A 3-year-old girl is brought to the emergency department by her parents with sudden onset shortness of breath. They tell the emergency physician that their daughter was lying on the bed watching television when she suddenly began gasping for air. They observed a bowl of peanuts lying next to her when they grabbed her up and brought her to the emergency department. Her respirations are 25/min, the pulse is 100/min and the blood pressure is 90/65 mm Hg. The physical findings as of now are apparently normal. She is started on oxygen and is sent in for a chest X-ray. Based on her history and physical exam findings, the cause of her current symptoms would be seen on the X-ray at which of the following sites?

The posterior segment of the right lower lobe

The superior segment of the right lower lobe

The lingula of the left upper lobe

The apical segment of the right upper lobe

The apical segment of the left upper lobe

A 76-year-old woman with hypertension and coronary artery disease is brought to the emergency department after the sudden onset of right-sided weakness. Her pulse is 83/min and blood pressure is 156/90 mm Hg. Neurological examination shows right-sided facial drooping and complete paralysis of the right upper and lower extremities. Tongue position is normal and she is able to swallow liquids without difficulty. Knee and ankle deep tendon reflexes are exaggerated on the right. Sensation to vibration, position, and light touch is normal bilaterally. She is oriented to person, place, and time, and is able to speak normally. Occlusion of which of the following vessels is the most likely cause of this patient's current symptoms?

Contralateral lenticulostriate artery

Ipsilateral anterior cerebral artery

Contralateral middle cerebral artery

Ipsilateral posterior inferior cerebellar artery

A 65-year-old man presents to the emergency department with vague, constant abdominal pain, and worsening shortness of breath for the past several hours. He has baseline shortness of breath and requires 2–3 pillows to sleep at night. He often wakes up because of shortness of breath. Past medical history includes congestive heart failure, diabetes, hypertension, and hyperlipidemia. He regularly takes lisinopril, metoprolol, atorvastatin, and metformin. His temperature is 37.0°C (98.6°F), respiratory rate 25/min, pulse 67/min, and blood pressure 98/82 mm Hg. On physical examination, he has bilateral crackles over both lung bases and a diffusely tender abdomen. His subjective complaint of abdominal pain is more severe than the observed tenderness on examination. Which of the following vessels is involved in the disease affecting this patient?

Celiac artery and superior mesenteric artery

A young researcher is responsible for graphing laboratory data involving pulmonary blood flow and ventilation pattern obtained from a healthy volunteer who was standing in an upright position. After plotting the following graph, the researcher realizes he forgot to label the curves and the x-axis (which represents the position in the lung). Which of the following is the appropriate label for each point on the graph?

A: Ventilation B: Blood flow C: Base of the lung D: Apex of the lung

A: Ventilation B: Blood flow C: Mid-portion of the lung D: Apex of the lung

A: Dead Space B: Shunt C: Base of the lung D: Apex of the lung

A: Blood flow B: Ventilation C: Base of the lung D: Lung hilum

A: Blood flow B: Ventilation C: Apex of the lung D: Lung hilum

Vascular radiologic landmarks for USMLE Step 3: High-Yield Anatomy Lessons

Head & Neck Vessels - Brainy Blood Flow

Circle of Willis: Diagram vs. MRA

Circle of Willis: A critical arterial anastomosis at the base of the brain ensuring collateral circulation.
- Anterior Cerebral Artery (ACA): Supplies medial brain surfaces; occlusion causes contralateral leg/foot deficits.
- Middle Cerebral Artery (MCA): Supplies lateral hemispheres, including speech centers; the most common site for strokes.
- Posterior Cerebral Artery (PCA): Supplies occipital lobe; occlusion leads to visual field defects.
- Communicating Arteries (AComm, PComm): Connect anterior/posterior circulations.
Other Key Landmarks:
- Carotid Siphon: An S-shaped curve of the internal carotid artery.
- Dural Venous Sinuses: Superior sagittal and transverse sinuses are major venous drainage pathways.

⭐ The lenticulostriate arteries, branching from the MCA, are prone to hypertensive hemorrhage due to their small size and sharp angle.

Thoracic Vessels - Heart of the Matter

Aortic Arch Branches:
- Brachiocephalic trunk (bifurcates into R. subclavian & R. common carotid)
- L. common carotid artery
- L. subclavian artery
- 📌 Mnemonic: ABC'S (Aortic arch, Brachiocephalic, Common carotid, Subclavian)
Key Radiographic Silhouettes:
- Chest X-ray (PA):
  - Aortic knob/arch: Left upper mediastinum.
  - Pulmonary trunk: Below aortic knob.
  - Superior Vena Cava (SVC): Right superior cardiac border.
- CT (Axial):
  - Ascending aorta is anterior to the descending aorta.
  - Pulmonary artery is anterior and to the left of the aorta.

Axial CT chest: Labeled great vessels and mediastinum

⭐ On a PA chest X-ray, the Superior Vena Cava (SVC) and the right atrium form the right border of the cardiac silhouette.

Abdominal & Pelvic Vessels - Gut Feelings & Power

Artery	Gut Region	Key Branches/Territory
Celiac Trunk	Foregut	Stomach, spleen, liver, 1st part of duodenum. 📌 Mnemonic: Left Hand Side (Left Gastric, Splenic, Common Hepatic).
SMA	Midgut	2nd part of duodenum to proximal 2/3 of transverse colon.
IMA	Hindgut	Distal 1/3 of transverse colon to upper rectum.

Portal Venous System:
- Formed by the union of the Splenic Vein and Superior Mesenteric Vein (SMV).
- Drains the GI tract from the lower esophagus to the upper anal canal.

⭐ The watershed area at the splenic flexure (Griffiths' point), between SMA and IMA territories, is a common site for ischemic colitis.

High‑Yield Points - ⚡ Biggest Takeaways

The aortic knob on a PA chest X-ray represents the distal aortic arch.

The carina (tracheal bifurcation) is a key landmark at the T4/T5 vertebral level, near the aortic arch.

The right heart border on a PA view is formed by the right atrium.

The left ventricular apex forms the inferolateral portion of the cardiac silhouette.

The aortopulmonary (AP) window, between the aorta and pulmonary artery, is a critical site for lymphadenopathy.

The celiac trunk and SMA are vital landmarks branching from the abdominal aorta.

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