Histology Practice Questions

Q: Which band in a sarcomere does not overlap with actin?

H band. ### Explanation The sarcomere is the functional unit of striated muscle, composed of thin (actin) and thick (myosin) filaments [1]. Understanding the spatial arrangement of these filaments is crucial for neuroanatomy and physiology. **Why H band is correct:** The **H band** (from the German *heller*, meaning brighter) is the central region of the **A band** [1]. It consists **exclusively of thick (myosin) filaments**. In a relaxed muscle, the thin actin filaments do not reach the center of the sarcomere, leaving this zone free of any actin overlap [1]. During muscle contraction (Sliding Filament Theory), the actin filaments slide toward the M-line, causing the H band to narrow or disappear [1]. **Why other options are incorrect:** * **A band (Anisotropic):** This represents the entire length of the thick filament. While it contains the H band, it also includes the **zone of overlap** where both actin and myosin filaments interdigitate [1]. Therefore, the A band as a whole *does* overlap with actin. * **I band (Isotropic):** This zone consists **exclusively of thin (actin) filaments** [1]. Since it is composed of actin, it cannot be described as "not overlapping" with itself; rather, it is the region where myosin is absent. **High-Yield NEET-PG Pearls:** * **Mnemonic (M-line):** The **M**-line is in the **M**iddle of the **H**-zone, which is in the **M**iddle of the **A**-band [1]. * **Contraction Dynamics:** During contraction, the **A band remains constant** in length, while the **I band and H zone shorten** [1]. * **Z-line:** Defines the boundaries of a single sarcomere; actin filaments are anchored here via the protein **alpha-actinin**. * **Titin:** The largest known protein, which anchors myosin to the Z-line, providing passive elasticity.

Q: What is the specific name for tissue macrophages?

Histiocytes. The correct answer is **B. Histiocytes**. **1. Why Histiocytes is Correct:** Macrophages are derived from circulating **monocytes** that migrate into various tissues [1]. Once these cells settle in connective tissue and mature, they are specifically referred to as **histiocytes**. They are part of the Mononuclear Phagocytic System (MPS) and function as professional phagocytes, clearing debris and acting as antigen-presenting cells (APCs). **2. Analysis of Incorrect Options:** * **A. Monocytes:** These are the precursor cells found in the **bloodstream** [1]. They only become macrophages/histiocytes after they extravasate into the tissues [2]. * **C. Plasma cells:** These are mature B-lymphocytes responsible for **antibody production**. They are characterized by a "clock-face" nucleus and a perinuclear halo (Golgi apparatus). * **D. Epithelioid cells:** These are **activated macrophages** that resemble epithelial cells (elongated with indistinct borders). They are a hallmark of granulomatous inflammation (e.g., Tuberculosis). **3. High-Yield Clinical Pearls for NEET-PG:** The Mononuclear Phagocytic System has specific names depending on the organ: * **Liver:** Kupffer cells [1] * **Lung:** Alveolar macrophages (Dust cells) [1] * **CNS:** Microglia (the only CNS cells of mesodermal origin) [1] * **Skin:** Langerhans cells * **Bone:** Osteoclasts * **Placenta:** Hofbauer cells * **Kidney:** Mesangial cells **Key Concept:** While "macrophage" is a general functional term, **"histiocyte"** is the specific histological term for these cells when located in stationary connective tissue.

Q: Type of collagen present in circumvallate sutures?

Type I. **Explanation:** The correct answer is **Type I Collagen**. **1. Why Type I is correct:** Sutures of the skull (including the circumvallate or coronal sutures) are classified as **syndesmoses**, which are fibrous joints. The primary tissue component of these sutures is **dense regular connective tissue**. Type I collagen is the hallmark of tissues that require high tensile strength, such as bone, tendons, ligaments, and the fibrous matrix of cranial sutures [2]. It provides the mechanical stability necessary to hold the cranial bones together while allowing for minor expansion during brain growth [1]. **2. Why the other options are incorrect:** * **Type II:** This is the primary collagen found in **hyaline and elastic cartilage** (e.g., articular surfaces, trachea) [4]. Sutures are fibrous, not cartilaginous. * **Type III:** Also known as **reticulin**, this forms a structural framework for soft organs like the liver, spleen, and lymph nodes. It is also prevalent in early wound healing (granulation tissue) but is not the dominant collagen in mature sutures. * **Type IV:** This is a non-fibrillar collagen that forms the **basal lamina** (base membrane) of epithelial cells [3]. It does not provide the structural bulk required for skeletal joints. **Clinical Pearls for NEET-PG:** * **Collagen Mnemonic:** "Be (I) So (II) Totally (III) Cool (IV)" → **I:** Bone/Tendon/Suture; **II:** Cartilage; **III:** Reticular fibers; **IV:** Basement membrane. * **Suture Development:** Sutures remain unossified during infancy [1] to allow for brain growth. Premature closure of these sutures is called **Craniosynostosis**. * **Osteogenesis Imperfecta:** This condition involves a defect in **Type I collagen** synthesis, often leading to "Wormian bones" (small intrasutural bones) within the cranial sutures.

Q: What filament is present in the H zone of a sarcomere?

Only myosin. **Explanation:** The sarcomere is the functional unit of a myofibril, extending between two adjacent Z-lines. To understand the **H zone**, one must visualize the arrangement of thick (myosin) and thin (actin) filaments [1]. 1. **Why Option A is Correct:** The **H zone** (from the German *Heller*, meaning brighter) is the central part of the **A band**. In a relaxed muscle, the thin actin filaments do not extend all the way to the center of the sarcomere. Therefore, the H zone consists **exclusively of thick myosin filaments** [1]. During muscle contraction (Sliding Filament Theory), actin filaments slide toward the M-line, causing the H zone to narrow or disappear [1]. 2. **Why Other Options are Incorrect:** * **Option B (Actin and Myosin):** This describes the peripheral parts of the **A band** (the zone of overlap). The H zone is specifically defined by the absence of actin [1]. * **Option C (Alpha actinin):** This protein is the major component of the **Z-line**, serving to anchor actin filaments. It is not found in the H zone. * **Option D:** Incorrect, as myosin is the definitive component. **High-Yield NEET-PG Pearls:** * **M-line:** The dark line in the center of the H zone where myosin filaments are anchored by the protein myomesin [1]. * **I-band:** Contains **only actin** (thin) filaments; it shortens during contraction [1]. * **A-band:** Contains the full length of myosin; its width **remains constant** during contraction [1]. * **Titin:** The largest known protein; it connects the Z-line to the M-line, acting as a molecular spring.

Q: Which of the following layers of the GIT is absent in the esophagus?

Serosa. The gastrointestinal tract (GIT) typically consists of four histological layers: Mucosa, Submucosa, Muscularis Propria, and Serosa. However, the esophagus is a unique exception in the thoracic cavity. [1] ### **Explanation of the Correct Answer** **D. Serosa:** Unlike the stomach and intestines, the esophagus lacks a true **serosa** (visceral peritoneum). Instead, it is covered by a layer of loose connective tissue called the **adventitia**. The adventitia anchors the esophagus to surrounding structures in the mediastinum (like the trachea and aorta). Because it lacks a tough serosal layer, esophageal cancers tend to spread more easily into the mediastinum, and surgical anastomoses are more prone to leakage. [1] ### **Why Other Options are Incorrect** * **A. Mucosa:** The esophagus has a well-developed mucosa lined by **non-keratinized stratified squamous epithelium** to protect against mechanical abrasion from food boluses. * **B. Muscularis propria:** This layer is essential for peristalsis. In the esophagus, it is unique because the upper 1/3 is skeletal muscle, the middle 1/3 is mixed, and the lower 1/3 is smooth muscle. * **C. Submucosa:** This layer contains the **Meissner’s plexus** and esophageal glands that secrete mucus for lubrication. ### **High-Yield Clinical Pearls for NEET-PG** * **Surgical Significance:** The absence of serosa is the primary reason why the esophagus is the most difficult part of the GIT to suture and why it has a high rate of anastomotic breakdown. * **Epithelial Transition:** The abrupt change from stratified squamous epithelium (esophagus) to simple columnar epithelium (stomach) occurs at the **Z-line**. * **Barrett’s Esophagus:** Chronic acid reflux causes metaplasia, changing the squamous lining to columnar epithelium (goblet cells).

Q: Where are Meissner's plexuses located?

Submucosa. **Explanation:** The Enteric Nervous System (ENS) is composed of two primary plexuses that coordinate the gastrointestinal tract's functions. **1. Why Submucosa is correct:** **Meissner’s plexus** (also known as the **Submucosal plexus**) is located specifically within the **submucosa** of the intestinal wall [3]. Its primary physiological role is to regulate local secretions (mucus and enzymes), absorption, and local blood flow. It is most prominent in the small and large intestines but is sparse or absent in the esophagus and stomach. **2. Why other options are incorrect:** * **Mucosa:** While the mucosa contains sensory nerve endings [1], it does not house the organized ganglionated plexus known as Meissner’s. * **Muscularis layer:** This layer contains the **Auerbach’s plexus** (Myenteric plexus), located between the inner circular and outer longitudinal muscle layers [2], [3]. Auerbach’s plexus primarily regulates GI motility (peristalsis) [2]. * **Serosa:** This is the outermost epithelial layer and does not contain an intrinsic nervous plexus. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Origin:** Both Meissner’s and Auerbach’s plexuses are derived from **Neural Crest Cells**. * **Hirschsprung Disease:** This condition results from the failure of neural crest cells to migrate, leading to a **congenital absence** of both Meissner’s and Auerbach’s plexuses in the distal colon (aganglionic segment), causing severe constipation and megacolon. * **Mnemonic:** **M**eissner’s = **M**ucosal secretions/Submucosa; **A**uerbach’s = **A**ction (Motility)/Between muscle layers.

Q: Which of the following is NOT a feature of neuroglia cells?

Central neuroglial cells are derived from Schwann cells.. ### Explanation **1. Why Option D is the Correct Answer (The False Statement):** In the nervous system, there is a clear distinction between the origins of central and peripheral glia. **Central neuroglial cells** (astrocytes, oligodendrocytes, and ependymal cells) are derived from the **neuroectoderm** (specifically the neural tube). In contrast, **Schwann cells** [3] are derived from the **neural crest** and are responsible for myelination in the Peripheral Nervous System (PNS). Therefore, central neuroglia are not derived from Schwann cells; rather, they share a common embryonic origin with neurons of the CNS. **2. Analysis of Other Options:** * **Option A:** Astrocytes are classified into two types: **Protoplasmic astrocytes** (found primarily in the **grey matter** with thick, short processes) and **Fibrous astrocytes** (found in the **white matter** with thin, long processes). * **Option B:** Oligodendrocytes, like most CNS cells, originate from the **neuroectoderm** of the neural tube [1]. They are the myelin-forming cells of the CNS [2]. * **Option C:** **Microglia** are the "odd ones out." They are the resident macrophages of the CNS and are derived from **mesoderm** (specifically yolk sac progenitors), unlike other neuroglia which are ectodermal [1]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Origin Rule:** All CNS cells are Ectodermal EXCEPT **Microglia** (Mesodermal) and **Blood vessels** [1]. * **Myelination:** One **Oligodendrocyte** can myelinate multiple axons (CNS), whereas one **Schwann cell** myelinates only one segment of a single axon (PNS) [2], [4]. * **Blood-Brain Barrier (BBB):** Protoplasmic astrocytes contribute to the BBB via their "perivascular feet." * **Tumor Marker:** **GFAP** (Glial Fibrillary Acidic Protein) is a high-yield marker for identifying tumors of astrocytic origin (Astrocytomas).

Q: Which type of epithelium is present in the oesophagus?

Oesophagus. The lining of the gastrointestinal tract and respiratory system varies based on the physiological function of the specific organ. The **oesophagus** is primarily a conduit for food, subjected to significant mechanical friction during swallowing [1]. To withstand this "wear and tear," it is lined by **Non-keratinized Stratified Squamous Epithelium**. **Analysis of Options:** * **Oesophagus (Correct):** The stratified nature (multiple layers) provides protection against abrasion from boluses of food. Unlike the skin, it remains moist and lacks a keratin layer. * **Skin (Incorrect):** The skin is lined by **Keratinized Stratified Squamous Epithelium**. The presence of keratin provides a waterproof barrier and protection against desiccation, which is unnecessary in the moist environment of the oesophagus. * **Ileum (Incorrect):** The small intestine requires a high surface area for nutrient absorption. It is lined by **Simple Columnar Epithelium** with microvilli (brush border) and goblet cells. * **Alveolus (Incorrect):** To facilitate rapid gas exchange via diffusion, the alveoli are lined by **Simple Squamous Epithelium** (Type I pneumocytes), which is the thinnest possible cellular barrier. **High-Yield Clinical Pearls for NEET-PG:** * **Barrett’s Oesophagus:** Chronic gastroesophageal reflux (GERD) can cause **metaplasia**, where the normal stratified squamous epithelium of the lower oesophagus changes to **simple columnar epithelium** (intestinal metaplasia). This is a premalignant condition. * **Transition Point:** The abrupt change from stratified squamous (oesophagus) to simple columnar (stomach) occurs at the **Z-line** (Gastroesophageal junction) [1]. * **Cancer Correlation:** Squamous cell carcinoma is the most common oesophageal cancer globally, while Adenocarcinoma (arising from Barrett’s) is increasing in Western populations.

Q: Mucin is not secreted by which of the following cells/structures?

Paneth cell. The core of this question lies in distinguishing between the secretory products of various cells in the gastrointestinal tract. **Mucin** is a high-molecular-weight glycoprotein that forms protective mucus, whereas **Paneth cells** are specialized for innate immunity and antimicrobial defense [1]. **1. Why Paneth cell is the correct answer:** Paneth cells, located at the base of the Crypts of Lieberkühn (primarily in the small intestine), are characterized by large, eosinophilic apical granules [1]. Their primary function is the secretion of antimicrobial substances such as **Lysozyme**, **Alpha-defensins (cryptidins)**, and **Zinc**. They do not produce mucin. **2. Analysis of incorrect options:** * **Goblet cells:** These are unicellular glands found throughout the GI and respiratory tracts specifically designed to synthesize and secrete **mucin** to lubricate and protect the epithelial surface [1]. * **Brunner’s glands:** Located in the submucosa of the **duodenum**, these glands secrete an alkaline fluid rich in **mucin** and bicarbonate to neutralize acidic chyme from the stomach. * **Crypts of Lieberkühn:** These are simple tubular glands found in the intestinal mucosa [1]. While they contain various cell types, they house numerous **Goblet cells** that actively secrete mucin into the intestinal lumen. **High-Yield Clinical Pearls for NEET-PG:** * **Paneth Cells:** They are a key marker of the small intestine; their presence in the stomach or distal colon is usually a sign of **metaplasia** (e.g., in Barrett’s esophagus or Inflammatory Bowel Disease). * **Staining:** Mucin is best visualized using **PAS (Periodic Acid-Schiff)** or **Alcian Blue** stains. * **Brunner’s Glands:** They are the distinguishing histological feature of the **duodenum** (submucosal glands).

Question 1

Which band in a sarcomere does not overlap with actin?

Accepted Answer

H band

Answer

I band

Answer

A band

Answer

All of the above

Question 2

What is the specific name for tissue macrophages?

Accepted Answer

Histiocytes

Answer

Monocytes

Answer

Plasma cells

Answer

Epithelioid cells

Question 3

Type of collagen present in circumvallate sutures?

Accepted Answer

Type I

Answer

Type II

Answer

Type III

Answer

Type IV

Question 4

What filament is present in the H zone of a sarcomere?

Accepted Answer

Only myosin

Answer

Actin and myosin

Answer

Alpha actinin

Answer

None of the above

Question 5

What describes the anal transition zone?

Accepted Answer

Columnar - cuboidal - squamous

Answer

Columnar - squamous - cuboidal

Answer

Squamous - cuboidal - columnar

Answer

Cuboidal - squamous - columnar

Question 6

Which of the following layers of the GIT is absent in the esophagus?

Accepted Answer

Serosa

Answer

Mucosa

Answer

Muscularis propria

Answer

Submucosa

Question 7

Where are Meissner's plexuses located?

Accepted Answer

Submucosa

Answer

Mucosa

Answer

Muscularis layer

Answer

Serosa

Question 8

Which of the following is NOT a feature of neuroglia cells?

Accepted Answer

Central neuroglial cells are derived from Schwann cells.

Answer

Protoplasmic astrocytes are found in grey matter.

Answer

Oligodendrocytes are derived from ectoderm.

Answer

Microglia are mesodermal in origin.

Question 9

Which type of epithelium is present in the oesophagus?

Accepted Answer

Oesophagus

Answer

Skin

Answer

Ileum

Answer

Alveolus

Question 10

Mucin is not secreted by which of the following cells/structures?

Accepted Answer

Paneth cell

Answer

Goblet cell

Answer

Brunner's gland

Answer

Crypts of Lieberkuhn

Histology — MCQs

Histology — MCQs

On this page

Practice by Chapter

Want unlimited practice?