Portland State University. Department of Biology
Stanley S. Hillman
Date of Award
Master of Science (M.S.) in Biology
1 online resource, (48 p.)
Bufo marinus -- Physiology, Lymphatics
Lymph hearts play an important role in blood volume regulation in anurans by controlling the movement of fluid from the lymphatic spaces to the vasculature. The anatomical continuity between lymph sacs and lymph hearts predicts a coupling of pressure between the two structures which may represent a physical basis for lymph heart regulation. The precise relationship between lymph heart pressure and lymph heart output was not examined so that conclusions regarding changes in work performed by the hearts as a result of changing lymph sac pressure could not be made. However, increases in lymph sac pressure led to increases in both diastolic and systolic pressures generated by the hearts. A given rise in lymph sac pressure also led to a proportionally larger increase in diastolic pressure than systolic pressure.
The rates of pressure development were examined in relation to increasing lymph sac pressure and it was found that diastolic pressure decreases were more rapid with increased lymph sac pressure indicating that filling of the hearts was enhanced. The filling of the lymph hearts is passive, and under higher pressure, this occurs more rapidly.
An increase in lymph sac pressure led to a decrease in the maximum rate of systolic pressure development. This suggests that the lymph hearts may have become over distended by excessive filling such that contraction was impeded. The fact that the rapidity of systolic pressure development decreased when lymph sac pressure was elevated provides evidence that the load on the heart was increased but that the hearts were not necessarily responding to this load by ejecting the fluid any more vigorously.
Examining the effects of lymph sac pressure on lymph heart pressure development allowed passive and active components of the lymph heart pressure trace to be distinguished. Diastolic pressures demonstrated a closer correlation to increased lymph sac pressure than did systolic pressures. It remains unresolved whether this constitutes a basis for physical regulation of the lymph hearts as work output was not directly measured.
Georgitsis, Michael, "The Effect of Lymph Sac Pressure on Lymph Heart Pressure Development in the Toad Bufo Marinus" (1997). Dissertations and Theses. Paper 5359.