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Hemodynamics in the leech: blood flow in two hearts switching between two constriction patterns


Wenning, A; Meyer, E P (2007). Hemodynamics in the leech: blood flow in two hearts switching between two constriction patterns. Journal of Experimental Biology, 210(Pt. 15):2627-2636.

Abstract

Two tubular, segmented hearts propel blood through the closed circulatory system of the medicinal leech and switch every 20-40 beats between two constriction patterns. We showed recently that within one heartbeat cycle, heart segments on one side constrict peristaltically rear-to-front (;peristaltic heart'), followed by nearly synchronous front-to-rear constrictions in the contralateral heart segments (;synchronous heart'). Using optical recordings from intact leeches, we now characterize the hemodynamic properties of the cardiac cycle of individual heart segments in different regions to ask whether the reversal of constrictions affects flow into, out of, and along the hearts. We measured total vessel capacity in corrosion casts and blood volume in individual heart segments of dissected leeches. We show that the peristaltic heart provides the propulsive force for forward and rearward flow and supplies the peripheral circulation through segmental efferent vessels. In comparison, the synchronous heart pumps less blood, most of which enters the segmental circulation. The heart sphincter, located in the posterior section of each heart segment, directs blood flow differently in the two modes. In the peristaltic heart, the sphincter prevents backflow and promotes longitudinal, forward flow while in the synchronous heart the sphincter restricts longitudinal, rearward flow and instead promotes flow into the segmental circulation. Blood is shunted via the contractile latero-dorsal arches from the dorsal intestinal vessel into the peristaltic heart in posterior segments 14 to 18. Switching between the two constriction patterns provides nutrient-rich blood to the vascular beds on both sides.

Abstract

Two tubular, segmented hearts propel blood through the closed circulatory system of the medicinal leech and switch every 20-40 beats between two constriction patterns. We showed recently that within one heartbeat cycle, heart segments on one side constrict peristaltically rear-to-front (;peristaltic heart'), followed by nearly synchronous front-to-rear constrictions in the contralateral heart segments (;synchronous heart'). Using optical recordings from intact leeches, we now characterize the hemodynamic properties of the cardiac cycle of individual heart segments in different regions to ask whether the reversal of constrictions affects flow into, out of, and along the hearts. We measured total vessel capacity in corrosion casts and blood volume in individual heart segments of dissected leeches. We show that the peristaltic heart provides the propulsive force for forward and rearward flow and supplies the peripheral circulation through segmental efferent vessels. In comparison, the synchronous heart pumps less blood, most of which enters the segmental circulation. The heart sphincter, located in the posterior section of each heart segment, directs blood flow differently in the two modes. In the peristaltic heart, the sphincter prevents backflow and promotes longitudinal, forward flow while in the synchronous heart the sphincter restricts longitudinal, rearward flow and instead promotes flow into the segmental circulation. Blood is shunted via the contractile latero-dorsal arches from the dorsal intestinal vessel into the peristaltic heart in posterior segments 14 to 18. Switching between the two constriction patterns provides nutrient-rich blood to the vascular beds on both sides.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Zoology (former)
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:1 August 2007
Deposited On:11 Feb 2008 12:14
Last Modified:06 Dec 2017 12:44
Publisher:Company of Biologists
ISSN:0022-0949
Additional Information:Free full text article
Publisher DOI:https://doi.org/10.1242/jeb.001644
PubMed ID:17644677

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