Histology Practice Questions

Q: Identify the marked layer in the given histological section.

Inner plexiform layer. ***Inner plexiform layer*** - The arrow points to a **synaptic layer** characterized by a dense network of **axons, dendrites**, and synapses between bipolar cells, amacrine cells, and ganglion cells. - This layer is distinguished by its **reticular appearance** and its position between the inner nuclear layer (nuclei of bipolar, amacrine, and horizontal cells) and the ganglion cell layer. *Outer plexiform layer* - This layer is located more externally in the retina, between the **outer nuclear layer** and the **inner nuclear layer**. - It is where photoreceptors (rods and cones) synapse with bipolar and horizontal cells. *Inner limiting layer* - The **innermost layer** of the retina, adjacent to the vitreous humor. - It is a thin, acellular membrane formed by the basal laminae of the Müller cells. *Outer limiting layer* - This layer is situated internally to the **photoreceptor layer** (rods and cones). - It is not a true membrane but rather a series of intercellular junctions (adherens junctions) between photoreceptor cells and Müller cells.

Q: The cells marked as $X$ are called:

Supporting cells. ***Supporting cells*** - The cells marked as 'X' in the image are the **supporting cells**, also known as **sustentacular cells**, which are essential components of the **olfactory epithelium**. - These cells provide **structural support**, **nourishment**, and **electrical insulation** to the olfactory receptor neurons. - They are **columnar cells** with apical microvilli and contain **lipid droplets** and **pigment granules**. *Olfactory receptor neurons* - These are the **bipolar sensory neurons** that detect odors, located between the supporting cells. - They have a **dendritic knob** with cilia extending into the mucus layer and an **axon** that projects through the cribriform plate. - Not the cells marked as 'X' in this image. *Basal cells* - These are **small, round stem cells** located at the base of the olfactory epithelium. - They serve as **progenitor cells** for regeneration of olfactory receptor neurons. - Located at a different position than the cells marked 'X'. *Bowman's glands* - These are **serous glands** located in the lamina propria beneath the olfactory epithelium. - They secrete **mucus** that dissolves odorants and facilitates olfaction. - These are glandular structures, not the epithelial cells marked in the image.

Q: The area marked as $X$ is called:

Spiral canal of modiolus. ***Spiral canal of modiolus*** - The image shows a cross-section of the **organ of Corti** within the cochlea. Modiolus is the central bony pillar of the cochlea, and the **spiral canal of modiolus** contains the **spiral ganglion**, which consists of the cell bodies of the auditory nerve. The arrow points to a collection of neurons, clearly indicating this structure. - The spiral ganglion neurons receive input from the hair cells and transmit auditory information to the brain. *Endolymphatic sac* - The **endolymphatic sac** is located within the dura mater of the posterior cranial fossa and is involved in the absorption and regulation of **endolymph** fluid. - It is not depicted in this image, which focuses on the sensory structures of the **cochlea**. *Tunnel of Corti* - The **tunnel of Corti** is a triangular-shaped space within the organ of Corti, formed by the inner and outer pillar cells. It is filled with **cortilymph**. - While present in the organ of Corti, the area marked 'X' is clearly positioned to indicate the collection of **neuronal cell bodies** (ganglion) rather than this specific extracellular space. *Scala tympani* - The **scala tympani** is one of the three fluid-filled chambers of the cochlea, located below the basilar membrane. It contains **perilymph** and transmits sound vibrations. - The marked area 'X' indicates a cellular structure (spiral ganglion) within the modiolus, not a fluid-filled chamber of the cochlea.

Q: Which of the following layers has abundance of desmosomes? (AIIMS Nov 2017)

C. ***C*** - Layer C represents the **stratum spinosum** (prickle cell layer) of the epidermis, which is characterized by abundant **desmosomes**. - These desmosomes give the cells a **prickly appearance** when stained, as the cells shrink but the desmosomal attachments remain, pulling on the cell membranes. *A* - Layer A represents the **stratum corneum**, which is the outermost layer consisting of flattened, anucleated cells filled with **keratin**. - While desmosomes are present deeper in the epidermis, this layer is primarily involved in **protection** and shedding of dead cells. *B* - Layer B represents the **stratum granulosum**, characterized by cells containing **keratohyalin granules**. - These granules are precursors to keratin, and while desmosomes connect cells here, they are less prominent than in the stratum spinosum. *D* - Layer D represents the **stratum basale** (basal layer), which is the deepest epidermal layer of cuboidal or columnar cells. - These cells are responsible for **cell proliferation** and connect to the basement membrane via **hemidesmosomes**, and to each other via desmosomes, but not as abundantly as in the stratum spinosum.

Q: Which of the following layers contains Odland bodies?

B. ***B*** - The layer indicated by **B** is the **stratum granulosum**, which is characterized by the presence of **keratohyalin granules** and **Odland bodies** (lamellar bodies). - **Odland bodies** are crucial for forming the **epidermal water barrier** as they release lipids and enzymes into the intercellular space. *A* - The layer indicated by **A** is the **stratum corneum**, which consists of dead, flattened keratinocytes. - This layer is primarily involved in protection and does not contain Odland bodies, which are found in deeper layers. *C* - The layer indicated by **C** is the **stratum spinosum**, characterized by many **desmosomes** giving a "spiny" appearance. - While cells in this layer are metabolically active and produce keratin, Odland bodies primarily form and are extruded in the stratum granulosum. *D* - The layer indicated by **D** is the **stratum basale** (or stratum germinativum), the deepest layer of the epidermis. - This layer contains **stem cells** that are constantly dividing to replenish the epidermal layers and is also where melanocytes are located; it does not contain Odland bodies.

Q: Which of the following area is marked in the histology of lymph node? (AIIMS May 2017)

Germinal center. ***Germinal center*** - The image illustrates a **germinal center**, characterized by its **lighter staining** and a distinct network of cells (likely follicular dendritic cells) which are responsible for B-cell proliferation and differentiation. - The pointer indicates the surrounding, more basophilic lymphocytes, often seen adjacent to the paler germinal center. *Mantle zone* - The mantle zone surrounds the germinal center and consists of **small, inactive B-lymphocytes** that stain more densely (darker) than the cells within the germinal center. - It would be seen as a darker ring immediately outside the lighter germinal center. *Marginal zone* - The marginal zone is typically found in the **spleen** and is a region of B cells that surrounds the white pulp. - It is not a primary structural component identified within the follicular architecture of a lymph node in the manner depicted. *Paracortical area* - The paracortex is primarily a **T-cell zone**, located between the follicles and the medulla within the lymph node. - It would not exhibit the distinct follicular structure with a light center and surrounding darker cells as shown.

Q: Which one of the following is the myelinating cell of Central Nervous System?

Oligodendrocyte. ***Oligodendrocyte*** - **Oligodendrocytes** are the primary cells responsible for producing and maintaining the **myelin sheath** around axons in the **Central Nervous System (CNS)** [2], [3]. - Each oligodendrocyte can myelinate multiple axons or multiple segments of the same axon [3]. *Astrocyte* - **Astrocytes** are star-shaped glial cells that provide structural and metabolic support to neurons in the CNS [1]. - They are involved in forming the **blood-brain barrier** and regulating the chemical environment around neurons, but they do not produce myelin. *Microglia* - **Microglia** are the resident **immune cells** of the CNS, functioning as macrophages [1]. - They are primarily involved in immune surveillance, phagocytosis of cellular debris and pathogens, and inflammatory responses, not myelination [1]. *Schwann cell* - **Schwann cells** are the myelinating cells of the **Peripheral Nervous System (PNS)** [2], [3]. - Unlike oligodendrocytes, each Schwann cell typically myelinates only a single axon segment [3].

Q: Identify which of the following structure is a sebaceous gland:

2. ***Correct: (2) Sebaceous gland*** - The structure labeled (2) is a **sebaceous gland**, characterized by its **multicellular alveolar structure** typically associated with a hair follicle - Sebaceous glands are **holocrine glands** where the entire cell disintegrates to release sebum (oily secretion) - These glands are found throughout the body except on palms and soles, and produce **sebum for lubrication** of hair and skin - Histologically identified by **grape-like clusters of cells** with foamy cytoplasm due to lipid content *Incorrect: (3) Inner root sheath* - The structure labeled (3) represents the **inner root sheath** of the hair follicle - This is a **structural component**, not a glandular structure - Functions to provide support and guidance to the developing hair shaft - Composed of three layers: Henle's layer, Huxley's layer, and the cuticle *Incorrect: (4) Hair matrix* - The structure labeled (4) indicates the **hair matrix**, located at the base of the hair follicle - This is a **proliferative zone** with actively dividing cells responsible for hair growth - Not a glandular structure, but rather the germinative region where hair cells differentiate - Contains melanocytes that provide pigment to the growing hair *Incorrect: (1) Hair shaft* - The structure labeled (1) is the **hair shaft**, the visible keratinized portion of the hair - This is the **final product** of the hair follicle, composed of dead, keratinized cells - Not a glandular structure, but rather a modified epidermal structure - Extends from the hair follicle through the skin surface

Q: Identify the cell marked in the image below

Mast cell. ***Mast cell*** - The cell indicated by the arrow displays characteristic features of a **mast cell**, including its large size, prominent central nucleus, and cytoplasm densely packed with numerous large, basophilic (darkly stained) granules. - These granules contain powerful inflammatory mediators like **histamine** and **heparin**, which are key in allergic reactions and inflammation. *Macrophage* - Macrophages are typically larger than mast cells with an **irregular shape**, a kidney-shaped nucleus, and often contain phagocytosed material in their cytoplasm, which is not clearly visible here. - While they are also immune cells, they lack the characteristic dense, uniform basophilic granulation seen in the indicated cell. *Plasma cell* - Plasma cells are characterized by an **eccentric nucleus** with **chromatin clumping** (cartwheel or clock-face appearance) and a prominent Golgi apparatus (perinuclear halo), none of which are evident in the marked cell. - Their cytoplasm is typically basophilic but lacks the distinct large granules. *Fibroblast* - Fibroblasts are typically **spindle-shaped** or stellate cells with elongated nuclei and a sparse cytoplasm, responsible for producing extracellular matrix. - They do not possess the abundant, dense cytoplasmic granules that are a hallmark of the cell shown.

Question 1

Identify the marked layer in the given histological section.

Accepted Answer

Inner plexiform layer

Answer

Outer plexiform layer

Answer

Inner limiting layer

Answer

Outer limiting layer

Question 2

The cells marked as $X$ are called:

Accepted Answer

Supporting cells

Answer

Olfactory receptor neurons

Answer

Bowman's glands

Answer

Basal cells

Question 3

The area marked as $X$ is called:

Accepted Answer

Spiral canal of modiolus

Answer

Endolymphatic sac

Answer

Tunnel of Corti

Answer

Scala tympani

Question 4

Which of the following layers has abundance of desmosomes? (AIIMS Nov 2017)

Accepted Answer

C

Answer

A

Answer

B

Answer

D

Question 5

Which of the following layers contains Odland bodies?

Accepted Answer

B

Answer

A

Answer

C

Answer

D

Question 6

Which of the following area is marked in the histology of lymph node? (AIIMS May 2017)

Accepted Answer

Germinal center

Answer

Mantle zone

Answer

Marginal zone

Answer

Paracortical area

Question 7

Which one of the following is the myelinating cell of Central Nervous System?

Accepted Answer

Oligodendrocyte

Answer

Astrocyte

Answer

Microglia

Answer

Schwann cell

Question 8

Identify the structures labeled A, B, C, and D in the given histological section of skin

Accepted Answer

A: Sebaceous gland; B: Arrector pili muscle; C: Apocrine gland; D: Eccrine gland

Answer

A: Eccrine gland; B: Arrector pili muscle; C: Sebaceous gland; D: Apocrine gland

Answer

A: Sebaceous gland; B: Apocrine gland; C: Eccrine gland; D: Arrector pili muscle

Answer

A: Apocrine gland; B: Eccrine gland; C: Sebaceous gland; D: Arrector pili muscle

Question 9

Identify which of the following structure is a sebaceous gland:

Accepted Answer

2

Answer

3

Answer

4

Answer

1

Question 10

Identify the cell marked in the image below

Accepted Answer

Mast cell

Answer

Macrophage

Answer

Plasma cell

Answer

Fibroblast

Histology — MCQs

Histology — MCQs

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