Histology Practice Questions

Q: Which one of the following statements about cilia is true?

They contain ciliary dynein arms.. ### Explanation **1. Why the Correct Answer is Right:** Cilia are motile, hair-like projections of the plasma membrane. The core of a motile cilium is the **axoneme**, which consists of a central pair of microtubules surrounded by nine peripheral doublets (**9 + 2 arrangement**) [2]. The movement of cilia is powered by **ciliary dynein arms** (adenosine triphosphatase/ATPase) [1]. These arms are attached to the 'A' microtubule of each doublet and reach out to the 'B' microtubule of the adjacent doublet, facilitating the sliding motion required for ciliary beating. **2. Analysis of Incorrect Options:** * **Option A:** Motile cilia have a **9 + 2** configuration [2]. A **9 + 0** configuration is characteristic of **primary (non-motile) cilia**, which lack the central pair and function as sensory receptors. * **Option B:** The **axoneme** is the structural backbone of the cilium; saying they do not contain one is anatomically incorrect. * **Option D:** Cilia are structurally distinct from centrioles. While the **basal body** (which anchors the cilium) has a 9 + 0 triplet arrangement similar to a centriole, the cilium itself has a doublet arrangement (9 + 2 or 9 + 0). **3. Clinical Pearls & High-Yield Facts:** * **Kartagener Syndrome:** A subset of Primary Ciliary Dyskinesia (PCD) caused by a **deficiency in dynein arms**. Clinical triad: *Situs inversus, chronic sinusitis, and bronchiectasis* [3]. * **Infertility:** Ciliary dysfunction leads to male infertility (immotile spermatozoa) and female subfertility (impaired ovum transport in fallopian tubes). * **Location:** Motile cilia are primarily found in the respiratory epithelium (mucociliary escalator) and the female reproductive tract [3].

Q: Myelin sheath is absent in which of the following?

Pre-axon. ### Explanation **1. Why "Pre-axon" is Correct:** The **pre-axon** (also known as the **axon hillock**) is the specialized part of the neuronal cell body (soma) where the axon originates. Myelination begins only after the initial segment of the axon [1]. The axon hillock and the initial segment are characterized by a high density of voltage-gated sodium channels to initiate action potentials [3], but they **lack a myelin sheath** and Nissl granules [2]. **2. Analysis of Incorrect Options:** * **Axons of the CNS:** These are myelinated by **Oligodendrocytes** [1]. While some CNS fibers are unmyelinated, the statement "myelin is absent" is factually incorrect as a general rule for CNS axons. * **Optic Nerve:** This is a unique "nerve" because it is embryologically an outgrowth of the diencephalon (CNS). Therefore, it is **heavily myelinated** by oligodendrocytes [2]. This is a classic exam trap; despite being called a "nerve," it follows CNS myelination patterns. * **Motor Roots:** These are part of the Peripheral Nervous System (PNS) and are **myelinated by Schwann cells** [4]. They require rapid conduction to innervate skeletal muscles [4]. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Myelinating Cells:** CNS = Oligodendrocytes (one cell myelination multiple segments); PNS = Schwann cells (one cell myelination one segment) [1], [2]. * **Nissl Granules:** Present in the dendrites and soma, but notably **absent in the axon hillock** and the axon itself [2]. * **Nodes of Ranvier:** These are the periodic gaps in the myelin sheath where saltatory conduction occurs [4]. * **Demyelinating Diseases:** Multiple Sclerosis affects CNS myelin (Oligodendrocytes), while Guillain-Barré Syndrome (GBS) affects PNS myelin (Schwann cells) [2].

Q: Intercalated discs are present in which type of muscle cell?

Cardiac myocytes. ### Explanation **Correct Answer: C. Cardiac myocytes** **Underlying Medical Concept:** Intercalated discs are specialized junctional complexes found exclusively in **cardiac muscle**. They represent the interface between adjacent cardiac myocytes and are essential for the heart to function as a **functional syncytium** [1]. These discs contain three types of cell-to-cell junctions: 1. **Fascia adherens:** Anchors actin filaments and transmits contractile forces. 2. **Desmosomes (Macula adherens):** Provide structural stability by preventing cells from pulling apart during contraction. 3. **Gap junctions:** Facilitate low-resistance electrical coupling, allowing rapid spread of action potentials across the myocardium [2]. **Analysis of Incorrect Options:** * **A. Smooth muscle cell:** These are non-striated, spindle-shaped cells. They lack intercalated discs and instead use **dense bodies** (analogous to Z-discs) and gap junctions for communication [3]. * **B. Skeletal muscle cell:** These are long, multinucleated cylinders. While they are striated, they lack intercalated discs because each fiber is an independent structural unit stimulated by a motor neuron [1]. * **C. Adipose tissue:** This is a connective tissue composed of adipocytes (fat cells) characterized by a "signet ring" appearance. It does not possess contractile properties or intercalated discs. **High-Yield Facts for NEET-PG:** * **Microscopic Appearance:** Intercalated discs appear as dark, transverse lines under light microscopy (H&E stain). * **Step-like Pattern:** They have a "staircase" appearance with transverse (horizontal) and longitudinal (vertical) components. * **Clinical Pearl:** Mutations in proteins of the intercalated disc (e.g., desmoplakin) are linked to **Arrhythmogenic Right Ventricular Dysplasia (ARVD)**, a common cause of sudden cardiac death in young athletes.

Q: Which of the following is not a component of the buffer system in embalming fluid?

Sodium chloride. ### Explanation **Concept Overview:** Embalming fluid is a complex mixture of preservatives, germicides, buffers, wetting agents, and dyes. The **buffer system** is critical because it maintains the pH of the fluid (ideally between 7.2 and 7.4). Maintaining an alkaline pH is essential to prevent the polymerization of formaldehyde and to ensure that the formaldehyde reacts optimally with tissue proteins to achieve preservation. **Why Sodium Chloride is the Correct Answer:** * **Sodium Chloride (NaCl):** This is an **osmotic agent** (crystalloid), not a buffer. It is added to embalming fluid to adjust the tonicity (osmolarity) of the solution. It helps in drawing excess fluid out of edematous tissues or maintaining osmotic balance to prevent tissue swelling [1]. It does not possess the chemical capacity to resist changes in pH. **Analysis of Incorrect Options (Buffers):** * **Sodium Borate (Borax):** A classic alkaline buffer used in embalming to stabilize the pH and reduce the hardening effect of aldehydes. * **Sodium Carbonate and Sodium Bicarbonate:** These are common inorganic salts used to maintain the alkalinity of the solution [2]. They prevent the solution from becoming too acidic, which would otherwise lead to "formaldehyde gray" (discoloration of the body). **High-Yield Facts for NEET-PG:** * **Primary Preservative:** Formalin (37%–40% solution of formaldehyde gas in water). * **Humectants:** Glycerin and Sorbitol (added to prevent excessive dehydration of the cadaver). * **Anticoagulants:** Sodium citrate and Sodium oxalate (used to prevent blood clotting, ensuring better fluid distribution). * **The "Buffer Goal":** Embalming fluid must be slightly alkaline to mimic physiological pH and ensure the best cosmetic result for the cadaver.

Q: Goblet cells are present in all of the following except?

Stomach. **Explanation:** The correct answer is **Stomach (Option D)**. Goblet cells are specialized unicellular glands that secrete mucin. While the stomach is lined by a mucus-secreting epithelium, it consists of **Simple Columnar Mucous Surface Cells**, not Goblet cells. The presence of Goblet cells in the stomach is a pathological finding known as **Intestinal Metaplasia**, often associated with chronic gastritis or *H. pylori* infection, which is a precursor to gastric adenocarcinoma. **Analysis of other options:** * **Small Intestine (Option A):** Goblet cells are abundant here, increasing in number from the duodenum to the ileum [1]. They provide lubrication and protect the lining from digestive enzymes. * **Large Intestine (Option B):** The density of Goblet cells is highest in the colon and rectum to facilitate the passage of increasingly solid fecal matter. * **Oesophagus (Option C):** While the normal esophagus is lined by non-keratinized stratified squamous epithelium (lacking Goblet cells), the question asks where they are *normally* present in the GI tract. However, in the context of NEET-PG, the stomach is the classic "except" answer because the stomach has its own unique secretory cells (Mucous Neck Cells). *Note: The presence of Goblet cells in the esophagus is the hallmark of Barrett’s Esophagus.* **High-Yield NEET-PG Pearls:** 1. **Staining:** Goblet cells stain positive with **PAS (Periodic Acid-Schiff)** and **Alcian Blue** due to their carbohydrate-rich mucin content. 2. **Respiratory System:** Goblet cells are also found in the trachea and bronchi but disappear at the level of the **Terminal Bronchioles**. 3. **Key Distinction:** The stomach secretes "visible mucus" (alkaline), whereas Goblet cells secrete "acidic mucin."

Q: Satellite bodies and acrocentric chromosomes are present in which chromosomal group?

Group D. ### Explanation Human chromosomes are classified into seven groups (**A to G**) based on their length and the position of the centromere (Denver Classification). **Why Group D is Correct:** Group D consists of chromosomes **13, 14, and 15**. These are **medium-sized acrocentric** chromosomes. Acrocentric chromosomes have centromeres located very near one end, resulting in one very short arm (p-arm) and one long arm (q-arm). The short arms of these chromosomes typically possess **satellites** (small masses of chromatin) attached by a thin filament called a secondary constriction. This region contains the Nucleolar Organizer Regions (NORs), which code for ribosomal RNA (rRNA). **Analysis of Incorrect Options:** * **Group A (1, 2, 3):** These are the largest chromosomes. 1 and 3 are metacentric, while 2 is submetacentric. They do not have satellites. * **Group B (4, 5):** These are large submetacentric chromosomes. * **Group C (6–12 and X):** These are medium-sized submetacentric chromosomes. * **Note on Group G (21, 22, and Y):** While Group G chromosomes (21 and 22) are also acrocentric and possess satellites, the question specifically targets the characteristics of Group D. In many contexts, both D and G are the "acrocentric groups." **High-Yield Clinical Pearls for NEET-PG:** * **Acrocentric Chromosomes:** In humans, these are **13, 14, 15 (Group D)** and **21, 22 (Group G)**. The Y chromosome is acrocentric but lacks satellites. * **Robertsonian Translocation:** This occurs specifically between acrocentric chromosomes (e.g., 14 and 21), which is a significant cause of familial Down Syndrome [1]. * **Satellites:** These are involved in the formation of the **nucleolus** during interphase. * **Denver Classification:** Group E (16-18), Group F (19-20).

Q: The definitive colour of the iris depends upon the:

Anterior limiting layer. The color of the iris is determined by the distribution and density of melanocytes within its layers, specifically the **Anterior Limiting Layer**. [1] ### Why the Anterior Limiting Layer is Correct The iris consists of several layers, but the **Anterior Limiting Layer** (a condensation of the stroma) is the primary determinant of definitive eye color. [1] While the number of melanocytes is relatively constant across individuals, the **amount of melanin pigment** within these cells in the anterior limiting layer varies. * **Brown eyes:** Result from a thick anterior limiting layer with heavy melanin deposition. * **Blue/Grey eyes:** Result from a thin layer with very little melanin; the color is produced by the "Tyndall effect" (scattering of light) as it reflects off the deeper pigmented layers. ### Why Other Options are Incorrect * **Stroma:** While the stroma contains melanocytes and blood vessels, it is the density of pigment in the *superficial* anterior limiting layer that dictates the final visible hue. * **Anterior & Posterior Pigmented Epithelium:** These layers (located posteriorly) are heavily pigmented in almost all individuals (except albinos) to prevent light from leaking through the iris. [1] They provide the "dark backdrop" but do not determine the specific color (blue vs. brown). ### High-Yield Clinical Pearls for NEET-PG * **Heterochromia Iridis:** A condition where the two irises are different colors, often seen in **Waardenburg Syndrome** or **Horner’s Syndrome** (congenital). * **Iris Muscles:** The **Sphincter pupillae** (parasympathetic; CN III) and **Dilator pupillae** (sympathetic; T1) are derived from **neuroectoderm**, making them unique among muscles. * **Albinism:** The lack of pigment in all layers, including the epithelium, causes the iris to appear pinkish due to visible blood vessels.

Q: Collagen present in skin is?

Type I. **Explanation:** The correct answer is **Type I Collagen**. Collagen is the most abundant protein in the human body, providing structural integrity to various tissues. **1. Why Type I is correct:** Type I collagen is the most prevalent type (constituting about 90% of the body's collagen). It forms thick, robust fibers that provide high tensile strength [1]. It is the primary structural component of the **dermis of the skin**, as well as **bone, tendons, ligaments, and cornea** [1]. In the skin, it provides the necessary resistance to stretching and tearing. **2. Why other options are incorrect:** * **Type II:** Found primarily in **cartilage** (hyaline and elastic) and the vitreous humor [1]. It forms thinner fibrils compared to Type I. (Mnemonic: "Type **Two** is for Car-**two**-lage"). * **Type IV:** This type does not form fibrils; instead, it forms a mesh-like network. It is a key component of the **Basal Lamina** (Basement membrane) and the lens capsule [2], [3]. * **Type V:** Typically found in the placenta, fetal membranes, and hair. It often co-distributes with Type I collagen to regulate fiber diameter. **High-Yield Clinical Pearls for NEET-PG:** * **Type III Collagen:** Also known as **Reticular fibers**. It is found in extensible organs like blood vessels, uterus, and during the early stages of **wound healing** (later replaced by Type I) [2]. * **Osteogenesis Imperfecta:** Caused by a defect in **Type I** collagen (presents with blue sclera and brittle bones) [1]. * **Alport Syndrome:** Caused by a defect in **Type IV** collagen (presents with nephritis and sensorineural deafness). * **Ehlers-Danlos Syndrome (Vascular type):** Associated with a deficiency in **Type III** collagen.

Question 1

Which one of the following statements about cilia is true?

Accepted Answer

They contain ciliary dynein arms.

Answer

They possess a 9 + 0 configuration of microtubules.

Answer

They do not contain an axoneme.

Answer

They are nearly identical to centrioles.

Question 2

Myelin sheath is absent in which of the following?

Accepted Answer

Pre-axon

Answer

Axons of the Central Nervous System (CNS)

Answer

Optic nerve

Answer

Motor roots

Question 3

Intercalated discs are present in which type of muscle cell?

Accepted Answer

Cardiac myocytes

Answer

Smooth muscle cell

Answer

Skeletal muscle cell

Answer

Adipose tissue

Question 4

Which of the following is not a component of the buffer system in embalming fluid?

Accepted Answer

Sodium chloride

Answer

Sodium borate

Answer

Sodium bicarbonate

Answer

Sodium carbonate

Question 5

Histologically, what classification does the internal thoracic artery fall under?

Accepted Answer

Large-sized artery

Answer

Medium-sized artery

Answer

Small-sized artery

Answer

Capillary

Question 6

Which of the following is present in cartilage but not in bone tissue?

Accepted Answer

Chondroitin sulfate

Answer

Type 1 collagen

Answer

Blood

Answer

Nerves

Question 7

Goblet cells are present in all of the following except?

Accepted Answer

Stomach

Answer

Small intestine

Answer

Large intestine

Answer

Oesophagus

Question 8

Satellite bodies and acrocentric chromosomes are present in which chromosomal group?

Accepted Answer

Group D

Answer

Group A

Answer

Group B

Answer

Group C

Question 9

The definitive colour of the iris depends upon the:

Accepted Answer

Anterior limiting layer

Answer

Stroma

Answer

Anterior pigmented epithelium

Answer

Posterior pigmented epithelium

Question 10

Collagen present in skin is?

Accepted Answer

Type I

Answer

Type II

Answer

Type IV

Answer

Type V

Histology — MCQs

Histology — MCQs

On this page

Practice by Chapter

Want unlimited practice?