Anatomy
3 questionsAll of the following arteries are branches of the coeliac trunk, EXCEPT which one?
The nutrient artery to the femur is?
The right coronary artery supplies blood to all of the following structures, except?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 251: 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.
Question 252: The nutrient artery to the femur is?
- A. Profunda femoris artery (Correct Answer)
- B. Femoral artery
- C. Popliteal artery
- D. Medial circumflex femoral artery
Explanation: ***Profunda femoris artery*** - The **profunda femoris artery** (deep femoral artery) is the main blood supply to the **femur's diaphysis** via its perforating branches. - Typically, the **second perforating branch** gives rise to the nutrient artery, which enters the bone through the **nutrient foramen** in the middle third of the femoral shaft. *Femoral artery* - The **femoral artery** is the main artery of the thigh and gives off several branches, including the profunda femoris artery. - While it is the source of blood for the entire lower limb, it does not directly give rise to the main **nutrient artery of the femur**. *Popliteal artery* - The **popliteal artery** is a continuation of the femoral artery in the popliteal fossa behind the knee. - It primarily supplies structures around the knee joint and the lower leg, not the direct **diaphyseal nutrient supply** to the femur. *Medial circumflex femoral artery* - The **medial circumflex femoral artery** primarily supplies the head and neck of the femur, crucial for its vascularity, especially in children. - It does not serve as the **main nutrient artery** for the femoral shaft (diaphysis).
Question 253: 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.
Biochemistry
3 questionsWhich of the following is an amino sugar formed from fructose-6-phosphate?
Which of the following is a true difference between gangliosides and cerebrosides?
Apoenzyme is ?
NEET-PG 2012 - Biochemistry NEET-PG Practice Questions and MCQs
Question 251: Which of the following is an amino sugar formed from fructose-6-phosphate?
- A. N-acetylglucosamine-6-phosphate
- B. Glucosamine-6-phosphate (Correct Answer)
- C. Galactosamine-6-phosphate
- D. UDP-N-acetylglucosamine
Explanation: ***Glucosamine-6-phosphate*** - This amino sugar is directly synthesized from **fructose-6-phosphate** via a transamidation reaction, where an amino group replaces a hydroxyl group. - It is a key intermediate in the biosynthesis of other **amino sugars** and **glycosaminoglycans**. *N-acetylglucosamine-6-phosphate* - This is formed from **glucosamine-6-phosphate** by the addition of an **acetyl group**, making it a subsequent product, not the initial amino sugar from fructose-6-phosphate. - The N-acetylation step is crucial for its role in cellular signaling and structural components. *Galactosamine-6-phosphate* - While an amino sugar, **galactosamine-6-phosphate** is derived from UDP-N-acetylglucosamine, not directly from fructose-6-phosphate. - Its formation involves an **epimerization** step of an existing N-acetylglucosamine structure. *UDP-N-acetylglucosamine* - This is an **activated form** of N-acetylglucosamine, formed by the addition of UTP to N-acetylglucosamine-1-phosphate. - It serves as a precursor for the synthesis of complex **carbohydrates** and glycoproteins, far downstream from fructose-6-phosphate.
Question 252: Which of the following is a true difference between gangliosides and cerebrosides?
- A. Specific carbohydrate composition
- B. Charge difference (Correct Answer)
- C. Location in the nervous system
- D. Presence of glucose
Explanation: ***Charge difference*** - **Gangliosides** contain **sialic acid (N-acetylneuraminic acid)** residues, which are negatively charged, making gangliosides **anionic**. - **Cerebrosides** are **neutral glycosphingolipids** as they lack charged sugar residues. *Specific carbohydrate composition* - While both have carbohydrate components, referring to "specific carbohydrate composition" as the *true difference* is too broad. Both have characteristic sugar groups, but the **presence of sialic acid** in gangliosides is the key differentiator in charge. - Cerebrosides typically contain a single sugar (either glucose or galactose), whereas gangliosides have a more complex oligosaccharide chain including sialic acid. *Presence of glucose* - Both cerebrosides (specifically **glucocerebrosides**) and gangliosides can contain **glucose** in their carbohydrate moieties. - This is not a distinguishing feature; the *type* and *arrangement* of sugars, particularly the presence of sialic acid, are more specific. *Location in the nervous system* - Both gangliosides and cerebrosides are abundant in the **nervous system**, particularly in cell membranes. - Their presence in the nervous system is a similarity, not a differentiating factor.
Question 253: Apoenzyme is ?
- A. Protein moiety (Correct Answer)
- B. Organic cofactor
- C. Inactive enzyme component
- D. Non-protein component required for enzyme activity
Explanation: ***Protein moiety*** - An **apoenzyme** is the **protein component of an enzyme** that is catalytically inactive by itself. - It requires a **non-protein cofactor** (either an inorganic ion or an organic molecule) to become active. *Organic cofactor* - An **organic cofactor** is also known as a **coenzyme**, which binds to the apoenzyme to form a functional holoenzyme. - While essential for enzyme activity, the apoenzyme itself is the protein part, not the organic cofactor. *Inactive enzyme component* - While an apoenzyme is **inactive on its own**, this description is too broad and doesn't specify its chemical nature. - It is specifically the **protein component** that is inactive until bound to its cofactor. *Non-protein component required for enzyme activity* - This describes a **cofactor** (either inorganic or organic), not the apoenzyme itself. - The apoenzyme is the **protein portion**, which *requires* the non-protein component for activity.
Physiology
4 questionsWhich of the following statements regarding the lower esophageal sphincter is TRUE?
What is the consequence of tibial nerve injury/palsy?
What is the fixed length of a myosin filament?
Gastric secretions are essential for absorption of -
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 251: 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.
Question 252: 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 253: What is the fixed length of a myosin filament?
- A. 0.16 nm
- B. 1.6 micrometers (Correct Answer)
- C. 16 nm
- D. 1.6 mm
Explanation: ***1.6 micrometers*** - Myosin filaments, also known as **thick filaments**, are integral components of muscle contraction and have a characteristic fixed length. This length is precisely **1.6 micrometers** in mammalian skeletal muscle. - This consistent length is crucial for the **sliding filament model** of muscle contraction, ensuring proper overlap with actin filaments and efficient force generation. *0.16 nm* - This value is significantly too small; **nanometers (nm)** are typically used for atomic or molecular distances, not for entire protein filaments like myosin. - A myosin filament is composed of hundreds of myosin molecules, making its overall length much larger than a fraction of a nanometer. *16 nm* - While nanometers are used for molecular structures, 16 nm is still too small for a myosin filament. The entire filament is roughly **100 times larger** than this value. - This dimension might be more appropriate for the diameter of a single myosin molecule's head region, but not the entire filament's length. *1.6 mm* - This value is significantly too large; **millimeters (mm)** are visible to the naked eye and represent macroscopic objects. - Muscle filaments are microscopic structures, and a length of 1.6 mm would imply they are many times longer than an entire muscle cell.
Question 254: Gastric secretions are essential for absorption of -
- A. Cobalamin (Correct Answer)
- B. Fat
- C. Thiamine
- D. Folic acid
Explanation: ***Cobalamin*** - **Intrinsic factor**, secreted by gastric parietal cells, is crucial for the absorption of **vitamin B12 (cobalamin)** in the terminal ileum [1]. - Without sufficient intrinsic factor, **pernicious anemia** can develop due to impaired B12 absorption [2]. *Fat* - Fat digestion primarily occurs in the **small intestine** with the help of **bile salts** and **pancreatic lipases**. - While gastric lipase begins some fat digestion, it's not essential for overall fat absorption. *Thiamine* - **Thiamine (vitamin B1)** is absorbed in the jejunum and ileum, primarily via **active transport** and passive diffusion. - Gastric secretions do not play a direct, essential role in its absorption. *Folic acid* - **Folic acid** is absorbed in the **duodenum and jejunum** as monoglutamates after being deconjugated from polyglutamate forms. - This process is not directly dependent on gastric secretions [2].