Anatomy
3 questionsWhich of the following is not a derivative of foregut?
Seminal colliculus is present in ?
What structure passes through the quadrangular space?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 211: Which of the following is not a derivative of foregut?
- A. Cecum (Correct Answer)
- B. Liver
- C. Pancreas
- D. First part of the duodenum
Explanation: ***Cecum*** - The **cecum** and the entire large intestine (except the distal third of the transverse colon) are derivatives of the **midgut** [1]. - The midgut is supplied by the **superior mesenteric artery**, differentiating it developmentally from the foregut. *First part of the duodenum* - The **first part of the duodenum** (from the pylorus to the major duodenal papilla) is derived from the **foregut**. - This section receives its blood supply from branches of the **celiac trunk**, consistent with its foregut origin. *Liver* - The **liver** develops as a budding from the distal foregut and is therefore a **foregut derivative** [2]. - It plays a crucial role in metabolism and detoxification, consistent with its early development from this segment. *Pancreas* - The **pancreas** develops from dorsal and ventral buds of the distal foregut, making it a **foregut derivative**. - Both its exocrine and endocrine functions are vital for digestion and glucose homeostasis.
Question 212: Seminal colliculus is present in ?
- A. Testis
- B. Prostate
- C. Urethra (Correct Answer)
- D. Scrotum
Explanation: ***Correct: Urethra*** - The **seminal colliculus** (also known as the **verumontanum**) is a prominent ridge located on the posterior wall of the **prostatic urethra** - It contains the openings of the **ejaculatory ducts** and the **prostatic utricle** - This is a key anatomical landmark in the male urethra during endoscopic procedures *Incorrect: Prostate* - While the seminal colliculus is located within the portion of the urethra that passes through the prostate (prostatic urethra), it is not a structure *of* the prostate gland itself - The prostate is a gland that surrounds the urethra and contributes to seminal fluid - The seminal colliculus is an intraluminal urethral structure, not prostatic tissue *Incorrect: Testis* - The testis is the primary male reproductive organ responsible for **spermatogenesis** and hormone synthesis (testosterone) - It does not contain the seminal colliculus, which is located in the pelvic urethra *Incorrect: Scrotum* - The scrotum is an external dermal sac that houses the testes, epididymis, and lower spermatic cords - It provides temperature regulation for spermatogenesis - The seminal colliculus is an internal pelvic structure, not present in the scrotum
Question 213: What structure passes through the quadrangular space?
- A. Axillary nerve (Correct Answer)
- B. Radial nerve
- C. Median nerve
- D. Brachial Artery
Explanation: Axillary nerve - The axillary nerve and the posterior circumflex humeral artery are the primary structures that pass through the quadrangular space. - Compression or injury within this space can lead to deficits in the axillary nerve's distribution, affecting the deltoid and teres minor muscles. *Radial nerve* - The radial nerve passes through the triangular interval, not the quadrangular space. - It supplies the triceps muscle and all muscles in the posterior compartment of the forearm. *Median nerve* - The median nerve travels through the cubital fossa and then down the anterior forearm, supplying most of the forearm flexors and some hand muscles. - It does not pass through any of the posterior axillary spaces. *Brachial Artery* - The brachial artery is the main arterial supply to the arm and runs anteriorly in the arm, deep to the biceps brachii muscle. - It does not pass through the quadrangular space; rather, the posterior circumflex humeral artery (a branch of the axillary artery) traverses this space.
Biochemistry
4 questionsHow many molecules of Acetyl CoA are produced from β-oxidation of palmitic acid?
Which of the following compounds is not formed with the involvement of glycine?
What is the respiratory quotient of carbohydrates?
What type of receptor is the insulin receptor?
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 211: How many molecules of Acetyl CoA are produced from β-oxidation of palmitic acid?
- A. 3 acetyl CoA
- B. 16 Acetyl CoA
- C. 6 acetyl CoA
- D. 8 acetyl CoA (Correct Answer)
Explanation: ***8 acetyl CoA*** - Palmitic acid is a **16-carbon saturated fatty acid (C16:0)**. During β-oxidation, each cycle cleaves two carbons as **acetyl CoA**. - The formula for acetyl CoA produced is **n/2**, where n = number of carbons. For palmitic acid: 16/2 = **8 acetyl CoA molecules**. - Alternatively: Palmitic acid undergoes **7 cycles of β-oxidation** [(n/2) - 1 = 7], each producing 1 acetyl CoA (7 total), plus the final 2-carbon fragment forming the 8th acetyl CoA. *3 acetyl CoA* - This number is too low for a 16-carbon fatty acid. **Short-chain fatty acids** would produce fewer acetyl CoA molecules. - This value corresponds to β-oxidation of a **6-carbon fatty acid** (hexanoic acid), not palmitic acid. *6 acetyl CoA* - This number is also too low for a 16-carbon fatty acid. - This quantity would be produced from a **12-carbon fatty acid** (lauric acid), not palmitic acid. *16 Acetyl CoA* - This number is too high and would incorrectly imply that each carbon forms an acetyl CoA independently. - Sixteen acetyl CoA molecules would be produced from a **32-carbon fatty acid**, which is extremely rare in biological systems.
Question 212: Which of the following compounds is not formed with the involvement of glycine?
- A. Purines
- B. Glutathione
- C. Thyroxine (Correct Answer)
- D. Heme
Explanation: ***Thyroxine*** - **Thyroxine** (and other thyroid hormones) are derived from the amino acid **tyrosine**. - Their synthesis involves iodination and coupling reactions of tyrosine residues within the protein **thyroglobulin**. *Heme* - **Glycine** is a direct precursor for the initial step in **heme synthesis**. - It condenses with **succinyl CoA** to form α-amino-β-ketoadipate, which then decarboxylates to form δ-aminolevulinate (ALA). *Purines* - **Glycine** contributes part of its structure to the **purine ring**. - Specifically, the **nitrogen at position 7** and the **carbons at positions 4 and 5** of the purine ring are derived from glycine. *Glutathione* - **Glutathione** is a tripeptide composed of three amino acids: **glutamate**, **cysteine**, and **glycine**. - **Glycine** is the C-terminal amino acid of glutathione and is essential for its structure and function as an antioxidant.
Question 213: What is the respiratory quotient of carbohydrates?
- A. 0.5
- B. 0.8
- C. 0.75
- D. 1 (Correct Answer)
Explanation: ***Option: 1 (Correct Answer)*** - The **respiratory quotient (RQ)** is the ratio of **carbon dioxide produced to oxygen consumed** during metabolism. - For carbohydrates, complete oxidation yields equal moles of CO2 and O2, resulting in an **RQ of 1.0**. - Example: C6H12O6 + 6O2 → 6CO2 + 6H2O, giving RQ = 6CO2/6O2 = 1.0 - This value reflects that carbohydrates are highly oxygenated molecules, requiring less external oxygen for their oxidation relative to the CO2 produced. *Option: 0.5* - An RQ of 0.5 is not observed for any major macronutrient during complete oxidation. - This value would imply significantly lower CO2 production relative to O2 consumption, which doesn't match any physiological substrate metabolism. *Option: 0.8* - An RQ of approximately 0.8 is characteristic of a **mixed diet** or the average value sometimes cited for **protein metabolism**. - Protein RQ typically ranges from 0.8-0.85, as proteins require more oxygen for their oxidation compared to the CO2 produced. - The exact RQ can vary depending on the specific amino acids being metabolized. *Option: 0.75* - An RQ around 0.7-0.75 may represent **fat-predominant metabolism** or a mixed diet with fats and carbohydrates. - Pure **fat metabolism** has an RQ of approximately **0.7**, as fats require substantial oxygen for oxidation due to their lower oxygen content relative to carbon and hydrogen. - Fats contain many C-H bonds and few C-O bonds, necessitating more oxygen for complete combustion.
Question 214: What type of receptor is the insulin receptor?
- A. Guanylyl cyclase
- B. Adenylyl cyclase
- C. IP3-DAG
- D. Tyrosine kinase (Correct Answer)
Explanation: ***Tyrosine kinase*** - The insulin receptor is a **receptor tyrosine kinase (RTK)**, meaning it has intrinsic tyrosine kinase activity that phosphorylates specific tyrosine residues on itself and other intracellular proteins upon insulin binding. - This phosphorylation initiates a **signaling cascade** involving molecules like IRS proteins, PI3K/Akt, and MAPK pathways, leading to glucose uptake and metabolic regulation. *Guanylyl cyclase* - Guanylyl cyclase receptors, such as the **atrial natriuretic peptide receptor**, catalyze the conversion of GTP to **cGMP**, which acts as a second messenger. - This mechanism is distinct from the insulin receptor's direct protein phosphorylation. *Adenylyl cyclase* - Adenylyl cyclase is typically activated by **G-protein coupled receptors (GPCRs)**, leading to the conversion of ATP to **cAMP**, another second messenger. - The insulin receptor does not couple to G proteins or directly activate adenylyl cyclase. *IP3-DAG* - The **inositol triphosphate (IP3)** and **diacylglycerol (DAG)** pathway is primarily activated by certain **GPCRs** and involves the hydrolysis of PIP2 by phospholipase C, leading to calcium release and protein kinase C activation. - This pathway is not the primary signaling mechanism initiated by the insulin receptor.
Physiology
2 questionsAcrosome reaction is seen in?
Which of the following cell types is considered insulin-dependent?
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 211: Acrosome reaction is seen in?
- A. Spermatogenesis
- B. Oogenesis
- C. Fertilization (Correct Answer)
- D. Menstruation
Explanation: ***Fertilization*** - The **acrosome reaction** is a crucial event that occurs when a **spermatozoon** comes into contact with the **zona pellucida** surrounding the oocyte. - This reaction involves the release of **hydrolytic enzymes** from the acrosome, which are essential for the sperm to penetrate the zona pellucida and fuse with the oocyte membrane. *Spermatogenesis* - **Spermatogenesis** is the process of sperm formation in the testes, involving meiosis and spermiogenesis. - While it produces the sperm cell with an acrosome, the **acrosome reaction itself does not occur** during this developmental stage. *Oogenesis* - **Oogenesis** is the process of egg cell formation in the ovaries. - This process is entirely **separate from sperm function** and does not involve the acrosome or the acrosome reaction. *Menstruation* - **Menstruation** is the monthly shedding of the uterine lining in females when fertilization does not occur. - This process is part of the female reproductive cycle and has **no direct involvement with sperm or the acrosome reaction**.
Question 212: Which of the following cell types is considered insulin-dependent?
- A. Myocytes (Correct Answer)
- B. Pituitocytes
- C. Adipocytes
- D. RBCs
Explanation: ***Myocytes*** - **Myocytes** (skeletal muscle cells) are **insulin-dependent** and represent the **largest site of insulin-mediated glucose disposal** in the body - Insulin promotes translocation of **GLUT4 transporters** to the cell membrane, enabling glucose uptake - Skeletal muscle accounts for approximately **70-80% of postprandial glucose disposal**, making it the most quantitatively significant insulin-dependent tissue *Adipocytes* - **Adipocytes** (fat cells) are also **insulin-dependent** and utilize **GLUT4 transporters** for glucose uptake - Insulin stimulates glucose uptake and conversion to triglycerides for storage - However, adipose tissue accounts for only **10-15% of glucose disposal**, making it less quantitatively significant than skeletal muscle - Both myocytes and adipocytes are considered the two major insulin-dependent tissues in the body *Pituitocytes* - **Pituitocytes** are supporting cells in the pituitary gland - They use **insulin-independent glucose transporters** (GLUT1/GLUT3) - The pituitary gland requires constant glucose supply independent of insulin status *RBCs* - **Red blood cells** lack mitochondria and depend entirely on **anaerobic glycolysis** - Glucose uptake occurs via **insulin-independent GLUT1 transporters** - RBCs must maintain glucose uptake at all times, regardless of insulin levels
Surgery
1 questionsWhich of the following structures does NOT pass through Calot's triangle?
NEET-PG 2015 - Surgery NEET-PG Practice Questions and MCQs
Question 211: Which of the following structures does NOT pass through Calot's triangle?
- A. Right hepatic artery
- B. Lymph node of Lund
- C. Portal vein (Correct Answer)
- D. Cystic artery
Explanation: ***Portal vein*** - The **portal vein** is located within the **porta hepatis** and does not pass through Calot's triangle, making it the correct answer to this question. - It carries venous blood from the **gastrointestinal tract** and **spleen** to the liver and is positioned medial and posterior to the structures within Calot's triangle. *Right hepatic artery* - The **right hepatic artery** is a key structure that passes through Calot's triangle and forms one of its boundaries. - It typically gives rise to the **cystic artery** within or near the triangle, making it an important anatomical landmark during **cholecystectomy**. *Lymph node of Lund* - The **lymph node of Lund** (cystic lymph node) is consistently found within Calot's triangle and serves as an important landmark. - Its presence helps surgeons identify the **boundaries of the triangle** and assess for inflammation or malignancy related to the gallbladder. *Cystic artery* - The **cystic artery** is a consistent structure within Calot's triangle, typically arising from the **right hepatic artery**. - It is routinely **ligated during cholecystectomy** and is one of the key structures surgeons must identify within the triangle.