Diaphragm development US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Diaphragm development. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Diaphragm development US Medical PG Question 1: During the third week of development, the blastocyst undergoes a variety of differentiation processes responsible for the formation of the gastrula and, eventually, the embryo. This differentiation creates cell lineages that eventually become a variety of body systems. What cell lineage, present at this date, is responsible for the formation of the liver?
- A. Neuroectoderm
- B. Syncytiotrophoblasts
- C. Ectoderm
- D. Endoderm (Correct Answer)
- E. Mesoderm
Diaphragm development Explanation: ***Endoderm***
- The **endoderm** is one of the three primary germ layers that develops during gastrulation and is responsible for forming the lining of the **gastrointestinal tract** and associated organs, including the **liver** and pancreas.
- Liver development begins from an outgrowth of the **foregut endoderm**, which differentiates into hepatocytes and bile duct cells, forming the hepatic parenchyma.
*Neuroectoderm*
- **Neuroectoderm** is a specialized part of the ectoderm that gives rise to the entire **nervous system**, including the brain, spinal cord, and peripheral nerves.
- It does not contribute to the formation of visceral organs like the liver.
*Syncytiotrophoblasts*
- **Syncytiotrophoblasts** are a layer of the **trophoblast** that form part of the placenta, specifically involved in hormone production and nutrient exchange between the mother and fetus.
- They are part of the supporting structures for pregnancy and do not contribute to the embryonic germ layers or organ formation within the embryo itself.
*Ectoderm*
- The **ectoderm** is the outermost germ layer and gives rise to the **epidermis of the skin**, hair, nails, nervous system, and sensory organs.
- While it forms the outer coverings and nervous system, it does not directly form internal organs like the liver.
*Mesoderm*
- The **mesoderm** is the middle germ layer, responsible for forming **muscle**, **bone**, connective tissue, the circulatory system, kidneys, and gonads.
- While mesoderm contributes supporting structures to the liver (blood vessels, connective tissue, hematopoietic cells), the **hepatic parenchyma** (hepatocytes and bile ducts) is derived from the endoderm, making endoderm the primary cell lineage responsible for liver formation.
Diaphragm development US Medical PG Question 2: A 50-year-old man is brought in by ambulance to the emergency department with difficulty breathing and speaking. His wife reports that he might have swallowed a fishbone. While taking his history the patient develops a paroxysmal cough. Visualization of his oropharynx and larynx shows a fishbone lodged in the right piriform recess. After successfully removing the fishbone the patient feels comfortable, but he is not able to cough like before. Damage to which of the following nerves is responsible for the impaired cough reflex in this patient?
- A. Inferior laryngeal nerve
- B. Internal laryngeal nerve (Correct Answer)
- C. External laryngeal nerve
- D. Superior laryngeal nerve
- E. Recurrent laryngeal nerve
Diaphragm development Explanation: ***Internal laryngeal nerve***
- The internal laryngeal nerve is the **sensory nerve** of the larynx above the vocal cords, including the piriform recess. Damage to this nerve, often due to trauma from a foreign body like a fishbone, impairs the **afferent limb of the cough reflex**.
- A fishbone lodged in the **piriform recess** directly implicates the sensory function of the internal laryngeal nerve, explaining the subsequent loss of the cough reflex even after removal of the foreign body.
*Inferior laryngeal nerve*
- This nerve is primarily **motor** to almost all intrinsic laryngeal muscles and provides **sensory innervation** below the vocal folds. Damage would primarily affect phonation (hoarseness) or breathing due to vocal cord paralysis.
- It would not directly affect the sensory input initiating a cough reflex from the piriform recess, which is above the vocal folds.
*External laryngeal nerve*
- The external laryngeal nerve is a **motor nerve** supplying the **cricothyroid muscle**, which is responsible for tensing the vocal cords and altering voice pitch.
- Damage to this nerve would lead to **hoarseness** and difficulty with high-pitched sounds, not an impaired cough reflex from the piriform recess.
*Superior laryngeal nerve*
- The superior laryngeal nerve divides into the internal and external laryngeal nerves. While it contains sensory fibers that lead to the internal laryngeal nerve, stating damage to the entire superior laryngeal nerve is less specific than identifying the internal laryngeal nerve as the direct cause of the sensory deficit.
- Damage to the superior laryngeal nerve would encompass both sensory and motor deficits (internal and external branches), but the specific symptom of impaired cough reflex primarily points to the internal laryngeal branch.
*Recurrent laryngeal nerve*
- This nerve is another name for the **inferior laryngeal nerve** and is primarily **motor** to the intrinsic laryngeal muscles (except cricothyroid) and provides sensory innervation below the vocal cords.
- Damage to this nerve primarily results in **vocal cord paralysis** and voice changes (hoarseness), not the sensory loss affecting the cough reflex from the piriform recess.
Diaphragm development US Medical PG Question 3: A 31-year-old man presents for his annual physical exam. The physician fails to palpate a ductus deferens on the left side. An ultrasound confirms absence of the left ductus deferens and further reveals absence of the left epididymis, seminal vesicle, and kidney. Spermogram and reproductive hormones panel are within normal limits. Left-sided agenesis of an embryonic anlage is suspected. Which two structures are connected by this anlage during embryogenesis?
- A. Metanephros and coelom
- B. Mesonephros and coelom
- C. Pronephros and cloaca
- D. Mesonephros and cloaca (Correct Answer)
- E. Pronephros and coelom
Diaphragm development Explanation: ***Mesonephros and cloaca***
- The **mesonephros** forms the **mesonephric (Wolffian) duct**, which connects to the **cloaca**.
- In males, this duct gives rise to the **epididymis**, **vas deferens**, **seminal vesicles**, and **ureteric bud** (which forms the kidney collecting system). The simultaneous absence of the kidney, epididymis, and seminal vesicle indicates a defect in this developmental pathway.
*Metanephros and coelom*
- The **metanephros** is a later stage of kidney development, forming the definitive kidney parenchyma, but it does **not connect directly to the coelom**.
- Its excretory ducts develop from an interaction with the ureteric bud (derived from the mesonephric duct), not directly from the coelom.
*Mesonephros and coelom*
- While the **mesonephros** develops within the intermediate mesoderm adjacent to the **coelom**, its primary connection relevant to these structures is to the cloaca via the mesonephric duct.
- The **coelom** is the primitive body cavity, and direct connections to the adult reproductive/urinary tracts in this manner are not embryologically accurate for this defect.
*Pronephros and cloaca*
- The **pronephros** is a transient, non-functional embryonic kidney structure that degenerates early in development and does **not form the definitive male reproductive or urinary structures** seen here.
- Its connection to the cloaca is not as direct or as developmentally critical for the structures described in the case.
*Pronephros and coelom*
- Similar to the previous option, the **pronephros** is an early and transient structure.
- It does **not develop into the adult genitourinary structures** affected in this patient, and its relationship with the coelom is not the key to understanding this specific congenital anomaly.
Diaphragm development US Medical PG Question 4: A newborn infant is resuscitated and transferred to the neonatal intensive care unit. The infant has notable limb deformities as well as low-set ears and a flattened nose. He was born at 34 weeks gestation to a healthy mother who received regular obstetric follow-up. Resuscitation was notable for difficulty maintaining oxygenation in the newborn. Despite appropriate interventions, the infant is still struggling to maintain adequate oxygenation. Which of the following is most likely the cause of this patient's symptoms?
- A. PKD1 gene mutation
- B. Cystic dilation of the collecting ducts in the kidney (Correct Answer)
- C. Chromosomal abnormality
- D. Maternal diabetes
- E. Failure to administer betamethasone
Diaphragm development Explanation: ***Cystic dilation of the collecting ducts in the kidney***
- This finding is characteristic of **autosomal recessive polycystic kidney disease (ARPKD)**, which leads to **Potter sequence/Potter syndrome**.
- **Potter sequence** results from severe **oligohydramnios** (often due to bilateral renal disease causing inadequate urine production), leading to:
- **Pulmonary hypoplasia** (lungs cannot expand properly without adequate amniotic fluid)
- **Characteristic facial features** (Potter facies): low-set ears, flattened nose, recessed chin
- **Limb deformities** (positional abnormalities from mechanical compression in utero)
- The **persistent difficulty maintaining oxygenation despite appropriate interventions** is the key clinical clue - this indicates **structural pulmonary hypoplasia**, not simply respiratory distress from prematurity or other causes that would respond to treatment.
- Potter sequence is the most likely diagnosis given this specific constellation of findings.
*Chromosomal abnormality*
- While **trisomy 18 (Edwards syndrome)** or **trisomy 13 (Patau syndrome)** can present with multiple congenital anomalies including facial dysmorphisms and limb deformities, they typically have additional characteristic findings (cardiac defects, rocker-bottom feet, holoprosencephaly, etc.).
- The **specific triad** of Potter facies + limb deformities + **refractory respiratory distress due to pulmonary hypoplasia** is pathognomonic for Potter sequence, not chromosomal abnormalities.
- Chromosomal abnormalities would not typically cause the severe oligohydramnios that leads to pulmonary hypoplasia.
*Maternal diabetes*
- Maternal diabetes can cause **macrosomia**, **hypoglycemia**, **respiratory distress syndrome (RDS)**, and rarely congenital anomalies (cardiac, neural tube defects).
- It does not cause the specific pattern of **Potter facies** (low-set ears, flattened nose) and **limb deformities** seen in Potter sequence.
- The mother is described as healthy with regular obstetric follow-up, making uncontrolled diabetes unlikely.
*PKD1 gene mutation*
- **PKD1 mutation** causes **autosomal dominant polycystic kidney disease (ADPKD)**, which typically presents in **adulthood** with hypertension, flank pain, and progressive renal failure.
- While rare severe cases can present in utero, PKD1 mutation does not cause the **cystic dilation of collecting ducts** - that finding is specific to **ARPKD** (associated with PKHD1 gene mutation).
- ADPKD involves cysts throughout the cortex and medulla, not specifically in collecting ducts.
*Failure to administer betamethasone*
- **Betamethasone** is given to mothers at risk of preterm delivery (before 34 weeks) to accelerate **fetal lung maturity** and reduce the severity of **respiratory distress syndrome (RDS)**.
- While this infant is preterm (34 weeks) and has respiratory distress, betamethasone failure would cause RDS due to **surfactant deficiency**, which typically **responds to surfactant administration and respiratory support**.
- This does not explain the **structural pulmonary hypoplasia** (indicated by refractory oxygenation issues) or the **facial and limb deformities**.
- Betamethasone is typically given before 34 weeks; at 34 weeks, the benefit is limited.
Diaphragm development US Medical PG Question 5: A 2600-g (5-lb 8-oz) male newborn is delivered at 34 weeks' gestation to a 22-year-old woman. The mother did not have prenatal care. Upon examination in the delivery room, the newborn's skin appears blue. He is gasping and breathing irregularly. The ears are low-set with broad auricles, and the nasal tip is flattened. The lower jaw is small and displaced backward. The right foot is clubbed. Which of the following is the most likely underlying cause of this patient's condition?
- A. Pulmonary hypoplasia
- B. Posterior urethral valves (Correct Answer)
- C. Fetal anemia
- D. Anencephaly
- E. Esophageal atresia
Diaphragm development Explanation: ***Posterior urethral valves***
- The combination of **respiratory distress** and distinctive craniofacial and limb abnormalities (low-set ears, broad auricles, flattened nasal tip, micrognathia, club foot) in a premature infant suggests **Potter sequence**, which is usually caused by **severe oligohydramnios**.
- **Posterior urethral valves** are the most common cause of lower urinary tract obstruction in male infants, leading to **oligohydramnios** and subsequent Potter sequence.
*Pulmonary hypoplasia*
- While present in this case due to Potter sequence, **pulmonary hypoplasia** is a consequence, not the underlying cause.
- It results from the lung compression due to **oligohydramnios**, preventing normal lung development.
*Fetal anemia*
- Fetal anemia typically manifests as **hydrops fetalis**, characterized by severe edema, ascites, and pleural effusions, which are not described here.
- It does not directly lead to the specific constellation of craniofacial and limb anomalies seen in this patient.
*Anencephaly*
- **Anencephaly** is a severe form of neural tube defect involving absence of a major portion of the brain and skull.
- While associated with **polyhydramnios** (due to impaired fetal swallowing), it does not cause the specific features of Potter sequence.
*Esophageal atresia*
- **Esophageal atresia** often presents with **polyhydramnios** due to the inability of the fetus to swallow amniotic fluid.
- The primary clinical sign after birth is excessive salivation and inability to pass a feeding tube, not the craniofacial and limb anomalies described.
Diaphragm development US Medical PG Question 6: A child is in the nursery one day after birth. A nurse notices a urine-like discharge being expressed through the umbilical stump. What two structures in the embryo are connected by the structure that failed to obliterate during the embryologic development of this child?
- A. Kidney - large bowel
- B. Liver - umbilical vein
- C. Bladder - small bowel
- D. Pulmonary artery - aorta
- E. Bladder - umbilicus (Correct Answer)
Diaphragm development Explanation: ***Bladder - umbilicus***
- A **urine-like discharge** from the umbilical stump indicates a **patent urachus**, which is the embryonic remnant of the allantois.
- The **allantois** (which becomes the urachus) is an embryonic structure that connects the **fetal bladder** to the **umbilicus** during development.
- Normally, the allantois obliterates after birth to form the **median umbilical ligament**, but failure to obliterate results in a patent urachus allowing urine to discharge through the umbilicus.
*Kidney - large bowel*
- These two structures are not directly connected by an obliterating embryonic structure relevant to urine discharge from an umbilical stump.
- The kidneys form urine, and the large bowel is part of the digestive tract, with no direct embryonic communication to the umbilicus for urine expression.
*Liver - umbilical vein*
- The umbilical vein connects the **placenta to the fetal liver** (and ductus venosus) to transport oxygenated blood, not urine.
- Failure of the umbilical vein to obliterate would result in a patent umbilical vein, typically presenting as a vascular anomaly, not urine discharge.
*Pulmonary artery - aorta*
- These structures are connected by the **ductus arteriosus** in fetal circulation, bypassing the pulmonary circulation.
- While important for fetal development, a patent ductus arteriosus (PDA) is a cardiovascular anomaly and would not manifest as urine discharge from the umbilical stump.
*Bladder - small bowel*
- While both structures are involved in waste elimination, there is no normal embryonic structure directly connecting the bladder and small bowel that obliterates to prevent urine discharge from the umbilicus.
- An abnormal connection between the bladder and bowel would typically involve a **fistula** and present with stool in urine or urine in stool, not umbilical discharge.
Diaphragm development US Medical PG Question 7: During development, a fetus is found to have incomplete fusion of the neural tube. Which of the following structures would most likely be affected by this developmental defect?
- A. Notochord
- B. Somites
- C. Vertebral bodies
- D. Spinal cord and meninges (Correct Answer)
Diaphragm development Explanation: ***Spinal cord and meninges***
- Incomplete fusion of the neural tube directly results in defects of the **neural tube closure**, which include the formation of the **spinal cord** and its protective coverings, the **meninges**. [1, 2]
- Conditions like **spina bifida** (meningocele, myelomeningocele) are direct consequences of these fusion failures, exposing or abnormally developing the spinal cord and meninges. [1, 2]
*Notochord*
- The **notochord** is a transient embryonic structure that induces the formation of the neural tube by signaling to the overlying ectoderm; it is not directly formed by the neural tube itself.
- While it plays a critical role in neural tube development, its own structural integrity is typically not primarily affected by neural tube fusion defects.
*Somites*
- **Somites** are blocks of paraxial mesoderm that differentiate into sclerotome (vertebrae and ribs), myotome (skeletal muscle), and dermatome (dermis of the skin).
- While somite development is closely coordinated with neural tube formation, incomplete neural tube fusion primarily affects the neural structures themselves, not the somites directly.
*Vertebral bodies*
- **Vertebral bodies** develop from the sclerotome portion of the somites, which migrate to surround the neural tube and notochord.
- While vertebral defects can be associated with severe neural tube defects (e.g., in spina bifida, the vertebral arches may fail to close), the primary defect of incomplete neural tube fusion directly impacts the neural tissue (spinal cord and meninges), with skeletal defects being secondary or associated. [1, 2]
Diaphragm development US Medical PG Question 8: A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?
- A. "Does the diarrhea typically precede the constipation, or vice-versa?"
- B. "Is the diarrhea foul-smelling?"
- C. "Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"
- D. "Are the symptoms worse in the morning or at night?"
- E. "Can you tell me more about the symptoms you have been experiencing?" (Correct Answer)
Diaphragm development Explanation: ***Can you tell me more about the symptoms you have been experiencing?***
- This **open-ended question** encourages the patient to provide a **comprehensive narrative** of their symptoms, including details about onset, frequency, duration, alleviating/aggravating factors, and associated symptoms, which is crucial for diagnosis.
- In a patient presenting with vague, intermittent symptoms like alternating constipation and diarrhea, allowing them to elaborate freely can reveal important clues that might not be captured by more targeted questions.
*Does the diarrhea typically precede the constipation, or vice-versa?*
- While knowing the sequence of symptoms can be helpful in understanding the **pattern of bowel dysfunction**, it is a very specific question that might overlook other important aspects of the patient's experience.
- It prematurely narrows the focus without first obtaining a broad understanding of the patient's overall symptomatic picture.
*Is the diarrhea foul-smelling?*
- Foul-smelling diarrhea can indicate **malabsorption** or **bacterial overgrowth**, which are important to consider in some gastrointestinal conditions.
- However, this is a **specific symptom inquiry** that should follow a more general exploration of the patient's symptoms, as it may not be relevant if other crucial details are missed.
*Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life*
- Quantifying pain intensity is useful for assessing the **severity of discomfort** and monitoring changes over time.
- However, for a patient with intermittent rather than acute, severe pain, understanding the **character, location, and triggers** of the pain is often more diagnostically valuable than just a numerical rating initially.
*Are the symptoms worse in the morning or at night?*
- Diurnal variation can be relevant in certain conditions, such as inflammatory bowel diseases where nocturnal symptoms might be more concerning, or functional disorders whose symptoms might be stress-related.
- This is another **specific question** that should come after gathering a more complete initial picture of the patient's symptoms to ensure no key information is overlooked.
Diaphragm development US Medical PG Question 9: A 35-year-old man is brought to the trauma bay by ambulance after sustaining a gunshot wound to the right arm. The patient is in excruciating pain and states that he can't move or feel his hand. The patient states that he has no other medical conditions. On exam, the patient's temperature is 98.4°F (36.9°C), blood pressure is 140/86 mmHg, pulse is 112/min, and respirations are 14/min. The patient is alert and his Glasgow coma scale is 15. On exam, he has a single wound on his right forearm without continued bleeding. The patient has preserved motor and sensation in his right elbow; however, he is unable to extend his wrist or extend his fingers further. He is able to clench his hand, but this is limited by pain. On sensory exam, the patient has no sensation to the first dorsal web space but has preserved sensation on most of the volar surface. Which of the following structures is most likely injured?
- A. Recurrent motor branch of the median nerve
- B. Main median nerve
- C. Lower trunk
- D. Ulnar nerve
- E. Radial nerve (Correct Answer)
Diaphragm development Explanation: ***Radial nerve***
- The inability to **extend the wrist and fingers** (wrist drop) is a classic sign of **radial nerve injury**, as it innervates the extensors of the forearm and hand.
- **Loss of sensation in the first dorsal web space** is also characteristic of radial nerve damage, as this area is supplied by the superficial radial nerve.
*Recurrent motor branch of the median nerve*
- This nerve primarily innervates the **thenar muscles** (flexor pollicis brevis, abductor pollicis brevis, opponens pollicis), affecting **thumb opposition**.
- Injury would primarily lead to **weakness in thumb movements**, not wrist or finger extension, and would spare sensation in the first dorsal web space.
*Main median nerve*
- The median nerve primarily innervates the **flexors of the forearm and hand**, and contributes to sensation on the **volar aspect of the thumb**, index, middle, and radial half of the ring finger.
- Injury would cause difficulty with **flexion of the wrist and fingers**, and loss of sensation on the volar surface, which is largely preserved in this patient.
*Lower trunk*
- The lower trunk of the brachial plexus (C8-T1) gives rise to the ulnar nerve and part of the median nerve, affecting **flexion of the wrist and fingers**, and intrinsic hand muscles.
- Injury would result in more widespread weakness affecting the **intrinsic hand muscles** and flexion, and would include sensory loss in the **ulnar nerve distribution**, which is not described.
*Ulnar nerve*
- The ulnar nerve primarily innervates the **intrinsic hand muscles** (excluding the thenar group) and the **flexor carpi ulnaris** and **medial half of flexor digitorum profundus**.
- Injury would typically cause **weakness in intrinsic hand functions** (e.g., finger abduction/adduction, ring and little finger flexion) and sensory loss on the **ulnar side of the hand**, not the dorsal web space.
Diaphragm development US Medical PG Question 10: A previously healthy 20-year-old man comes to the physician because of a 6-month history of a painless mass in his left groin that has been gradually increasing in size. Physical examination shows a 3x3-cm oval, non-tender left inguinal mass and a fluctuant, painless left scrotal swelling that increase in size with coughing. Which of the following is the most likely cause of this patient's symptoms?
- A. Weakening of transversalis fascia
- B. Widening of femoral ring
- C. Reduced fluid reabsorption at tunica vaginalis
- D. Failure of processus vaginalis to close (Correct Answer)
- E. Obstruction of left spermatic vein
Diaphragm development Explanation: ***Failure of processus vaginalis to close***
- The combination of a left inguinal mass and a scrotal swelling that both **increase in size with coughing** (suggesting **reducibility** and a connection to the abdominal cavity) in a young man points towards an **indirect inguinal hernia**.
- Indirect inguinal hernias occur due to the **persistence of the processus vaginalis**, which normally obliterates, allowing abdominal contents to herniate through the **deep inguinal ring** into the inguinal canal and potentially the scrotum.
*Weakening of transversalis fascia*
- This typically leads to a **direct inguinal hernia**, where abdominal contents protrude directly through the **posterior wall of the inguinal canal** through **Hesselbach's triangle**, medial to the inferior epigastric vessels.
- While it can cause an inguinal mass, it is less common to have an associated scrotal swelling that increases with coughing in the same manner as an indirect hernia, especially in a young, previously healthy individual without risk factors for fascial weakening.
*Widening of femoral ring*
- Widening of the femoral ring is the underlying cause of a **femoral hernia**.
- Femoral hernias typically present as a mass **below the inguinal ligament** and medial to the femoral vein, and are more common in women due to a wider pelvis.
*Reduced fluid reabsorption at tunica vaginalis*
- This pathology results in a **hydrocele**, which is an accumulation of fluid within the **tunica vaginalis**.
- While it presents as a **painless scrotal swelling**, a hydrocele typically does not involve an inguinal mass, nor does it increase in size with coughing (unless it's a **communicating hydrocele**, which means the processus vaginalis is still patent, essentially linking it back to the correct answer).
*Obstruction of left spermatic vein*
- Obstruction of the left spermatic vein usually leads to a **varicocele**, which is a dilation of the **pampiniform venous plexus**.
- A varicocele typically presents as a "bag of worms" sensation in the scrotum, often on the left side, and usually **decreases in size when lying down**, which is different from the symptoms described.
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