NEET-PG 2012 Practice Questions

Q: Pancreas divisum indicates which of the following?

Failure of fusion of dorsal & ventral pancreatic buds. ***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.

Q: Which structure is not seen at the L3 level?

Coeliac trunk. ***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.

Q: Which of the following is NOT an anterior relation of the right kidney?

4th part of duodenum. ***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.

Q: Which of the following is NOT a surface marking of the oblique fissure of the lung?

7th rib. ***7th rib*** - The **oblique fissure** typically extends from the spine at approximately the **T3 vertebral level** anteriorly to the **6th costal cartilage**. [1] - The **7th rib** is generally inferior to the typical anterior termination point of the oblique fissure. [1] *T3* - The **oblique fissure** begins posteriorly at the level of the **spinous process of T3**. [1] - This marks the superior-posterior extent of the fissure on the surface. *5th rib* - The **oblique fissure** crosses the **5th intercostal space** on the lateral chest wall. [1] - This point helps map the fissure's path between its posterior and anterior endpoints. *6th costal cartilage* - The **oblique fissure** terminates anteriorly near the **6th costal cartilage** in the midclavicular line. [1] - This represents the inferior-anterior most point of the fissure on the chest wall.

Q: During incision and drainage of ischiorectal abscess, which nerve is most likely to be injured?

Inferior rectal nerve. ***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.

Q: Km value is defined as:

Substrate concentration at Vmax/2. ***Substrate concentration at Vmax/2*** - The **Michaelis constant (Km)** is defined as the **substrate concentration** at which the reaction velocity is **half of the maximum velocity (Vmax/2)**. - It reflects the **affinity of an enzyme for its substrate**; a lower Km indicates higher affinity. *Substrate concentration at which reaction rate is maximum* - The **maximum reaction rate (Vmax)** is achieved when the enzyme is **saturated with substrate**, meaning all active sites are occupied. - Km specifically refers to the substrate concentration needed to reach **half of this maximum rate**, not the maximum rate itself. *Substrate concentration at Vmax* - At **Vmax**, the enzyme is fully saturated with substrate, and the reaction rate cannot increase further by adding more substrate. - The **Km value** is a measure related to the **efficiency of substrate binding** at conditions below saturation, specifically at half Vmax. *Substrate concentration at which enzyme activity is optimal* - **Optimal enzyme activity** is generally influenced by factors such as **pH and temperature**, which affect the enzyme's structure and catalytic efficiency. - Km is specifically related to the **substrate concentration** required to achieve a specific reaction rate, not the overall optimal environmental conditions for the enzyme.

Q: Enzymes that move a molecular group from one molecule to another are known as -

Transferases. ***Transferases*** - **Transferases** are a class of enzymes that catalyze the transfer of a specific functional group (e.g., methyl, acetyl, phosphate) from one molecule (the donor) to another (the acceptor). - This broad category includes enzymes vital for many metabolic pathways, such as **kinases** (transferring phosphate groups) and **transaminases** (transferring amino groups). *Ligases* - **Ligases** are enzymes responsible for joining two large molecules together, typically by forming a new chemical bond. - This process usually involves the concomitant hydrolysis of a small, energy-rich molecule such as **ATP**, to provide the necessary energy for bond formation. *Dipeptidases* - **Dipeptidases** are a type of hydrolase enzyme that specifically cleaves the peptide bond within a **dipeptide**, releasing two free amino acids. - They are crucial for the final stages of protein digestion, breaking down small peptides into absorbable **amino acid units**. *Oxido-reductases* - **Oxido-reductases** are enzymes that catalyze **oxidation-reduction reactions** (redox reactions), where electrons are transferred from one molecule to another. - This class includes enzymes like **dehydrogenases** and **oxidases**, which play critical roles in cellular respiration and energy production.

Q: Insensible water loss per day is ?

1000 ml. ***1000 ml*** - **Insensible water loss** occurs through the skin (evaporation) and respiratory tract (exhalation) without conscious perception. - The typical daily insensible water loss in an adult is approximately **800-1000 ml/day**. - **Breakdown**: Skin evaporation (~400-500 ml) + Respiratory tract (~300-400 ml) = **~900-1000 ml total**. - **1000 ml** is the standard value cited in major physiology textbooks (Guyton & Hall, Ganong) and is the most commonly accepted answer for NEET PG examinations. *100 ml* - This value is significantly **lower** than the actual insensible water loss, which occurs continuously throughout the day. - Such a low volume would imply negligible evaporation and respiratory loss, which is not physiologically accurate. *300 ml* - While greater than 100 ml, 300 ml is still **far below** the typical range for daily insensible water loss. - This amount represents only about one-third of the actual insensible losses from the skin and respiratory system combined. *700 ml* - Although this value is sometimes mentioned in literature, it is at the **lower end** of the physiological range. - The more widely accepted standard value for insensible water loss in a healthy adult under normal conditions is **900-1000 ml/day**. - 700 ml would underestimate the normal daily insensible losses.

Q: Which of the following factors increases the rate of particle diffusion across the cell membrane?

Maintaining a concentration gradient across the membrane. ***Maintaining a concentration gradient across the membrane*** - **Diffusion** is the net movement of particles from an area of higher concentration to an area of lower concentration, driven by the **concentration gradient**. - A steeper gradient means a larger difference in concentration, leading to a faster rate of net diffusion until equilibrium is reached. - According to **Fick's Law**, the rate of diffusion is directly proportional to the concentration gradient across the membrane. *Decreasing the lipid solubility of the substance* - The cell membrane is primarily composed of a **lipid bilayer**, meaning that substances with **higher lipid solubility** can more easily pass through it via simple diffusion. - Decreasing lipid solubility would **hinder** the substance's ability to cross the membrane, thus slowing down or preventing diffusion. *Increasing the size of the opening in the cell membrane* - While increasing channel or pore diameter can increase diffusion rate for **channel-mediated transport**, this option is less comprehensive than maintaining a concentration gradient. - The concentration gradient is the **primary driving force** for diffusion across all types of membrane transport (simple diffusion through lipid bilayer, channel-mediated, and carrier-mediated). - Channel size is relevant only for specific facilitated diffusion pathways, not for general particle diffusion. *Increasing the size of the particle* - **Smaller particles** generally diffuse faster than larger particles because they have higher diffusion coefficients and can more easily navigate through the membrane. - According to the **Stokes-Einstein equation**, diffusion rate is inversely proportional to particle size. - Increasing particle size would therefore **decrease** the rate of diffusion.

Q: What is the average daily volume of pancreatic secretion in humans?

1.5 L. ***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 1

Pancreas divisum indicates which of the following?

Accepted Answer

Failure of fusion of dorsal & ventral pancreatic buds

Answer

Duplication of the pancreas

Answer

Formation of more than two pancreatic buds

Answer

Formation of only one pancreatic bud

Question 2

Which structure is not seen at the L3 level?

Accepted Answer

Coeliac trunk

Answer

Iliac vessels

Answer

Aorta

Answer

IVC

Question 3

Which of the following is NOT an anterior relation of the right kidney?

Accepted Answer

4th part of duodenum

Answer

Hepatic flexure

Answer

Liver

Answer

2nd part of duodenum

Question 4

Which of the following is NOT a surface marking of the oblique fissure of the lung?

Accepted Answer

7th rib

Answer

6th costal cartilage

Answer

T3

Answer

5th rib

Question 5

During incision and drainage of ischiorectal abscess, which nerve is most likely to be injured?

Accepted Answer

Inferior rectal nerve

Answer

Superior rectal nerve

Answer

Superior gluteal nerve

Answer

Inferior gluteal nerve

Question 6

Km value is defined as:

Accepted Answer

Substrate concentration at Vmax/2

Answer

Substrate concentration at which reaction rate is maximum

Answer

Substrate concentration at Vmax

Answer

Substrate concentration at which enzyme activity is optimal

Question 7

Enzymes that move a molecular group from one molecule to another are known as -

Accepted Answer

Transferases

Answer

Ligases

Answer

Dipeptidases

Answer

Oxido-reductases

Question 8

Insensible water loss per day is ?

Accepted Answer

1000 ml

Answer

100 ml

Answer

700 ml

Answer

300 ml

Question 9

Which of the following factors increases the rate of particle diffusion across the cell membrane?

Accepted Answer

Maintaining a concentration gradient across the membrane

Answer

Decreasing the lipid solubility of the substance

Answer

Increasing the size of the opening in the cell membrane

Answer

Increasing the size of the particle

Question 10

What is the average daily volume of pancreatic secretion in humans?

Accepted Answer

1.5 L

Answer

5.0 L

Answer

10 L

Answer

2.5 L

NEET-PG 2012

Anatomy

Biochemistry

Physiology