Anatomy
5 questionsWaldeyer's fascia lies?
Which of the following is a tributary of the coronary sinus?
Lymphatic drainage of cervix is to
What is the lower limit of the retropharyngeal space?
The thyrocervical trunk is a branch of which part of subclavian artery?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 111: Waldeyer's fascia lies?
- A. In front of the bladder.
- B. Behind the rectum. (Correct Answer)
- C. Between the bladder and uterus.
- D. Between the uterus and rectum.
Explanation: ***Behind the rectum*** - **Waldeyer’s fascia**, also known as the **sacrorectal fascia**, is a retrorectal connective tissue sheet located between the **rectum** and the **sacrum**. - It plays a crucial role in supporting the rectum and forms part of the posterior rectosacral space, separating the rectum from the sacral bone and nerves. *In front of the bladder* - The space in front of the bladder is typically referred to as the **retropubic space of Retzius**, containing loose connective tissue and fat. - No specific fascial layer named Waldeyer's fascia is located in this anterior position relative to the bladder. *Between the bladder and uterus* - This space, known as the **vesicouterine pouch** or **anterior cul-de-sac**, is a peritoneal reflection between the bladder and the uterus [1]. - It does not contain a structure known as Waldeyer's fascia. *Between the uterus and rectum* - This space is the **rectouterine pouch** or **Pouch of Douglas**, which is the deepest part of the peritoneal cavity in females [2]. - While important surgically, it does not correspond to the location of Waldeyer's fascia.
Question 112: Which of the following is a tributary of the coronary sinus?
- A. Anterior cardiac vein
- B. Smallest cardiac vein
- C. Thebesian vein
- D. Great cardiac vein (Correct Answer)
Explanation: ***Great cardiac vein*** - The **great cardiac vein** is a major tributary that drains into the **coronary sinus**, carrying deoxygenated blood from the anterior and left ventricular walls [1]. - It travels alongside the **anterior interventricular artery** (LAD) and then wraps around the left side of the heart to join the coronary sinus [1]. *Anterior cardiac vein* - The **anterior cardiac veins** typically collect blood directly into the **right atrium**, bypassing the coronary sinus [1]. - They primarily drain the anterior wall of the right ventricle. *Thebesian vein* - **Thebesian veins** (or venae cordis minimae) are small veins that drain blood from the **myocardium directly into the heart chambers**, predominantly the atria [1]. - They represent a direct communication between the myocardial capillaries and the heart chambers, not tributaries of the coronary sinus. *Smallest cardiac vein* - The term "smallest cardiac vein" is often used synonymously with **Thebesian veins** [1]. - These veins empty directly into the **heart chambers**, serving as an ancillary drainage system, rather than converging into the coronary sinus.
Question 113: Lymphatic drainage of cervix is to
- A. Iliac lymph nodes (Correct Answer)
- B. Para-aortic lymph nodes
- C. Deep inguinal lymph nodes
- D. Superficial inguinal lymph nodes
Explanation: ***Iliac lymph nodes*** - The primary lymphatic drainage of the cervix is to the **internal**, **external**, and **common iliac lymph nodes**. - This pathway is crucial for understanding the spread of **cervical cancer**. *Para-aortic lymph nodes* - While sometimes involved in advanced cases, the **para-aortic nodes** are typically considered a secondary drainage site, usually after the iliac nodes are affected. - They are the primary drainage for organs like the **ovaries** and **testes**. *Deep inguinal lymph nodes* - These nodes primarily drain structures of the **lower limb** and some external genital areas, but not the cervix directly. - They are located deeper in the groin region, distinct from the internal pelvic drainage. *Superficial inguinal lymph nodes* - These nodes drain the **skin of the lower abdomen**, perineum, and external genitalia, as well as the lower limbs. - They do not receive direct lymphatic drainage from the **cervix**.
Question 114: What is the lower limit of the retropharyngeal space?
- A. Bifurcation of trachea (Correct Answer)
- B. 4th esophageal constriction
- C. C7
- D. None of the options
Explanation: Bifurcation of trachea - The retropharyngeal space extends inferiorly to approximately the level of T4-T5 vertebrae, corresponding to the bifurcation of the trachea and the superior mediastinum. - This space lies between the buccopharyngeal fascia (posterior to pharynx) and the alar layer of prevertebral fascia. - Clinically, infections or abscesses in this space can descend into the posterior mediastinum, making knowledge of this inferior extent crucial for surgical management. - Note: Some anatomical texts describe the space ending at T1-T2, but for clinical and surgical purposes, the functional inferior limit extends to the bifurcation of the trachea. C7 - While some texts describe the retropharyngeal space as terminating around C7 (level of the lower border of cricoid cartilage), this represents the narrower definition. - The clinical and surgical definition extends the space further inferiorly to allow for tracking of infections into the chest. - C7 alone does not represent the accepted lower limit for examination purposes. 4th esophageal constriction - The fourth esophageal constriction is not a standard anatomical landmark (esophagus has 3-4 constrictions depending on classification). - Esophageal constrictions are luminal narrowings within the esophagus itself and do not define the boundaries of the retropharyngeal space, which is a fascial space posterior to both pharynx and esophagus. None of the options - This is incorrect because bifurcation of the trachea is the recognized lower limit of the retropharyngeal space for clinical and examination purposes. - Understanding this anatomical boundary is essential for predicting the spread of deep neck space infections.
Question 115: The thyrocervical trunk is a branch of which part of subclavian artery?
- A. 1st part (Correct Answer)
- B. 2nd part
- C. 3rd part
- D. 4th part
Explanation: ***1st part*** - The **thyrocervical trunk** is one of the three primary branches arising from the **first part** of the subclavian artery. - The first part lies medial to the **anterior scalene muscle**. *2nd part* - The **second part** of the subclavian artery gives rise to the **costocervical trunk**. - This part lies posterior to the **anterior scalene muscle**. *3rd part* - The **third part** of the subclavian artery typically has no branches or may give off the **dorsal scapular artery**. - This part lies lateral to the **anterior scalene muscle**. *4th part* - This option is incorrect as the **subclavian artery has only three parts**, divided by their relationship to the anterior scalene muscle. - There is no anatomical fourth part of the subclavian artery.
Biochemistry
1 questionsAt which positions does pancreatic lipase hydrolyze the ester linkages of triacylglycerides?
NEET-PG 2012 - Biochemistry NEET-PG Practice Questions and MCQs
Question 111: At which positions does pancreatic lipase hydrolyze the ester linkages of triacylglycerides?
- A. 1 and 2
- B. 2 and 3
- C. Only 3
- D. 1 and 3 (Correct Answer)
Explanation: **Correct: 1 and 3** - Pancreatic lipase specifically targets the **ester bonds at the sn-1 and sn-3 positions** (primary alcohol positions) on the glycerol backbone of triacylglycerides. - This positional specificity results in the formation of **2-monoacylglycerol (2-MAG)** and **two free fatty acids**. - This is the characteristic action of pancreatic triacylglycerol lipase during fat digestion in the intestinal lumen. *Incorrect: 1 and 2* - Hydrolysis at positions 1 and 2 would produce a 3-monoacylglycerol and free fatty acids, which is not the physiological product of pancreatic lipase. - The enzyme's positional specificity favors the outer sn-1 and sn-3 positions, not the middle sn-2 position. *Incorrect: 2 and 3* - Hydrolysis at positions 2 and 3 would yield a 1-monoacylglycerol and free fatty acids, which does not reflect pancreatic lipase activity. - The enzyme specifically spares the sn-2 position due to its structural specificity. *Incorrect: Only 3* - If only position 3 were hydrolyzed, the product would be a 1,2-diacylglycerol and one free fatty acid. - This represents incomplete hydrolysis; pancreatic lipase typically hydrolyzes **both outer positions (sn-1 and sn-3)** due to its regiospecificity.
Physiology
4 questionsWhich of the following statements about lung compliance is NOT true?
What is the normal range of interstitial pressure?
ANP acts at which site?
What is the effect of acetylcholine on the Lower Esophageal Sphincter (LES)?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 111: Which of the following statements about lung compliance is NOT true?
- A. Measured by intrapleural pressure at different lung volumes. (Correct Answer)
- B. Decreased at the height of inspiration.
- C. Increased in emphysema.
- D. Increased by surfactant.
Explanation: ***Measured by intrapleural pressure at different lung volumes.*** - Lung compliance is measured by the **change in lung volume (ΔV)** divided by the **change in transpulmonary pressure (ΔP)**, which is the difference between alveolar and intrapleural pressure. - While intrapleural pressure is a component of transpulmonary pressure, compliance is not measured solely by intrapleural pressure at different lung volumes. *Increased in emphysema.* - This statement is **true**. Emphysema involves the destruction of **elastic fibers** in the lung tissue. - Loss of elastic recoil leads to an **increase in compliance**, meaning the lungs are easier to distend but collapse more readily. *Decreased at the height of inspiration.* - This statement is **true**. At high lung volumes (height of inspiration), the **elastic limit** of the lung tissue is approached. - The lungs become **stiffer** and less compliant, requiring a greater pressure change for a given volume change. *Increased by surfactant.* - This statement is **true**. Surfactant reduces **surface tension** in the alveoli. - By lowering surface tension, surfactant prevents alveolar collapse and **increases overall lung compliance**, making it easier to inflate the lungs.
Question 112: What is the normal range of interstitial pressure?
- A. -3 to 0 mmHg
- B. -5 to 0 mmHg (Correct Answer)
- C. 0 to 5 mmHg
- D. 5 to 10 mmHg
Explanation: ***-5 to 0 mmHg*** - The interstitial fluid is normally under a **slight negative pressure**, typically ranging from **-5 to 0 mmHg** - This negative pressure helps pull fluid from the capillaries into the interstitial space and facilitates **lymphatic drainage** - Maintained by continuous drainage of fluid and proteins by the **lymphatic system** - This range is the commonly accepted value in standard physiology references for Indian medical exams *-3 to 0 mmHg* - While this range acknowledges the typically **negative nature** of interstitial pressure, it represents a slightly narrower range - Some sources cite this as the average range, but **-5 to 0 mmHg** is the more commonly accepted standard range - Not the most precise or widely cited range for exam purposes *0 to 5 mmHg* - This range suggests a **positive interstitial pressure**, which is generally **abnormal** - Indicates **edema formation** due to excess fluid accumulation in the interstitial space - Positive pressure impairs fluid reabsorption and lymphatic drainage - Represents pathological fluid dynamics *5 to 10 mmHg* - Represents significant **positive interstitial pressure** leading to severe **interstitial edema** - Markedly impairs tissue function and fluid exchange - Indicates pathological conditions where capillary filtration far exceeds lymphatic drainage capacity - Associated with severe edematous states
Question 113: ANP acts at which site?
- A. Glomerulus
- B. Loop of Henle
- C. PCT
- D. Collecting duct (Correct Answer)
Explanation: ***Collecting duct*** - Atrial Natriuretic Peptide (**ANP**) exerts its primary effect on the **collecting duct** by inhibiting sodium reabsorption, leading to increased sodium and water excretion (natriuresis and diuresis). - This action helps to reduce blood volume and blood pressure in conditions like **hypervolemia**. *Glomerulus* - While ANP does cause **afferent arteriolar dilation** and **efferent arteriolar constriction**, increasing **glomerular filtration rate** (GFR), its direct tubular action is most prominent in the collecting duct. - The primary function of the glomerulus is **filtration**, influenced by many factors including pressure, but it is not the main site of ANP's direct tubular reabsorptive effects. *Loop of Henle* - The loop of Henle is responsible for establishing the **medullary osmotic gradient** and reabsorbing a significant amount of sodium and water. - ANP has minor effects on the loop of Henle, but its most impactful reabsorptive modulation occurs downstream in the collecting duct. *PCT* - The **proximal convoluted tubule (PCT)** is where the bulk of reabsorption of filtered substances (e.g., glucose, amino acids, most sodium and water) occurs. - ANP has very little direct influence on the reabsorptive processes of the PCT.
Question 114: What is the effect of acetylcholine on the Lower Esophageal Sphincter (LES)?
- A. Causes contraction (Correct Answer)
- B. Causes relaxation
- C. No effect on LES
- D. Contraction followed by relaxation
Explanation: ***Correct Option: Causes contraction*** - Acetylcholine acts on **M3 muscarinic receptors** on LES smooth muscle cells to cause **contraction** - This is part of the **excitatory cholinergic pathway** that maintains LES tone and prevents gastroesophageal reflux - Acetylcholine is released from **excitatory motor neurons** in the myenteric plexus *Incorrect: Causes relaxation* - LES relaxation during swallowing is mediated by **nitric oxide (NO)** and **vasoactive intestinal peptide (VIP)**, NOT acetylcholine - These inhibitory neurotransmitters are released from separate **inhibitory motor neurons** - The relaxation response during swallowing is due to activation of the inhibitory pathway, which suppresses cholinergic tone *Incorrect: No effect on LES* - Acetylcholine has a significant effect on the LES - It is one of the key neurotransmitters maintaining basal LES tone - Loss of cholinergic input can lead to decreased LES pressure *Incorrect: Contraction followed by relaxation* - Acetylcholine itself causes only contraction - The swallowing reflex involves coordinated activation of inhibitory (NO/VIP) and suppression of excitatory (acetylcholine) pathways - The sequence of events is neural, not a biphasic response to acetylcholine alone