Spleen development US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Spleen development. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Spleen development US Medical PG Question 1: A 34-year-old woman comes to the emergency department because of a 2-hour history of abdominal pain, nausea, and vomiting that began an hour after she finished lunch. Examination shows abdominal guarding and rigidity; bowel sounds are reduced. Magnetic resonance cholangiopancreatography shows the dorsal pancreatic duct draining into the minor papilla and a separate smaller duct draining into the major papilla. The spleen is located anterior to the left kidney. A disruption of which of the following embryological processes is the most likely cause of this patient's imaging findings?
- A. Proliferation of mesenchyme in the dorsal mesentery
- B. Differentiation of the proximal hepatic diverticulum
- C. Fusion of the pancreatic buds (Correct Answer)
- D. Rotation of the midgut
- E. Rotation of the dorsal mesogastrium
Spleen development Explanation: ***Fusion of the pancreatic buds***
- The imaging findings describe **pancreas divisum**, a congenital anomaly where the **dorsal and ventral pancreatic buds fail to fuse** completely.
- This leads to the dorsal pancreatic duct (containing most of the gland volume) draining through the **minor papilla**, which is functionally insufficient and can cause recurrent pancreatitis as seen in this patient with signs of peritonitis.
*Proliferation of mesenchyme in the dorsal mesentery*
- This process is primarily associated with the development of the **spleen**, which is derived from mesenchymal cells in the dorsal mesogastrium.
- While the spleen's position is mentioned, its development or abnormal position is not the cause of the pancreatic ductal anomaly described.
*Differentiation of the proximal hepatic diverticulum*
- The **hepatic diverticulum** gives rise to the liver, gallbladder, and biliary tree.
- Abnormalities in this process would lead to issues with these organs, not with the pancreatic ductal system.
*Rotation of the dorsal mesogastrium*
- The **dorsal mesogastrium** rotates during embryological development and gives rise to structures including the spleen and the greater omentum.
- While abnormal rotation could explain splenic malposition, it does not directly explain the pancreatic ductal anomaly (pancreas divisum) described in the imaging.
*Rotation of the midgut*
- The **midgut rotation** is a complex embryological process involving the looping and rotation of the intestines around the superior mesenteric artery.
- Errors in this process can lead to malrotation, volvulus, or intestinal atresia, but not pancreatic ductal anomalies.
Spleen development US Medical PG Question 2: During a surgical procedure to repair an abdominal aortic aneurysm, the surgeon must be careful to avoid injury to which of the following arterial structures that originates near the level of the renal vessels?
- A. Left renal artery (Correct Answer)
- B. Celiac trunk
- C. Right renal artery
- D. Superior mesenteric artery
Spleen development Explanation: ***Left renal artery***
- The **left renal artery** arises from the aorta usually just below the superior mesenteric artery, making it susceptible to injury during an **abdominal aortic aneurysm (AAA) repair** if the aneurysm extends proximally.
- Its proximity to the typical location of AAA, often near or involving the **infrarenal aorta**, necessitates careful identification and protection during clamping or graft placement.
*Celiac trunk*
- The **celiac trunk** originates higher up from the aorta, typically at the level of **T12-L1 vertebrae**, well above the common infrarenal AAA repair site.
- While important, it is generally less directly threatened during a typical infrarenal AAA repair compared to arteries immediately adjacent to or within the aneurysm sac.
*Right renal artery*
- The **right renal artery** also originates from the aorta near the level of the renal veins, but it is typically located more posteriorly and usually passes behind the inferior vena cava.
- Although it can be at risk, the left renal artery's course is often more anterior and directly in the field of dissection for the **aortic neck** during AAA repair.
*Superior mesenteric artery*
- The **superior mesenteric artery (SMA)** originates from the aorta proximal to the renal arteries, typically around the L1 vertebral level.
- While crucial, its origin is usually cephalad to the infrarenal aneurysm neck, making it generally less prone to direct injury during infrarenal AAA repair, though flow must be monitored.
Spleen development US Medical PG Question 3: A 2-year-old girl with a history of SS-hemoglobin is brought to her pediatrician by her mother, who noted an abdominal mass. On exam, the girl's spleen is palpably enlarged, and her palms and conjunctiva are noted to be extremely pale. Serum haptoglobin levels are decreased. Which of the following is the most likely cause of this patient's symptoms?
- A. Intravascular hemolysis
- B. Extravascular hemolysis (Correct Answer)
- C. Hemolytic uremic syndrome
- D. Complement-mediated hemolysis
- E. Decreased red blood cell production
Spleen development Explanation: ***Extravascular hemolysis***
- This patient presents with **anemia** (pale conjunctiva and palms) and an **enlarged spleen**, which are classic signs of **extravascular hemolysis**. **Sickle cell disease** is a condition known to cause chronic hemolysis through this mechanism, where damaged red blood cells are removed by the reticuloendothelial system, primarily in the spleen.
- In **extravascular hemolysis**, red blood cells are destroyed outside of the bloodstream by macrophages in the spleen, liver, and bone marrow. While this process releases less **free hemoglobin** into circulation than intravascular hemolysis, **chronic hemolysis in sickle cell disease still leads to decreased haptoglobin levels** due to ongoing red cell destruction and some degree of intravascular hemolysis.
- The **splenomegaly** in this young patient is characteristic, as the spleen becomes engorged with sequestered and destroyed sickled red blood cells before it undergoes autoinfarction in later childhood.
*Intravascular hemolysis*
- **Intravascular hemolysis** involves the destruction of red blood cells within the circulation, leading to the release of **free hemoglobin**.
- While sickle cell disease does have some intravascular component, the **primary mechanism is extravascular**, and the presence of **significant splenomegaly** with palpable abdominal mass points to splenic sequestration and extravascular destruction as the dominant process.
*Hemolytic uremic syndrome*
- **Hemolytic uremic syndrome (HUS)** is characterized by a triad of **microangiopathic hemolytic anemia**, **thrombocytopenia**, and **acute kidney injury**.
- While it involves hemolysis, the patient's presentation lacks **thrombocytopenia** and evidence of **renal failure**, making HUS less likely. Additionally, HUS is not typically associated with **sickle cell disease**.
*Complement-mediated hemolysis*
- **Complement-mediated hemolysis** is seen in conditions like **paroxysmal nocturnal hemoglobinuria (PNH)** or some autoimmune hemolytic anemias.
- This typically results in **intravascular hemolysis** due to complement activation on red cell surfaces. The patient's known diagnosis of **sickle cell disease** makes this mechanism less likely as the primary cause.
*Decreased red blood cell production*
- Conditions with **decreased red blood cell production**, such as **aplastic anemia** or **pure red cell aplasia**, would present with anemia but not typically with an **enlarged spleen** or evidence of significant red blood cell destruction.
- The patient's history of **SS-hemoglobin (sickle cell disease)** and **decreased haptoglobin** point towards a hemolytic process rather than bone marrow suppression as the primary cause of anemia.
Spleen development US Medical PG Question 4: A 46-year-old woman presents to her primary care physician with complaints of increasing left upper quadrant discomfort. She has a known history of type 1 Gaucher disease. On physical examination, her spleen is palpable 8 cm below the costal margin. Routine laboratory work reveals severe pancytopenia. After consultation with the patient on the risks of her condition, the patient decides to undergo a splenectomy. Which of the following is more likely to occur as a consequence of splenectomy in this patient?
- A. Thrombocytopenia
- B. Leukopenia
- C. Pneumococcal septicemia (Correct Answer)
- D. Staphylococcal septicemia
- E. Anemia
Spleen development Explanation: ***Pneumococcal septicemia***
- Patients who undergo splenectomy are at significantly increased risk of **overwhelming post-splenectomy infection (OPSI)**, particularly from **encapsulated bacteria** like *Streptococcus pneumoniae*.
- The spleen plays a crucial role in filtering encapsulated bacteria and producing opsonizing antibodies, and its removal compromises this immune function.
*Thrombocytopenia*
- **Thrombocytopenia** is typically a symptom *before* splenectomy in Gaucher disease due to hypersplenism.
- After splenectomy, the platelet count often **increases**, not decreases, due to the removal of the organ that sequesters platelets and destroys them.
*Leukopenia*
- **Leukopenia** (specifically neutropenia) is a pre-existing condition in severe Gaucher disease due to hypersplenism and bone marrow involvement.
- Post-splenectomy, the white blood cell count, particularly neutrophils, generally **increases** as the sequestration and destruction in the spleen are eliminated.
*Staphylococcal septicemia*
- While *Staphylococcus* can cause serious infections, it is **not the primary pathogen** associated with OPSI in asplenic patients.
- Encapsulated bacteria like *Streptococcus pneumoniae* are the most common and dangerous cause of post-splenectomy sepsis.
*Anemia*
- **Anemia** is a common finding in Gaucher disease due to hypersplenism and bone marrow infiltration.
- Splenectomy typically **improves** anemia by removing the site of red blood cell destruction and reducing abnormal cytokine production that inhibits erythropoiesis.
Spleen development US Medical PG Question 5: A 3-year-old boy is brought to the physician because of a 5-day history of yellowing of his eyes and skin. He has had generalized fatigue and mild shortness of breath over the past 2 months. Examination shows pale conjunctivae and scleral jaundice. The spleen is palpated 4 cm below the left costal margin. Laboratory studies show a hemoglobin concentration of 8.5 g/dL and a mean corpuscular volume of 76 μm3. A peripheral blood smear shows round erythrocytes that lack central pallor. Which of the following is the most likely cause of the splenomegaly seen in this child?
- A. Metabolite accumulation
- B. Work hypertrophy (Correct Answer)
- C. Neoplastic infiltration
- D. Reticuloendothelial hyperplasia
- E. Extramedullary hematopoiesis
Spleen development Explanation: ***Work hypertrophy***
- The patient's presentation is consistent with **hereditary spherocytosis**, characterized by **hemolytic anemia**, jaundice, and **splenomegaly**.
- **Work hypertrophy** of the spleen's red pulp occurs due to its increased function in removing abnormal, rigid spherocytes from circulation, leading to its enlargement.
*Metabolite accumulation*
- This typically occurs in **lysosomal storage diseases** where defective enzymes lead to the buildup of specific metabolites within splenic macrophages.
- Conditions like **Gaucher disease** or **Niemann-Pick disease** cause splenomegaly through this mechanism, but do not present with spherocytes and hemolytic anemia.
*Neoplastic infiltration*
- This type of splenomegaly results from the infiltration of the spleen by **malignant cells**, such as in **leukemias** or **lymphomas**.
- While neoplastic infiltration can cause anemia, it is generally associated with different peripheral smear findings and systemic symptoms, not hereditary spherocytosis.
*Reticuloendothelial hyperplasia*
- While related to increased splenic activity, **reticuloendothelial hyperplasia** is a broader term encompassing the proliferation of macrophages and other immune cells in response to chronic infections or certain immune disorders.
- In hemolytic anemia, the primary driver of splenic enlargement is the excessive workload of removing red blood cells, which is best described as **work hypertrophy**.
*Extramedullary hematopoiesis*
- This refers to blood cell production occurring outside the bone marrow, often in the spleen or liver, as a compensatory mechanism in severe **bone marrow failure** or chronic hemolytic states.
- While it can contribute to splenomegaly in some chronic hemolytic anemias (e.g., thalassemia major), the primary cause of splenomegaly in hereditary spherocytosis is the *increased destruction* of abnormal RBCs by the spleen.
Spleen development US Medical PG Question 6: A researcher is investigating the blood supply of the adrenal gland. While performing an autopsy on a patient who died from unrelated causes, he identifies a vessel that supplies oxygenated blood to the inferior aspect of the right adrenal gland. Which of the following vessels most likely gave rise to the vessel in question?
- A. Inferior phrenic artery
- B. Abdominal aorta
- C. Renal artery (Correct Answer)
- D. Superior mesenteric artery
- E. Common iliac artery
Spleen development Explanation: ***Renal artery***
- The **inferior suprarenal artery**, which supplies the inferior part of the adrenal gland, typically arises from the **renal artery**.
- The adrenal glands receive a rich blood supply from three main arterial sources: superior, middle, and inferior suprarenal arteries.
*Inferior phrenic artery*
- The **superior suprarenal arteries** typically arise from the **inferior phrenic arteries** and supply the superior aspect of the adrenal glands.
- While critical for adrenal blood supply, they do not typically contribute to the inferior aspect directly.
*Abdominal aorta*
- The **middle suprarenal artery** usually arises directly from the **abdominal aorta**.
- This vessel supplies the central part of the adrenal gland, but not primarily the inferior aspect.
*Superior mesenteric artery*
- The **superior mesenteric artery** primarily supplies structures of the midgut (e.g., small intestine, ascending colon) and does not typically give rise to vessels supplying the adrenal glands.
- It is located inferior to the origin of the renal arteries and the adrenal glands.
*Common iliac artery*
- The **common iliac arteries** supply the lower limbs and pelvic organs, originating from the abdominal aorta bifurcation.
- These arteries are located much too far inferior to supply the adrenal glands, which are retroperitoneal structures in the upper abdomen.
Spleen development US Medical PG Question 7: A newborn boy born vaginally to a healthy 37-year-old G3P1 from a pregnancy complicated by hydramnios fails to pass meconium after 24 hours of life. The vital signs are within normal limits for his age. The abdomen is distended, the anus is patent, and the rectal examination reveals pale mucous with non-pigmented meconium. Based on a barium enema, the boy is diagnosed with sigmoid colonic atresia. Disruption of which structure during fetal development could lead to this anomaly?
- A. Inferior mesenteric artery (Correct Answer)
- B. Superior mesenteric artery
- C. Vitelline duct
- D. Cloaca
- E. Celiac artery
Spleen development Explanation: ***Inferior mesenteric artery***
- **Sigmoid colonic atresia**, as observed in this case, results from an ischemic event affecting the segment of the bowel supplied by the **inferior mesenteric artery** during fetal development.
- Interruption of blood flow to this region can lead to subsequent **atresia** as the affected part of the intestine necroses and is reabsorbed.
*Superior mesenteric artery*
- The **superior mesenteric artery** primarily supplies the midgut structures, including the small intestine and parts of the large intestine up to the transverse colon.
- Disruption of the superior mesenteric artery would typically lead to atresias higher up in the **gastrointestinal tract**, such as jejunal or ileal atresias, not sigmoid colonic atresia.
*Vitelline duct*
- The **vitelline duct** (also known as the omphalomesenteric duct) connects the midgut to the yolk sac during early fetal development.
- Persistent patency or partial obliteration of the vitelline duct can lead to anomalies like **Meckel's diverticulum** or vitelline cysts, which are distinct from colonic atresia.
*Cloaca*
- The **cloaca** is a common cavity for the digestive, urinary, and reproductive tracts during early embryonic development.
- Defects in cloacal development lead to complex malformations involving these systems, such as **imperforate anus** or persistent cloaca, rather than isolated colonic atresia with a patent anus.
*Celiac artery*
- The **celiac artery** supplies the foregut structures, including the stomach, duodenum, liver, and spleen.
- Disruption of the celiac artery during fetal development would result in malformations of these upper gastrointestinal organs, not the sigmoid colon.
Spleen development US Medical PG Question 8: A 60-year-old gentleman passes away after a car accident. On routine autopsy it is incidentally noted that he has both a ventral and dorsal pancreatic duct. This incidental finding observed by the pathologist is generated due to failure of which of the following embryological processes?
- A. Apoptosis
- B. Stem cell differentiation
- C. Notochord signaling
- D. Neural crest cell migration
- E. Fusion (Correct Answer)
Spleen development Explanation: ***Fusion***
- The pancreas develops from a **ventral and a dorsal bud** that typically **fuse** during development.
- Failure of these two pancreatic buds (and their associated ducts) to completely fuse can result in **pancreas divisum**, where two separate ductal systems persist, corresponding to the dorsal and ventral pancreatic ducts.
*Apoptosis*
- **Apoptosis** (programmed cell death) is crucial for the removal of unwanted cells and sculpting tissues during embryogenesis, such as the formation of digits or the regression of certain structures.
- It does not directly explain the persistence of two separate pancreatic ducts due to non-fusion of developmental buds.
*Stem cell differentiation*
- **Stem cell differentiation** is the process by which less specialized stem cells become more specialized cell types, which is fundamental to organ development and tissue formation.
- While essential for pancreatic development, it doesn't specifically account for the anatomical anomaly of two persistent ducts.
*Notochord signaling*
- **Notochord signaling** is vital for inducing the formation of the neural tube and defining the dorsal-ventral axis of the embryo, as well as influencing the development of other nearby structures.
- This process is not directly related to the fusion of pancreatic buds, which occurs later and is influenced by interactions between mesenchymal and endodermal tissues.
*Neural crest cell migration*
- **Neural crest cells** are multipotent cells that migrate extensively throughout the embryo to form a wide variety of tissues, including parts of the peripheral nervous system, melanocytes, and bone/cartilage of the face and skull.
- Their migratory pathways and derivatives are not directly involved in the development and fusion of the pancreatic ductal system.
Spleen development US Medical PG Question 9: A 23-year-old woman presents to her primary care physician with 3 days of fatigue and back pain after she started a drug for malaria prophylaxis. She says that her urine has also been darker over the same time period. Her past medical history is significant for allergies as well as a broken elbow that was treated in a cast 10 years ago. She does not take any medications, does not smoke, and drinks socially. Peripheral blood smear reveals both red blood cells with dark intracellular inclusions as well as abnormally shaped red blood cells. The immune cells responsible for the shape of these red blood cells are located in which of the following places?
- A. Lymph nodes
- B. Red pulp of the spleen (Correct Answer)
- C. Bone marrow
- D. White pulp of the spleen
- E. Blood vessels
Spleen development Explanation: ***Red pulp of the spleen***
- The patient's symptoms (fatigue, back pain, dark urine after malaria prophylaxis) and lab findings (**dark intracellular inclusions** and abnormally shaped red blood cells) suggest **G6PD deficiency**, leading to **hemolytic anemia**.
- The **red pulp of the spleen** is where old or damaged red blood cells, including those with Heinz bodies (intracellular inclusions) or abnormal shapes, are **phagocytosed** by macrophages, thus "shaping" them or removing severely affected cells.
*Lymph nodes*
- **Lymph nodes** are primarily involved in filtering lymph and are major sites for adaptive immune responses, housing B and T lymphocytes.
- They are not the primary sites for the destruction or "shaping" of red blood cells.
*Bone marrow*
- The **bone marrow** is the primary site of **hematopoiesis**, where red blood cells are produced, not where they are destroyed or undergo physical shaping due to immune cell action in hemolysis.
- While macrophages are present, their main role in marrow is related to erythropoiesis (e.g., central macrophage in erythroblastic islands) and debris clearance, not erythrocyte shaping in peripheral circulation.
*White pulp of the spleen*
- The **white pulp of the spleen** is rich in lymphocytes and is the site of immune responses, similar to lymph nodes.
- It is involved in adaptive immunity and not directly engaged in the physical destruction or "shaping" of red blood cells during hemolysis.
*Blood vessels*
- **Blood vessels** are conduits for blood transport and are not primary sites for the physical destruction or shaping of red blood cells by immune cells.
- While some hemolysis can occur intravascularly, the immune cells responsible for removing and "shaping" damaged red blood cells (like macrophages) are predominantly organ-resident.
Spleen development US Medical PG Question 10: A newborn is rushed to the neonatal ICU after becoming cyanotic shortly after birth. An ultrasound is performed which shows the aorta coming off the right ventricle and lying anterior to the pulmonary artery. The newborn is given prostaglandin E1 and surgery is planned to correct the anatomic defect. Which of the following developmental processes failed to occur in the newborn?
- A. Failure of the membranous ventricular septum to fuse with the muscular interventricular septum
- B. Failure of the septum primum to fuse with the septum secundum
- C. Failure of the aorticopulmonary septum to spiral (Correct Answer)
- D. Failure of the ductus venosus to close
- E. Failure of the ductus arteriosus to close
Spleen development Explanation: ***Failure of the aorticopulmonary septum to spiral***
- **Transposition of the great arteries (TGA)**, characterized by the aorta originating from the right ventricle and the pulmonary artery from the left ventricle, results from the **aorticopulmonary septum** failing to spiral properly during embryological development.
- This defect leads to two separate circulatory systems, causing severe **cyanosis** shortly after birth and requiring **prostaglandin E1** to maintain a patent ductus arteriosus for mixing of oxygenated and deoxygenated blood.
- This is a ductal-dependent lesion requiring urgent intervention.
*Failure of the membranous ventricular septum to fuse with the muscular interventricular septum*
- This specific failure leads to a **ventricular septal defect (VSD)**, which allows blood to shunt between ventricles.
- While VSDs can cause cyanosis if large and associated with pulmonary hypertension (Eisenmenger syndrome), the description of **great artery transposition** is not caused by this developmental failure.
*Failure of the septum primum to fuse with the septum secundum*
- This developmental anomaly results in a **patent foramen ovale (PFO)** or an **atrial septal defect (ASD)**.
- These defects typically cause a left-to-right shunt and present with symptoms later in life, not with severe immediate cyanosis.
- In TGA, an ASD may actually be beneficial as it allows some mixing of blood.
*Failure of the ductus venosus to close*
- The **ductus venosus** shunts oxygenated blood from the umbilical vein directly to the inferior vena cava, bypassing the fetal liver during intrauterine life.
- Persistent patency of the ductus venosus after birth is rare and does not cause the severe cyanosis and specific great artery anatomy seen in TGA.
*Failure of the ductus arteriosus to close*
- A **patent ductus arteriosus (PDA)** allows blood to flow from the aorta to the pulmonary artery after birth, which can lead to pulmonary overcirculation.
- In **transposition of the great arteries**, a PDA is actually crucial for survival as it provides a pathway for mixing of oxygenated and deoxygenated blood; maintaining PDA patency with PGE1 is the initial management, not a cause of the condition.
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