Anatomy
7 questionsFibrous stroma of liver is derived from -
Inferior pancreaticoduodenal artery is a branch of which of the following arteries?
Nephron is derived from ?
Fossa ovalis is a remnant of -
The internal anal sphincter is a part of which of the following?
Which artery passes through the anatomical snuffbox?
What is the posterior relation of the neck of the pancreas?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 151: Fibrous stroma of liver is derived from -
- A. Endoderm from the foregut
- B. Endoderm from the midgut
- C. Endoderm from the hindgut
- D. Mesoderm from the septum transversum (Correct Answer)
Explanation: ***Mesoderm from the septum transversum*** - The **fibrous stroma of the liver**, which provides its structural framework, develops from the **mesoderm** of the **septum transversum** [1]. - The septum transversum is a thick mass of mesoderm that contributes to the formation of the **diaphragm** and the connective tissue elements of the liver [1]. *Endoderm from the foregut* - While the **parenchymal cells (hepatocytes)** of the liver are derived from the **endoderm of the foregut**, this tissue forms the functional units, not the fibrous supporting stroma. - The endoderm forms the glandular tissue, while the mesoderm forms the connective tissue [1]. *Endoderm from the midgut* - The midgut endoderm gives rise to structures like the **small intestine**, cecum, appendix, ascending colon, and part of the transverse colon, but not the liver's stroma [2]. - Its primary role is in forming the epithelial lining of these digestive organs. *Endoderm from the hindgut* - The hindgut endoderm develops into the distal third of the transverse colon, descending colon, sigmoid colon, rectum, and superior part of the anal canal, - It plays no role in the development of the liver's fibrous stroma.
Question 152: Inferior pancreaticoduodenal artery is a branch of which of the following arteries?
- A. Splenic artery
- B. Left gastric artery
- C. Gastroduodenal artery
- D. Superior mesenteric artery (Correct Answer)
Explanation: ***Superior mesenteric artery*** - The **inferior pancreaticoduodenal artery** is a direct branch of the **superior mesenteric artery (SMA)**. - It supplies the **head of the pancreas** and the **duodenum**, anastomosing with branches from the gastroduodenal artery. *Splenic artery* - The splenic artery is a branch of the **celiac trunk** and primarily supplies the **spleen**, stomach, and pancreas (via pancreatic branches). - It does not give rise to the inferior pancreaticoduodenal artery. *Left gastric artery* - The left gastric artery is a branch of the **celiac trunk** and supplies the **lesser curvature of the stomach** and distal esophagus. - It has no direct connection to the inferior pancreaticoduodenal artery. *Gastroduodenal artery* - The gastroduodenal artery is a branch of the **common hepatic artery** (from the celiac trunk) and gives off the **anterior and posterior superior pancreaticoduodenal arteries**. - While it supplies the head of the pancreas and duodenum, it is not the origin of the inferior pancreaticoduodenal artery, which arises from the SMA.
Question 153: Nephron is derived from ?
- A. Ureteric bud
- B. Mesonephric duct
- C. Metanephros (Correct Answer)
- D. Mesonephros
Explanation: ***Metanephros*** - The **metanephric mesenchyme**, also known as the **metanephros**, gives rise to the excretory units of the kidney, which are the nephrons. - This mesenchymal tissue differentiates to form the **glomerulus**, Bowman's capsule, proximal and distal convoluted tubules, and the loop of Henle. *Ureteric bud* - The **ureteric bud** originates from the mesonephric duct and forms the collecting system of the kidney, including the ureter, renal pelvis, calyces, and collecting ducts. - It induces the differentiation of the metanephric mesenchyme but does not directly form the nephron itself. *Mesonephric duct* - The **mesonephric duct** (Wolffian duct) is a primitive embryonic structure that gives rise to the ureteric bud and parts of the male reproductive system. - It does not directly form any part of the nephron. *Mesonephros* - The **mesonephros** is a transient embryonic kidney that functions briefly during fetal development. - It degenerates and does not contribute to the formation of the definitive nephrons in the mature kidney.
Question 154: Fossa ovalis is a remnant of -
- A. Septum primum (Correct Answer)
- B. Septum secundum
- C. Septum spurium
- D. AV cushion
Explanation: ***Septum primum*** - The **fossa ovalis** is a depression in the right atrium that represents the sealed-off foramen ovale [2]. - It is formed from the **septum primum**, which becomes the floor of the fossa ovalis. *Septum secundum* - The **septum secundum** forms the limbus or rim of the fossa ovalis, not the fossa itself. - This structure develops later than the septum primum and partially covers the foramen ovale during fetal development [2]. *Septum spurium* - The **septum spurium** is an embryonic ridge in the right atrium that typically regresses during development and does not contribute to the fossa ovalis. - It is a transient structure formed by the confluence of the right and left venous valves. *AV cushion* - The **atrioventricular (AV) cushions** contribute to the formation of the AV valves and the atrial and ventricular septa, but not directly to the fossa ovalis [1]. - They are crucial for separating the atria from the ventricles and forming the mitral and tricuspid valves.
Question 155: The internal anal sphincter is a part of which of the following?
- A. Puborectalis muscle
- B. Deep perineal muscles
- C. Internal longitudinal fibers
- D. Internal circular fibers (Correct Answer)
Explanation: ***Internal circular fibers*** - The **internal anal sphincter** is an involuntary muscle formed by the thickening of the **circular smooth muscle layer** of the rectum. - This sphincter maintains **tonic contraction** and is responsible for about 80% of resting anal pressure [1]. *Puborectalis muscle* - The **puborectalis muscle** is a voluntary muscle, forming a sling around the anorectal junction to maintain the **anorectal angle** [1]. - It is part of the **levator ani muscles**, which are skeletal muscles, not smooth muscle [1]. *Deep perineal muscles* - The **deep perineal muscles** are a group of skeletal muscles located in the urogenital diaphragm. - They are involved in functions such as **urinary continence** and **erection**, but do not form the internal anal sphincter. *Internal longitudinal fibers* - The **longitudinal muscle layer** of the rectum continues downwards as the conjoined longitudinal muscle, which blends with the external anal sphincter. - These fibers contribute to the **anorectal ring** and support the anal canal but do not form the internal anal sphincter itself.
Question 156: Which artery passes through the anatomical snuffbox?
- A. Radial artery (Correct Answer)
- B. Brachial artery
- C. Ulnar artery
- D. Interosseus artery
Explanation: ***Radial artery*** - The **radial artery** is palpable within the **anatomical snuffbox**, as it courses over the scaphoid and trapezium bones towards the deep palmar arch. - This location is clinically significant for feeling the pulse and is vulnerable to injury, especially during **scaphoid fractures**. *Brachial artery* - The **brachial artery** is found in the **arm**, typically running in the cubital fossa, well proximal to the anatomical snuffbox. - It bifurcates into the radial and ulnar arteries at the level of the elbow, not within the wrist structures. *Ulnar artery* - The **ulnar artery** typically lies on the **medial side of the forearm** and wrist, contributing to the superficial palmar arch. - It does not pass through the anatomical snuffbox, which is located on the lateral aspect of the wrist. *Interosseus artery* - The **interosseus arteries** (anterior and posterior) run between the radius and ulna in the forearm, supplying muscles and bones. - These arteries are deep within the forearm compartments and do not traverse the superficial anatomical snuffbox at the wrist.
Question 157: What is the posterior relation of the neck of the pancreas?
- A. IVC
- B. Aorta
- C. Common bile duct
- D. Origin of portal vein (Correct Answer)
Explanation: ***Origin of portal vein*** - The **neck of the pancreas** is intimately associated with the formation of the **hepatic portal vein** [1]. - The **superior mesenteric vein** and **splenic vein** unite behind the pancreatic neck to form the **hepatic portal vein** [1]. *IVC* - The **inferior vena cava (IVC)** lies posterior to the **head of the pancreas**, not the neck. - While it's in proximity, it does not directly relate to the neck in the same way the portal vein does. *Aorta* - The **abdominal aorta** lies posterior to the **body** and **tail of the pancreas**, further superior and to the left. - It is not a direct posterior relation of the pancreatic neck. *Common bile duct* - The **common bile duct** passes through a groove on the posterior surface of the pancreatic **head**, sometimes even embedded within it. - It is not a direct posterior relation of the pancreatic neck, which is a different segment.
Physiology
2 questionsWhich of the following is not a recognized stage of prophase I in meiosis?
Spermatogenesis begins at -
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 151: Which of the following is not a recognized stage of prophase I in meiosis?
- A. Diakinesis
- B. Leptotene
- C. Zygotene
- D. Arachytene (Correct Answer)
Explanation: ***Arachytene*** - **Arachytene** is not a recognized stage of prophase I in meiosis. - The correct stages are leptotene, zygotene, pachytene, diplotene, and diakinesis. *Diakinesis* - **Diakinesis** is the final stage of prophase I, where homologous chromosomes condense further, and the nuclear envelope begins to break down. - Chiasmata terminalize, and the bivalents are ready for metaphase I. *Leptotene* - **Leptotene** is the first stage of prophase I, characterized by the condensation of chromatin into visible chromosomes. - Chromosomes appear as long, thin threads. *Zygotene* - **Zygotene** is the second stage of prophase I, where homologous chromosomes pair up in a process called **synapsis**, forming bivalents. - The synaptonemal complex begins to form between homologous chromosomes.
Question 152: Spermatogenesis begins at -
- A. Birth
- B. 5 years
- C. Puberty (Correct Answer)
- D. 18 years
Explanation: ***Puberty*** - **Spermatogenesis**, the process of sperm production, is initiated and sustained by the surge of **gonadotropin-releasing hormone (GnRH)**, which begins at puberty. - This hormonal signal leads to the secretion of **luteinizing hormone (LH)** and **follicle-stimulating hormone (FSH)**, crucial for testicular function and sperm development. *Birth* - At birth, the male testes contain **spermatogonia**, but these cells remain dormant and do not begin active sperm production. - Hormonal levels at birth are not conducive to initiating spermatogenesis. *5 years* - While some hormonal changes occur in early childhood, they are not sufficient to trigger the full process of spermatogenesis. - The reproductive system is still in a quiescent state before puberty. *18 years* - By 18 years, spermatogenesis is typically well-established and has been ongoing for several years, having started at puberty. - This age marks a period of full reproductive maturity, not the initiation of sperm production.
Surgery
1 questionsWhich of the following statements is true about branchial cysts?
NEET-PG 2015 - Surgery NEET-PG Practice Questions and MCQs
Question 151: Which of the following statements is true about branchial cysts?
- A. Branchial cysts are more common in males than females.
- B. They mostly arise from the second branchial cleft. (Correct Answer)
- C. Surgical intervention is not always necessary.
- D. They can cause dysphagia and hoarseness if infected.
Explanation: ***They mostly arise from the second branchial cleft.*** - **Second branchial cleft cysts** are the most common type, accounting for approximately **95%** of all branchial anomalies. - They typically present as a smooth, fluctuant mass along the **anterior border of the sternocleidomastoid muscle** at the junction of the upper and middle third of the neck. - These cysts result from **incomplete obliteration** of the second branchial cleft during embryonic development. *Branchial cysts are more common in males than females.* - Branchial cysts have **no significant sex predilection**, affecting males and females with roughly equal frequency. - The overall incidence is relatively rare, with most cases presenting in late childhood or early adulthood. *Surgical intervention is not always necessary.* - **Complete surgical excision** is the **definitive treatment** and is strongly recommended for all branchial cysts. - Indications for surgery include: prevention of **recurrent infections**, risk of **abscess formation**, elimination of cosmetic concerns, and removal due to potential (though rare) **malignant transformation**. - While very small asymptomatic cysts may occasionally be observed, this carries significant risk of future complications, making surgery the standard of care in clinical practice. *They can cause dysphagia and hoarseness if infected.* - While an **infected branchial cyst** causes local inflammatory signs (pain, swelling, warmth, erythema), it **rarely causes dysphagia or hoarseness** unless exceptionally large. - These symptoms would require the cyst to compress the **pharynx** (dysphagia) or involve the **recurrent laryngeal nerve** (hoarseness), which is uncommon even with infection. - The primary presentation of infected cysts includes **tender neck mass** with overlying skin changes and possible **abscess formation**.