Anatomy
6 questionsNucleus gracilis and nucleus cuneatus are seen in?
Which of the following is an operculated sulcus ?
Which structure is not seen at the L3 level?
Which of the following is NOT an anterior relation of the right kidney?
In which region of the human spine is the number of vertebrae usually constant?
Pancreas divisum indicates which of the following?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 41: Nucleus gracilis and nucleus cuneatus are seen in?
- A. Medulla (Correct Answer)
- B. Temporal lobe
- C. Midbrain
- D. Pons
Explanation: ***Medulla*** - The **nucleus gracilis** and **nucleus cuneatus** are located in the **dorsal medulla** and are crucial for processing **conscious proprioception**, **vibration**, and **fine touch**. - These nuclei receive input from the fasciculus gracilis and fasciculus cuneatus (dorsal column tracts) and are part of the dorsal column-medial lemniscus pathway. - They give rise to the **internal arcuate fibers** which decussate and form the **medial lemniscus**. *Pons* - The pons contains several important nuclei, including the **pontine nuclei** (involved in motor coordination), nuclei of cranial nerves V, VI, VII, and VIII, and the **locus coeruleus**. - The dorsal column nuclei are not located in the pons. *Temporal lobe* - The **temporal lobe** is part of the cerebral cortex and is primarily involved in **auditory processing**, memory formation, and language comprehension. - It contains structures like the hippocampus and amygdala, but not the dorsal column nuclei. *Midbrain* - The **midbrain** contains nuclei such as the **red nucleus**, **substantia nigra**, and nuclei of cranial nerves III and IV, involved in motor control and eye movements. - The nucleus gracilis and nucleus cuneatus are not found in the midbrain.
Question 42: Which of the following is an operculated sulcus ?
- A. Lunate
- B. Calcarine
- C. Central
- D. Sylvian fissure (lateral sulcus) (Correct Answer)
Explanation: ***Sylvian fissure (lateral sulcus)*** - The **lateral sulcus**, also known as the Sylvian fissure, is a deep groove on the lateral surface of the brain that **separates the frontal and parietal lobes from the temporal lobe**. - It is considered an **operculated sulcus** because its banks contain the insula, which is a buried part of the cerebral cortex covered by the surrounding cortical folds called opercula. *Calcarine* - The **calcarine sulcus** is located on the medial surface of the occipital lobe, forming the primary visual cortex, and is not an operculated sulcus. - It delineates the **upper and lower banks of the visual cortex** and does not involve overlying cortical structures. *Lunate* - The **lunate sulcus** is found on the posterior part of the occipital lobe and is not typically described as an operculated sulcus. - It represents a boundary in the visual cortex, but its banks do not hide a buried cortical region like the insula. *Central* - The **central sulcus** (Rolandic fissure) separates the frontal lobe from the parietal lobe and is a prominent sulcus, but it is not operculated. - Its banks contain the **precentral gyrus** (primary motor cortex) and **postcentral gyrus** (primary somatosensory cortex) directly facing each other.
Question 43: Which structure is not seen at the L3 level?
- A. Iliac vessels
- B. Aorta
- C. Coeliac trunk (Correct Answer)
- D. IVC
Explanation: ***Coeliac trunk*** - The **coeliac trunk** typically arises from the abdominal **aorta** at the level of **T12-L1**, which is significantly higher than L3. - It then immediately branches into the **left gastric**, **splenic**, and **common hepatic arteries** to supply foregut structures. *Iliac vessels* - The **common iliac arteries** and veins typically bifurcate from the **aorta** and **IVC** around the L4-L5 level. - Their presence, or the start of their formation, can be observed near or just above **L3**, depending on individual anatomical variation and how "at the L3 level" is interpreted (e.g., within the L3 vertebral body's span). *Aorta* - The **abdominal aorta** descends along the posterior abdominal wall and is a prominent structure at the **L3 level**. - It typically bifurcates into the common iliac arteries at the level of **L4**, meaning it is still a large, undivided vessel at L3. *IVC* - The **inferior vena cava (IVC)** ascends through the abdomen and is a significant vascular structure at the **L3 level**. - It is formed by the union of the common iliac veins at the level of **L5** and continues superiorly.
Question 44: Which of the following is NOT an anterior relation of the right kidney?
- A. Hepatic flexure
- B. Liver
- C. 4th part of duodenum (Correct Answer)
- D. 2nd part of duodenum
Explanation: ***4th part of duodenum*** - The **4th part of the duodenum** is located to the **left of the vertebral column** and is related to the **left kidney**, not the right kidney. - This segment passes superiorly along the left side of the aorta to become continuous with the jejunum at the duodenojejunal flexure. *Liver* - The **right kidney's superior part** is in direct contact with the **right lobe of the liver**, often separated only by the peritoneum [1]. - This is a significant anterior relation, explaining why liver enlargement can sometimes displace the right kidney. *Hepatic flexure* - The **hepatic flexure** (right colic flexure) of the colon lies immediately inferior to the liver and anterior to the **lower part of the right kidney**. - This anatomical relationship means that the right kidney can be affected by diseases of the colon in this region. *2nd part of duodenum* - The **descending (2nd) part of the duodenum** lies anterior to the **hilum and medial part of the right kidney** [1]. - Its retroperitoneal position places it in close proximity to the renal structures, making it a key anterior relation.
Question 45: In which region of the human spine is the number of vertebrae usually constant?
- A. Cervical (Correct Answer)
- B. Thoracic
- C. Lumbar
- D. Sacral
Explanation: ***Cervical*** - The human cervical spine almost universally consists of **seven vertebrae (C1-C7)**, making it the most constant region in terms of vertebral number. - This consistent number is crucial for normal neck movement and protection of vital neurological structures. *Thoracic* - While typically having **12 vertebrae**, variations in the thoracic region can occur, with some individuals having 11 or 13 due to transitional vertebrae. - These variations are less common but indicate that the number is not as strictly constant as in the cervical spine. *Lumbar* - The lumbar spine commonly has **five vertebrae (L1-L5)**, but variations such as four or six lumbar vertebrae can be seen due to lumbarization or sacralization. - **Lumbarization** involves the first sacral segment detaching, while **sacralization** involves the fifth lumbar vertebra fusing with the sacrum. *Sacral* - The sacrum is formed by the fusion of **five sacral vertebrae (S1-S5)**, but the number of *individual identifiable* vertebrae before fusion, or in cases of incomplete fusion, can vary. - The sacral region itself is a fused structure, and while it originates from five segments, the concept of "number of vertebrae" can be ambiguous due to its characteristic fusion.
Question 46: Pancreas divisum indicates which of the following?
- A. Duplication of the pancreas
- B. Formation of more than two pancreatic buds
- C. Formation of only one pancreatic bud
- D. Failure of fusion of dorsal & ventral pancreatic buds (Correct Answer)
Explanation: ***Failure of fusion of dorsal & ventral pancreatic buds*** - **Pancreas divisum** is a congenital anomaly where the **dorsal and ventral pancreatic buds fail to fuse** during embryonic development [1]. - This results in the **bulk of the pancreas (dorsal bud)** draining through the **accessory pancreatic duct** into the minor duodenal papilla, while the ventral bud drains via the main pancreatic duct [1]. *Duplication of the pancreas* - This condition involves the presence of **multiple, distinct pancreatic tissues**, which is different from pancreas divisum where the existing buds simply do not fuse. - Pancreas divisum is a failure of fusion of two normally formed buds, not the formation of extra pancreatic tissue. *Formation of more than two pancreatic buds* - Normal embryonic development typically involves two pancreatic buds (dorsal and ventral), not more than two [1]. - The issue in pancreas divisum is with the **fusion process**, not the number of initial buds [1]. *Formation of only one pancreatic bud* - Pancreatic development normally involves **two distinct buds (dorsal and ventral)** [1]. - The formation of only one bud would lead to pancreatic agenesis or severe hypoplasia, which is a different anomaly than pancreas divisum.
Physiology
3 questionsWhat is the average daily volume of pancreatic secretion in humans?
What is the difference between the amount of Oxygen consumed and Carbon Dioxide produced per minute at rest?
Peripheral and central chemoreceptors may both contribute to the increased ventilation that occurs as a result of which of the following?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 41: What is the average daily volume of pancreatic secretion in humans?
- A. 5.0 L
- B. 10 L
- C. 1.5 L (Correct Answer)
- D. 2.5 L
Explanation: ***1.5 L*** - The **pancreas** produces approximately **1.5 liters (1200-1500 mL) of pancreatic juice** daily in humans. - This secretion is rich in **digestive enzymes** (amylase, lipase, proteases) and **bicarbonate** for neutralization of gastric acid in the duodenum. - This is the standard value cited in **major physiology textbooks** (Ganong, Guyton & Hall). *2.5 L* - **2.5 liters** overestimates the typical daily pancreatic secretion volume. - This value may represent **combined secretions** from multiple sources or confuse pancreatic output with total upper GI secretions. - Normal pancreatic secretion ranges from **1-2 liters**, making 2.5 L above the physiological range. *5.0 L* - **5.0 liters** represents an abnormally high volume for daily pancreatic secretion alone. - This volume is closer to the **total daily secretions** from stomach, pancreas, and bile combined. - Not consistent with **normal pancreatic physiology**. *10 L* - **10 liters** is grossly excessive for pancreatic secretion and represents approximately the **total volume of all gastrointestinal secretions** (saliva, gastric, pancreatic, bile, intestinal) combined daily. - This is **not physiologically realistic** for pancreatic output alone.
Question 42: What is the difference between the amount of Oxygen consumed and Carbon Dioxide produced per minute at rest?
- A. 20 ml/min
- B. 50 ml/min (Correct Answer)
- C. 75 ml/min
- D. 100 ml/min
Explanation: ***50 ml/min*** - The body typically consumes about **250 ml/min of oxygen** at rest and produces approximately **200 ml/min of carbon dioxide**. - The difference between oxygen consumed and carbon dioxide produced is therefore **50 ml/min** (250 - 200 = 50). - This difference exists because the **respiratory quotient (RQ)** is approximately **0.8** (200/250), meaning less CO2 is produced than O2 consumed on a molar basis. *20 ml/min* - This value is **too low** and underestimates the physiological difference between oxygen consumption and carbon dioxide production. - With typical O2 consumption of 250 ml/min and RQ of 0.8, the difference cannot be this small. *75 ml/min* - This value represents an **overestimation** of the difference between oxygen consumption and carbon dioxide production under normal resting conditions. - This would imply an RQ of approximately 0.7, which is lower than the typical mixed diet RQ of 0.8. *100 ml/min* - This value is a significant **overestimation** of the physiological difference. - This would suggest an RQ of 0.6, which is not physiologically normal for resting conditions on a mixed diet.
Question 43: Peripheral and central chemoreceptors may both contribute to the increased ventilation that occurs as a result of which of the following?
- A. A decrease in arterial oxygen content
- B. A decrease in arterial blood pressure
- C. An increase in arterial carbon dioxide tension (Correct Answer)
- D. A decrease in arterial oxygen tension
Explanation: ***An increase in arterial carbon dioxide tension*** - An increase in **arterial PCO2** (hypercapnia) leads to a rapid decrease in the **pH of the cerebrospinal fluid (CSF)**, which strongly stimulates **central chemoreceptors** in the medulla. - While overwhelmingly driven by central chemoreceptors, a significant increase in **arterial PCO2** also causes a slight decrease in **arterial pH**, which can additionally stimulate **peripheral chemoreceptors** in the carotid and aortic bodies, leading to increased ventilation. *A decrease in arterial oxygen content* - A decrease in **arterial oxygen content** (e.g., due to anemia or carbon monoxide poisoning) without a significant drop in **arterial PO2** primarily affects oxygen delivery to tissues. - It does not directly stimulate peripheral chemoreceptors, which are sensitive to **PO2**, not content, nor does it affect central chemoreceptors directly to increase ventilation in this manner. *A decrease in arterial blood pressure* - A decrease in **arterial blood pressure** is sensed by **baroreceptors** and primarily triggers cardiovascular reflexes (e.g., increased heart rate and vasoconstriction) to restore blood pressure. - It does not directly stimulate peripheral or central chemoreceptors to significantly increase ventilation unless severe hypoperfusion leads to significant changes in arterial blood gases. *A decrease in arterial oxygen tension* - A decrease in **arterial oxygen tension (PO2)**, especially when it falls below approximately 60 mmHg, acts as a potent stimulus for **peripheral chemoreceptors**. - However, **central chemoreceptors** are primarily sensitive to **PCO2** and CSF pH, and a decrease in **arterial PO2** alone has little direct effect on their activity.
Surgery
1 questionsDuring incision and drainage of ischiorectal abscess, which nerve is most likely to be injured?
NEET-PG 2012 - Surgery NEET-PG Practice Questions and MCQs
Question 41: During incision and drainage of ischiorectal abscess, which nerve is most likely to be injured?
- A. Superior rectal nerve
- B. Inferior rectal nerve (Correct Answer)
- C. Superior gluteal nerve
- D. Inferior gluteal nerve
Explanation: ***Inferior rectal nerve*** - The **inferior rectal nerve** innervates the **external anal sphincter** and the skin around the anus, making it vulnerable during an incision and drainage of an **ischiorectal abscess** due to its anatomical proximity. - Injury to this nerve can lead to **fecal incontinence** or altered sensation in the perianal region. *Superior rectal nerve* - The **superior rectal nerve** is primarily involved in the innervation of the **rectum** and is not directly located in the area of an **ischiorectal abscess**. - This nerve supplies the smooth muscle of the rectum and is not anatomically vulnerable during incision and drainage of an abscess in the ischiorectal fossa. *Superior gluteal nerve* - The **superior gluteal nerve** supplies the **gluteus medius**, **gluteus minimus**, and **tensor fasciae latae muscles**, which are typically located much more superior and lateral to an **ischiorectal abscess**. - Damage to this nerve causes a characteristic **Trendelenburg gait**, which is unrelated to perianal surgery. *Inferior gluteal nerve* - The **inferior gluteal nerve** innervates the **gluteus maximus muscle**, which is also located more superiorly and laterally relative to the **ischiorectal fossa**. - Injury to this nerve would primarily affect hip extension and is not a common complication of **ischiorectal abscess** drainage.