Organ system anatomy Practice Questions
20 free Organ system anatomy practice questions for the USMLE Step 1. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
During abdominal surgery, a surgeon identifies the hepatoduodenal ligament. Which structure is NOT contained within this ligament?
- A Common bile duct
- B Portal vein
- C Hepatic artery proper
- D Right gastric artery
Correct answer: Right gastric artery
The hepatoduodenal ligament contains the portal triad: common bile duct, hepatic artery proper, and portal vein. The right gastric artery lies outside this ligament.
A patient has a perforated gastric ulcer on the posterior wall of the stomach. Which structure is most at risk?
- A Left lobe of the liver
- B Spleen
- C Pancreas
- D Transverse colon
Correct answer: Pancreas
The posterior surface of the stomach lies adjacent to the pancreas. A posterior gastric ulcer can erode into the pancreas, causing referred back pain.
A patient presents with right lower quadrant pain. McBurney’s point corresponds to which anatomical landmark?
- A Midpoint between ASIS and umbilicus
- B One-third the distance from ASIS to umbilicus
- C Two-thirds the distance from ASIS to umbilicus
- D Intersection of midclavicular line and costal margin
Correct answer: One-third the distance from ASIS to umbilicus
McBurney’s point is one-third of the distance from the anterior superior iliac spine to the umbilicus. It corresponds to the location of the base of the appendix.
A trauma patient has difficulty swallowing and hoarseness. Injury to which structure in the neck is most likely involved?
- A Thyroid cartilage
- B Cricoid cartilage
- C Epiglottis
- D Hyoid bone
Correct answer: Cricoid cartilage
The cricoid cartilage is the only complete ring of cartilage in the airway and lies below the vocal cords. Injury can affect voice and swallowing.
Which structure passes through the diaphragm at the T10 level?
- A Inferior vena cava
- B Esophagus
- C Aorta
- D Thoracic duct
Correct answer: Esophagus
The esophageal hiatus is located at the T10 vertebral level. The mnemonic I 8 10 Eggs At 12 helps recall IVC (T8), Esophagus (T10), Aorta (T12).
A patient has hematuria due to a stone lodged where the ureter crosses the pelvic brim. Which vessel does the ureter cross at this point?
- A External iliac artery
- B Internal iliac artery
- C Femoral artery
- D Common iliac vein
Correct answer: External iliac artery
The ureter crosses over the external iliac artery at the pelvic brim. This is a common site of ureteral obstruction.
A surgeon ligates the splenic artery. Perfusion to which part of the stomach remains intact due to collateral circulation?
- A Fundus
- B Greater curvature
- C Cardia
- D Lesser curvature
Correct answer: Lesser curvature
The lesser curvature of the stomach receives blood from the left and right gastric arteries, allowing collateral flow even if the splenic artery is ligated.
A patient experiences hoarseness after carotid endarterectomy. Which nerve is most likely injured?
- A Recurrent laryngeal nerve
- B Hypoglossal nerve
- C Glossopharyngeal nerve
- D Spinal accessory nerve
Correct answer: Recurrent laryngeal nerve
The recurrent laryngeal nerve runs near the carotid artery and innervates intrinsic laryngeal muscles. Injury leads to hoarseness due to vocal cord paralysis.
A kidney transplant is placed in the iliac fossa. Which vessel typically supplies the transplanted kidney?
- A Common iliac artery
- B External iliac artery
- C Internal iliac artery
- D Inferior epigastric artery
Correct answer: External iliac artery
The renal artery of the transplanted kidney is usually anastomosed to the external iliac artery. This provides adequate blood supply in the pelvis.
A patient with portal hypertension develops caput medusae. This involves dilation of veins around which structure?
- A Umbilicus
- B Rectum
- C Distal esophagus
- D Bare area of liver
Correct answer: Umbilicus
Caput medusae occurs due to dilation of paraumbilical veins around the umbilicus. These veins form portosystemic anastomoses.
Which part of the large intestine is retroperitoneal?
- A Transverse colon
- B Ascending colon
- C Sigmoid colon
- D Cecum
Correct answer: Ascending colon
The ascending and descending colon are secondarily retroperitoneal. The transverse and sigmoid colon are intraperitoneal.
A patient experiences pancreatic head enlargement. Which structure may become obstructed first?
- A Splenic artery
- B Common bile duct
- C Gastroduodenal artery
- D Portal vein
Correct answer: Common bile duct
The common bile duct runs through the head of the pancreas. Enlargement may compress it, causing obstructive jaundice.
A patient is unable to extend the trunk and maintain posture. Which back muscle is primarily responsible for this action?
- A Latissimus dorsi
- B Trapezius
- C Erector spinae
- D Rhomboid major
Correct answer: Erector spinae
The erector spinae muscle group extends the vertebral column and maintains erect posture. Weakness impairs trunk extension.
Which organ lies primarily in the left upper quadrant and is protected by ribs 9–11?
- A Liver
- B Spleen
- C Stomach
- D Left kidney
Correct answer: Spleen
The spleen lies under ribs 9–11 in the left upper quadrant. Trauma can rupture it, causing intraperitoneal bleeding.
A patient has difficulty swallowing solids and liquids. Dysfunction of which muscular structure is most likely involved?
- A Upper esophageal sphincter
- B Lower esophageal sphincter
- C Pharyngotympanic tube
- D Cricothyroid muscle
Correct answer: Upper esophageal sphincter
The upper esophageal sphincter, formed primarily by the cricopharyngeus muscle, regulates entry into the esophagus. Dysfunction causes dysphagia.
A patient has severe right upper quadrant pain during gallbladder inflammation. Which nerve carries referred pain to the shoulder region?
- A Phrenic nerve
- B Intercostal nerves
- C Vagus nerve
- D Splanchnic nerves
Correct answer: Phrenic nerve
The phrenic nerve (C3–C5) provides sensory innervation to the diaphragm and gallbladder. Referred pain is felt in the shoulder via C3–C5 dermatomes.
Which structure is located at the hilum of the lung?
- A Pulmonary vessels
- B Pulmonary alveoli
- C Terminal bronchioles
- D Pleural recesses
Correct answer: Pulmonary vessels
The hilum contains bronchi, pulmonary arteries, pulmonary veins, lymphatics, and nerves. These structures enter and exit the lung at the hilum.
A patient has an enlarged prostate compressing the urethra. Which part of the urethra is most affected?
- A Prostatic urethra
- B Membranous urethra
- C Spongy urethra
- D Preprostatic urethra
Correct answer: Prostatic urethra
Benign prostatic hyperplasia compresses the prostatic urethra, leading to urinary hesitancy and weak stream. This region traverses the prostate gland.
During a splenectomy, which ligament must be ligated to avoid excessive bleeding from short gastric vessels?
- A Gastrosplenic ligament
- B Splenorenal ligament
- C Falciform ligament
- D Hepatogastric ligament
Correct answer: Gastrosplenic ligament
The gastrosplenic ligament contains the short gastric vessels. It must be ligated during splenectomy to prevent hemorrhage.
A patient experiences pain during palpation of the costovertebral angle. This finding most likely indicates pathology of which organ?
- A Liver
- B Spleen
- C Kidney
- D Gallbladder
Correct answer: Kidney
The costovertebral angle overlies the kidneys. Pain on palpation often indicates kidney inflammation or infection, such as pyelonephritis.