Thorax Anatomy & Development
Pulmonary Physiology
Abdominal Anatomy & Development
Renal & Urinary Physiology
Endocrine & Amino Acid Metabolism
100
The Nuss procedure is the gold standard surgical treatment for pectus excavatum, which involves placing metal bars behind the sternum for 2-4 years to push the chest forward. This procedure is most likely to injure which vessels, potentially complicating future need for coronary artery bypass grafts?
Answer: Internal thoracic arteries
100
Alpha-1 antitrypsin deficiency (AATD) is a common genetic disease that allows neutrophils to destroy the elastic fibers of the alveolar walls and causes a leftward shift in the flow-volume curve. This results in ______ (increased/decreased/normal) lung compliance and ______ (upward/downward/no) shift in the equal pressure point.
Answers: increased, downward
Just like with the loss of elastic recoil seen in emphysema, AATD causes increased lung compliance and a distal/downward shift in EPP.
100
During kidney transplant surgery, a retroperitoneal approach is taken to access the donor kidney, which requires cutting through the layer of fascia just anterior to the pararenal fat. This fascia is continuous posteriorly with the fascia of what muscle?
Answer: Psoas major
The renal fascia is just anterior to the pararenal fat, and is continuous posteriorly with the psoas major fascia, and is superiorly continuous with the deep fascia of the diaphragm.
100
Dwight Schrute is on his first-ever vacation when he becomes alarmed that his urine is a clear, light-yellow color instead of the usual red. Urinalysis rules out hematuria and proteinuria and after discussing his at-home diet you suspect he previously had chronic beeturia due to lifelong high intake of beets, a harmless condition. It can be reasonably assumed that the red pigment is ______ (bound/not bound) to albumin in the blood and its renal clearance is closer to ______ (glucose/inulin).
Answers: not bound, inulin
The presence of red pigment in the urine despite an intact glomerular barrier indicates it is not bound to the much larger albumin protein. Because the pigment is filtered but not reabsorbed, its removal from the plasma follows similar physiologic principles as inulin.
100
What is the substrate of the enzyme that is unique to the circled region?
Answer: Corticosterone
200
You and a fellow medical student have been standing in the OR for 6 hours straight watching a CABG surgery when your peer begins to sway before passing out. Vasovagal syncope can occur due to standing for long periods, causing a massive spike in vagal tone. This causes constriction of the smooth muscle located between which two specific layers in the structure below?
Answer: Muscosa and submucosa
In an intrapulmonary bronchus, the smooth muscle of the muscularis mucosae layer is between the mucosa and the submucosa.
200
The mitochondrial dysfunction seen in MERRF causes cells to shunt pyruvate into lactic acid fermentation instead of oxidative phosphorylation. The effect of decreased CO2 production on blood pH is outweighed by the increase in lactic acid. This shifts the O2-Hb dissociation curve to the _____ (left/right) and causes bicarbonate reabsorption to _____ (increase/decrease).
Answers: right, increase
Lactic acid decreases blood pH which decreases hemoglobin's affinity for oxygen via the Bohr effect, shifting the curve to the right. Decreased pH causes elevated baseline bicarbonate reabsorption as the kidneys try to compensate.
200
The structures indicated by the ______ (color) arrows are directly continuous with the area cribrosa and are embryologically derived from what specific structure?
Answers: blue, ureteric bud
The blue arrows indicate collecting ducts, while the green and red arrows indicate the thin LoH and the vasa recta, respectively.
200
After days of being stranded on the open ocean, Chuck Noland becomes dehydrated. In his desperation, he decides to drink the ocean water to try to quench his thirst. The amount he drinks does not meaningfully increase blood volume but significantly increases blood osmolarity. This is expected to ______ (increase/decrease) ADH activity and ______ (increase/decrease) intracellular fluid volume, which can cause intracranial hemorrhage and death.
Answers: increase, decrease
Hypertonicity in the ECF draws water out of the cells, while the high plasma osmolarity triggers the hypothalamus to stimulate ADH release. This cellular shrinkage can pull the brain away from the skull, tearing bridging veins and causing fatal hemorrhage.
200
The shift from foraging to a high-protein hunting-based diet forced the livers of early humans to evolve. To handle the ammonia load of a carnivorous diet, humans up-regulated the mitochondrial enzyme that generates citrulline. In order to keep this enzyme running, it requires a substrate formed in the mitochondria. Name this substrate.
Answer: Carbamoyl phosphate
OTC produces citrulline by condensing recycled ornithine with carbamoyl phosphate, the latter being the only substrate in this step that is de novo synthesized within the mitochondrial (by CPS I).
300
Will Campbell develops a cough and finds himself out of breath and unable to protect Drake Maye during the Super Bowl, essentially creating a turnstile at left tackle. Chest x-ray after the game reveals a 50 mm lung mass as shown below. Lymph from this area enters systemic circulation by draining at the junction of which two vessels on which side?
Answer: Right subclavian and internal jugular veins
The left lower lobe generally drains to the carinal nodes before crossing midline to join the right lymphatic duct.
300
In 2008, magician David Blaine set a world record after holding his breath for 17 minutes. At some point during this feat, it is almost certain that his PO2 dropped below 60 mm Hg. Of the chemoreceptors that detect this change, which is generally the most important?
Answer: Carotid chemoreceptors
While both carotid and aortic chemoreceptors sense PO2 and PCO2, the carotid bodies provide nearly all hypoxic ventilatory drive and are uniquely sensitive to arterial pH changes that the aortic bodies ignore.
300
Turner syndrome (45,X) can cause horseshoe kidney, where the lower poles of the kidneys fuse. As it ascends up from the pelvis during development, the horseshoe kidney is most likely to get trapped under which vessel, limiting its ascent?
Answer: Inferior mesenteric artery
300
You find Jesse Pinkman nodding off with pinpoint pupils and a respiration rate of 7. Assuming this is an isolated opioid overdose and he is not yet hypoxic, you would expect his chloride reabsorption to be ______ (increased/decreased/normal) and his anion gap to be ______ (increased/decreased/normal).
Answers: decreased, normal
To compensate for respiratory acidosis, the kidneys increase bicarbonate reabsorption and simultaneously decrease chloride reabsorption to maintain electrical neutrality, keeping the anion gap normal. If RR dropped further and tissues became hypoxic, cells would switch to anaerobic metabolism and start dumping lactate into the blood, which would increase the anion gap.
300
Tom Brady runs slowly and physical exam reveals bradycardia and hypotension. Labs confirm low ACTH levels. If his pathology were instead localized to the zona fasciculata, the feedback loop would cause excessive cleavage of POMC, directly resulting in what distinct physical exam finding?
Answer: Hyperpigmentation
The absence of ACTH in secondary insufficiency prevents the excessive synthesis and cleavage of the pro-hormone POMC, which normally yields the pigment-inducing peptide α-MSH in primary adrenal failure
400
The compound that prevented alveolar collapse during baby LeBron's first breath was produced by cells that first appeared in what stage of his pulmonary development?
Answer: Terminal sac stage
The terminal sac stage (weeks 26 to birth) is characterized by the thinning of the blood-air barrier and the differentiation of type II pneumocytes, which begin producing the surfactant necessary to overcome surface tension and prevent atelectasis upon the first breath.
400
After putting your friend onto fava beans, he starts eating excessive amounts of them and subsequently develops dark urine, fatigue, and jaundice. Genetic testing reveals he has G6PD deficiency, the most common genetic enzyme deficiency in the world, causing increased levels of 2,3-BPG and hemolytic anemia. What effect is this expected to have on the A-a gradient?
Answer: Nothing (normal)
Neither hemolytic anemia nor increased 2,3-BPG levels affect the diffusion of gases across alveoli, so partial pressures remain the same, thus the alveolar-arterial gradient is unaffected. The main consequence of this disease is a rightward shift in the HbO2 dissociation curve.
400
A Greenfield IVC filter is surgically placed in the inferior vena cava at the L3 level through a femoral vein access point and functions to trap blood clots, preventing pulmonary embolisms while maintaining blood flow. The device is anatomically closer to the kidney that has the ______ (longer/shorter) ureter and an anterior relationship with the ______ (ascending/descending) colon.
Answers: shorter, ascending
400
Myasthenia gravis causes ptosis and muscle weakness due to autoimmune attack of nicotinic acetylcholine receptors, which can also manifest as incontinence and a diminished guarding reflex. The muscle responsible for this deficit is supplied by a nerve whose cell bodies are specifically located where?
Answer: Onuf's nucleus (S2-S4)
400
If left untreated, classic phenylketonuria (PKU) is severely debilitating and often fatal by early adulthood. The function of which cell population below is most affected in PKU?
Answer: D
Phenylalanine hydroxylase deficiency prevents the synthesis of tyrosine, which is the precursor to all catecholamines. The adrenal medulla specializes in producing catecholamines.
500
Snoop Dogg's physician estimates he has over 100 blunt-years worth of lung damage from constantly smoking Backwoods, leading to significant squamous metaplasia. In a healthy nonsmoker, this type of epithelium is normally found in the respiratory tract just deep to the thyroid cartilage at which specific site?
Answer: True vocal fold
500
Just before his death due to cerebral hemorrhage, President Franklin D. Roosevelt had a blood pressure of 350/195 mmHg. The extreme afterload faced by his left ventricle was expected to back-up the pulmonary circulation, causing a significant increase in pulmonary venous pressure. Assuming no hypoxia and no change in ventilation, this likely caused West's lung zone ______ to dominate and the average V/Q ratio throughout his lungs to be ______ (</>/~) 1.
Answers: 3, <
500
King James is in the gym when he suffers an indirect inguinal hernia during a heavy set of squats. As his doctor, you take this excellent opportunity to gently stroke his inner thigh, which elicits a moan from the King, confirming no sensory deficit, yet the ipsilateral testis fails to elevate. Identify the specific nerve affected.
Answer: Genital branch of genitofemoral nerve
The afferent limb of the cremaster reflex is via the ilioinguinal nerve (L1), while the efferent limb is via the genital branch of the genitofemoral nerve (L1-2).
500
When older adults fall and remain immobilized on the ground for an extended period of time, they often develop rhabdomyolysis, the destruction of muscles due to the pressure-induced ischemia. Muscle cytoplasmic contents spill into the blood causing hyperkalemia, which directly stimulates the release of a hormone that indirectly increases the activity of what cation-secreting channel in the apical membrane of the collecting duct?
Answer: ROMK channel
Hyperkalemia directly stimulates aldosterone release independent of angiotensin II. Aldosterone increases ROMK, ENaC, and Na/K ATPase activity in principal cells, but ENaC is cation-reabsorbing and Na/K ATPase is a pump in the basolateral membrane. NKCC2 activity is also increased but is located in the TAL of the LoH and is cation-reabsorbing. The BK channel is activated by high tubular flow, not aldosterone.
500
A female neonate presents with ambiguous genitalia and early virilization. While the physician expects the salt-wasting and hypotension typical of the most common adrenal hyperplasia, labs surprisingly reveal hypertension. This genetic deficiency is caused by the buildup of which specific steroid intermediate that acts as a mineralocorticoid agonist?
Answer: 11-deoxycorticosterone (DOC)
11B-hydroxylase deficiency prevents the formation of aldosterone (and cortisol), which is expected to cause hypotension, but the buildup of DOC (mineralocorticoid agonist) actually ends up causing hypertension.
