Histology Practice Questions

Q: Barr body was first detected in:

Brain. ***Brain*** - The **Barr body** (sex chromatin) was first discovered by **Murray Barr and Ewart Bertram in 1949** in the **neurons of cats**. - This historical discovery was made while studying **nerve cells**, where they observed a distinct chromatin mass at the periphery of the nucleus in female cells. - The structure was later identified as the **inactive X chromosome** and named after its discoverer. *Buccal mucosa* - While buccal mucosa became the **most popular site for clinical sex chromatin testing** due to its **easy accessibility** and non-invasive collection method, it was **not** the site of original discovery. - Buccal smears became widely used for **routine screening** and sex determination, but this was **after** the initial discovery in neurons. *Skin* - Skin cells do contain Barr bodies in females, but they were neither the site of first detection nor commonly used for sex chromatin analysis. - Skin biopsies are **more invasive** than buccal swabs, making them less practical for routine testing. *Liver* - Liver cells are nucleated and can show Barr bodies, but they were not involved in the **historical first detection** of sex chromatin. - Liver tissue is **difficult to access** and not suitable for routine cytogenetic screening.

Q: Cells as they approach towards stratum corneum show the following features

All of the options. ***All of the options*** - As **keratinocytes** differentiate and migrate towards the **stratum corneum**, they undergo a programmed process of maturation and senescence. - This process involves the loss of the nucleus, flattening and dehydration of cells, and significant reduction in mitotic and metabolic activity, all contributing to the protective barrier function of the skin. *Nucleus lost* - The loss of the nucleus is a characteristic feature of **terminal differentiation** of keratinocytes, particularly when they reach the **stratum granulosum** and eventually the stratum corneum. - This anucleated state allows for the formation of a dense, protective layer of **keratin**. *Cells become flat and dehydrated* - As keratinocytes move upwards, they accumulate **keratin filaments** and lose water content, leading to their characteristic flattened and desiccated appearance in the outer layers of the epidermis. - This structural change is crucial for forming a tight, waterproof barrier. *Loss of mitotic and metabolic activity* - Cells in the **stratum corneum** are essentially dead cells, having lost their capacity for division (mitotic activity) and most metabolic processes. - Their primary role shifts from active cellular functions to providing a **physical and chemical barrier**.

Q: Which of the following site doesn't contain brown adipose tissues?

Scapula. ***Scapula*** - While brown adipose tissue (BAT) is strategically located for **thermoregulation**, it is not typically found directly within the **scapular bone** itself. - BAT is primarily found in soft tissue depots around the shoulder girdle, but not as part of the bone structure. *Subcutaneous tissue* - **Brown adipose tissue** is present in the subcutaneous layers, particularly in neonates and to some extent in adults, where it contributes to **non-shivering thermogenesis**. - These subcutaneous depots are crucial for maintaining **body temperature** in colder environments. *Around blood vessel* - BAT is often found in close proximity to **large blood vessels**, such as in the neck and mediastinum. - This strategic location allows for efficient transfer of heat generated by BAT directly into the **circulatory system**, warming the blood. *Around adrenal cortex* - Significant deposits of **brown adipose tissue** are found in perirenal areas, including around the **adrenal glands**. - This location is important for **local heat production** and protection of vital organs.

Q: Which of the following statements is TRUE about osteoblasts and chondroblasts?

Derived from mesenchymal stem cells.. ***Derived from mesenchymal stem cells*** - Both **osteoblasts** (bone-forming cells) and **chondroblasts** (cartilage-forming cells) originate from **mesenchymal stem cells**, which are multipotent stromal cells [2]. - These stem cells can differentiate into various connective tissue cells, including those responsible for building bone and cartilage [3]. *Osteoblasts and chondroblasts are terminally differentiated cells.* - Osteoblasts can further differentiate into **osteocytes** once they become embedded in the bone matrix, while chondroblasts can mature into **chondrocytes** [1]. - While they undergo differentiation, the term "terminally differentiated" usually implies a cell that has reached its final development stage and cannot differentiate further, which is not entirely accurate for osteoblasts before becoming osteocytes. *Osteoblasts and chondroblasts communicate via gap junctions.* - **Osteocytes**, not osteoblasts, communicate via **gap junctions** through their cytoplasmic processes within the bone matrix. - Chondrocytes (mature chondroblasts) in cartilage are generally isolated within the matrix and do not extensively form gap junctions for direct cell-to-cell communication. *Osteoblasts and chondroblasts are both found in lacunae.* - **Chondrocytes** (mature chondroblasts) are typically found in **lacunae** within the cartilage matrix. - **Osteocytes** (mature osteoblasts) are found in lacunae within the bone matrix, but **osteoblasts** themselves are typically found on the surface of developing bone, laying down new matrix, not within lacunae [1].

Q: Space of Disse is seen in

Liver. ***Liver*** - The **Space of Disse**, also known as the perisinusoidal space, is a crucial area located between the **endothelial cells** of the liver sinusoids and the **hepatocytes** [1]. - This space is vital for the exchange of plasma constituents between blood and hepatocytes, containing **hepatic stellate cells (Ito cells)** that store vitamin A and can become fibrogenic in liver injury [1]. *Spleen* - The spleen is characterized by **red pulp** (involved in filtering blood) and **white pulp** (involved in immune responses), without a structure analogous to the Space of Disse. - It contains **splenic cords (cords of Billroth)** and **splenic sinusoids**, which are structurally distinct from the liver's perisinusoidal space. *Kidney* - The kidney's filtering units are **nephrons**, comprising **glomeruli** and **renal tubules**, neither of which feature a Space of Disse. - The kidney has specialized structures like the **Bowman's capsule** and the **juxtaglomerular apparatus** for filtration and regulation, which serve entirely different functions. *Small intestine* - The small intestine is lined with **villi** and **crypts of Lieberkühn**, which are epithelial structures designed for nutrient absorption. - It contains specialized cells like **enterocytes**, **goblet cells**, and **Paneth cells**, but lacks the unique perisinusoidal space found in the liver.

Q: Stem cells in skin are found in all, EXCEPT:

Stratum corneum. ***Stratum corneum*** - The **stratum corneum** is the outermost layer of the epidermis consisting of **dead, anucleated keratinocytes** (corneocytes) that have undergone terminal differentiation [1]. - This layer contains **no viable cells** and therefore **no stem cells**, as it is composed entirely of flattened, keratinized cells that serve as a protective barrier [1]. - Stem cells require viable cellular machinery for self-renewal and differentiation, which is absent in this dead layer. *Hair follicle* - The **hair follicle bulge** region contains a population of multipotent **stem cells** responsible for hair regeneration and contributing to epidermal repair [1]. - These stem cells can differentiate into various cell types, including keratinocytes, sebocytes, and pigment cells [1]. *Sebaceous glands* - **Stem cells** are located in the **basal layer of sebaceous glands** and contribute to the maintenance and repair of the gland [1]. - These cells facilitate the continuous production of sebum and the structural integrity of the gland. *Sweat glands* - **Stem cells** are present in the **sweat glands**, particularly in the ductal regions, and play a role in the regeneration and repair of this glandular tissue [1]. - They are important for maintaining the function of eccrine and apocrine glands [1].

Q: In articular cartilage, most active chondrocytes are seen in ?

Zone 2. ***Zone 2*** - The **transitional zone (Zone 2)** contains chondrocytes that are more metabolically active and contribute significantly to **collagen and proteoglycan synthesis**. [1] - These chondrocytes are typically **larger and more rounded** than those in the superficial layer and are organized in columns. *Zone 1* - **Zone 1 (superficial or tangential zone)** consists of **flattened chondrocytes** that are metabolically less active. - Its primary role is to resist **shear forces** and reduce friction. [1] *Zone 4* - **Zone 4 (calcified zone)** is the deepest layer of articular cartilage, characterized by **chondrocytes embedded in a calcified matrix**. - This zone anchors the cartilage to the subchondral bone and has **minimal metabolic activity**. *Zone 3* - **Zone 3 (deep or radial zone)** has chondrocytes arranged in **columns perpendicular to the articular surface**. [1] - While active in matrix production, their activity is generally **less pronounced** compared to the transitional zone.

Q: At which of the following sites do osteoclasts remove bone?

Both Howship's lacunae and resorption bays.. ***Both Howship's lacunae and resorption bays.*** - **Howship's lacunae** and **resorption bays** are **synonymous terms** referring to the same anatomical structures - These are the **characteristic shallow depressions or pits** on bone surfaces where osteoclasts attach via their ruffled border and actively resorb bone [1] - Osteoclasts create an acidic microenvironment in these lacunae that dissolves the mineral matrix, followed by enzymatic digestion of the organic matrix [1] - Both terms are used interchangeably in histology and pathology to describe these sites of active bone resorption *Howship's lacunae* - This is an **incomplete answer** - while Howship's lacunae are indeed sites where osteoclasts remove bone, this option ignores that resorption bays refer to the same structures - Selecting only one term when both are synonymous makes this answer **technically incomplete** *Resorption bays* - This is also an **incomplete answer** - resorption bays are correct sites of osteoclastic bone resorption, but this option excludes the more commonly used term Howship's lacunae - Since both terms describe identical structures, this answer is **incomplete** *Neither Howship's lacunae nor resorption bays.* - This is **completely incorrect** - both terms specifically describe the anatomical sites where osteoclasts perform bone resorption - These lacunae/bays are the **definitive histological markers** of osteoclastic activity and bone remodeling **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1182-1184.

Q: Desmosomes are helpful in connecting -

Keratinocytes. ***Keratinocytes*** - **Desmosomes** are specialized cell junctions that provide strong adhesion between adjacent cells, particularly abundant in tissues subject to mechanical stress like the **epidermis** [1]. - They link the **intermediate filaments** (keratin in keratinocytes) of neighboring cells, forming a robust network that resists pulling forces. *Langerhans cells* - **Langerhans cells** are antigen-presenting cells found in the epidermis, but they do not form extensive desmosomal connections with keratinocytes or other cells [1]. - They are primarily involved in immune surveillance and can migrate within the epidermis [1]. *Dermis and epidermis* - The connection between the **dermis and epidermis** is primarily mediated by the **basement membrane**, involving structures like **hemidesmosomes** and anchoring fibrils, not desmosomes between cells. - Hemidesmosomes connect basal keratinocytes to the basement membrane, while desmosomes connect keratinocytes to each other. *Melanocytes* - **Melanocytes** are pigment-producing cells located in the basal layer of the epidermis [1]. - While they are in close proximity to keratinocytes, they do not form significant desmosomal junctions with them; they primarily interact through dendrites that transfer melanin [1].

Q: In the electron micrograph, the arrow indicates small, membrane-bound, electron-dense granules clustered near the plasma membrane of a secretory cell. These granules store products before their release by exocytosis. What are they?

Secretory vesicles. Secretory vesicles are membrane-bound granules that store hormones, enzymes, or other products and release them when they fuse with the plasma membrane during exocytosis. Golgi cisternae appear as stacks of flattened membranes, mitochondria have cristae, and rough endoplasmic reticulum consists of ribosome-studded membrane cisternae.

Question 1

Barr body was first detected in:

Accepted Answer

Brain

Answer

Liver

Answer

Skin

Answer

Buccal mucosa

Question 2

Cells as they approach towards stratum corneum show the following features

Accepted Answer

All of the options

Answer

Nucleus lost

Answer

Cells become flat and dehydrated

Answer

Loss of mitotic and metabolic activity

Question 3

Which of the following site doesn't contain brown adipose tissues?

Accepted Answer

Scapula

Answer

Subcutaneous tissue

Answer

Around blood vessel

Answer

Around adrenal cortex

Question 4

Which of the following statements is TRUE about osteoblasts and chondroblasts?

Accepted Answer

Derived from mesenchymal stem cells.

Answer

Osteoblasts and chondroblasts are terminally differentiated cells.

Answer

Osteoblasts and chondroblasts communicate via gap junctions.

Answer

Osteoblasts and chondroblasts are both found in lacunae.

Question 5

Space of Disse is seen in

Accepted Answer

Liver

Answer

Spleen

Answer

Kidney

Answer

Small intestine

Question 6

Stem cells in skin are found in all, EXCEPT:

Accepted Answer

Stratum corneum

Answer

Hair follicle

Answer

Sebaceous glands

Answer

Sweat glands

Question 7

In articular cartilage, most active chondrocytes are seen in ?

Accepted Answer

Zone 2

Answer

Zone 1

Answer

Zone 4

Answer

Zone 3

Question 8

At which of the following sites do osteoclasts remove bone?

Accepted Answer

Both Howship's lacunae and resorption bays.

Answer

Howship's lacunae

Answer

Resorption bays

Answer

Neither Howship's lacunae nor resorption bays.

Question 9

Desmosomes are helpful in connecting -

Accepted Answer

Keratinocytes

Answer

Langerhans cells

Answer

Dermis and epidermis

Answer

Melanocytes

Question 10

In the electron micrograph, the arrow indicates small, membrane-bound, electron-dense granules clustered near the plasma membrane of a secretory cell. These granules store products before their release by exocytosis. What are they?

Accepted Answer

Secretory vesicles

Answer

Golgi cisternae

Answer

Mitochondria

Answer

Rough endoplasmic reticulum

Histology — MCQs

Histology — MCQs

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