Epithelial/Connective tissues US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Epithelial/Connective tissues. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Epithelial/Connective tissues US Medical PG Question 1: A 35-year-old woman presents to a pre-operative evaluation clinic prior to an elective cholecystectomy. She has a 5 pack-year smoking history. The anesthesiologist highly recommends to discontinue smoking for at least 8 weeks prior to the procedure for which she is compliant. What is the most likely histology of her upper respiratory tract's epithelial lining at the time of her surgery?
- A. Simple squamous
- B. Simple columnar
- C. Pseudostratified columnar (Correct Answer)
- D. Stratified squamous
- E. Stratified columnar
Epithelial/Connective tissues Explanation: ***Pseudostratified columnar***
- The upper respiratory tract is normally lined by **pseudostratified ciliated columnar epithelium** with goblet cells, which is crucial for mucociliary clearance.
- While smoking can initially cause **squamous metaplasia**, discontinuing smoking for 8 weeks allows for significant, if not complete, **reversal of these changes** back to the normal pseudostratified columnar epithelium.
*Simple squamous*
- This type of epithelium is found in areas designed for efficient **gas exchange** (e.g., alveoli of the lungs) and is not typical for the conductive airways of the upper respiratory tract.
- It lacks the **cilia and goblet cells** necessary for clearing inhaled particles and pathogens.
*Simple columnar*
- **Simple columnar epithelium** is found in regions like the lining of the gastrointestinal tract (e.g., stomach, small and large intestines) and is not characteristic of the upper respiratory tract.
- While it can have goblet cells, it typically lacks **cilia** for respiratory clearance.
*Stratified squamous*
- **Stratified squamous epithelium** is found in areas subject to friction and abrasion, such as the oral cavity, pharynx, and esophagus.
- While chronic smoking can induce **squamous metaplasia** in the respiratory tract, an 8-week cessation period would likely result in the reversal of this change back to the normal type.
*Stratified columnar*
- **Stratified columnar epithelium** is a relatively rare type found in specific locations like parts of the male urethra and some large excretory ducts.
- It is not the normal or even a common metaplastic lining for the human upper respiratory tract.
Epithelial/Connective tissues US Medical PG Question 2: A 28-year-old woman and her husband are admitted to the office due to difficulties conceiving a child for the past year. Her menarche was at the age of 15 years, and her periods have been regular since then. Her medical history is positive for an abortion with curettage 5 years ago. A spermogram on the partner is performed, and it shows motile sperm cells. An ultrasound is performed on the patient and it is unremarkable. The laboratory results show that the FSH, LH, TSH, and prolactin levels are within normal ranges. A hysteroscopy is additionally performed and multiple adhesions are found in the uterus (refer to the image). Which of the following is the most likely composition of the scar tissue present in the uterus?
- A. Type 3 collagen
- B. Type 4 collagen
- C. Type 2 collagen
- D. Type 1 collagen (Correct Answer)
- E. Elastin
Epithelial/Connective tissues Explanation: ***Type 1 collagen***
- This patient presents with **Asherman's syndrome**, characterized by intrauterine adhesions, often following uterine surgery like **curettage**. These adhesions are primarily composed of **Type 1 collagen**, which is the most abundant type of collagen in the human body and a major component of scar tissue.
- **Type 1 collagen** provides tensile strength and is crucial for wound healing and forming scar tissue in most connective tissues, including the uterus.
*Type 3 collagen*
- **Type 3 collagen** is found in distensible tissues like blood vessels, the uterus, and skin, and is important during the **early stages of wound healing**.
- While present in the uterus and initially involved in wound repair, **mature scar tissue** predominantly consists of **Type 1 collagen**.
*Type 4 collagen*
- **Type 4 collagen** is a major component of the **basal lamina**, a specialized extracellular matrix that underlies epithelial and endothelial cells.
- It does not form fibrillar structures and is not the primary component of robust scar tissue found in Asherman's syndrome.
*Type 2 collagen*
- **Type 2 collagen** is the main collagen type found in **hyaline cartilage** and elastic cartilage, providing resistance to pressure.
- It is not found in significant amounts in uterine tissue or scar tissue formed within the uterus.
*Elastin*
- **Elastin** is a protein that provides **elasticity** to tissues like blood vessels, skin, and lungs, allowing them to stretch and recoil.
- While present in the uterus for its contractile properties, it is not the primary constituent of **fibrotic scar tissue** forming adhesions.
Epithelial/Connective tissues US Medical PG Question 3: A 65-year-old man with a 40-pack-year smoking history presents with hemoptysis and a persistent cough. Chest CT shows a 3.5 cm centrally located mass in the right main bronchus. Positron emission tomography confirms a malignant nodule. Bronchoscopy with transbronchial biopsy is performed and a specimen sample of the nodule is sent for frozen section analysis. The tissue sample is most likely to show which of the following tumor types?
- A. Carcinoid tumor
- B. Metastasis of colorectal cancer
- C. Small cell lung carcinoma
- D. Large cell carcinoma
- E. Squamous cell carcinoma (Correct Answer)
Epithelial/Connective tissues Explanation: ***Squamous cell carcinoma***
- This is the most likely diagnosis given the **central location** in the main bronchus, **heavy smoking history**, and presentation with **hemoptysis**.
- **Squamous cell carcinoma** accounts for 25-30% of lung cancers and characteristically arises in **central/proximal airways**, making it readily accessible by **bronchoscopy**.
- Histologically, it shows **keratin pearls** and **intercellular bridges** on biopsy.
- The **central endobronchial location** and ability to obtain tissue via transbronchial biopsy strongly favor squamous cell over peripheral tumors.
*Carcinoid tumor*
- **Carcinoid tumors** are **neuroendocrine tumors** that can present as central endobronchial masses and cause hemoptysis.
- However, they are typically **slow-growing** with more indolent presentation, and PET scans show **variable uptake** (often less intense than aggressive carcinomas).
- They represent only **1-2% of lung tumors** and occur more commonly in **younger, non-smoking patients**.
*Metastasis of colorectal cancer*
- While lung is a common site for **colorectal metastases**, these typically present as **multiple peripheral nodules** rather than a solitary central endobronchial mass.
- The clinical presentation strongly suggests **primary lung cancer** rather than metastatic disease.
- Without history of colorectal cancer, this is unlikely.
*Small cell lung carcinoma*
- **Small cell lung carcinoma** (SCLC) represents 15% of lung cancers and typically presents as a **large central mass** with early mediastinal involvement.
- However, SCLC is usually **too extensive at presentation** for transbronchial biopsy alone and often requires mediastinoscopy or CT-guided biopsy.
- Histology shows **small cells with scant cytoplasm**, **salt-and-pepper chromatin**, and **oat-cell morphology**.
- While possible, the single accessible endobronchial mass is more characteristic of squamous cell.
*Large cell carcinoma*
- **Large cell carcinoma** is a **diagnosis of exclusion** made when tumors lack features of adenocarcinoma, squamous cell, or small cell differentiation.
- It typically presents as **large peripheral masses** rather than central endobronchial lesions.
- It represents only **10% of lung cancers** and is less common than squamous cell carcinoma in this clinical scenario.
Epithelial/Connective tissues US Medical PG Question 4: An investigator is studying the interaction between epithelial cells and calcium ion concentration. When the calcium ion concentration available to a sample of epithelial tissue is decreased, an increased gap between adjacent epithelial cells is seen on electron microscopy. This observed decrease in cell adhesion is most likely due to an effect on which of the following proteins?
- A. Actin
- B. Integrin
- C. Cadherin (Correct Answer)
- D. Claudin
- E. Cytokeratin
Epithelial/Connective tissues Explanation: ***Cadherin***
- **Cadherins** are calcium-dependent adhesion proteins that mediate cell-to-cell adhesion, particularly in epithelial tissues.
- A decrease in calcium concentration would directly impair cadherin function, leading to reduced cell adhesion and increased intercellular gaps.
*Actin*
- **Actin** is a component of the cell's cytoskeleton, involved in cell shape, motility, and intracellular transport, but not directly responsible for calcium-dependent cell adhesion between epithelial cells.
- While actin filaments interact with adhesion junctions, their primary role is structural and dynamic rather than adhesive.
*Integrin*
- **Integrins** are primarily involved in cell-to-extracellular matrix adhesion, connecting the cell to the surrounding matrix, not directly mediating calcium-dependent cell-to-cell adhesion between epithelial cells.
- They can be affected by intracellular calcium signaling but do not directly bind calcium to mediate their adhesive function in the same way cadherins do.
*Claudin*
- **Claudins** are key components of **tight junctions**, which regulate paracellular permeability and form a barrier between cells, but they are not directly responsible for calcium-dependent cell-to-cell adhesion, which is characteristic of adherens junctions.
- While tight junctions contribute to overall cell-cell contact, the observation of an *increased gap* suggests an issue with adhesive complexes like adherens junctions, where cadherins are prominent.
*Cytokeratin*
- **Cytokeratins** are intermediate filaments found in epithelial cells, providing structural support and mechanical strength.
- They are linked to desmosomes and hemidesmosomes but are not directly involved in calcium-dependent cell-to-cell adhesion.
Epithelial/Connective tissues US Medical PG Question 5: A 37-year-old man presents to the clinic because of painful, severe blistering over his buttocks for the past week. About a year ago, he noticed a similar outbreak on his inner thighs, but it receded within a few days on its own. Physical examination shows the blisters are tense, and rubbing the affected skin does not result in ‘popping’ of the blisters. A biopsy shows the entire epidermis lifting away from the basal lamina with extensive inflammatory infiltrates abundant with eosinophils. Immunofluorescence shows a linear pattern of immune complex deposits. Which of the following cellular structures, if defective, is most likely involved in the formation of these blisters?
- A. Gap junctions
- B. Hemidesmosomes (Correct Answer)
- C. Lamellar bodies
- D. Zonula occludens
- E. Macula adherens
Epithelial/Connective tissues Explanation: ***Hemidesmosomes***
- The clinical picture of **tense blisters** that do not pop with rubbing (**negative Nikolsky sign**), along with the histological finding of the **entire epidermis lifting away from the basal lamina** (subepidermal blistering), strongly suggests **bullous pemphigoid**.
- **Immunofluorescence showing linear deposits** along the basement membrane zone is characteristic of bullous pemphigoid, which is caused by autoantibodies targeting proteins within the hemidesmosomes.
*Gap junctions*
- **Gap junctions** are involved in **intercellular communication** and the passage of small molecules between cells.
- Defects in gap junctions do not typically lead to blistering skin disorders.
*Lamellar bodies*
- **Lamellar bodies** are organelles in **keratinocytes** that release lipids to form the **skin barrier**.
- Defects in lamellar bodies are associated with disorders like **ichthyosis**, not blistering as described.
*Zonula occludens*
- **Zonula occludens**, also known as **tight junctions**, are crucial for forming a **seal between epithelial cells**, regulating paracellular transport.
- Dysfunctional tight junctions can lead to increased permeability but are not directly involved in the formation of subepidermal blisters.
*Macula adherens*
- **Macula adherens**, or **desmosomes**, are cell-to-cell adhesion structures that provide strong mechanical attachments between keratinocytes.
- Defects in desmosomes are associated with **pemphigus vulgaris** and **pemphigus foliaceus**, which typically present with **flaccid blisters** that show a **positive Nikolsky sign** and involve intraepidermal cleavage.
More Epithelial/Connective tissues US Medical PG questions available in the OnCourse app. Practice MCQs, flashcards, and get detailed explanations.
