Anatomy
4 questionsDevelopment of labia majora is from -
What type of joint is the 1st carpometacarpal joint?
The right coronary artery supplies blood to all of the following structures, except?
All of the following arteries are branches of the coeliac trunk, EXCEPT which one?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 91: Development of labia majora is from -
- A. Urogenital sinus
- B. Mullerian duct
- C. Genital ridge
- D. Genital swelling (Correct Answer)
Explanation: ***Genital swelling*** - The **labia majora** develop from the **genital (labioscrotal) swellings** in females, which are homologous to the scrotum in males [3]. - These swellings enlarge and fuse anteriorly to form the mons pubis and posteriorly to form the posterior commissures of the labia majora. *Urogenital sinus* - The **urogenital sinus** gives rise to structures like the **bladder**, **urethra**, and parts of the **vagina** in females [2]. - It does not contribute to the formation of the external labial structures. *Mullerian duct* - The **Mullerian (paramesonephric) ducts** develop into the **fallopian tubes**, **uterus**, and the **upper third of the vagina** [1], [2]. - These structures are internal reproductive organs and do not form external genitalia like the labia majora. *Genital ridge* - The **genital ridge** is the embryonic precursor to the **gonads** (ovaries or testes). - It differentiates into either ovaries or testes and does not directly form external genital structures.
Question 92: What type of joint is the 1st carpometacarpal joint?
- A. Pivot
- B. Hinge
- C. Ball and Socket
- D. Saddle (Correct Answer)
Explanation: ***Saddle*** - The **1st carpometacarpal joint** (thumb CMC joint) is a classic example of a **saddle joint** due to the reciprocal concave-convex opposing surfaces of the trapezium and the first metacarpal [1]. - This unique shape allows for a wide range of motion, including **flexion/extension**, **abduction/adduction**, and **opposition**, which is crucial for thumb function. *Pivot* - A **pivot joint** allows for rotational movement around a single axis, like the **atlantoaxial joint** (C1-C2) or the **proximal radioulnar joint**. - This type of motion is not characteristic of the 1st carpometacarpal joint. *Hinge* - A **hinge joint** permits movement in only one plane, like the **elbow** or **interphalangeal joints**, allowing for **flexion and extension**. - The 1st carpometacarpal joint has a greater degree of freedom than a hinge joint. *Ball and Socket* - A **ball and socket joint** offers the greatest range of motion, allowing for movement in all planes, including **circumduction and rotation**, such as the **shoulder** and **hip joints**. - While the 1st carpometacarpal joint is highly mobile, it does not achieve the full range of motion of a ball and socket joint.
Question 93: The right coronary artery supplies blood to all of the following structures, except?
- A. Posterior wall of left ventricle
- B. SA node
- C. Anterior 2/3 of ventricular septum (Correct Answer)
- D. AV node
Explanation: ***Anterior 2/3 of ventricular septum*** - The **anterior two-thirds of the interventricular septum** is primarily supplied by the **septal branches of the left anterior descending artery** (LAD) [1], a branch of the left coronary artery. - Therefore, the right coronary artery does not typically supply this region. *SA node* - The **SA node** (sinoatrial node) is the heart's natural pacemaker and receives its blood supply from the **right coronary artery** in about 60% of individuals. - Occlusion of the RCA can lead to symptomatic **bradycardia** or **SA node dysfunction**. *AV node* - The **AV node** (atrioventricular node), crucial for coordinating ventricular contraction, is supplied by the **right coronary artery** in approximately 90% of individuals [1]. - Infarcts in the RCA territory can manifest as various degrees of **heart block**. *Posterior wall of left ventricle* - The **posterior wall of the left ventricle** is predominantly supplied by the **posterior descending artery (PDA)**, which in about 80% of people, is a terminal branch of the **right coronary artery** [1]. - This supply is vital for the contractile function of the left ventricle's posterior aspect.
Question 94: All of the following arteries are branches of the coeliac trunk, EXCEPT which one?
- A. Splenic artery
- B. Left gastric artery
- C. Common hepatic artery
- D. Right gastric artery (Correct Answer)
Explanation: ***Right gastric artery*** - The **right gastric artery** typically originates from the **proper hepatic artery**, which is a branch of the common hepatic artery. - Therefore, it is not a direct branch of the coeliac trunk itself. *Left gastric artery* - The **left gastric artery** is one of the three main direct branches of the **coeliac trunk**. - It supplies the lesser curvature of the stomach and the abdominal esophagus. *Splenic artery* - The **splenic artery** is another major direct branch of the **coeliac trunk**. - It supplies the spleen, pancreas, and parts of the stomach via various branches. *Common hepatic artery* - The **common hepatic artery** is the third main direct branch of the **coeliac trunk**. - It gives rise to the proper hepatic artery and the gastroduodenal artery, supplying the liver, gallbladder, pylorus, and duodenum.
Biochemistry
4 questionsWhich of the following enzymes uses citrate in fatty acid synthesis?
Which of the following is an ω-6 fatty acid?
Which of the following is a lipotropic factor?
Which enzyme deficiency is responsible for Hyperammonemia type-1?
NEET-PG 2012 - Biochemistry NEET-PG Practice Questions and MCQs
Question 91: Which of the following enzymes uses citrate in fatty acid synthesis?
- A. Aconitase
- B. ATP citrate lyase (Correct Answer)
- C. Malic enzyme
- D. Citrate synthase
Explanation: ***ATP citrate lyase*** - This enzyme is crucial for fatty acid synthesis, as it cleaves **citrate** in the cytoplasm to generate **acetyl-CoA** and oxaloacetate. - The acetyl-CoA produced is then used as the primary building block for **fatty acid synthesis**. *Aconitase* - This enzyme isomerizes **citrate** to isocitrate within the **Krebs cycle** (TCA cycle) in the mitochondria. - It does not directly participate in the cytosolic pathway of fatty acid synthesis. *Citrate synthase* - This enzyme synthesizes **citrate** from acetyl-CoA and oxaloacetate, initiating the **Krebs cycle** in the mitochondrial matrix. - It is involved in citrate formation, not its utilization for fatty acid synthesis in the cytoplasm. *Malic enzyme* - This enzyme converts **malate** to pyruvate, generating **NADPH** in the cytoplasm. - While NADPH is essential for fatty acid synthesis, malic enzyme does not directly use citrate.
Question 92: Which of the following is an ω-6 fatty acid?
- A. Cervonic acid
- B. Linoleic acid (Correct Answer)
- C. Alpha linolenic acid
- D. Elaidic acid
Explanation: ***Linoleic acid*** - **Linoleic acid** (LA), an 18-carbon fatty acid with two double bonds (18:2), is classified as an **ω-6 fatty acid** because its first double bond is located at the sixth carbon atom from the methyl end of the fatty acid chain. - It is an **essential fatty acid** that must be obtained through diet, serving as a precursor for other ω-6 fatty acids like arachidonic acid. *Cervonic acid* - **Cervonic acid** is another name for **docosahexaenoic acid (DHA)**, which is an **ω-3 fatty acid** (22:6). - Its first double bond is located at the third carbon from the methyl end. *Alpha linolenic acid* - **Alpha-linolenic acid** (ALA) is an **ω-3 fatty acid** (18:3). - Its first double bond is located at the third carbon atom from the methyl end. *Elaidic acid* - **Elaidic acid** is a **trans fatty acid** (18:1 trans-9). - It is classified as an **ω-9 fatty acid** due to the position of its double bond, but its trans configuration is the primary distinguishing feature.
Question 93: Which of the following is a lipotropic factor?
- A. Sphingomyelin
- B. Histidine
- C. Bilirubin
- D. Methionine (Correct Answer)
Explanation: ***Methionine*** - **Methionine** is an essential amino acid that serves as a precursor for **choline** and **creatine**, both of which play crucial roles in lipid metabolism and transport. - Lipotropic factors prevent or reverse the accumulation of **fat in the liver** by promoting the synthesis of **lipoproteins**, which package and transport fats from the liver to other tissues. *Sphingomyelin* - **Sphingomyelin** is a type of **sphingolipid**, a component of cell membranes and myelin sheaths, but it does not directly act as a lipotropic factor to prevent fatty liver. - While it's involved in cellular signaling and membrane structure, it does not directly facilitate the metabolism or transport of **hepatic triglycerides** in the same way as lipotropic agents. *Histidine* - **Histidine** is an essential amino acid involved in protein synthesis and the production of **histamine**, but it is not considered a primary lipotropic factor. - Its main roles are in **immune response** and **neurotransmission**, not in preventing fat accumulation in the liver. *Bilirubin* - **Bilirubin** is a waste product from the breakdown of **heme**, primarily from red blood cells. It is excreted by the liver. - It is known for its **antioxidant properties** but does not play a direct role as a lipotropic factor in lipid metabolism or in preventing **fatty liver**.
Question 94: Which enzyme deficiency is responsible for Hyperammonemia type-1?
- A. Arginase deficiency
- B. Arginosuccinate lyase deficiency
- C. Arginosuccinate synthase deficiency
- D. Carbamoyl phosphate synthetase I (CPS-1) deficiency (Correct Answer)
Explanation: ***Carbamoyl phosphate synthetase I (CPS-1) deficiency*** - This enzyme deficiency is classified as **Hyperammonemia type-1**, or **CPS1 deficiency**, and results in the inability to initiate the urea cycle. - **CPS-1** catalyzes the first committed step of the urea cycle, combining ammonia and bicarbonate to form carbamoyl phosphate. *Arginase deficiency* - This deficiency causes **Hyperargininemia**, which is a disorder of the urea cycle distinct from Hyperammonemia type-1. - Arginase is involved in the final step of the urea cycle, converting arginine to urea and ornithine. *Arginosuccinate lyase deficiency* - This deficiency leads to **Argininosuccinic aciduria**, another urea cycle disorder. - **Arginosuccinate lyase** is responsible for breaking down argininosuccinate into arginine and fumarate. *Arginosuccinate synthase deficiency* - This deficiency causes **Citrullinemia type 1**, a metabolic disorder characterized by high levels of citrulline and ammonia. - **Arginosuccinate synthase** catalyzes the condensation of citrulline and aspartate to form argininosuccinate.
Physiology
2 questionsWhat is the consequence of tibial nerve injury/palsy?
Which of the following statements regarding the lower esophageal sphincter is TRUE?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 91: What is the consequence of tibial nerve injury/palsy?
- A. Loss of plantar flexion (Correct Answer)
- B. Dorsiflexion of foot at ankle joint
- C. Loss of sensation of dorsum of foot
- D. Paralysis of muscles of anterior compartment of leg
Explanation: **Loss of plantar flexion** - The **tibial nerve** innervates the muscles of the **posterior compartment of the leg**, which are primarily responsible for **plantar flexion** of the foot. - Injury to this nerve directly impairs the function of muscles like the gastrocnemius, soleus, and tibialis posterior, leading to a significant loss of the ability to point the foot downwards. *Dorsiflexion of foot at ankle joint* - **Dorsiflexion** is primarily mediated by muscles in the **anterior compartment of the leg**, such as the tibialis anterior, which are innervated by the **deep fibular nerve**. - Tibial nerve injury would not directly affect these muscles or their function; rather, it leads to issues with the opposing action. *Loss of sensation of dorsum of foot* - Sensation to the **dorsum of the foot** is primarily supplied by the **superficial fibular nerve** (for most of the dorsum) and the **deep fibular nerve** (for the first web space). - While the tibial nerve provides sensation to the sole of the foot, it does not typically innervate the dorsum. *Paralysis of muscles of anterior compartment of leg* - The muscles of the **anterior compartment of the leg** (e.g., tibialis anterior, extensor digitorum longus, extensor hallucis longus) are innervated by the **deep fibular nerve**. - A tibial nerve injury would paralyze muscles in the posterior compartment, not the anterior compartment.
Question 92: Which of the following statements regarding the lower esophageal sphincter is TRUE?
- A. It relaxes in response to swallowing. (Correct Answer)
- B. It remains contracted during swallowing to prevent regurgitation.
- C. Its tone is primarily influenced by the myogenic properties of the smooth muscle.
- D. It contracts in response to gastric distension.
Explanation: ***It relaxes in response to swallowing.*** - The **lower esophageal sphincter (LES)** normally maintains high resting tone to prevent gastroesophageal reflux but **relaxes completely during swallowing** to allow passage of food into the stomach. - This relaxation (called **receptive relaxation**) is mediated by **vagal nerve stimulation** through release of nitric oxide (NO) and vasoactive intestinal peptide (VIP). - The relaxation occurs **before the peristaltic wave arrives**, allowing coordinated transit of the bolus. *It remains contracted during swallowing to prevent regurgitation.* - This is **incorrect** - the LES must **relax during swallowing** to allow food passage into the stomach. - Failure of LES relaxation during swallowing is the pathophysiology of **achalasia**, leading to dysphagia. - The LES only maintains contraction between swallows to prevent reflux. *Its tone is primarily influenced by the myogenic properties of the smooth muscle.* - While the LES contains smooth muscle with intrinsic myogenic properties, its tone is **predominantly regulated by neural and hormonal factors**. - **Neural control:** Vagal cholinergic pathways (increase tone), non-adrenergic non-cholinergic (NANC) pathways with NO and VIP (decrease tone). - **Hormonal factors:** Gastrin increases tone, while progesterone, CCK, and secretin decrease tone. *It contracts in response to gastric distension.* - This is **incorrect** - gastric distension actually triggers **transient LES relaxations (TLESRs)**, which are the primary mechanism of physiological reflux. - TLESRs are vagally mediated reflex responses that allow venting of gastric air. - Increased LES contraction in response to gastric distension would be counterproductive.