Histology Practice Questions

Q: Merkel cells are found in which of the following tissues?

Epidermis. ***Epidermis*** - **Merkel cells** are specialized **neuroendocrine cells** located in the **stratum basale** (deepest layer) of the epidermis [1]. - They function as **mechanoreceptors**, playing a crucial role in **touch sensation**, particularly light touch and discrimination of shapes and textures [1]. *Reticular layer of dermis* - The **reticular layer** is the deeper, thicker layer of the dermis, composed of dense irregular connective tissue. - It primarily contains **collagen and elastic fibers** and is involved in the skin's strength and elasticity, not housing mechanoreceptors like Merkel cells. *Hypodermis* - The **hypodermis** (or superficial fascia) is the layer beneath the dermis, primarily composed of **adipose tissue** and loose connective tissue. - Its main functions include **insulation**, energy storage, and shock absorption; it does not contain Merkel cells. *Papillary layer of dermis* - The **papillary layer** is the superficial layer of the **dermis**, characterized by dermal papillae that interdigitate with the epidermis. - While it contains touch receptors like **Meissner's corpuscles**, it does not contain Merkel cells, which are epidermal.

Q: The slide of the testis is shown below. The supporting cells of the testis are:

Sertoli cells. ***Sertoli cells*** - **Sertoli cells** are also known as **nurse cells** because they provide structural and nutritional support to developing sperm cells (**spermatogonia, spermatocytes, and spermatids**). - They also form the **blood-testis barrier** and secrete hormones like **inhibin** and **androgen-binding protein**. *Spermatids* - **Spermatids** are immature male gametes that undergo spermiogenesis to mature into spermatozoa (sperm). - They are one of the types of cells being supported, not the supporting cells themselves. *Spermatogonia* - **Spermatogonia** are stem cells located at the base of the seminiferous tubules that initiate spermatogenesis. - These are the precursors to sperm cells and require support from Sertoli cells for their development. *Leydig cells* - **Leydig cells** are interstitial cells located between the seminiferous tubules and are responsible for producing and secreting **testosterone**. - While crucial for male reproductive function, they do not directly support the developing germ cells within the tubules.

Q: The main type of collagen in anchoring fibrils (component of dermoepidermal junction) is:

Type VII. ***Type VII*** - **Type VII collagen** is the primary component of **anchoring fibrils**, which are essential structures that firmly attach the **dermal epidermal junction** to the underlying dermis. [1] - Mutations in the gene encoding **Type VII collagen** can lead to **dystrophic epidermolysis bullosa**, a condition characterized by fragile skin and blister formation due to poor dermal-epidermal adhesion. *Type II* - **Type II collagen** is predominantly found in **hyaline cartilage** and **elastic cartilage**, providing tensile strength and resilience within these tissues. - It is crucial for maintaining the structural integrity of **joints** and the respiratory tract, rather than dermal-epidermal adhesion. *Type IV* - **Type IV collagen** is a major component of **basement membranes**, forming a mesh-like network that provides structural support and filtration properties. - Although present at the **dermal epidermal junction** as part of the **basement membrane**, it does not primarily form the anchoring fibrils themselves. *Type III* - **Type III collagen** is widely distributed in **reticular fibers** in various tissues, including skin, blood vessels, and internal organs. - It provides elasticity and support to tissues, often co-localizing with **Type I collagen**, but does not form anchoring fibrils at the dermal-epidermal junction.

Q: Periosteal matrix acts on bone tissue to bring about:

Bone modeling. ***Bone modeling*** - The **periosteum** is a vital outer layer of bone that plays a crucial role in bone growth, repair, and **modeling** [1]. - **Bone modeling** involves changes in bone size and shape, often through independent processes of bone formation and resorption on different surfaces, which the periosteal matrix actively contributes to [1]. *Bone resorption only* - While **bone resorption** is a component of bone remodeling, the periosteal matrix is involved in both bone formation and resorption, not exclusively resorption [2]. - Focusing solely on resorption neglects the periosteum's role in **bone deposition** and overall bone shape changes [1]. *Cartilage formation* - The periosteum does not primarily lead to **cartilage formation**; its main role is in bone tissue [3]. - Cartilage formation is typically mediated by chondrocytes, usually in different developmental contexts or repair processes [4]. *Bone mineralization only* - **Bone mineralization** is the process by which inorganic minerals (chiefly calcium phosphate) are deposited into the organic matrix of bone [3]. - While the periosteum contributes to the formation of the organic matrix, its role extends beyond just mineralization to the overall **structuring and reshaping of bone** [1].

Q: Langerhans cells in skin fall under which category?

Antigen presenting cell. ***Antigen presenting cell*** - **Langerhans cells** are specialized **dendritic cells** found in the epidermis of the skin and play a crucial role in the immune system [1], [3]. - Their primary function is to capture and process antigens from the skin environment and present them to **T lymphocytes**, initiating an immune response [1], [2]. *Keratin synthesising cell* - **Keratinocytes** are the primary cells responsible for synthesizing **keratin**, providing structural integrity to the epidermis [3]. - Langerhans cells originate from bone marrow and are not involved in keratin production. *Sensory neurons* - **Sensory neurons** (e.g., Merkel cells and nerve endings) are responsible for transmitting sensations like touch, pressure, and pain [3]. - Langerhans cells are immune cells and do not have neuronal functions. *Pigment producing cells* - **Melanocytes** are the cells responsible for producing **melanin**, the pigment that gives skin, hair, and eyes their color [3]. - Langerhans cells do not produce pigment; their role is immune surveillance [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 200. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 174-175. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1144.

Q: In which of the following structures is regularly arranged parallel collagen present?

Cornea. ### Cornea - The cornea contains **Type I collagen fibers** that are arranged in a precise, orthogonal, and parallel pattern within its lamellae [1]. - This highly organized arrangement is crucial for its **transparency** and its ability to refract light effectively [1]. *Basement membrane* - The basement membrane consists primarily of **Type IV collagen**, **laminin**, and **heparan sulfate proteoglycans** [2]. - Its collagen fibers form a **mesh-like network** rather than a regularly arranged parallel structure [2]. *Diaphragm* - The diaphragm is composed of **skeletal muscle tissue**, which contains contractile proteins (actin and myosin) and connective tissue elements like **endomysium**, **perimysium**, and **epimysium**. - While it contains collagen, it is not arranged in the highly parallel, organized fashion found in structures like the cornea; its primary function is muscle contraction, not transparency or tensile strength from parallel fibers. *Tympanic membrane* - The tympanic membrane (eardrum) has a fibrous middle layer that is largely composed of **collagen fibers**. - These fibers are generally arranged in **radial and circular patterns** to provide tensile strength and flexibility for sound transmission, but not in the regular, parallel arrangement characteristic of the cornea.

Q: Submucosal plexus is -

Meissner's plexus. ***Meissner's plexus*** - The **submucosal plexus** is also known as **Meissner's plexus**, located in the submucosal layer of the **gastrointestinal tract** [1]. - It primarily controls local **secretions**, **absorption**, and **blood flow** within the gut [2]. *Myenteric plexus* - The **myenteric plexus** is also known as **Auerbach's plexus**, located between the longitudinal and circular muscle layers of the **gastrointestinal tract** [1]. - It primarily controls **gastrointestinal motility**, not local secretions [1]. *Tympanic plexus* - The **tympanic plexus** is a network of nerves in the **middle ear** that provides sensory innervation to the tympanic cavity. - It is unrelated to the gastrointestinal tract or its intrinsic nervous system. *Auerbach's plexus* - **Auerbach's plexus** is another name for the **myenteric plexus**, which is located between the muscle layers [1]. - It is responsible for gut motility and distinct from the submucosal plexus.

Q: Inorganic component of bone is:

65%. **65%** - The inorganic component of bone, primarily **hydroxyapatite crystals**, makes up approximately **60-70%** of the bone's dry weight [1]. - This high percentage of inorganic material is responsible for the bone's **hardness and compressive strength**. *85%* - This percentage is **too high** for the inorganic component, as it would leave insufficient room for organic material, making bones exceedingly brittle and prone to fracture. - While bone is very hard, reaching 85% inorganic content would significantly compromise its **flexibility and tensile strength**. *35%* - This percentage is **too low** for the inorganic component; such a composition would result in bones that are overly flexible and weak, unable to provide adequate structural support [1]. - Bones with only 35% inorganic material would lack the necessary **rigidity and resistance to deformation**. *45%* - While closer than 35%, 45% is still **below the typical range** for the inorganic component of bone. - Such a composition would still lead to **reduced bone density** and increased susceptibility to fractures compared to normal bone.

Q: The bone matrix has the following crystals -

Calcium hydroxyapatite. ***Calcium hydroxyapatite*** - The primary mineral component of bone matrix is **calcium hydroxyapatite**, which gives bone its rigidity and strength [1]. - These crystals are formed from **calcium and phosphate ions** arranged in a specific crystalline structure within the collagen fibers [1]. *Calcium pyrophosphate* - **Calcium pyrophosphate dihydrate (CPPD)** crystals are associated with **pseudogout**, a condition causing joint inflammation, not the normal bone matrix [1]. - They are found in articular cartilage and synovial fluid, not as a structural component of healthy bone. *Calcium phosphate* - While hydroxyapatite is a form of **calcium phosphate**, simply "calcium phosphate" is too general and does not specify the exact crystalline structure found in bone [1]. - Many calcium phosphate compounds exist, but **hydroxyapatite** is the specific and most abundant one in bone [1]. *Calcium sulphate* - **Calcium sulfate** is not a naturally occurring mineral component of the bone matrix in vertebrates. - It is sometimes used in medical applications as a **bone graft substitute** or a drug delivery system, but not as an endogenous component.

Q: The Eustachian tube is made up of

Elastic cartilage. ***Elastic cartilage*** - The **cartilaginous portion** of the Eustachian tube (medial 2/3) is primarily composed of **elastic cartilage**. - This tissue provides the necessary **flexibility and resilience** for tube opening during swallowing and yawning, which is essential for **middle ear ventilation**. - Elastic cartilage contains abundant **elastic fibers** that allow the tube to change shape and return to its original position. *Fibro-elastic cartilage* - This term is sometimes used descriptively to refer to **elastic cartilage with fibrous components**, which is what forms the Eustachian tube. - However, as a standalone option separate from "elastic cartilage," it may cause confusion since the standard classification recognizes elastic cartilage as the primary cartilage type. - The cartilaginous Eustachian tube is best classified as **elastic cartilage**. *Hyaline cartilage* - **Hyaline cartilage** is found in the nose, trachea, larynx, and articular surfaces of joints. - It has a smooth, glassy appearance but lacks the **elastic fiber content** needed for the dynamic function of the Eustachian tube. - Would not provide the necessary **flexibility for tube opening** required during pressure equalization. *Fibrocartilage* - **Fibrocartilage** is found in intervertebral discs, pubic symphysis, and menisci, providing **high tensile strength**. - While durable, it lacks the **elastic recoil** necessary for the Eustachian tube to repeatedly open and close. - The Eustachian tube requires **flexibility with elastic recovery**, not primarily tensile strength.

Question 1

Merkel cells are found in which of the following tissues?

Accepted Answer

Epidermis

Answer

Reticular layer of dermis

Answer

Hypodermis

Answer

Papillary layer of dermis

Question 2

The slide of the testis is shown below. The supporting cells of the testis are:

Accepted Answer

Sertoli cells

Answer

Spermatids

Answer

Spermatogonia

Answer

Leydig cells

Question 3

The main type of collagen in anchoring fibrils (component of dermoepidermal junction) is:

Accepted Answer

Type VII

Answer

Type II

Answer

Type IV

Answer

Type III

Question 4

Periosteal matrix acts on bone tissue to bring about:

Accepted Answer

Bone modeling

Answer

Bone resorption only

Answer

Cartilage formation

Answer

Bone mineralization only

Question 5

Langerhans cells in skin fall under which category?

Accepted Answer

Antigen presenting cell

Answer

Keratin synthesising cell

Answer

Sensory neurons

Answer

Pigment producing cells

Question 6

In which of the following structures is regularly arranged parallel collagen present?

Accepted Answer

Cornea

Answer

Basement membrane

Answer

Diaphragm

Answer

Tympanic membrane

Question 7

Submucosal plexus is -

Accepted Answer

Meissner's plexus

Answer

Myenteric plexus

Answer

Tympanic plexus

Answer

Auerbach's plexus

Question 8

Inorganic component of bone is:

Accepted Answer

65%

Answer

85%

Answer

35%

Answer

45%

Question 9

The bone matrix has the following crystals -

Accepted Answer

Calcium hydroxyapatite

Answer

Calcium pyrophosphate

Answer

Calcium phosphate

Answer

Calcium sulphate

Question 10

The Eustachian tube is made up of

Accepted Answer

Elastic cartilage

Answer

Fibro-elastic cartilage

Answer

Hyaline cartilage

Answer

Fibrocartilage

Histology — MCQs

Histology — MCQs

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