Histology Practice Questions

Q: What is the lining epithelium of the ventricles of the brain?

Ependyma. The ventricles of the brain and the central canal of the spinal cord are lined by a specialized type of neuroglia known as **Ependyma**. **1. Why Ependyma is correct:** Ependymal cells are derived from the neuroectoderm. They typically form a single layer of cuboidal to columnar cells. Their apical surfaces often possess **microvilli** (to absorb CSF) and **cilia** (to facilitate the flow of CSF). A unique histological feature of ependyma is the absence of a basement membrane; instead, the bases of these cells interdigitate with the processes of underlying astrocytes. **2. Why other options are incorrect:** * **B & C (Ciliated/Non-ciliated columnar cells):** While ependymal cells can appear columnar and are often ciliated, "Ependyma" is the specific anatomical and histological term for this neuroglial lining. In medical exams, the most specific tissue-specific term is preferred over general histological descriptions. * **D (Squamous epithelium):** Squamous cells are flat. While ependymal cells may flatten slightly in areas of high pressure, they are fundamentally cuboidal/columnar. **3. High-Yield Clinical Pearls for NEET-PG:** * **Choroid Plexus:** Modified ependymal cells and vascular capillaries form the choroid plexus, which is responsible for the **secretion of CSF**. * **Blood-CSF Barrier:** The tight junctions between the epithelial cells of the choroid plexus form the Blood-CSF barrier. * **Tanycytes:** These are specialized ependymal cells found in the floor of the 3rd ventricle that transport hormones from the CSF to the hypophyseal portal system. * **Ependymoma:** A tumor arising from these cells, most commonly found in the **fourth ventricle** in children and the spinal cord in adults [1].

Q: Which of the following types of dendritic cells are characteristically found in the thymus?

Interdigitating dendritic cells. The **interdigitating dendritic cell (IDC)** is the characteristic dendritic cell of the **thymus**, primarily located in the **medulla** and at the corticomedullary junction. These cells are highly specialized Antigen Presenting Cells (APCs) that express high levels of MHC Class I and II molecules. Their primary role in the thymus is **Negative Selection**: they present self-antigens to developing T-cells; those T-cells that bind too strongly to self-antigens undergo apoptosis, ensuring central self-tolerance and preventing autoimmunity. **Analysis of Incorrect Options:** * **A. Interstitial dendritic cells:** These are found in the connective tissue of most organs (e.g., heart, lungs, liver) but are not the characteristic functional cells of the thymic parenchyma. * **C. Circulating dendritic cells:** These are immature dendritic cells (veiled cells) found in the blood or lymph, currently in transit to peripheral tissues or secondary lymphoid organs. * **D. Follicular dendritic cells (FDCs):** These are found in the **germinal centers of B-cell follicles** in the lymph nodes and spleen. They trap antigen-antibody complexes to present to B-cells. Since the thymus is a primary lymphoid organ for T-cell maturation and lacks B-cell follicles, FDCs are not typically found there. **High-Yield Facts for NEET-PG:** * **Hassall’s Corpuscles:** These are characteristic acidophilic structures in the thymic medulla formed by Type VI epithelioreticular cells. * **Blood-Thymus Barrier:** Found only in the **cortex**, preventing premature exposure of developing T-cells to blood-borne antigens. * **DiGeorge Syndrome:** Failure of the 3rd and 4th pharyngeal pouches to develop, leading to thymic aplasia and T-cell deficiency [1].

Q: Which cells of the liver play a role in the absorption of Vitamin A and Vitamin D?

Stellate cells of Ito. **Explanation:** The correct answer is **Stellate cells of Ito** (also known as Hepatic Stellate Cells or Lipocytes) [1]. **1. Why Stellate cells of Ito is correct:** These cells are located in the **Space of Disse** (the perisinusoidal space between hepatocytes and sinusoidal endothelium) [1]. Their primary physiological function is the **storage of exogenous Vitamin A** (retinoids) and other fat-soluble vitamins like **Vitamin D** in the form of cytoplasmic lipid droplets. In a healthy liver, they store approximately 80% of the body's total Vitamin A. **2. Why other options are incorrect:** * **Kupffer cells:** These are specialized **macrophages** located within the liver sinusoids [1]. Their primary role is phagocytosis of pathogens, cell debris, and old red blood cells; they do not store vitamins. * **Stem cells:** In the liver, these are often referred to as "Oval cells" (located in the Canals of Hering). They function in regeneration and differentiation into hepatocytes or cholangiocytes during severe injury, not in vitamin metabolism. * **Sinusoids:** These are low-pressure vascular channels (capillaries) that allow for the exchange of substances between blood and hepatocytes [2]. They are a structural space, not a cell type responsible for vitamin storage. **3. Clinical Pearls for NEET-PG:** * **Fibrosis:** In chronic liver injury (e.g., cirrhosis), Ito cells lose their vitamin-storing capacity and transform into **myofibroblasts**, which secrete excess **Type I collagen**, leading to liver fibrosis [1]. * **Marker:** Desmin is a common histological marker for these cells. * **Space of Disse:** It is the site where nutrient exchange occurs and where lymph formation begins [2].

Q: The classical lobule of the liver is centred around which vascular structure?

Central vein. ### Explanation The liver's microanatomy is organized into three different types of units based on function and blood flow. The **Classical Lobule** is the structural unit of the liver, defined by its hexagonal shape [1]. **1. Why the Central Vein is Correct:** The classical lobule is centered around the **Central Vein** (terminal hepatic venule) [1]. In this model, blood flows centripetally (from the periphery toward the center) through the hepatic sinusoids, draining into the central vein [2]. This model emphasizes the endocrine function of the liver (secretion of substances into the blood). **2. Why the Other Options are Incorrect:** * **Portal Vein, Bile Duct, and Hepatic Artery:** These three structures together form the **Portal Triad**, which is located at the **periphery** (corners) of the classical lobule, not the center [1]. * **Portal Lobule:** If the question asked about the *Portal Lobule* (triangular unit), the center would be the **Bile Duct**. This model emphasizes the exocrine function (bile drainage). * **Hepatic Acinus (of Rappaport):** This diamond-shaped functional unit is centered around the **interlobular vessels** (branches of the portal vein and hepatic artery) [3]. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Kupffer Cells:** Specialized macrophages found within the hepatic sinusoids. * **Space of Disse:** The site between hepatocytes and sinusoids where metabolic exchange occurs; it contains **Ito cells** (Stellate cells) which store Vitamin A and are responsible for fibrosis in cirrhosis [4]. * **Zonation:** In the Hepatic Acinus, **Zone 1** (periportal) is best oxygenated (first to see toxins), while **Zone 3** (centrilobular/around the central vein) is the most susceptible to hypoxia and ischemia (e.g., "nutmeg liver" in congestive heart failure) [3].

Q: Vasa vasorum are functionally analogous to what?

Coronary arteries. The **vasa vasorum** (literally "vessels of the vessels") are a network of small blood vessels that supply the walls of large blood vessels, such as the aorta and its major branches. **Why Coronary Arteries are the correct answer:** The analogy lies in the **functional role** of these vessels. Just as the heart is a muscular pump filled with blood but cannot meet its own high metabolic demands via simple diffusion from its chambers, large blood vessels have walls too thick for nutrients to reach the outer layers (tunica media and adventitia) from the lumen. Therefore, the **coronary arteries** supply the heart muscle itself [1][2], just as the **vasa vasorum** supply the walls of the large vessels. Both represent a specialized system providing nutrition to the organ responsible for transporting blood [2]. **Analysis of Incorrect Options:** * **Valves:** These are structural folds (primarily in veins and the heart) that prevent the backflow of blood; they do not serve a nutritive function [1]. * **Basal lamina:** This is a layer of extracellular matrix secreted by epithelial cells; it provides structural support but is not a vascular supply system. * **Endothelial diaphragms:** These are thin structures spanning the pores of fenestrated capillaries to regulate permeability; they are involved in filtration, not the macro-nutrition of vessel walls. **Clinical Pearls for NEET-PG:** * **Location:** Vasa vasorum are most abundant in large **veins** compared to arteries because venous blood is poorly oxygenated. * **Pathology:** In **Syphilitic Aortitis**, the vasa vasorum of the ascending aorta undergo "endarteritis obliterans" (narrowing), leading to ischemia of the aortic wall, weakening of the media, and subsequent aneurysm formation. * **Zone of Diffusion:** In humans, the inner 0.5–1.0 mm of an arterial wall is nourished by direct diffusion from the lumen; the vasa vasorum supply everything beyond that depth.

Q: The cortex of the ovary consists of all the following structures except:

Hilus. ### Explanation The ovary is structurally divided into two distinct zones: an outer **cortex** and an inner **medulla** [1]. **1. Why "Hilus" is the correct answer:** The **Hilus** (or Hilum) is the part of the ovary where blood vessels, nerves, and lymphatics enter and exit. It is continuous with the **medulla**, the central core of the ovary. The medulla consists of loose connective tissue, elastic fibers, and large convoluted blood vessels. Crucially, the hilus also contains **Hilus cells** (homologous to Leydig cells in males), which secrete androgens. Therefore, the hilus is a medullary structure, not a cortical one. **2. Analysis of Incorrect Options:** * **Cortex Composition:** The cortex is the peripheral layer containing the **ovarian follicles** embedded in a cellular connective tissue stroma [1]. * **Primordial Follicles (Option C):** These are the most immature follicles found in the superficial cortex [2]. * **Graafian Follicle (Option A):** This is the mature, liquid-filled follicle ready for ovulation, located within the cortex. * **Corpus Luteum (Option D):** This is the temporary endocrine structure formed from the remains of the ovarian follicle after ovulation, also residing in the cortex [2]. **3. NEET-PG High-Yield Pearls:** * **Germinal Epithelium:** The ovary is covered by a single layer of cuboidal cells (modified peritoneum) called the germinal epithelium of Waldeyer [1]. * **Tunica Albuginea:** A dense connective tissue layer located between the germinal epithelium and the cortex. * **Hilus Cell Tumors:** These are rare androgen-secreting tumors that can cause virilization in women; they are characterized by the presence of **Reinke crystals** (similar to Leydig cell tumors). * **Blood Supply:** The ovarian artery arises directly from the **Abdominal Aorta** at the level of L2.

Q: Which one of the following sensory receptors is found in the epidermis?

Merkel disc. ### Explanation The skin is divided into the **epidermis** (outer epithelial layer) and the **dermis** (inner connective tissue layer). Most specialized sensory receptors are located within the dermis; however, the **Merkel disc** is a notable exception. **1. Why Merkel Disc is Correct:** Merkel discs (or Merkel cell-neurite complexes) are located in the **basal layer (stratum basale) of the epidermis** [1]. They consist of a specialized epithelial cell (Merkel cell) in close contact with an expanded nerve terminal. They are **slowly adapting Type I mechanoreceptors** responsible for sensing fine touch, pressure, and texture (e.g., reading Braille). **2. Analysis of Incorrect Options:** * **Meissner’s corpuscles:** These are rapidly adapting mechanoreceptors for fine touch and low-frequency vibration. They are located in the **dermal papillae** (just beneath the epidermis), not within the epidermis itself. * **Ruffini endings:** These are slowly adapting receptors that detect skin stretch and torque. They are located deep within the **dermis**. * **Pacinian corpuscles:** These are large, onion-like structures that detect deep pressure and high-frequency vibration. They are found in the **deep dermis and hypodermis** (subcutaneous tissue). **Clinical Pearls & High-Yield Facts:** * **Free Nerve Endings:** Along with Merkel discs, these are the only other receptors that penetrate the epidermis. * **Merkel Cell Carcinoma:** A rare but highly aggressive neuroendocrine skin cancer derived from these cells. * **Location Density:** Meissner’s and Merkel receptors are most numerous in hairless (glabrous) skin, such as fingertips and lips. * **Mnemonics:** Remember "**M**erkel and **M**eissner are for **M**apping touch," but only **M**erkel stays in the **M**alpighian (basal) layer of the epidermis.

Q: What is the type of cartilage?

Elastic cartilage. ***Elastic cartilage*** - Contains abundant **elastic fibers** within the matrix, giving it flexibility and resilience to return to original shape after deformation. - Found in structures requiring flexibility like the **ear pinna**, **epiglottis**, and parts of the **larynx** (arytenoid and corniculate cartilages). *Hyaline cartilage* - Contains **type II collagen** but lacks elastic fibers, making it less flexible than elastic cartilage. - Found in **articular surfaces**, **tracheal rings**, and **costal cartilages** where smooth surfaces are needed. *Fibrocartilage* - Contains **type I collagen fibers** arranged in bundles, providing tensile strength rather than flexibility. - Found in **intervertebral discs** and **menisci** where shock absorption and durability are required. *Articular cartilage* - This is actually a **subtype of hyaline cartilage** that covers joint surfaces, not a distinct cartilage type. - Lacks **perichondrium** and has specialized zonal organization for load-bearing in synovial joints.

Q: Which of the following best describes the centromere position of the human X chromosome?

Submetacentric. **Explanation:** The classification of chromosomes is based on the position of the **centromere**, which divides the chromosome into a short arm (**p arm**) and a long arm (**q arm**). **1. Why Submetacentric is correct:** The human **X chromosome** is a large **submetacentric** chromosome (specifically belonging to Group C in the Denver classification). In submetacentric chromosomes, the centromere is located slightly away from the center, resulting in an unequal length of arms where the p arm is distinctly shorter than the q arm. **2. Analysis of Incorrect Options:** * **Metacentric:** The centromere is in the exact middle, creating arms of equal length. Examples include chromosomes **1, 3, 16, 19, and 20**. * **Acrocentric:** The centromere is located very near one end. These chromosomes possess "satellites" and stalks containing rDNA. Examples include chromosomes **13, 14, 15, 21, 22, and the Y chromosome**. * **Telocentric:** The centromere is at the very tip (telomere). **Telocentric chromosomes do not occur in humans**; they are found in other species like mice. **Clinical Pearls & High-Yield Facts:** * **Denver Classification:** Chromosomes are grouped A-G based on size and centromere position. The X chromosome is in **Group C**, while the Y chromosome is in **Group G** (Acrocentric). * **Robertsonian Translocation:** This occurs only in **acrocentric** chromosomes (13, 14, 15, 21, 22) because the loss of their short arms (satellites) does not result in the loss of essential genetic material. * **Lyonization:** In females, one X chromosome is randomly inactivated to form a **Barr body** (facultative heterochromatin) to ensure dosage compensation.

Question 1

What is the lining epithelium of the ventricles of the brain?

Accepted Answer

Ependyma

Answer

Ciliated columnar cells

Answer

Non-ciliated columnar cells

Answer

Squamous epithelium

Question 2

Which of the following types of dendritic cells are characteristically found in the thymus?

Accepted Answer

Interdigitating dendritic cells

Answer

Interstitial dendritic cells

Answer

Circulating dendritic cells

Answer

Follicular dendritic cells

Question 3

Which cells of the liver play a role in the absorption of Vitamin A and Vitamin D?

Accepted Answer

Stellate cells of Ito

Answer

Kupffer cells

Answer

Stem cells

Answer

Sinusoids

Question 4

The classical lobule of the liver is centred around which vascular structure?

Accepted Answer

Central vein

Answer

Portal vein

Answer

Bile duct

Answer

Hepatic artery

Question 5

Vasa vasorum are functionally analogous to what?

Accepted Answer

Coronary arteries

Answer

Valves

Answer

Basal lamina

Answer

Endothelial diaphragms

Question 6

The cortex of the ovary consists of all the following structures except:

Accepted Answer

Hilus

Answer

Graafian follicle

Answer

Primordial follicle

Answer

Corpus luteum

Question 7

The small intestine has three histologically distinct regions. Which of the following statements concerning the histological differences in the three regions is true?

Accepted Answer

Peyer patches are present only in the ileum

Answer

Goblet cells are present only in the epithelium of the duodenum

Answer

Brunner glands are located in the duodenum and jejunum but not the ileum

Answer

Lacteals are present only in the lamina propria of the ileum

Question 8

Which one of the following sensory receptors is found in the epidermis?

Accepted Answer

Merkel disc

Answer

Meissner's corpuscles

Answer

Ruffini ending

Answer

Pacinian corpuscles

Question 9

What is the type of cartilage?

Accepted Answer

Elastic cartilage

Answer

Hyaline cartilage

Answer

Fibrocartilage

Answer

Articular cartilage

Question 10

Which of the following best describes the centromere position of the human X chromosome?

Accepted Answer

Submetacentric

Answer

Metacentric

Answer

Acrocentric

Answer

Telocentric

Histology — MCQs

Histology — MCQs

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