An elephant can swim or walk withits chest several meters underwater while the animal breathes throughits trunk, which remains above the water surface and acts like a snorkel.The elephant’s tissues are at an increased pressure due to the surroundingwater, but the lungs are at atmospheric pressure because theyare connected to the air through the trunk. The figure shows the gaugepressures in an elephant’s lungs and abdomen when the elephant’s chestis submerged to a particular depth in a lake. In this situation, the elephant’sdiaphragm, which separates the lungs from the abdomen, mustsustain the difference in pressure between the lungs and the abdomen.The diaphragm of an elephant is typically 3.0 cm thick and 120 cm indiameter. (See “Why Doesn’t the Elephant Have a Pleural Space?” byJohn B. West, Physiology, Vol. 17:47–50, April 1, 2002.)How does the force the diaphragm experiences due to the difference in pressure between the lungs and abdomen depend on the abdomen’s distance below the water surface? The force (a) increases linearly with distance; (b) increases as distance squared; (c) increases as distance cubed; (d) increases exponentially with distance.

An elephant can swim or walk withits chest several meters underwater while the animal breathes throughits trunk, which remains above the water surface and acts like a snorkel.The elephant’s tissues are at an increased pressure due to the surroundingwater, but the lungs are at atmospheric pressure because theyare connected to the air through the trunk. The figure shows the gaugepressures in an elephant’s lungs and abdomen when the elephant’s chestis submerged to a particular depth in a lake. In this situation, the elephant’sdiaphragm, which separates the lungs from the abdomen, mustsustain the difference in pressure between the lungs and the abdomen.The diaphragm of an elephant is typically 3.0 cm thick and 120 cm indiameter. (See “Why Doesn’t the Elephant Have a Pleural Space?” byJohn B. West, Physiology, Vol. 17:47–50, April 1, 2002.)How does the force the diaphragm experiences due to the difference in pressure between the lungs and abdomen depend on the abdomen’s distance below the water surface? The force (a) increases linearly with distance; (b) increases as distance squared; (c) increases as distance cubed; (d) increases exponentially with distance.