* - This outermost layer primarily consists of **dead, flattened keratinocytes** (corneocytes) filled with keratin [1]. - While desmosomes are present, they are in a process of degradation and are not as numerous or prominent as in the stratum spinosum. *Stratum granulosum* - This layer is known for the presence of **keratohyalin granules** and **lamellar granules**, which are involved in keratinization and lipid secretion, respectively [1]. - While cells here still have desmosomes, their primary function shifts towards preparing for the final differentiation into the stratum corneum. *Stratum basale* - This is the deepest layer, containing **mitotically active keratinocytes** that attach to the basement membrane via **hemidesmosomes**. - While desmosomes are present to connect these basal cells to each other and to the cells of the stratum spinosum, they are not as abundant or characteristic as in the stratum spinosum [1].

Question 228: Billroth's cords are present in which part of the spleen?

A. White pulp
B. Red pulp (Correct Answer)
C. Both
D. Capsule

Explanation: ***Red pulp*** - **Billroth's cords**, also known as **splenic cords**, are a prominent histological feature found exclusively within the **red pulp** of the spleen [1]. - They are composed of a meshwork of reticular cells and fibers, with large numbers of **macrophages**, red blood cells, and other leukocytes, which are critical for **blood filtration** and old red blood cell destruction [1]. *White pulp* - The white pulp is primarily composed of lymphoid tissue, including **lymphocytes** clustered around central arteries, forming the periarteriolar lymphoid sheaths (PALS) and lymphoid nodules (follicles). - Its main function is immunological, involving **lymphocyte proliferation** and immune responses, rather than blood filtration via Billroth's cords [1]. *Both* - This option is incorrect because Billroth's cords are specifically located in the red pulp and are not a feature of the white pulp. - The architectural and functional roles of the white and red pulp are distinct, with specialized structures allocated to each region. *Capsule* - The **capsule** is the outermost connective tissue layer that encloses and protects the entire spleen. - It contains smooth muscle cells and fibroblasts but does not house the splenic parenchyma, including Billroth's cords.

Question 229: Pituicytes are seen in ?

A. Anterior lobe
B. Posterior lobe (Correct Answer)
C. Intermediate lobe
D. All of the options

Explanation: ***Posterior lobe*** - **Pituicytes** are specialized glial cells found exclusively in the **posterior pituitary** (neurohypophysis). [1] - They provide structural support and regulation for the nerve terminals that release **antidiuretic hormone (ADH)** and **oxytocin**. [1] *Anterior lobe* - The anterior pituitary, or **adenohypophysis**, consists of glandular epithelial cells that synthesize and secrete various hormones. [2] - It does not contain pituicytes, which are glial cells. [2] *Intermediate lobe* - The intermediate lobe is a rudimentary part of the pituitary gland in humans, primarily producing **melanocyte-stimulating hormone (MSH)**. [1] - While it is part of the pituitary, it does not contain pituicytes. *All of the options* - Pituicytes are specific to the posterior pituitary, so they are not found in all parts of the gland. - Different lobes of the pituitary gland have distinct cellular compositions and functions.

Question 230: Podocytes are seen in -

A. Bowman's capsule (Correct Answer)
B. Proximal convoluted tubule
C. Distal convoluted tubule
D. Collecting tubule of the kidney

Explanation: **Bowman's capsule** - **Podocytes** are specialized epithelial cells that form the **visceral layer** of Bowman's capsule. They have foot processes (pedicels) that interdigitate to form slit diaphragms, which are crucial for the **filtration barrier** of the glomerulus [1]. - These cells facilitate the selective passage of water and small solutes from the blood into Bowman's space, while preventing the filtration of large proteins and blood cells. *Proximal convoluted tubule* - The **proximal convoluted tubule** is primarily involved in the **reabsorption** of essential nutrients, ions, and water from the filtrate back into the bloodstream [1]. - Its cells are characterized by a **brush border** (microvilli) and numerous mitochondria, indicating high metabolic activity, and are not podocytes [1]. *Distal convoluted tubule* - The **distal convoluted tubule** plays a role in fine-tuning the reabsorption of ions and water, under the influence of hormones like **aldosterone** and **ADH**. - Its cells lack the specialized foot processes and filtration function characteristic of podocytes. *Collecting tubule of the kidney* - The **collecting tubule** (or collecting duct) is involved in regulating water reabsorption and acid-base balance, responding to **ADH** to concentrate urine. - Its epithelial cells are principal cells and intercalated cells, which are different in structure and function from podocytes.

Practice by Chapter

Cellular Ultrastructure

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Microscopic Anatomy of Epithelial Tissues

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Microscopic Anatomy of Connective Tissues

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Microscopic Anatomy of Muscle Tissues

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Microscopic Anatomy of Nervous Tissues

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Microscopic Anatomy of Blood and Immune System

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Microscopic Anatomy of Endocrine Glands

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Microscopic Anatomy of Digestive System

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Microscopic Anatomy of Respiratory System

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Microscopic Anatomy of Urinary System

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Microscopic Anatomy of Reproductive System

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Techniques in Microscopic Anatomy

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