Histology Practice Questions

Q: Which of the following is a holocrine gland?

Sebaceous gland. ### Explanation Exocrine glands are classified based on their **mode of secretion**, which describes how the secretory product is released from the cell. **1. Why the Correct Answer is Right:** * **Sebaceous Glands (Option D):** These are classic examples of **Holocrine glands**. In this mechanism, the entire cell matures, dies, and disintegrates to release its contents (sebum). The term "holocrine" is derived from *holos* (whole), signifying that the **whole cell is lost** as part of the secretion. **2. Analysis of Incorrect Options:** * **Sweat Glands (Option A):** Most sweat glands (eccrine) are **Merocrine**. Secretion occurs via exocytosis without any loss of cellular cytoplasm. *Note: Apocrine sweat glands (axilla/pubis) use the apocrine method.* * **Breast/Mammary Gland (Option B):** These are primarily **Apocrine glands**. In this mode, the apical portion of the cell cytoplasm is pinched off and released along with the secretory product (milk fats). * **Pancreas (Option C):** The exocrine part of the pancreas (acinar cells) is **Merocrine**. It secretes digestive enzymes through exocytosis, keeping the cell membrane intact. **3. NEET-PG High-Yield Clinical Pearls:** * **Mnemonic for Holocrine:** "**S**ebaceous = **S**uicide" (The cell commits suicide to secrete). * **Meibomian Glands:** These are modified sebaceous glands in the eyelid and are also **holocrine**. * **Goblet Cells:** These are unicellular **merocrine** glands. * **Mode of Secretion Summary:** * **Merocrine:** Most common; no cell loss (e.g., Salivary glands, Eccrine sweat). * **Apocrine:** Apical loss (e.g., Mammary gland, Moll’s glands in eyelids). * **Holocrine:** Total cell loss (e.g., Sebaceous gland, Zeis glands).

Q: The blood-air barrier consists of all of the following except?

Alveolar pores. ### Explanation The **blood-air barrier** (respiratory membrane) is the physical interface through which gas exchange occurs between the alveolar air and the pulmonary capillary blood [1]. For efficient diffusion, this barrier must be extremely thin (approximately 0.2 to 0.6 μm). **Why Alveolar Pores are the Correct Answer:** **Alveolar pores (Pores of Kohn)** are openings in the interalveolar septa that allow communication and collateral ventilation between adjacent alveoli. While they help equalize pressure and provide an alternate pathway for air if a bronchiole is obstructed, they are **not a layer** that oxygen must cross to reach the blood. Therefore, they do not form part of the blood-air barrier. **Analysis of Other Options:** * **Layer of Surfactant (B):** This is the innermost lining of the alveolus. It reduces surface tension and is the first substance oxygen encounters [1][3]. * **Type I Alveolar Cell Cytoplasm (C):** These are extremely thin squamous cells covering 95% of the alveolar surface, specialized for gas exchange [1][2]. * **Fused Basal Lamina (D):** The basement membrane of the Type I pneumocyte and the capillary endothelial cell fuse together to minimize the diffusion distance [1]. (Note: The capillary endothelial cytoplasm is the final layer). **High-Yield Clinical Pearls for NEET-PG:** * **Components of the Barrier (Inside to Out):** Surfactant → Type I Pneumocyte → Fused Basal Lamina → Capillary Endothelial Cell [1]. * **Type II Pneumocytes:** These are cuboidal cells that produce surfactant and act as stem cells to replace Type I cells after injury [1]. * **Diffusion Capacity:** Gas exchange is governed by **Fick’s Law**; the rate is inversely proportional to the thickness of the barrier. In conditions like **Pulmonary Fibrosis** or **Edema**, the barrier thickens, leading to impaired gas exchange.

Q: What are the intermediate filaments typically found in epithelial cells?

Keratin. **Explanation:** Intermediate filaments (IFs) are essential components of the cytoskeleton that provide mechanical strength to cells [1]. They are tissue-specific, making them highly reliable markers in diagnostic pathology (especially in identifying the origin of metastatic tumors) [1]. **1. Why Keratin is Correct:** **Keratin** (also known as cytokeratin) is the characteristic intermediate filament of **epithelial cells** [1]. It is found in both keratinizing (skin) and non-keratinizing (mucosa) epithelium. In clinical practice, immunohistochemistry (IHC) staining for cytokeratin is used to confirm the diagnosis of **Carcinomas**. **2. Analysis of Incorrect Options:** * **Vimentin:** This is the IF of **mesenchymal cells** [1]. It is found in fibroblasts, endothelial cells, and smooth muscle cells. It is a marker for **Sarcomas**. * **Desmin:** This is the IF specific to **muscle cells** (skeletal, cardiac, and smooth). It is used to identify tumors like rhabdomyosarcomas or leiomyosarcomas. * **Lamin:** Unlike the others which are cytoplasmic, **Nuclear Lamins** (A, B, and C) are found in the **nucleus** of almost all nucleated cells, forming the nuclear lamina just inside the nuclear envelope. **3. High-Yield Clinical Pearls for NEET-PG:** * **Glial Fibrillary Acidic Protein (GFAP):** The IF found in glial cells (astrocytes). It is the marker for **Astrocytomas/Glioblastomas**. * **Neurofilaments:** The IF found in **neurons** (axons and dendrites). * **Peripherin:** Found in peripheral nervous system neurons. * **Synaptophysin:** While not an IF, it is a high-yield marker for neuroendocrine tumors often tested alongside these filaments. * **Mallory Bodies:** These are eosinophilic cytoplasmic inclusions found in the liver (alcoholic hepatitis) composed of damaged **keratin (intermediate) filaments**.

Q: The juxtaglomerular apparatus is located in relation to which structure?

Glomerulus. **Explanation:** The **Juxtaglomerular Apparatus (JGA)** is a specialized structure formed by the distal part of the thick ascending limb of the loop of Henle (specifically the **Macula Densa**) coming into direct contact with the afferent and efferent arterioles of its parent nephron. This contact occurs at the **vascular pole of the Glomerulus**. Its primary function is to regulate blood pressure and the glomerular filtration rate (GFR) through the Renin-Angiotensin-Aldosterone System (RAAS) and tubuloglomerular feedback. **Why the other options are incorrect:** * **Proximal Convoluted Tubule (PCT):** The PCT is located at the urinary pole of the glomerulus, opposite to the JGA. It is primarily involved in bulk reabsorption, not autoregulation. * **Ascending/Descending Loop of Henle:** While the Macula Densa is technically the terminal part of the thick ascending limb, the JGA as a functional unit (comprising JG cells, Lacis cells, and Macula Densa) is defined by its anatomical relationship and physical proximity to the **Glomerulus** and its arterioles. **High-Yield NEET-PG Pearls:** 1. **Components of JGA:** * **Juxtaglomerular (JG) cells:** Modified smooth muscle cells in the *afferent arteriole* that act as baroreceptors and secrete **Renin**. * **Macula Densa:** Specialized cells in the distal tubule that act as **chemoreceptors** (sensing NaCl levels). * **Lacis Cells (Extraglomerular Mesangial cells):** Provide structural support and signaling. 2. **Function:** It is the site of **Tubuloglomerular Feedback (TGF)**—if NaCl at the macula densa increases, the JGA causes afferent arteriolar constriction to decrease GFR. 3. **Innervation:** JG cells are primarily innervated by **Sympathetic (Beta-1)** receptors, which stimulate renin release.

Q: What are the myelin-forming cells in the peripheral nervous system (PNS)?

Schwann cells. **Explanation:** The formation of the myelin sheath is a critical process for increasing the velocity of nerve impulse conduction (saltatory conduction). The specific cell responsible for this process depends entirely on the anatomical location of the nerve fiber [1]. **Why Schwann Cells are Correct:** In the **Peripheral Nervous System (PNS)**, which includes cranial and spinal nerves, **Schwann cells** are the sole producers of myelin. A unique characteristic of Schwann cells is that **one cell myelinates only one segment (internode) of a single axon** [1]. They also play a vital role in nerve regeneration following injury by forming the "Bands of Büngner" to guide axonal regrowth [2]. **Why Other Options are Incorrect:** * **Oligodendrocytes:** These are the myelinating cells of the **Central Nervous System (CNS)**—the brain and spinal cord [1]. Unlike Schwann cells, one oligodendrocyte can extend its processes to myelinate segments of **multiple axons** (up to 50) [1]. * **Both/None:** These are incorrect because the blood-brain barrier and the transition zone (Obersteiner-Redlich zone) strictly demarcate the territories of these two cell types. **High-Yield Clinical Pearls for NEET-PG:** 1. **Demyelinating Diseases:** **Multiple Sclerosis** affects the CNS (Oligodendrocytes), whereas **Guillain-Barré Syndrome (GBS)** affects the PNS (Schwann cells) [1]. 2. **Origin:** Schwann cells are derived from the **Neural Crest**, while Oligodendrocytes are derived from the **Neural Tube (Neuroectoderm)**. 3. **Acoustic Neuroma:** This is a tumor of Schwann cells (Schwannoma) typically affecting the vestibular nerve (CN VIII). 4. **Unmyelinated Fibers:** In the PNS, even unmyelinated fibers are enveloped by the cytoplasm of Schwann cells (Remak bundles), though no spiral myelin sheath is formed [1].

Q: G-cells are primarily located in which region of the stomach?

Pyloric antrum. The stomach is histologically divided into regions based on the predominant cell types and glandular structure. **G-cells** are specialized neuroendocrine cells responsible for secreting **gastrin**, a hormone that stimulates gastric acid secretion. [1] **1. Why Pyloric Antrum is Correct:** G-cells are primarily located within the **pyloric antrum** (and to a lesser extent, the duodenum) [1][2]. These cells are found in the gastric pits of the antral mucosa. They respond to mechanical distension, presence of amino acids/peptides, and vagal stimulation (via Gastrin-Releasing Peptide) to release gastrin into the bloodstream, which then acts on parietal cells in the body of the stomach [3]. **2. Why Other Options are Incorrect:** * **Fundus and Body:** These regions contain **oxyntic (gastric) glands**. These glands are rich in **Parietal cells** (secreting HCl and Intrinsic Factor) and **Chief cells** (secreting Pepsinogen) [2]. They do not contain G-cells. * **Cardia:** This region primarily contains mucus-secreting glands to protect the esophagus from reflux; it lacks a significant population of G-cells or parietal cells [2]. **3. High-Yield Clinical Pearls for NEET-PG:** * **D-cells:** Located in the antrum (and body), they secrete **Somatostatin**, which inhibits gastrin release (paracrine inhibition) [3]. * **Zollinger-Ellison Syndrome:** Caused by a gastrinoma (usually in the "Gastrinoma Triangle"), leading to hypergastrinemia and refractory peptic ulcers [4]. * **Pernicious Anemia:** Associated with atrophy of the fundus/body (loss of parietal cells), leading to secondary G-cell hyperplasia in the antrum due to loss of negative feedback from gastric acid [4]. * **H. pylori:** Often colonizes the antrum first, potentially leading to increased gastrin secretion and duodenal ulcers.

Q: What is true about the fallopian tube?

It is lined by ciliated epithelium.. The fallopian tube (uterine tube) is a muscular tube approximately 10 cm long that facilitates the transport of ova and sperm. [1] ### **Explanation of Options** * **Correct Answer (C):** The fallopian tube is lined by **simple columnar ciliated epithelium**. These cilia beat toward the uterus, creating a current that helps transport the ovum and zygote. [2] Interspersed among these are non-ciliated **Peg cells**, which provide nutrition to the gametes. * **Option A:** The fallopian tube **lacks a submucosa**. The mucosa (endometrium-like but thinner) sits directly on the muscularis layer. * **Option B:** The tube is highly **hormone-dependent**. Estrogen increases the height of the epithelium and the number of cilia, while progesterone increases the number of secretory Peg cells. * **Option D:** The fallopian tube lies in the **upper free margin of the broad ligament** (specifically the **mesosalpinx**), not the round ligament. [1] ### **High-Yield NEET-PG Clinical Pearls** 1. **Narrowest Part:** The **Interstitial (Intramural) part** is the narrowest segment (1 mm diameter). 2. **Widest Part:** The **Ampulla** is the widest and longest part; it is the most common site for **fertilization** and **ectopic pregnancy**. [2] 3. **Blood Supply:** It has a dual supply from both the **Uterine artery** (medial 2/3) and the **Ovarian artery** (lateral 1/3). [1] 4. **Lymphatic Drainage:** Lymph drains primarily into the **Para-aortic (Pre-aortic) nodes**, following the ovarian vessels. 5. **Kartagener Syndrome:** Patients with primary ciliary dyskinesia may face subfertility due to impaired tubal ciliary movement.

Question 1

Which one of the following statements concerning Loose Connective Tissue is true?

Accepted Answer

It acts as a medium for exchange of nutrients and wastes between the blood and tissues.

Answer

It is less abundant than Dense Connective Tissue.

Answer

It has a lower proportion of cells to fibers than does Dense Connective Tissue.

Answer

It provides structural support for organs.

Question 2

Which of the following is a holocrine gland?

Accepted Answer

Sebaceous gland

Answer

Sweat gland

Answer

Breast

Answer

Pancreas

Question 3

Which one of the following statements concerning liver sinusoids is true?

Accepted Answer

The space of Disse is located between sinusoidal cells and hepatocytes.

Answer

Their lining includes Ito cells.

Answer

They receive bile from the hepatocytes.

Answer

They are lined by fenestrated endothelial cells.

Question 4

The blood-air barrier consists of all of the following except?

Accepted Answer

Alveolar pores

Answer

A layer of surfactant

Answer

Type I alveolar cell cytoplasm

Answer

Fused basal lamina of alveolar and endothelial cells

Question 5

What are the intermediate filaments typically found in epithelial cells?

Accepted Answer

Keratin

Answer

Vimentin

Answer

Desmin

Answer

Lamin

Question 6

The juxtaglomerular apparatus is located in relation to which structure?

Accepted Answer

Glomerulus

Answer

Proximal convoluted tubule

Answer

Ascending loop of Henle

Answer

Descending loop of Henle

Question 7

What are the myelin-forming cells in the peripheral nervous system (PNS)?

Accepted Answer

Schwann cells

Answer

Oligodendrocytes

Answer

Both

Answer

None

Question 8

What does the Node of Ranvier represent?

Accepted Answer

A gap between two adjacent Schwann cells.

Answer

An indentation of a Schwann cell due to the synapsing of an adjacent unipolar neuron.

Answer

Gaps between dendrites and Schwann cells.

Answer

Gaps between the Schwann cell and the axon.

Question 9

G-cells are primarily located in which region of the stomach?

Accepted Answer

Pyloric antrum

Answer

Fundus

Answer

Cardia

Answer

Body

Question 10

What is true about the fallopian tube?

Accepted Answer

It is lined by ciliated epithelium.

Answer

It has a glandular submucosa.

Answer

It is independent of hormonal influence.

Answer

It lies in the round ligament.

Histology — MCQs

Histology — MCQs

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