Mean arterial pressure is 100 mmHg in the aorta, 100 mmHg in the large arteries, 85 mmHg at the start of the terminal arterioles, and 30 mmHg at the arterial end of the capillaries. The greatest fractional drop in pressure, and therefore the site of highest vascular resistance, occurs across the:

• A Large elastic arteries
• B Venules and veins
• C Capillaries
• D Arterioles ✓

Explanation

The largest single pressure decrement in the systemic circuit occurs across the arterioles, where roughly 50 to 60 percent of total peripheral resistance resides. Their thick smooth muscle coat and small caliber allow fine regulation of both regional flow and arterial pressure, making them the chief resistance vessels. Pressure actually changes little across the aorta and large arteries, and capillary resistance is low because the enormous total cross-sectional area offsets each vessel's small bore.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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