Histology Practice Questions

Q: The type of cartilage shown in the color plate is:

Hyaline cartilage. ***Hyaline cartilage*** - Characterized by a **homogeneous, glassy matrix** with evenly distributed **chondrocytes** in lacunae, appearing translucent under microscopy. - Most common type found in **articular surfaces**, **tracheal rings**, **costal cartilages**, and **nasal septum**. *Elastic cartilage* - Contains abundant **elastic fibers** in the matrix, giving it a yellowish appearance and greater flexibility. - Primarily found in the **external ear (auricle)**, **epiglottis**, and **auditory tube**, not matching typical hyaline cartilage locations. *Fibrocartilage* - Distinguished by dense bundles of **collagen fibers** arranged in parallel rows between chondrocytes. - Found in **intervertebral discs**, **menisci**, and **pubic symphysis** where tensile strength is required. *Mixed cartilage* - This is not a recognized histological classification of cartilage tissue. - Cartilage is categorized into only **three main types**: hyaline, elastic, and fibrocartilage based on matrix composition.

Q: Which of the following cells is NOT present in the parathyroid gland?

Parietal cells. The parathyroid gland is an endocrine organ responsible for calcium homeostasis [1]. To identify the correct answer, one must distinguish between the cellular components of the endocrine system and the gastrointestinal system. **Why Parietal Cells is the correct answer:** **Parietal cells** (also known as oxyntic cells) are located in the **gastric glands of the stomach**, not the parathyroid gland. Their primary function is the secretion of hydrochloric acid (HCl) and intrinsic factor. Confusingly, "oxyntic" sounds similar to "oxyphil," which is a common trap in histology questions. **Analysis of Incorrect Options:** * **Chief cells:** These are the most numerous cells in the parathyroid gland [1][2]. They are small, polygonal cells with central nuclei that secrete **Parathyroid Hormone (PTH)** in response to low serum calcium [3]. * **Oxyphil cells:** These are larger, acidophilic cells that appear after puberty [2]. They contain abundant mitochondria [1]. While their exact function is unclear, they increase in number with age [2]. * **Water-clear cells (Wasserhelle cells):** These are rare cells with abundant cytoplasmic glycogen, giving them a "clear" appearance [1]. They are considered a variant of chief cells and are often prominent in cases of parathyroid hyperplasia. **High-Yield Clinical Pearls for NEET-PG:** * **Embryology:** The superior parathyroids develop from the **4th pharyngeal pouch**, while the inferior parathyroids develop from the **3rd pharyngeal pouch** (along with the thymus). * **PTH Action:** PTH increases bone resorption, increases renal calcium reabsorption, and stimulates the synthesis of active Vitamin D (1,25-dihydroxycholecalciferol) in the kidneys [3]. * **Histology Tip:** If a question mentions "nests of cells" with "adipocytes" in an endocrine gland, think Parathyroid. In older adults, adipose tissue can make up to 50% of the gland [1].

Q: Fenestrated capillaries are present in which of the following locations?

Small intestine. **Explanation:** Capillaries are classified into three types based on the continuity of their endothelial lining and basal lamina. **Fenestrated capillaries** are characterized by the presence of small circular pores (fenestrae) in the endothelial cells, which are often covered by a thin diaphragm [1]. These allow for the rapid exchange of molecules and are found in tissues where high rates of filtration or absorption occur [1], [2]. **Why the Correct Answer is Right:** * **Small Intestine:** The primary function here is the absorption of nutrients from the lumen into the bloodstream. Fenestrated capillaries in the villi facilitate this rapid transport [1]. Other typical locations include the **Glomeruli of the kidney**, **Exocrine glands**, and **Endocrine glands** (for hormone release) [1]. **Why the Other Options are Incorrect:** * **Skin, Skeletal Muscle, and Brain (Options A, B, C):** These tissues contain **Continuous capillaries**. These are the most common type, featuring tight junctions and an uninterrupted endothelial lining [1]. * In the **Brain**, these continuous capillaries are further specialized with thick tight junctions to form the **Blood-Brain Barrier (BBB)** [3]. * In **Skin and Muscle**, they allow for regulated transport via pinocytotic vesicles. **High-Yield Clinical Pearls for NEET-PG:** 1. **Sinusoidal (Discontinuous) Capillaries:** These have large gaps and a discontinuous basement membrane. They are found in the **Liver, Spleen, and Bone Marrow** to allow the passage of whole cells and large proteins [1]. 2. **Mnemonic for Fenestrated:** "**P**ancreas, **I**ntestine, **K**idney, **E**ndocrine" (**PIKE**). 3. **Blood-Thymus Barrier:** Also utilizes continuous capillaries to prevent premature antigenic exposure to T-cells.

Q: Which of the following cellular structures is functionally equivalent to the rough endoplasmic reticulum?

Nissl bodies. **Explanation:** **Why Nissl bodies are the correct answer:** Nissl bodies (also known as Nissl substance or chromophilic substance) are large granular structures found in the cytoplasm of neurons. Ultrastructurally, they are composed of **rosettes of free ribosomes and stacks of Rough Endoplasmic Reticulum (RER)** [1]. Their primary function is protein synthesis, specifically for the production of neurotransmitters and structural proteins required for neuronal maintenance. Because they contain high concentrations of RNA, they stain intensely with basic dyes (like Cresyl violet or Methylene blue), a property known as basophilia. **Why the other options are incorrect:** * **Axon:** The axon is a long projection specialized for the conduction of nerve impulses [2]. Crucially, axons **lack Nissl bodies** and a Golgi apparatus. Therefore, they cannot synthesize proteins locally and must rely on axonal transport from the cell body (soma). * **Dendrites:** While dendrites do contain some Nissl bodies in their proximal segments (near the cell body) [2], they are primarily receptive structures. They are not "functionally equivalent" to the RER; rather, they are extensions of the cell that may contain some RER. * **All of the above:** This is incorrect because the presence of RER is highly localized within the neuron. **High-Yield Clinical Pearls for NEET-PG:** * **Axon Hillock:** This is the cone-shaped area where the axon leaves the cell body [2]. It is characterized by the **absence of Nissl bodies**, making it a key histological landmark. * **Chromatolysis:** When an axon is injured, the Nissl bodies disappear or disperse (undergo lysis) as the cell body shifts its metabolic activity to repair. This is a classic pathological finding. * **Location:** Nissl bodies are found in the **soma (cell body)** and **proximal dendrites**, but never in the axon or axon hillock [2].

Q: Schwann cells are supporting cells of:

Peripheral Nervous System (PNS). **Explanation:** The correct answer is **Peripheral Nervous System (PNS)**. Schwann cells are the primary glial cells of the PNS, derived from the **neural crest** [1]. Their fundamental role is to support both myelinated and unmyelinated nerve fibers [2]. In myelinated axons, a single Schwann cell wraps its plasma membrane repeatedly around a segment of one axon to form the myelin sheath, which facilitates rapid saltatory conduction [4]. **Analysis of Options:** * **A. Central Nervous System (CNS):** This is incorrect because the CNS (brain and spinal cord) utilizes **Oligodendrocytes** for myelination [2]. Unlike Schwann cells, one oligodendrocyte can myelinate segments of multiple different axons [1]. * **C. Autonomic Nervous System (ANS):** While Schwann cells do support autonomic fibers, the ANS is functionally a division that spans both the CNS and PNS [4]. However, anatomically, Schwann cells are defined specifically as the supporting cells of the **PNS**. * **D. All of the above:** Incorrect due to the distinct cellular localization of Schwann cells (PNS) versus Oligodendrocytes (CNS). **NEET-PG High-Yield Pearls:** * **Regeneration:** Schwann cells are vital for peripheral nerve regeneration [3]. They form **Bands of Büngner** to guide regrowing axons. * **Tumor Correlation:** **Schwannomas** (e.g., Acoustic Neuroma) and Neurofibromas originate from these cells. * **Clinical Sign:** In **Guillain-Barré Syndrome (GBS)**, there is an autoimmune destruction of Schwann cells, leading to peripheral demyelination. * **Key Difference:** Schwann cell = 1 cell per 1 axon segment; Oligodendrocyte = 1 cell per multiple axons [4].

Q: Lamin is present in:

Inner nuclear membrane.. Explanation: **Nuclear Lamins** are type V intermediate filament proteins that provide structural support to the cell nucleus [1]. They form a dense meshwork called the **nuclear lamina**, which is located specifically on the inner aspect of the **Inner Nuclear Membrane (INM)**. This lamina provides mechanical stability, organizes chromatin, and anchors nuclear pore complexes. **Analysis of Options:** * **Option B (Correct):** Lamins (Lamin A, B, and C) specifically localize to the inner face of the inner nuclear membrane [1]. They link the nuclear envelope to chromatin, maintaining the shape and integrity of the nucleus. * **Option A:** This is a common distractor. **Laminin** (a glycoprotein) is a major component of the **Basement Membrane**, whereas **Lamin** is an intermediate filament in the **Nucleus**. Do not confuse the two. * **Option C:** The outer nuclear membrane is continuous with the Rough Endoplasmic Reticulum (RER) and is studded with ribosomes; it does not contain a lamin meshwork. * **Option D:** Mitochondria have their own internal structure (cristae) and circular DNA but do not possess a nuclear lamina or lamin proteins. **High-Yield Clinical Pearls for NEET-PG:** 1. **Laminopathies:** Mutations in the *LMNA* gene (encoding Lamin A/C) lead to a group of disorders, most notably **Hutchinson-Gilford Progeria Syndrome** (premature aging) and Emery-Dreifuss muscular dystrophy. 2. **Cell Division:** During mitosis (prophase), lamins are **phosphorylated**, leading to the disassembly of the nuclear envelope. They are dephosphorylated during telophase to re-form the nucleus. 3. **Identification:** Remember: **Lamin** = Nucleus (Intermediate Filament); **Laminin** = Basement Membrane (Glycoprotein).

Q: Which of the following structures histologically shows Henle's and Huxley's layers?

Bulb of hair follicle. **Explanation:** The correct answer is **A. Bulb of hair follicle.** **Why it is correct:** The hair follicle is a complex structure derived from the invagination of the epidermis [1]. The **Inner Root Sheath (IRS)**, which surrounds the growing hair shaft, is composed of three distinct layers (from outermost to innermost): 1. **Henle’s layer:** A single layer of flattened cells (the outermost layer of the IRS). 2. **Huxley’s layer:** One or two layers of flattened or cuboidal cells containing trichohyalin granules. 3. **IRS Cuticle:** Overlaps with the cuticle of the hair shaft. These layers are most prominent in the lower portion of the hair follicle, specifically near the **bulb**. **Why the other options are incorrect:** * **B. Tongue:** Histologically characterized by stratified squamous epithelium (keratinized or non-keratinized), skeletal muscle fibers in three planes, and various types of papillae (filiform, fungiform, etc.), but no root sheath layers [3]. * **C. Salivary gland:** Composed of acini (serous, mucous, or mixed) and a ductal system (intercalated, striated, and excretory ducts). * **D. Sweat gland:** Consists of a secretory coil (simple cuboidal/columnar epithelium) and a duct (stratified cuboidal epithelium). **High-Yield Facts for NEET-PG:** * **Glassy Membrane:** The thickened basement membrane that separates the hair follicle from the surrounding dermis. * **Arrector Pili:** The smooth muscle responsible for "goosebumps," attached to the connective tissue sheath of the follicle [2]. * **Hair Matrix:** The actively proliferating area of the bulb where melanocytes provide pigment to the hair. * **Mnemonic:** Remember the IRS layers from outside to inside as **He-Hu-Cu** (Henle, Huxley, Cuticle).

Q: Which stain is used to detect myelin?

Luxol fast blue. Luxol Fast Blue is the gold-standard histological stain for visualizing **myelin** in the central and peripheral nervous systems [1]. The mechanism involves an acid-base ion exchange reaction where the copper phthalocyanine dye (LFB) binds to the **phospholipids** found in the myelin sheath. Under a microscope, myelinated fibers appear bright blue, while the background (neuropil) remains colorless or is counterstained pink with eosin or cresyl violet. **2. Why the other options are incorrect:** * **Methylene Blue:** This is a basic dye primarily used as a counterstain or to highlight nucleic acids (DNA/RNA). In neuroanatomy, it is often used to demonstrate **Nissl bodies** (rough endoplasmic reticulum) in the cell bodies of neurons, but it does not specifically target the lipid-rich myelin sheath. * **Options C & D:** Since LFB is specific for myelin and Methylene blue is not, these options are incorrect. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Demyelinating Diseases:** LFB is clinically significant in pathology for diagnosing conditions like **Multiple Sclerosis (MS)**, where "plaques" appear as areas of myelin loss (pale areas) against the blue-stained healthy tissue [1]. * **Other Myelin Stains:** Apart from LFB, **Weigert’s stain** and **Osmium tetroxide** (which turns lipids/myelin black) are also used to detect myelin [2]. * **Nissl Stains:** To visualize the cell body (soma), stains like **Cresyl Violet** or **Toluidine Blue** are used. * **Axon Stains:** Silver stains (e.g., **Bielschowsky’s** or **Bodians’s**) are preferred for visualizing the cytoskeleton of the axon itself.

Q: Which of the following is true about articular cartilage?

It is hyaline cartilage on the articular surface of bones.. **Explanation:** Articular cartilage is a specialized form of **hyaline cartilage** that covers the articulating surfaces of bones within synovial joints. Its primary function is to provide a smooth, lubricated surface for low-friction movement and to facilitate the transmission of loads to the underlying subchondral bone [1]. **Why Option B is correct:** Articular cartilage is histologically classified as hyaline cartilage. It is unique because it **lacks a perichondrium** (the fibrous connective tissue covering found in most other cartilages), which allows for a perfectly smooth surface but limits its regenerative capacity. **Analysis of Incorrect Options:** * **Option A:** Elastic cartilage contains elastic fibers (e.g., in the pinna and epiglottis). Articular cartilage does not contain elastic fibers; it is designed for load-bearing, not extreme flexibility. * **Option C:** Articular cartilage is primarily composed of **Type II collagen**, not Type I [1]. Type I collagen is characteristic of fibrocartilage (e.g., intervertebral discs) and bone. * **Option D:** While the growth plate (epiphyseal plate) is also made of hyaline cartilage, it is a temporary structure responsible for longitudinal bone growth, whereas articular cartilage is a permanent structure on the joint surface. **High-Yield Clinical Pearls for NEET-PG:** * **Composition:** 70-80% water, Type II collagen (10%), and Proteoglycans [1]. * **Nutrition:** Since it is avascular and lacks a perichondrium, it receives nutrition via **diffusion from the synovial fluid** (facilitated by the "pumping action" of joint movement) [1]. * **Osteoarthritis:** Characterized by the progressive loss and degradation of articular cartilage. * **Zones:** It is organized into four distinct histological zones: Superficial (Tangential), Intermediate (Transitional), Deep (Radial), and Calcified zone.

Q: Which of the following statements about osteoclasts is not true?

They stain strongly with alkaline phosphatase. The correct answer is **B**, as osteoclasts do not stain for alkaline phosphatase; instead, they are characterized by high levels of **Acid Phosphatase**, specifically the isoenzyme **Tartrate-Resistant Acid Phosphatase (TRAP)**. **Why Option B is the correct choice (False statement):** Alkaline phosphatase (ALP) is a marker of **osteoblast** activity (bone formation) [1]. Osteoclasts are bone-resorbing cells that function in an acidic environment to dissolve bone minerals. Therefore, they express TRAP, which serves as a definitive histological marker for identifying osteoclasts [2]. **Analysis of other options (True statements):** * **Option A:** Osteoclasts have **acidophilic (eosinophilic) cytoplasm** due to an abundance of lysosomes and mitochondria required for active transport and enzymatic degradation [2]. * **Option C:** The **ruffled border** consists of deep plasma membrane infoldings that increase surface area for proton pumps ($H^+$-ATPase) to acidify the resorption pit [2]. The **clear zone** (sealing zone) contains actin filaments that anchor the cell to the bone matrix, creating an isolated microenvironment for resorption [2]. * **Option D:** Osteoclasts reside in shallow enzymatic pits on the bone surface known as **Howship’s lacunae** [2]. **High-Yield NEET-PG Pearls:** * **Origin:** Osteoclasts are derived from the **Monocyte-Macrophage lineage** (GM-CFU), not osteoprogenitor cells. * **Regulation:** Stimulated by **RANKL** (secreted by osteoblasts) and inhibited by **Osteoprotegerin (OPG)** and **Calcitonin**. * **Clinical Correlation:** In **Osteopetrosis** (marble bone disease), osteoclast function is defective (often due to carbonic anhydrase II deficiency), leading to increased bone density but high fragility [3].

Question 1

The type of cartilage shown in the color plate is:

Accepted Answer

Hyaline cartilage

Answer

Elastic cartilage

Answer

Fibrocartilage

Answer

Mixed cartilage

Question 2

Which of the following cells is NOT present in the parathyroid gland?

Accepted Answer

Parietal cells

Answer

Chief cells

Answer

Oxyphil cells

Answer

Water-clear cells

Question 3

Fenestrated capillaries are present in which of the following locations?

Accepted Answer

Small intestine

Answer

Skin

Answer

Brain

Answer

Skeletal muscle

Question 4

Which of the following cellular structures is functionally equivalent to the rough endoplasmic reticulum?

Accepted Answer

Nissl bodies

Answer

Axon

Answer

Dendrites

Answer

All of the above

Question 5

Schwann cells are supporting cells of:

Accepted Answer

Peripheral Nervous System (PNS)

Answer

Central Nervous System (CNS)

Answer

Autonomic Nervous System (ANS)

Answer

All of the above

Question 6

Lamin is present in:

Accepted Answer

Inner nuclear membrane.

Answer

Basement membrane.

Answer

Outer nuclear membrane.

Answer

Mitochondria.

Question 7

Which of the following structures histologically shows Henle's and Huxley's layers?

Accepted Answer

Bulb of hair follicle

Answer

Tongue

Answer

Salivary gland

Answer

Sweat gland

Question 8

Which stain is used to detect myelin?

Accepted Answer

Luxol fast blue

Answer

Methylene blue

Answer

Both

Answer

None

Question 9

Which of the following is true about articular cartilage?

Accepted Answer

It is hyaline cartilage on the articular surface of bones.

Answer

It is a type of elastic cartilage.

Answer

It is type 1 cartilage providing compressive strength.

Answer

It is hyaline cartilage found in the growth plate of bones.

Question 10

Which of the following statements about osteoclasts is not true?

Accepted Answer

They stain strongly with alkaline phosphatase

Answer

They have acidophilic cytoplasm

Answer

The cytoplasmic surface that abuts the bone being resorbed is characterized by a clear zone and a ruffled border

Answer

They are found in Howship's lacunae

Histology — MCQs

Histology — MCQs

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