Final answer:
The absence of calcium in Tyrode's solution can impair intestinal motility due to the necessity of calcium for the contraction of smooth muscle cells in the intestines. Vitamin D plays a critical role in calcium absorption essential for muscle function, and the parathyroid gland is involved in regulating calcium levels affecting gut motility.
Step-by-step explanation:
The lack of calcium in Tyrode's solution can significantly affect intestinal motility. In the digestive system, the contraction of smooth muscle, including that which controls intestinal motility, relies on the influx of extracellular Ca++ ions. These ions diffuse into the sarcoplasm to reach calmodulin, ultimately triggering the contraction of smooth muscle cells. Without sufficient calcium, smooth muscle cells cannot contract effectively, which could reduce or impair intestinal motility. This effect is in agreement with the role of activated vitamin D in stimulating the intestines to absorb calcium, thus supporting smooth muscle function in the gut. Moreover, a lack of responsiveness by the parathyroid gland to calcium could also decrease intestinal absorption of calcium, exacerbating the condition.