Fossils of Lystrosaurus, a dicynodont therapsid, are most common in parts of modern-day South America, South Africa, Madagascar, India, South Australia, and Antarctica. It apparently lived in arid regions, and was mostly herbivorous. It originated during the mid-Permian period, survived the Permian extinction, and dwindled by the late Triassic, though there is evidence of a relict population in Australia during the Cretaceous. The dicynodonts had two large tusks, extending down from their upper jaws; the tusks were not used for food gathering, and in some species were limited to males. Food was gathered using an otherwise toothless beak. Judging from the fossil record, these pig-sized organisms were the most common mammal-like reptiles of the Permian. Anatomically, what was true of Lystrosaurus?

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#Question id: 12560

#Unit 7. System Physiology – Animal

If GFR suddenly decreases from 150 ml/min to 75 ml/min and tubular fluid reabsorption simultaneously decreases from 149 ml/min to 75 ml/min, which of the following changes will occur (assuming that the changes in GFR and tubular fluid reabsorption are maintained)?

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#Question id: 12559

#Unit 7. System Physiology – Animal

Which part of the renal tubule would have the lowest tubular fluid osmolarity in a patient who has complete lack of antidiuretic hormone due to “central” diabetes insipidus?

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#Question id: 12514

#Unit 7. System Physiology – Animal

Acute metabolic acidosis tends to _____ in intracellular K+ concentration and _____ in K+ secretion by the cortical collecting tubules.

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#Question id: 12513

#Unit 7. System Physiology – Animal

A 26-year-old construction worker is brought to the emergency room with a change in mental status after working a 10-hour shift on a hot summer day (average outside temperature was 97°F). The man had been sweating profusely during the day but did not drink fluids. He has a fever of 102°F, heart rate of 140 beats/min, and blood pressure of 100/55 mm Hg in the supine position. On examination, he has no perspiration, appears to have dry mucous membranes, and is poorly oriented to person, place, and time. Assuming that his kidneys were normal yesterday, which of the following sets of hormone levels describes his condition, compared with normal?

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#Question id: 12512

#Unit 7. System Physiology – Animal

Which of the following changes would you expect to find in a patient consuming a high-sodium diet (200 mEq/day) compared with the same patient on a normal-sodium diet (100 mEq/day), assuming steady-state conditions?

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#Question id: 12480

#Unit 7. System Physiology – Animal

A patient’s one remaining kidney has moderate renal artery stenosis that reduces renal artery pressure distal to the stenosis to 85 mm Hg, compared with the normal level of 100 mm Hg. Which of the following is most likely decreased in this patient 2 weeks after the stenosis has occurred, assuming that his diet is unchanged?