Anatomy
1 questionsWhich part of the stomach is primarily responsible for receiving and storing ingested food?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 361: Which part of the stomach is primarily responsible for receiving and storing ingested food?
- A. Antrum
- B. Pylorus
- C. Body (Correct Answer)
- D. Fundus
Explanation: ***Body*** - The **body (corpus)** is the largest part of the stomach, situated between the fundus and the antrum [1]. - This region is **primarily responsible for receiving and storing ingested food** as the main reservoir [2]. - It also produces **gastric acid and enzymes** (like pepsinogen) for the initial digestion of food [1]. - The body serves as the **principal storage chamber** where food accumulates after passing through the cardia [2]. *Fundus* - The **fundus** is the dome-shaped upper part of the stomach, located superior to the cardia. - While it can temporarily hold food and gas, it is **not the primary storage site** [2]. - Its main role is to serve as a **pressure buffer** and accumulation site for gases during digestion [2]. *Antrum* - The **antrum** is the lower, narrower part of the stomach, located before the pylorus. - It plays a crucial role in **mixing and grinding food with gastric juices** and propelling chyme towards the pylorus [1], [2]. - This is the **grinding chamber**, not a storage area [2]. *Pylorus* - The **pylorus** is the opening that connects the stomach to the duodenum, controlled by the pyloric sphincter. - Its main function is to **regulate the emptying of chyme** into the small intestine, not to store food [3].
Biochemistry
2 questionsChymotrypsinogen is activated into chymotrypsin by:
Which of the following is an example of an exopeptidase?
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 361: Chymotrypsinogen is activated into chymotrypsin by:
- A. Trypsin (Correct Answer)
- B. Pepsin
- C. Renin
- D. HCl
Explanation: ***Activation of Chymotrypsinogen by Trypsin*** - **Trypsin** is the primary enzyme responsible for the activation of **chymotrypsinogen** into its active form, **chymotrypsin**, by cleaving a specific peptide bond. - This activation is part of a cascade of proteolytic enzyme activations in the **pancreatic juice**, crucial for protein digestion in the small intestine. *Pepsin* - **Pepsin** is a protease active in the **stomach**, requiring an acidic environment for its activity, and is involved in the initial breakdown of proteins. - It does not play a role in the activation of pancreatic zymogens like chymotrypsinogen; its primary function is protein digestion in the gastric lumen. *Renin* - **Renin** is an enzyme primarily involved in the **renin-angiotensin-aldosterone system** (RAAS), which regulates blood pressure and fluid balance. - Its action involves cleaving **angiotensinogen** to form angiotensin I, and it has no role in the activation of digestive enzymes like chymotrypsinogen. *HCl* - **Hydrochloric acid (HCl)** is produced in the stomach and is essential for providing the acidic environment required for **pepsin's activity** and for denaturing proteins. - While HCl is crucial for digestion, it does not directly activate chymotrypsinogen; this activation is an enzymatic process carried out by another protease.
Question 362: Which of the following is an example of an exopeptidase?
- A. Trypsin
- B. Chymotrypsin
- C. Elastase
- D. Carboxypeptidases (Correct Answer)
Explanation: ***Carboxypeptidases*** - **Carboxypeptidases** are enzymes that cleave the **C-terminal** (carboxyl end) amino acid from a polypeptide chain, making them a type of exopeptidase. - They are crucial in protein digestion, releasing individual amino acids from the end of protein chains. *Trypsin* - **Trypsin** is an **endopeptidase** that cleaves peptide bonds within protein chains, specifically at the carboxyl side of **lysine** or **arginine** residues. - It does not cleave amino acids from the ends of polypeptide chains. *Chymotrypsin* - **Chymotrypsin** is an **endopeptidase** that cleaves peptide bonds within a polypeptide chain, primarily at the carboxyl side of **tyrosine**, **tryptophan**, or **phenylalanine**. - Its action is internal to the protein sequence, not at the termini. *Elastase* - **Elastase** is also an **endopeptidase** that cleaves peptide bonds internally, specifically targeting small, uncharged amino acid residues like **alanine**, **glycine**, and **valine**. - Its primary role is to break down elastin, an elastic protein in connective tissues, but it does so by internal cleavage.
Pathology
1 questionsCaseating necrosis most commonly occurs in
NEET-PG 2015 - Pathology NEET-PG Practice Questions and MCQs
Question 361: Caseating necrosis most commonly occurs in
- A. Brain
- B. Liver
- C. Kidney
- D. Lung (Correct Answer)
Explanation: ***lung*** - **Caseating necrosis** is classically associated with **tuberculosis**, which primarily affects the lungs [1]. - It is characterized by the presence of **granulomatous inflammation**, often leading to the formation of cavities in pulmonary tissue. *Brain* - While certain infections can lead to necrosis in the brain, they typically do not present as **caseating necrosis**, which is specific to certain conditions like tuberculosis. - The brain may show **liquefactive necrosis** or other types of necrosis, rather than **caseation**. *liver* - The liver usually shows **macrovesicular steatosis** or **apoptosis** in conditions like hepatitis, not caseating necrosis. - **Granulomatous hepatitis** can occur, but it does not typically result in **caseating** type necrosis associated with lung pathology. *kidney* - The kidneys can experience necrosis from various causes, but caseating necrosis is not typical; they are more often involved in **focal segmental glomerulosclerosis** or **acute tubular necrosis**. - Chronic kidney conditions may involve granulomas, but they usually are not characterized by **caseation** similar to that seen in pulmonary tissue. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, p. 55.
Physiology
6 questionsIncreased aldosterone and ADH secretion following major trauma results in all the following except?
Which carrier pump is responsible for transporting solutes in the thick ascending limb of the loop of Henle?
What is the primary function of the myenteric plexus?
Secretion of bile out of hepatocytes occurs via?
Intestinal absorption of calcium is mainly increased by?
Vitamin D absorption is decreased by ?
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 361: Increased aldosterone and ADH secretion following major trauma results in all the following except?
- A. Increased osmolarity of urine
- B. Increased water excretion (Correct Answer)
- C. Increased K+ excretion in urine
- D. Decreased Na+ excretion in urine
Explanation: ***Increased water excretion*** - **ADH (antidiuretic hormone)** increases water reabsorption in the collecting ducts, leading to a *decrease* in water excretion, not an increase. - Increased aldosterone and ADH would promote fluid retention to maintain blood volume following trauma, thus reducing water loss via urine. *Decreased Na+ excretion in urine* - **Aldosterone** acts on the renal tubules to increase **sodium reabsorption** and potassium excretion. - This response is crucial in **conserving sodium** and thereby maintaining extracellular fluid volume after trauma. *Increased K+ excretion in urine* - **Aldosterone** directly stimulates **potassium secretion** into the urine in the principal cells of the collecting ducts. - This is a normal physiological consequence of increased aldosterone levels. *Increased osmolarity of urine* - **ADH** increases the permeability of the collecting ducts to water, leading to **more water reabsorption** back into the bloodstream. - This removal of water from the urine concentrates the solutes, resulting in a **more concentrated (higher osmolarity)** urine.
Question 362: Which carrier pump is responsible for transporting solutes in the thick ascending limb of the loop of Henle?
- A. NaCl cotransporter
- B. Na+-H+ exchanger
- C. Na+-K+ exchanger
- D. Sodium-potassium-chloride cotransporter (Correct Answer)
Explanation: * **Sodium-potassium-chloride cotransporter.** * This transporter, specifically the **Na+-K+-2Cl- cotransporter (NKCC2)**, is highly expressed in the apical membrane of the thick ascending limb. * It actively reabsorbs **sodium, potassium, and chloride ions** from the filtrate, contributing significantly to the medullary interstitial osmotic gradient. * *NaCl- cotransporter* * The **NaCl cotransporter (NCC)** is primarily found in the **distal convoluted tubule**, not the thick ascending limb. * It reabsorbs sodium and chloride in a 1:1 ratio and is the target of thiazide diuretics. * *Na+-H+ exchanger* * The **Na+-H+ exchanger (NHE3)** is predominantly located in the **proximal tubule** where it plays a crucial role in bicarbonate reabsorption and acid-base balance. * While some NHE activity exists in other nephron segments, it is not the primary carrier in the thick ascending limb. * *Na+-K+ exchanger* * The **Na+-K+ exchanger** or **Na+/K+-ATPase pump** is located on the basolateral membrane of most renal tubular cells, including the thick ascending limb. * Its main function is to maintain the electrochemical gradient by pumping **sodium out of the cell** and potassium into the cell, which indirectly drives other transporters but is not the apical cotransporter responsible for initial solute reabsorption in the thick ascending limb.
Question 363: What is the primary function of the myenteric plexus?
- A. Regulating GI secretion
- B. Regulating local blood flow
- C. Regulating motility (Correct Answer)
- D. Regulating absorption
Explanation: ***Regulating motility*** - The myenteric plexus, also known as **Auerbach's plexus**, is primarily responsible for coordinating the **rhythmic contractions** and **relaxation of the gastrointestinal (GI) smooth muscle**. - Its strategic location between the **longitudinal and circular muscle layers** allows it to directly influence the strength and frequency of peristalsis, thus regulating the movement of food through the digestive tract. *Regulating GI secretion* - While it has some indirect influence, the **submucosal plexus** (Meissner's plexus) is the primary neural network regulating **secretory functions** of the GI tract. - The myenteric plexus's main role is more directly related to muscle contraction and relaxation rather than glandular secretion. *Regulating local blood flow* - Local blood flow in the GI tract is primarily regulated by the **sympathetic and parasympathetic nervous systems**, along with local metabolic factors and hormones. - The myenteric plexus has a minimal direct role in the control of **GI blood vessel smooth muscle**. *Regulating absorption* - Absorption is primarily a function of the **intestinal epithelial cells** and is regulated by various transport mechanisms, hormones, and local factors. - While the enteric nervous system influences mucosal function indirectly, the myenteric plexus's primary role is **motor control** rather than directly regulating nutrient absorption processes.
Question 364: Secretion of bile out of hepatocytes occurs via?
- A. Passive diffusion
- B. Facilitated diffusion
- C. Osmosis
- D. Active transport (Correct Answer)
Explanation: ***Active transport*** - Bile secretion by hepatocytes is an **energy-dependent process** against concentration gradients, requiring specific transporter proteins. - This active mechanism ensures efficient bile flow and prevents reflux, crucial for processes like **fat digestion and absorption**. *Passive diffusion* - **Passive diffusion** involves substances moving down their concentration gradient without energy expenditure. - Bile components, like bile salts, are highly concentrated within hepatocytes and need to be moved against this gradient. *Facilitated diffusion* - This type of diffusion utilizes **transmembrane proteins** to move substances down their concentration gradient, but still does not directly consume ATP. - Bile components are often transported against their concentration gradient, which is not facilitated diffusion. *Osmosis* - **Osmosis** specifically refers to the movement of water across a semipermeable membrane from a region of higher water concentration to a region of lower water concentration. - While water is a component of bile, the primary mechanism of moving bile solutes out of the hepatocyte is not osmosis.
Question 365: Intestinal absorption of calcium is mainly increased by?
- A. Calcitriol (Correct Answer)
- B. Parathormone
- C. Glucocorticoids
- D. ACTH
Explanation: ***Calcitriol*** - **Calcitriol** (1,25-dihydroxyvitamin D3) is the hormonally active form of vitamin D, which is essential for increasing **calcium absorption** from the intestines. - It stimulates the synthesis of **calcium-binding proteins** in intestinal epithelial cells, facilitating active transport of calcium. *Parathormone* - **Parathormone (PTH)** primarily regulates calcium by increasing its reabsorption in the **kidneys** and stimulating its release from **bones**. - While it indirectly promotes calcitriol synthesis, its *direct* effect on intestinal calcium absorption is minimal compared to calcitriol. *Glucocorticoids* - **Glucocorticoids** generally have an *inhibitory* effect on calcium absorption in the intestine and can also increase renal excretion of calcium. - Prolonged use can lead to **osteoporosis** due to their negative impact on bone formation and calcium balance. *ACTH* - **ACTH (adrenocorticotropic hormone)** primarily stimulates the adrenal cortex to produce **cortisol** and other glucocorticoids. - It has **no direct role** in regulating calcium absorption from the intestines.
Question 366: Vitamin D absorption is decreased by ?
- A. Proteins
- B. Acid
- C. Lactose
- D. Fat malabsorption (Correct Answer)
Explanation: ***Fat malabsorption*** - **Vitamin D** is a **fat-soluble vitamin**, meaning it requires dietary fat for proper absorption in the small intestine. - Conditions causing **fat malabsorption**, such as **cystic fibrosis**, **celiac disease**, or **pancreatic insufficiency**, significantly reduce the uptake of vitamin D. *Proteins* - **Proteins** do not directly decrease vitamin D absorption; in fact, some dietary proteins can enhance vitamin D binding and transport in the bloodstream. - Their primary role is in structural and enzymatic functions, not impeding fat-soluble vitamin uptake. *Acid* - **Gastric acid** is important for the absorption of some nutrients, but it generally does not directly hinder the absorption of **fat-soluble vitamins** like vitamin D. - Conditions like **achlorhydria** primarily affect the absorption of minerals and vitamin B12, rather than vitamin D. *Lactose* - **Lactose** is a sugar found in milk, and its malabsorption (lactose intolerance) primarily causes gastrointestinal symptoms like bloating and diarrhea. - It does not directly interfere with the absorption of **fat-soluble vitamins**; rather, it affects carbohydrate digestion.