Anatomy
1 questionsWhat is the typical length of a human sperm cell?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 381: What is the typical length of a human sperm cell?
- A. 55 micrometers (Correct Answer)
- B. 50 micrometers
- C. 100 micrometers
- D. 65 micrometers
Explanation: ***55 micrometers*** - A typical **human sperm cell** measures approximately **55 micrometers** from the head to the tip of the tail [1]. - This length allows for efficient motility and navigation within the female reproductive tract to reach the ovum [1]. *100 micrometers* - This length is significantly **longer** than the average size of a human sperm cell. - While some cells can achieve this size, it is not typical for **spermatozoa**. *65 micrometers* - Although closer to the actual size, **65 micrometers** is generally considered slightly larger than the average human sperm cell length. - Sperm length is critical for understanding their **mobility** and **fertility** [1]. *50 micrometers* - This measurement is slightly **shorter** than the typical length of a human sperm cell. - The precise length, including the **head** and **flagellum**, contributes to its function.
Biochemistry
3 questionsAt which positions does pancreatic lipase hydrolyze the ester linkages of triacylglycerides?
Which of the following GAG is not sulfated?
Male to male transmission is seen in -
NEET-PG 2012 - Biochemistry NEET-PG Practice Questions and MCQs
Question 381: 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.
Question 382: Which of the following GAG is not sulfated?
- A. Keratan sulfate
- B. Dermatan sulfate
- C. Chondroitin sulfate
- D. Hyaluronic acid (Correct Answer)
Explanation: ***Hyaluronic acid*** - **Hyaluronic acid** is unique among glycosaminoglycans (GAGs) because it is the only one that is **not sulfated**. - It also distinguishes itself by being the only GAG that does **not form proteoglycans** and is not synthesized in the Golgi apparatus. *Chondroitin sulfate* - **Chondroitin sulfate** is a sulfated glycosaminoglycan that is a major component of the **extracellular matrix**, particularly in cartilage. - Its sulfate groups contribute to its **negative charge**, allowing it to attract water and provide resistance to compression. *Dermatan sulfate* - **Dermatan sulfate** is another sulfated GAG, found predominantly in the skin, blood vessels, and heart valves. - It contains **sulfate groups**, which are crucial for its interactions with various proteins and its role in tissue structure. *Keratan sulfate* - **Keratan sulfate** is a sulfated GAG found in the cornea, cartilage, and bone. - It is distinct from other GAGs due to its **lack of uronic acid** and the presence of sulfate groups.
Question 383: Male to male transmission is seen in -
- A. Autosomal dominant diseases (Correct Answer)
- B. Autosomal recessive
- C. X-linked dominant
- D. Mitochondrial disease
Explanation: ***Autosomal dominant diseases*** - **Autosomal dominant** inheritance patterns involve a gene located on one of the **autosomes**, meaning it is not sex-linked. - Therefore, a father carrying an autosomal dominant gene can pass it to both sons and daughters with a **50% probability** for each child. - **Male-to-male transmission** is a hallmark feature that helps distinguish autosomal dominant from X-linked inheritance patterns. *Autosomal recessive* - **Autosomal recessive** diseases require **two copies** of the mutated gene (one from each parent) for the disease to manifest. - While a father can pass a recessive allele to his son, male-to-male transmission of the **disease phenotype** requires the mother to also be at least a carrier, making it not a defining feature of this inheritance pattern. - The key characteristic is horizontal pattern (affected siblings) rather than vertical transmission. *X-linked dominant* - In **X-linked dominant** inheritance, affected fathers **cannot** transmit the trait to their sons because sons inherit their **X chromosome** from their mother and their Y chromosome from their father. - All daughters of an affected father will inherit the affected X chromosome and thus the disease. - **Absence of male-to-male transmission** is a key distinguishing feature. *Mitochondrial disease* - **Mitochondrial diseases** are inherited exclusively from the **mother** to all her children, regardless of their sex. - Fathers with mitochondrial disease cannot transmit the condition to any of their children. - This shows **maternal inheritance only**, with no paternal transmission possible.
Pathology
3 questionsWhich of the following does not belong to the family of selectins?
In which type of Hodgkin's Lymphoma are lacunar cells typically observed?
What type of anaemia is primarily associated with leukaemia?
NEET-PG 2012 - Pathology NEET-PG Practice Questions and MCQs
Question 381: Which of the following does not belong to the family of selectins?
- A. P selectin
- B. L selectin
- C. A selectin (Correct Answer)
- D. E selectin
Explanation: ***A selectin*** - ***A selectin*** is not a recognized member of the selectin family, which includes other specific types. - The known selectins are **E-selectin**, **L-selectin**, and **P-selectin**, demonstrating a distinct classification [1]. *E selectin* - E selectin is a specific type of selectin expressed on **endothelial cells** activated by cytokines [1]. - It plays a crucial role in **leukocyte adhesion** during inflammation, distinguishing it as part of the selectin family [1]. *L selectin* - L selectin is involved in the **homing** of leukocytes to lymph nodes and forms part of the selectin family [1]. - Responsible for the initial tethering and rolling of leukocytes on **venular endothelium** [1]. *P selectin* - P selectin is found on platelets and endothelial cells and is critical in the **aggregation** of platelets and leukocytes. - It is also an established member of the selectin family, involved in **inflammatory responses** [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 87.
Question 382: In which type of Hodgkin's Lymphoma are lacunar cells typically observed?
- A. Mixed cellularity type
- B. Lymphocyte predominant type
- C. Nodular Sclerosis type (Correct Answer)
- D. All of the options
Explanation: ***Nodular Sclerosis Type*** - **Lacunar cells** are characteristically seen in **Nodular Sclerosis Hodgkin lymphoma**, which is the most common subtype [1][3]. - These cells are large **Reed-Sternberg cells** with a distinctive morphology, typically found in **fibrous areas** of the lymph node [1]. *Mixed cellularity type* - This subtype is associated with a diverse cell population but does not primarily feature **lacunar cells** [2][4]. - It predominantly contains **Reed-Sternberg cells** without the specific morphology seen in nodular sclerosis [2]. *Lymphocyte predominant* - Lymphocyte predominant type mainly consists of **lymphocytes** with few Reed-Sternberg cells, and lacks **lacunar cells** [5]. - The histology is significantly different, exhibiting a more lymphocytic composition and not the classic lucent spaces [5]. *All of the above* - This option is incorrect as neither **Mixed cellularity** nor **Lymphocyte predominant** types contain **lacunar cells** [2][4][5]. - Lacunar cells are a distinctive feature solely of the **Nodular Sclerosis type** in Hodgkin lymphoma [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 616. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 616-618. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 558-559. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 559-560. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 618.
Question 383: What type of anaemia is primarily associated with leukaemia?
- A. Aplastic anaemia
- B. Iron deficiency anaemia
- C. Megaloblastic anaemia
- D. Myelophthisic anaemia (Correct Answer)
Explanation: ***Myelophthisic anaemia*** - This condition arises from the **displacement of normal hematopoietic tissue** in the bone marrow by abnormal cells, like those seen in leukaemia, leading to **extramedullary hematopoiesis**. - Marrow infiltration causes **pancytopenia** and often results in the presence of **immature granulocytes** and **nucleated red blood cells** in the peripheral blood (leukoerythroblastosis). *Iron deficiency anaemia* - This type of anaemia is caused by insufficient iron for **hemoglobin synthesis**, often due to chronic blood loss or inadequate dietary intake. - While leukaemia patients can develop iron deficiency due to bleeding, it is not the **primary type of anaemia** directly resulting from the marrow infiltration by leukaemic cells. *Megaloblastic anaemia* - Characterized by the production of abnormally large, immature red blood cells, primarily due to **vitamin B12** or **folate deficiency**. - There is no direct causal link between leukaemia and the development of megaloblastic anaemia as a **primary haemato-pathological mechanism**. *Aplastic anaemia* - Characterized by **pancytopenia** due to bone marrow failure with hypocellular marrow, not marrow infiltration. - While both leukaemia and aplastic anaemia can present with cytopenias, aplastic anaemia shows a **hypocellular marrow** whereas leukaemia shows a **hypercellular marrow** with infiltration by malignant cells.
Physiology
2 questionsWhat happens to the pressure in the calf compartment during the heel touch phase of walking?
Which of the following statements is true regarding the function of the spinocerebellar tract?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 381: What happens to the pressure in the calf compartment during the heel touch phase of walking?
- A. Decreases compared to resting pressure
- B. First increases and then decreases
- C. Remains the same as resting pressure
- D. Increases compared to resting pressure (Correct Answer)
Explanation: ***Increases compared to resting pressure*** - During **heel strike (initial contact)**, the calf muscles (**gastrocnemius and soleus**) contract eccentrically to control ankle dorsiflexion and decelerate the foot - Simultaneous **weight bearing** and **muscle contraction** within the confined fascial compartment lead to increased intramuscular pressure - This is a well-documented phenomenon in gait biomechanics and exercise physiology *Decreases compared to resting pressure* - Incorrect: Muscle activation and weight bearing during initial contact inherently increase compartment pressure - Pressure decrease occurs during swing phase when the limb is unloaded and muscles are relaxed *First increases and then decreases* - While pressure varies throughout the complete gait cycle, the **heel touch phase specifically** is characterized by an initial pressure increase - The brief duration of heel strike does not typically show a biphasic pressure pattern within this single phase *Remains the same as resting pressure* - Incorrect: Active weight bearing and eccentric muscle contraction during heel strike necessarily elevate intramuscular pressure above resting levels - Resting pressure only occurs when the limb is unloaded and muscles are inactive
Question 382: Which of the following statements is true regarding the function of the spinocerebellar tract?
- A. Smoothens and coordinates movements (Correct Answer)
- B. Involved in planning and programming motor activities
- C. Involved in maintaining equilibrium
- D. Facilitates learning through vestibulo-ocular reflex changes
Explanation: ***Smoothens and coordinates movements*** - The spinocerebellar tract provides the cerebellum with **unconscious proprioceptive information** from muscle spindles and Golgi tendon organs. - This information allows the cerebellum to compare intended movements with actual movements, thereby **smoothing and coordinating voluntary motor activity**. *Involved in planning and programming motor activities* - This function is primarily attributed to the **cerebral cortex** (e.g., premotor and supplementary motor areas) and the **basal ganglia**. - While the cerebellum is involved in motor learning and fine-tuning, the initial **planning and programming** of complex movements are cortical functions. *Involved in maintaining equilibrium* - Maintaining equilibrium and balance is primarily a function of the **vestibulocerebellum** (flocculonodular lobe), which receives input from the vestibular system. - While the spinocerebellum indirectly influences balance by coordinating limb movements, its direct role is less pronounced than that of the vestibulocerebellum. *Facilitates learning through vestibulo-ocular reflex changes* - This function is specific to the **vestibulocerebellum** and is crucial for adapting the vestibulo-ocular reflex (VOR) to maintain visual stability during head movements. - The spinocerebellar tract's primary role is proprioception for limb coordination, not VOR adaptation.
Radiology
1 questionsWhat is the primary mechanism of heat loss in a modern X-ray tube?
NEET-PG 2012 - Radiology NEET-PG Practice Questions and MCQs
Question 381: What is the primary mechanism of heat loss in a modern X-ray tube?
- A. Radiation (Correct Answer)
- B. Evaporation
- C. Conduction
- D. Convection
Explanation: ***Radiation*** - The **primary mechanism** of heat loss in a modern X-ray tube is **radiation** (infrared emission). - The anode surface reaches extremely high temperatures (>1000°C) during X-ray production, causing it to emit significant **infrared radiation**. - Modern X-ray tubes use **high-emissivity materials** (tungsten-rhenium alloys) on the anode to maximize radiative heat transfer. - Since the tube operates in a **vacuum**, radiation is the only effective mechanism for heat dissipation from the anode itself. *Evaporation* - **Evaporation** requires a liquid-to-gas phase change, which is not applicable in the solid-state environment of an X-ray tube anode. - The **vacuum environment** inside the tube prevents any evaporative cooling. - This mechanism is irrelevant for heat loss from the anode. *Conduction* - **Conduction** does transfer heat from the focal spot through the anode body to the rotor bearings. - However, this is heat transfer *within* the tube components, not the primary mechanism for heat loss *from the tube*. - Heat conducted through components must ultimately be dissipated by **radiation** (from anode) or **convection** (from housing via cooling oil). *Convection* - **Convection** requires fluid movement (liquid or gas), which cannot occur in the **vacuum** inside the X-ray tube envelope. - While cooling oil outside the tube uses convection to remove heat from the housing, this is secondary heat removal, not the primary mechanism of heat loss from the anode. - The anode loses heat primarily via **radiation** first, then that heat may be further managed by convection in the cooling system.