LE3 .A278 2005

2005

Toews, Dan

Acadia University

Bachelor of Science

Honours

Biology

Biology

The filling mechanism of posterior lymph hearts of anurans has not been studied in detail. It has been proposed that filling occurs either by the recoil of elastic suspensory fibers creating a negative pressure in the lumen of the lymph heart, or by a positive pressure generated by skeletal muscles outside the lymph sacs. The pressures generated by the posterior lymph hearts of Bufo marinus and Rana catesbeiana were monitored through chronic canulation and recorded via pressure transducer and computer software. It was demonstrated that after each contraction the pressure inside the lymph heart dropped below a level of zero pressure prior to filling. This negative pressure was quantified and found to satisfy the proposed value needed to give directionality to lymph movement in the distal lymph sacs, toward the lymph heart. Observation of the lymph heart in vivo and of the pattern of the tracings obtained through canulation led to a proposed mechanism for the contraction cycle. A canula was also inserted into the lymph sac surrounding the lymph hearts to measure the pressure immediately adjacent to the heart. Pressures from the heart and sac were monitored simultaneously. This revealed that the negative pressure of the recoil of the lymph heart was detectable in the sac. The lymph sac tracings added to the understanding of the mechanism of contraction and lymph propulsion and movement.

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https://scholar.acadiau.ca/islandora/object/theses:445