Anatomy
5 questionsFibrous stroma of liver is derived from -
What structures are derived from the neural crest?
Heart tube is formed in a gelatinous matrix rich in:
What is the remnant of the umbilical artery?
Which of the following is a derivative of paramesonephric duct in males ?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 161: Fibrous stroma of liver is derived from -
- A. Endoderm from the foregut
- B. Endoderm from the midgut
- C. Endoderm from the hindgut
- D. Mesoderm from the septum transversum (Correct Answer)
Explanation: ***Mesoderm from the septum transversum*** - The **fibrous stroma of the liver**, which provides its structural framework, develops from the **mesoderm** of the **septum transversum** [1]. - The septum transversum is a thick mass of mesoderm that contributes to the formation of the **diaphragm** and the connective tissue elements of the liver [1]. *Endoderm from the foregut* - While the **parenchymal cells (hepatocytes)** of the liver are derived from the **endoderm of the foregut**, this tissue forms the functional units, not the fibrous supporting stroma. - The endoderm forms the glandular tissue, while the mesoderm forms the connective tissue [1]. *Endoderm from the midgut* - The midgut endoderm gives rise to structures like the **small intestine**, cecum, appendix, ascending colon, and part of the transverse colon, but not the liver's stroma [2]. - Its primary role is in forming the epithelial lining of these digestive organs. *Endoderm from the hindgut* - The hindgut endoderm develops into the distal third of the transverse colon, descending colon, sigmoid colon, rectum, and superior part of the anal canal, - It plays no role in the development of the liver's fibrous stroma.
Question 162: What structures are derived from the neural crest?
- A. Melanocytes
- B. Dental papillae
- C. Adrenal medulla
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - The **neural crest** is a multipotent, migratory cell population that contributes to the formation of many diverse tissues and organs during vertebrate development. - Neural crest cells give rise to a wide array of derivatives, including components of the nervous system, pigment cells, skeletal and connective tissues of the head and face, and endocrine glands [1]. *Melanocytes* - **Melanocytes**, the pigment-producing cells found in the skin, hair, eyes, and other tissues, are derived from the **neural crest** [2]. - These cells migrate extensively during development from the neural crest to their final destinations throughout the body. - Neural crest-derived melanocytes produce melanin, which provides pigmentation and protection against UV radiation [2]. *Dental papillae* - The **dental papilla** is crucial for tooth development and is formed from **ectomesenchymal cells** that are derived from the cranial neural crest. - These cells differentiate into the odontoblasts that produce dentin and also contribute to the pulp of the tooth. *Adrenal medulla* - The cells of the **adrenal medulla**, which produce catecholamines like epinephrine and norepinephrine, are specialized **postganglionic sympathetic neurons** derived from the neural crest. - They develop from neuroectodermal cells that migrate to the developing adrenal gland.
Question 163: Heart tube is formed in a gelatinous matrix rich in:
- A. Hyaluronic acid secreted by the endocardium
- B. Chondroitin sulfate secreted by the endocardium
- C. Hyaluronic acid secreted by the myocardium (Correct Answer)
- D. Chondroitin sulfate secreted by the myocardium
Explanation: ***Hyaluronic acid secreted by the myocardium*** - The developing **heart tube** forms within a gelatinous extracellular matrix that is rich in **hyaluronic acid**. - This **hyaluronic acid** is secreted by the **myocardium** (the developing heart muscle), which plays a crucial role in the initial formation and remodeling of the heart. *Hyaluronic acid secreted by the endocardium* - While the endocardium is an important layer of the heart, it is the **myocardium** that primarily secretes the **hyaluronic acid** critical for heart tube formation during early development. - The **endocardium** forms the inner lining and primarily acts in blood-tissue interaction and valvular development later on. *Chondroitin sulfate secreted by the endocardium* - **Chondroitin sulfate** is a component of the extracellular matrix, but it is not the primary proteoglycan responsible for the initial formation environment of the heart tube. - Furthermore, its secretion is not predominantly from the **endocardium** in this context. *Chondroitin sulfate secreted by the myocardium* - Although the myocardium is responsible for secreting extracellular matrix components, **chondroitin sulfate** is not the predominant or critical molecule responsible for the initial gelatinous matrix allowing heart tube formation. - **Hyaluronic acid** plays this key role in early cardiogenesis.
Question 164: What is the remnant of the umbilical artery?
- A. Ligamentum arteriosum
- B. Ligament teres
- C. Ligamentum venosum
- D. Medial umbilical ligament (Correct Answer)
Explanation: ***Medial umbilical ligament*** - The **umbilical arteries** (paired structures) carry deoxygenated blood from the fetus to the placenta during development [2]. - After birth, these arteries obliterate and persist as the **medial umbilical ligaments** (two in number, one on each side), extending from the internal iliac arteries to the umbilicus along the anterior abdominal wall. - The proximal portions of the umbilical arteries remain patent as the **superior vesical arteries**, which supply the bladder. *Ligamentum arteriosum* - This is the remnant of the **ductus arteriosus**, which shunted blood from the pulmonary artery to the aorta, bypassing the fetal lungs [2]. - It connects the arch of the aorta to the pulmonary artery. *Ligament teres* - Also known as the **round ligament of the liver**, this is the remnant of the **fetal umbilical vein** (a single midline structure) [1]. - The umbilical vein carried oxygenated blood from the placenta to the fetus [1], [2]. *Ligamentum venosum* - This is the fibrous remnant of the **ductus venosus**, a shunt in fetal circulation that bypassed the liver by connecting the umbilical vein to the inferior vena cava [1]. - It is located deep within the liver, forming a fissure.
Question 165: Which of the following is a derivative of paramesonephric duct in males ?
- A. Trigone of bladder
- B. Paraphoron
- C. Prostatic utricle (Correct Answer)
- D. Gartner's duct
Explanation: ***Prostatic utricle*** - The **prostatic utricle** is a blind-ending pouch located in the prostatic urethra. - It represents a **rudimentary derivative of the paramesonephric (Müllerian) duct** in males, which normally regresses due to the presence of Müllerian-inhibiting substance (MIS). *Trigone of bladder* - The trigone of the bladder is derived from the caudal ends of the **mesonephric ducts** (Wolffian ducts), not the paramesonephric ducts. - It forms through the incorporation of these ducts into the posterior wall of the bladder. *Paraphoron* - The **paraphoron** is a vestigial structure found in females, representing remnants of the caudal parts of the **epoophoron tubules**. - These are derived from the **mesonephric tubules**, not the paramesonephric ducts, and are not found in males. *Gartner's duct* - **Gartner's duct** is a remnant of the **mesonephric (Wolffian) duct** in females, typically running along the lateral wall of the vagina or uterus. - It is not found in males and is derived from a different embryonic structure than the paramesonephric duct.
Pathology
1 questionsWhat is the primary process involved in Wallerian degeneration?
NEET-PG 2015 - Pathology NEET-PG Practice Questions and MCQs
Question 161: What is the primary process involved in Wallerian degeneration?
- A. Nerve degeneration (Correct Answer)
- B. Muscle degeneration
- C. Nerve regeneration
- D. Muscle regeneration
Explanation: ***Nerve degeneration*** - **Wallerian degeneration** specifically refers to the process of **axon degeneration** that occurs distal to the site of injury when a nerve fiber is severed [2]. - This process involves the breakdown of the **axon** and its myelin sheath, leading to loss of function [1]. *Muscle degeneration* - While prolonged nerve degeneration can lead to muscle **atrophy** due to denervation, **muscle degeneration itself** is not the primary process of Wallerian degeneration. - Wallerian degeneration focuses on the **nerve itself**, not the target tissue. *Nerve regeneration* - **Nerve regeneration** is the process where damaged nerves attempt to regrow and re-establish connections [2]. - This is a subsequent, and not always successful, event that can occur *after* Wallerian degeneration has cleared the debris [1]. *Muscle regeneration* - **Muscle regeneration** refers to the repair and regrowth of damaged muscle tissue, typically involving satellite cells. - It is unrelated to Wallerian degeneration, which is a process affecting the **nerve**. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 697-698. [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. 109-110.
Physiology
3 questionsWhich of the following statements is true regarding the Bezold-Jarisch reflex?
Tetany in muscle occurs in spite of normal serum Ca2+ level. Which ion is responsible?
Which of the following is the primary factor involved in mesangial cell contraction?
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 161: Which of the following statements is true regarding the Bezold-Jarisch reflex?
- A. Hypertension
- B. Tachycardia
- C. Hyperpnea
- D. Hypotension (Correct Answer)
Explanation: ***Hypotension*** - The Bezold-Jarisch reflex is a **cardioinhibitory reflex** that is typically activated by strong ventricular contraction or noxious stimuli, leading to a triad of **bradycardia**, **peripheral vasodilation**, and subsequent **hypotension**. - This reflex is thought to be a protective mechanism to prevent excessive cardiac work or to trigger a "fainting" response to remove the body from danger. *Hypertension* - The Bezold-Jarisch reflex primarily causes a **decrease in blood pressure**, making hypertension an incorrect outcome. - Its activation directly opposes the mechanisms that would lead to increased blood pressure. *Tachycardia* - A key component of the Bezold-Jarisch reflex is **bradycardia** (slowing of the heart rate), not tachycardia. - This reflex is mediated by the vagus nerve, which primarily exerts inhibitory control over heart rate. *Hyperpnea* - The Bezold-Jarisch reflex primarily impacts **cardiovascular function** and does not directly cause hyperpnea (increased rate and depth of breathing). - While other reflexes can affect respiration, this particular reflex is not known for its respiratory effects.
Question 162: Tetany in muscle occurs in spite of normal serum Ca2+ level. Which ion is responsible?
- A. Mg2+
- B. K+
- C. Na+
- D. Ionized Ca2+ (Correct Answer)
Explanation: ***Ionized Ca2+*** - While total serum calcium might be normal, **tetany** is specifically caused by a decrease in the concentration of **ionized (free) calcium** in the extracellular fluid. - Ionized calcium is the physiologically active form of calcium responsible for neuromuscular excitability. *Mg2+* - **Hypomagnesemia** can exacerbate hypocalcemia and contribute to tetany, but it is not the primary ion directly responsible for tetany when **total serum calcium is normal**. - A deficiency in Mg2+ can impair the release of **parathyroid hormone** and reduce target organ responsiveness to PTH. *K+* - Abnormalities in **potassium levels** (hypokalemia or hyperkalemia) primarily affect cardiac and muscular excitability, leading to arrhythmias or muscle weakness/paralysis. - While electrolyte imbalances are interconnected, changes in potassium are not the direct cause of tetany due to calcium's role. *Na+* - **Sodium ions** are crucial for nerve impulse transmission and muscle contraction by establishing the resting membrane potential and initiating action potentials. - However, direct changes in sodium concentration do not typically cause tetany; rather, they can lead to neurological symptoms like seizures (hyponatremia) or altered mental status (hypernatremia).
Question 163: Which of the following is the primary factor involved in mesangial cell contraction?
- A. ANP
- B. Endothelin-1
- C. Angiotensin II (Correct Answer)
- D. Platelet-activating factor (PAF)
Explanation: ***Angiotensin II*** - **Angiotensin II** is a potent vasoconstrictor that directly stimulates **mesangial cell contraction**. - Contraction of mesangial cells reduces the **glomerular surface area** available for filtration, thereby decreasing the **glomerular filtration rate (GFR)**. *Endothelin-1* - **Endothelin-1** is a potent vasoconstrictor produced by endothelial cells, which can also induce mesangial cell contraction. - However, its role in **mesangial cell contraction** is generally considered secondary to **angiotensin II** in physiological regulation. *ANP* - **Atrial natriuretic peptide (ANP)** is a hormone that causes **vasodilation** and relaxation of mesangial cells. - Its primary effect is to **increase GFR** and sodium excretion, opposing the effects of vasoconstrictors. *Platelet-activating factor (PAF)* - PAF is a **phospholipid mediator** involved in inflammation and allergic reactions. - While it can affect renal hemodynamics, its role in directly and primarily causing **mesangial cell contraction** is less significant compared to angiotensin II.
Surgery
1 questionsWhich of the following statements is true about branchial cysts?
NEET-PG 2015 - Surgery NEET-PG Practice Questions and MCQs
Question 161: Which of the following statements is true about branchial cysts?
- A. Branchial cysts are more common in males than females.
- B. They mostly arise from the second branchial cleft. (Correct Answer)
- C. Surgical intervention is not always necessary.
- D. They can cause dysphagia and hoarseness if infected.
Explanation: ***They mostly arise from the second branchial cleft.*** - **Second branchial cleft cysts** are the most common type, accounting for approximately **95%** of all branchial anomalies. - They typically present as a smooth, fluctuant mass along the **anterior border of the sternocleidomastoid muscle** at the junction of the upper and middle third of the neck. - These cysts result from **incomplete obliteration** of the second branchial cleft during embryonic development. *Branchial cysts are more common in males than females.* - Branchial cysts have **no significant sex predilection**, affecting males and females with roughly equal frequency. - The overall incidence is relatively rare, with most cases presenting in late childhood or early adulthood. *Surgical intervention is not always necessary.* - **Complete surgical excision** is the **definitive treatment** and is strongly recommended for all branchial cysts. - Indications for surgery include: prevention of **recurrent infections**, risk of **abscess formation**, elimination of cosmetic concerns, and removal due to potential (though rare) **malignant transformation**. - While very small asymptomatic cysts may occasionally be observed, this carries significant risk of future complications, making surgery the standard of care in clinical practice. *They can cause dysphagia and hoarseness if infected.* - While an **infected branchial cyst** causes local inflammatory signs (pain, swelling, warmth, erythema), it **rarely causes dysphagia or hoarseness** unless exceptionally large. - These symptoms would require the cyst to compress the **pharynx** (dysphagia) or involve the **recurrent laryngeal nerve** (hoarseness), which is uncommon even with infection. - The primary presentation of infected cysts includes **tender neck mass** with overlying skin changes and possible **abscess formation**.