Histology Practice Questions

Q: Thyroid follicles are lined by which type of epithelium?

Cuboidal. **Explanation:** The thyroid gland is composed of functional units called **thyroid follicles**. These follicles are typically lined by a **Simple Cuboidal Epithelium** (follicular cells) which rests on a basement membrane and surrounds a central lumen filled with colloid (thyroglobulin) [1], [2]. **Why Cuboidal is Correct:** The height of the follicular epithelium reflects the **functional state** of the gland. In a normal, euthyroid state, the cells are cuboidal [2]. However, this epithelium is unique because it is highly dynamic: * **Active State (TSH stimulation):** Cells become **Columnar** as they actively synthesize and secrete hormones [2]. * **Inactive/Resting State:** Cells become **Squamous** (flat) as the follicle distends with stored colloid. For examination purposes, the standard histological classification for the thyroid follicle is **Simple Cuboidal**. **Analysis of Incorrect Options:** * **A. Squamous:** Simple squamous epithelium lines structures requiring rapid diffusion (e.g., alveoli, endothelium). In the thyroid, it only indicates an inactive/hypofunctioning follicle. * **C. Transitional:** This is a specialized "stretchable" epithelium (urothelium) found exclusively in the urinary tract (e.g., bladder, ureters). * **D. None:** Incorrect, as the thyroid has a distinct epithelial lining. **High-Yield NEET-PG Pearls:** 1. **Parafollicular Cells (C-cells):** Located between follicles; they secrete **Calcitonin** and are derived from the **Ultimobranchial body** (Neural crest cells). 2. **Origin:** The thyroid gland is the first endocrine gland to develop (24th day) from the **endoderm** of the floor of the primitive pharynx [1]. 3. **Colloid Scalloping:** In Graves' disease (hyperthyroidism), the epithelium becomes tall columnar, and "scalloping" or "moth-eaten" edges are seen in the colloid due to rapid reabsorption.

Q: Stratum germinativum is synonymous to which layer of the epidermis?

Stratum Basale. The epidermis is a keratinized stratified squamous epithelium composed of five distinct layers [1]. The **Stratum Basale** (the deepest layer) is synonymous with **Stratum Germinativum** because it contains the mitotically active stem cells (keratinocytes) responsible for the continuous "germination" or regeneration of the skin [1]. These cells divide and migrate superficially to replenish the upper layers. **Analysis of Options:** * **Stratum Basale (Correct):** It consists of a single layer of columnar or cuboidal cells resting on the basement membrane [1]. It is the site of active cell division and contains melanocytes and Merkel cells [1]. * **Stratum Spinosum:** Also known as the "prickle cell layer" due to the prominent desmosomal attachments (nodes of Bizzozero) that appear as spines under microscopy. * **Stratum Granulosum:** Characterized by cells containing basophilic keratohyalin granules and lamellar bodies (Odland bodies), which provide the water-impermeable lipid barrier. * **Stratum Corneum:** The outermost layer consisting of dead, flattened, enucleated cells (corneocytes) filled with keratin [1]. **High-Yield NEET-PG Pearls:** 1. **Mnemonic for layers (Deep to Superficial):** **B**asale, **S**pinosum, **G**ranulosum, **L**ucidum, **C**orneum (**B**ritish **S**pies **G**et **L**ucky **C**harms). 2. **Stratum Lucidum:** A clear, translucent layer found **only in thick skin** (palms and soles). 3. **Clinical Correlation:** Psoriasis involves an accelerated cell cycle in the stratum germinativum, leading to a thickened epidermis (acanthosis) and retained nuclei in the stratum corneum (parakeratosis). 4. **Bullous Pemphigoid:** Targets hemidesmosomes, which anchor the stratum basale to the basement membrane.

Q: For the growth of bone, which term is most appropriate?

Apposition. **Explanation:** The growth of bone is a unique biological process because bone is a rigid, mineralized tissue that cannot expand from within. Therefore, bone growth occurs primarily through **Apposition** [1]. **1. Why Apposition is Correct:** Appositional growth refers to the addition of new bone layers onto existing surfaces (periosteal or endosteal). Since the calcified matrix of bone is inflexible, it cannot undergo "interstitial growth" (growth from within), which is seen in cartilage. Osteoblasts in the periosteum deposit new bone matrix (osteoid), which then mineralizes, increasing the thickness and diameter of the bone [2]. **2. Why Other Options are Incorrect:** * **Enlargement:** This is a general descriptive term for an increase in size but is not a specific histological or biological mechanism of tissue growth. * **Hyperplasia:** This refers to an increase in the *number* of cells in an organ or tissue. While cell division occurs in the osteogenic layer, the growth of the bone as a structural unit is defined by the deposition of the extracellular matrix, not just cell count [1]. * **Hypertrophy:** This refers to an increase in the *size* of individual cells. While chondrocytes undergo hypertrophy in the epiphyseal plate during endochondral ossification, the overall growth of the bone tissue itself is attributed to the accumulation of mineralized matrix [2]. **Clinical Pearls for NEET-PG:** * **Interstitial Growth:** Occurs only in **cartilage**, where the pliable matrix allows cells to divide and push apart from within. * **Remodeling:** Bone growth is always a balance between apposition (by osteoblasts) and resorption (by osteoclasts) [1]. * **Length vs. Width:** Bone increases in **length** via interstitial growth of cartilage at the epiphyseal plate (later replaced by bone), but it increases in **width/thickness** solely through appositional growth [2].

Q: The node of Ranvier is seen in which part of a neuron?

Axons. The **Node of Ranvier** is a specialized structural feature of the **Axon**. These are periodic gaps (approximately 1 μm wide) in the insulating myelin sheath where the axonal membrane is exposed to the extracellular space [1]. **Why Axons are correct:** Myelin is formed by Schwann cells (PNS) or Oligodendrocytes (CNS). It does not form a continuous sleeve; instead, it is interrupted at regular intervals [1]. These gaps (Nodes of Ranvier) contain a high density of voltage-gated sodium channels [1]. This arrangement allows for **Saltatory Conduction**, where the action potential "jumps" from one node to the next, significantly increasing the speed of nerve impulse transmission compared to unmyelinated fibers [1]. **Why other options are incorrect:** * **Cell body (Soma):** Contains the nucleus and organelles (Nissl bodies) for protein synthesis. It is never myelinated [1]. * **Dendrites:** These are receptive processes that carry impulses toward the cell body [1]. While they can be branched, they lack a myelin sheath and nodes of Ranvier. * **Terminal buttons (Axon terminals):** These are the distal ends of the axon that form synapses. At this point, the myelin sheath has already terminated to allow for neurotransmitter release [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Saltatory Conduction:** Energy efficient because the $Na^+/K^+$ ATPase pump only needs to work at the nodes to restore gradients. * **Demyelinating Diseases:** In **Multiple Sclerosis** (CNS) and **Guillain-Barré Syndrome** (PNS), the destruction of myelin disrupts the function of these nodes, leading to slowed or blocked conduction. * **Internode:** The myelinated segment between two nodes; its length is proportional to the axon diameter.

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

Sertoli cells. ### Explanation The correct answer is **C. Sertoli cells**. **Why Sertoli cells are the correct answer:** Sertoli cells are the "nurse cells" of the **male reproductive system**. They are located within the seminiferous tubules of the testes. Their primary functions include supporting spermatogenesis, forming the blood-testis barrier, and secreting Inhibin B and Anti-Müllerian Hormone (AMH). In female development, the absence of the SRY gene prevents the differentiation of primitive gonadal cords into Sertoli cells; instead, these cells differentiate into **Granulosa cells** in the ovary [1]. Therefore, Sertoli cells are never found in a normal ovary. **Analysis of incorrect options:** * **A. Primary follicle:** These are the basic units of the female reproductive biology, consisting of a primary oocyte surrounded by a single layer of cuboidal granulosa cells. They are found in the ovarian cortex [3]. * **B. Graafian follicle:** This is the mature, liquid-filled follicle that is ready for ovulation [3]. It is a hallmark structure of the functioning ovary during the reproductive years. * **D. Corpus luteum:** This is a temporary endocrine structure formed from the remains of the ovarian follicle after ovulation [2]. It secretes progesterone to maintain the uterine lining. **High-Yield NEET-PG Pearls:** * **Homologues:** Sertoli cells in males are embryologically homologous to **Granulosa cells** in females. Both are derived from the surface epithelium (coelomic epithelium) of the genital ridge [1]. * **Leydig cells** in males are homologous to **Theca cells** in females (both derived from mesenchyme). * **Tumor Marker:** Sertoli cells can be a component of "Sertoli-Leydig cell tumors," which are rare ovarian tumors that often cause virilization due to androgen production [4].

Q: Which is the strongest layer of the esophagus?

Submucosa. The **submucosa** is the strongest layer of the esophagus. Unlike most of the gastrointestinal tract where the muscularis propria provides significant structural integrity, the esophageal submucosa contains a dense network of collagenous and elastic fibers. This dense connective tissue provides the highest **tensile strength**, making it the "holding layer" for sutures during esophageal surgeries (e.g., esophagectomy or repair of perforations). **Analysis of Options:** * **Submucosa (Correct):** It is rich in elastic tissue and collagen, allowing the esophagus to distend during swallowing while maintaining structural integrity. It also houses the Meissner’s plexus and esophageal glands. * **Mucosa:** This is the innermost layer consisting of stratified squamous epithelium. While it provides a protective barrier against friction, it lacks mechanical strength. * **Muscularis propria:** While thick, this layer is composed of muscle fibers (striated in the upper third, smooth in the lower third) which are easily friable and do not hold sutures well compared to the submucosa. * **Adventitia:** The esophagus lacks a serosa (except for a small intra-abdominal segment). The adventitia is a loose connective tissue layer that facilitates movement but provides minimal structural strength. **Clinical Pearls for NEET-PG:** 1. **Surgical Holding Layer:** In any GI anastomosis, the submucosa is the most important layer to include in sutures to prevent dehiscence. 2. **Lack of Serosa:** The absence of a serosal layer in the esophagus is a high-yield fact; it explains why esophageal cancer spreads early to mediastinal structures and why anastomotic leaks are more common than in the intestines. 3. **Killian’s Dehiscence:** A weak area in the muscular wall between the thyropharyngeus and cricopharyngeus muscles, leading to Zenker’s diverticulum.

Q: Which of the following cells are holocrine cells in the given slide?

c. ***c*** - Represents **sebaceous gland cells** which exhibit **holocrine secretion**, where the entire cell disintegrates to release its contents as the secretory product. - These cells appear as **large, pale, foamy cells** in histological sections due to lipid accumulation before cell breakdown. *a* - Likely represents **sweat gland cells** which use **merocrine/eccrine secretion** through exocytosis. - The cell membrane remains intact during secretion, unlike holocrine cells that completely disintegrate. *b* - Probably shows **ductal epithelium** or other glandular cells that do not undergo holocrine secretion. - These cells maintain their **structural integrity** during the secretory process, contrasting with holocrine mechanism. *d* - Most likely represents **apocrine gland cells** found in axillary regions, which use **apocrine secretion**. - In apocrine secretion, only the **apical portion** of the cell is shed, not the entire cell as in holocrine secretion.

Q: What is true about the fallopian tube?

The lumen is lined by ciliated and peg cells.. The fallopian tube (uterine tube) is a vital structure for gamete transport and fertilization. Understanding its histological and anatomical features is high-yield for NEET-PG. ### **Explanation of Options** * **Option A (Correct):** The mucosal lining of the fallopian tube consists of **simple columnar epithelium** [2] composed of two distinct cell types: 1. **Ciliated cells:** These are most numerous in the infundibulum and ampulla. Their ciliary beat helps transport the ovum toward the uterus [2]. 2. **Peg cells (Non-ciliated cells):** These are secretory cells that provide nutrients and a protective environment for the spermatozoa and the developing zygote [2]. * **Option B (Incorrect):** The lining is **simple columnar**, not simple cuboidal. Simple cuboidal epithelium is typically found in the ovary (germinal epithelium) or renal tubules. * **Option C (Incorrect):** The fallopian tube has a well-developed muscularis layer (myosalpinx) consisting of an **inner circular** and an **outer longitudinal** layer of smooth muscle. These layers are essential for the peristaltic movements that assist in gamete transport. ### **High-Yield Clinical Pearls for NEET-PG** * **Site of Fertilization:** Occurs in the **Ampulla** (the widest and longest part). * **Ectopic Pregnancy:** The Ampulla is the most common site for tubal ectopic pregnancies [2]. * **Blood Supply:** Dual supply from both the **Uterine artery** (medial 2/3) and the **Ovarian artery** (lateral 1/3) [1]. * **Histological Change:** The height of the epithelium and the activity of the ciliated cells are **estrogen-dependent**, reaching their peak during ovulation. * **Narrowest Part:** The **Interstitial (Intramural) part** is the narrowest segment of the tube.

Question 1

Which of the following cells is the germ cell closest to the basal lamina in the seminiferous tubule?

Accepted Answer

Spermatogonia

Answer

Primary spermatocyte

Answer

Secondary spermatocyte

Answer

Spermatid

Question 2

Thyroid follicles are lined by which type of epithelium?

Accepted Answer

Cuboidal

Answer

Squamous

Answer

Transitional

Answer

None

Question 3

Stratum germinativum is synonymous to which layer of the epidermis?

Accepted Answer

Stratum Basale

Answer

Stratum Spinosum

Answer

Stratum granulosum

Answer

Stratum corneum

Question 4

For the growth of bone, which term is most appropriate?

Accepted Answer

Apposition

Answer

Enlargement

Answer

Hyperplasia

Answer

Hypertrophy

Question 5

The node of Ranvier is seen in which part of a neuron?

Accepted Answer

Axons

Answer

Cell body

Answer

Dendrites

Answer

Terminal buttons

Question 6

The ovary consists of all the following structures except:

Accepted Answer

Sertoli cells

Answer

Primary follicle

Answer

Graafian follicle

Answer

Corpus luteum

Question 7

Which is the strongest layer of the esophagus?

Accepted Answer

Submucosa

Answer

Mucosa

Answer

Muscularis propria

Answer

Adventitia

Question 8

Ocular basement membrane is stained by which of the following?

Accepted Answer

Periodic acid-Schiff

Answer

Alcian blue

Answer

Giemsa stain

Answer

Methylene blue

Question 9

Which of the following cells are holocrine cells in the given slide?

Accepted Answer

c

Answer

a

Answer

b

Answer

d

Question 10

What is true about the fallopian tube?

Accepted Answer

The lumen is lined by ciliated and peg cells.

Answer

The lumen is lined by simple cuboidal cells.

Answer

The outer muscle layer is not well developed.

Answer

All are true.

Histology — MCQs

Histology — MCQs

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