Microscopic Anatomy — MCQs

Microscopic Anatomy Indian Medical PG Practice Questions and MCQs

Question 211: The given histology image is of which structure?

A. Pancreatic islet cells
B. Hassall's corpuscles
C. Glomerulus (Correct Answer)
D. Leydig cells in the testis

Explanation: ***Glomerulus*** - The glomerulus is characterized by a **tuft of capillaries** surrounded by Bowman's capsule, responsible for filtration in the kidney [1]. - Histological examination typically shows a **dense network of capillaries** and **mesangial cells**, which are distinct features of the glomeruli [1]. *Hassall's corpuscles* - Found in the **thymus**, they are round structures composed of epithelial cells, crucial in T-cell maturation. - Histologically, they present as concentric layers of **epithelial cells** and are not found in the kidney. *Leydig cells of testis* - Located in the **interstitial tissue** of the testes, these cells produce testosterone and are typically larger than glomerular cells. - They are characterized by their **eosinophilic cytoplasm** and round nuclei, differing markedly from the structures found in the glomerulus. *Pancreatic islet cells* - Islet cells are involved in **hormone production**, predominantly insulin and glucagon, and are located in the pancreas. - Histologically, they appear as small clusters dispersed among **exocrine pancreas**, which is different from the highly organized structure of the glomerulus. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 522-523.

Question 212: 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.

Question 213: Identify the type of cartilage shown in the image.

A. Hyaline cartilage
B. Elastic cartilage
C. Dense connective tissue
D. Fibrocartilage (Correct Answer)

Explanation: ***Fibrocartilage*** - The image displays **chondrocytes** arranged in rows between bundles of **collagen fibers**, characteristic of fibrocartilage. This structure provides high tensile strength and shock absorption. - Unlike other cartilage types, fibrocartilage lacks a distinct perichondrium and is found in structures requiring extreme strength, such as intervertebral discs and menisci. *Hyaline cartilage* - Hyaline cartilage has an amorphous, **glassy matrix** with chondrocytes typically arranged in small groups (isogenous groups) within lacunae, without prominent collagen bundles. - It is found in articular surfaces, tracheal rings, and the costal cartilages, providing smooth, low-friction surfaces. *Elastic cartilage* - Elastic cartilage is characterized by a high concentration of **elastic fibers** within its matrix, giving it flexibility and resilience. - Chondrocytes are typically scattered and the matrix stains darker due to the elastic fibers, which are not apparent in the image. *Dense connective tissue* - While dense connective tissue contains abundant **collagen fibers**, it lacks chondrocytes in lacunae, instead containing fibroblasts. - The presence of chondrocytes in the image confirms this is cartilage, not dense connective tissue.

Question 214: Which type of collagen is the most abundant in the human skin?

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

Explanation: ***Type I collagen*** - **Type I collagen** is the **most abundant type** of collagen in the human body, accounting for about 90% of the collagen, and is particularly prevalent in the **dermis** of the skin, where it provides tensile strength and elasticity [1]. - It forms **thick, striated fibrils** and is critical for the structural integrity of skin, bones, tendons, and ligaments [1]. *Type II collagen* - **Type II collagen** is primarily found in **cartilage**, especially **hyaline and elastic cartilage**, where it provides resistance to pressure. - It is not a major component of the skin's dermal structure. *Type III collagen* - **Type III collagen** is found alongside Type I collagen in the skin but is prominent in **reticular fibers** and plays a role in the elasticity and suppleness of the skin, particularly in rapidly growing tissues and blood vessels. - While present in the skin, it is less abundant than Type I collagen and its primary role is in supporting organ structure, not tensile strength. *Type IV collagen* - **Type IV collagen** is a major component of **basement membranes**, forming a mesh-like network that provides structural support and acts as a filter in tissues. - It is not found in the interstitial connective tissue of the dermis but rather underlies the epidermis, forming part of the dermoepidermal junction.

Question 215: Which of the following accurately describes the anatomical structure of the hard palate?

A. Non-keratinised mucosa with a submucosal layer and minor salivary glands.
B. Non-keratinised mucosa without a submucosal layer and minor salivary glands.
C. Keratinised mucosa without a submucosal layer and minor salivary glands.
D. Keratinised mucosa with a submucosal layer and minor salivary glands. (Correct Answer)

Explanation: ***Keratinised mucosa with a submucosal layer and minor salivary glands.*** - The hard palate is covered by **keratinised stratified squamous epithelium** to withstand the forces of chewing and mastication. - It contains a **submucosal layer** in its posterolateral region (near the molar teeth) and anteriorly (near the incisor teeth) where **minor salivary glands** (palatine glands) are present. *Non-keratinised mucosa with a submucosal layer and minor salivary glands.* - The hard palate is primarily covered by **keratinised epithelium**, not non-keratinised, due to its role in food processing. - While it does have a submucosal layer and minor salivary glands in specific regions, the mucosal type is incorrect. *Non-keratinised mucosa without a submucosal layer and minor salivary glands.* - This option incorrectly states that the hard palate has **non-keratinised mucosa** and no submucosal layer, which is false for several regions. - The presence of minor salivary glands is also incorrect for this description. *Keratinised mucosa without a submucosal layer and minor salivary glands.* - While the hard palate is indeed covered by **keratinised mucosa**, it is incorrect to state that it entirely lacks a submucosal layer or minor salivary glands. - These structures are present in the posterolateral and anterior regions of the hard palate.

Question 216: Ceruminous glands present in the ear are:

A. Modified eccrine glands
B. Modified apocrine glands (Correct Answer)
C. Mucous gland
D. Modified holocrine glands

Explanation: ***Modified apocrine glands*** - **Ceruminous glands** in the ear canal are specialized **apocrine glands** responsible for producing cerumen (earwax). - Like other apocrine glands, they secrete their product via **apical budding** of the cell, releasing fragments of the cell along with the secretion [1]. *Modified eccrine glands* - **Eccrine sweat glands** are distributed throughout the skin and produce a watery sweat for thermoregulation [1]. - They secrete their product directly onto the skin surface via **exocytosis**, without loss of cellular material. *Mucous gland* - **Mucous glands** (e.g., salivary glands, respiratory tract glands) produce **mucus**, a viscous secretion primarily for lubrication and protection. - Their secretions are rich in **mucin glycoproteins**, which is distinct from the lipid-rich cerumen. *Modified holocrine glands* - **Holocrine glands** (e.g., sebaceous glands) release their entire cell contents, including lipids and cellular debris, upon cell lysis. - While sebaceous glands contribute to earwax, ceruminous glands themselves operate via an **apocrine mechanism**, not holocrine [1].

Question 217: Which area in the spleen is considered primarily thymus-dependent?

A. Mantle layer
B. Malpighian corpuscle
C. Periarteriolar lymphoid sheath (PALS) (Correct Answer)
D. None of the options

Explanation: ***Periarteriolar lymphoid sheath (PALS)*** - PALS is the **T-cell zone** of splenic white pulp, containing predominantly **T-lymphocytes** arranged around central arterioles. [2] - This area is **thymus-dependent** as it houses mature T cells that have undergone thymic selection and education, making it the primary thymus-dependent area of the spleen. [1] *Mantle layer* - The mantle layer consists of **naïve B lymphocytes** that surround the germinal center within splenic follicles. - This area is **thymus-independent** and primarily involved in **B-cell responses** to antigens. *Malpighian corpuscle* - Also known as **splenic follicles** or white pulp, this area primarily functions as **B-cell aggregation zones**. - While containing both B and T cell areas, it's predominantly **thymus-independent** with its main role being B-cell activation and antibody production. *None of the options* - This option is incorrect because PALS clearly represents the primary **thymus-dependent area** in the spleen. - The spleen definitively contains thymus-dependent zones where **T-cell activation** and proliferation occur, specifically the PALS. [1]

Question 218: What is the type of epithelium of the adenoid?

A. Pseudostratified ciliated columnar epithelium (Correct Answer)
B. Non-keratinized squamous epithelium
C. Cuboidal epithelium
D. Columnar epithelium with goblet cells

Explanation: ***Pseudostratified ciliated columnar epithelium*** - The adenoid (pharyngeal tonsil) is located in the nasopharynx, which is part of the upper respiratory tract and is lined with **pseudostratified ciliated columnar epithelium** with goblet cells [1]. - This type of epithelium is also known as **respiratory epithelium**, and its cilia and mucus-producing goblet cells help to trap and clear inhaled particles and pathogens [1]. *Non-keratinized squamous epithelium* - This type of epithelium is found in areas subject to friction and abrasion, such as the oral cavity, oro- and laryngopharynx, and esophagus, not typically in the nasopharynx. - It provides protection but lacks the ciliated and mucus-producing cells necessary for clearing respiratory passages. *Cuboidal epithelium* - This epithelium is typically found in glands and ducts, secretory and absorptive surfaces, such as renal tubules and thyroid follicles. - It does not have the specialized functions (cilia, mucus production) required for the respiratory system's protective lining. *Columnar epithelium with goblet cells* - While the adenoid epithelium does contain **goblet cells** for mucus production, specifically stating "columnar epithelium" is not as precise as "pseudostratified ciliated columnar epithelium." - The key feature of being **pseudostratified** and **ciliated** is crucial for its function in the nasopharynx [1].

Question 219: 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 220: 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].

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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