When we are cold or the external temperature is low, most venous blood returning from the distal part of the arm travels in the deep veins where it picks up heat (by countercurrent exchange) from the nearby brachial artery en route. However, when we are hot, and especially during exercise, venous return from the distal arm travels in the superficial veins and those veins tend to bulge superficially in a person who is working out. Explain why venous return takes a different route in the second situation.

Video transcript

Hey, everyone. Let's take a look at this question together, Mr Johnson, a 65 year old man presents to the emergency department with symptoms of low blood pressure and dizziness. The medical team suspects inadequate venous return as the cause of his symptoms, which of the following factors can affect venous return. Is it answer choice. A contraction of skeletal muscles, answer choice B, exhalation during breathing, answer choice. C increased sympathetic nervous system activity or answer choice. D increased blood viscosity. Let's work this problem out together to try to figure out which of the following factors can affect Venus return. So, in order to determine which of the following factors affect that venous return, we have to recall what that term means. And we know that Venus return refers to the flow of the blood from the systemic veins back to the heart. And while there are several different factors that can affect the flow of the blood from the systemic veins back to the heart. The contraction of skeletal muscles such as during physical activity or exercise is an important factor that affects venous return. Since the contraction of skeletal muscles causes the veins inside of the body to compress and the compression of the veins helps propel the blood forward and aids in that venous return. Which means that answer choice. A, the contraction of skeletal muscles is a factor that can affect venous return. So answer choice A is the correct answer and answer choice B is incorrect. Since exhalation during breathing affects pulmonary circulation and not veinous return. Answer choice C is also incorrect. Since increased sympathetic nervous system activity can lead to the constriction of blood vessels but does not affect the venous return. And answer choice D is also incorrect. Since increased blood viscosity can affect blood flow but is not a primary factor that affects venous return. Leaving us with answer choice. A as the correct answer, I hope you found this video to be helpful. Thank you and goodbye.