Physiology: An actively controlled heart valve

  title={Physiology: An actively controlled heart valve},
  author={C. Franklin and M. Axelsson},
Vertebrate hearts typically have cardiac valves that are thin and leaf-like and which work passively, allowing blood to move forward during systole and preventing it from flowing back during diastole. Crocodilian hearts have nodules of connective tissue, resembling opposing knuckles, or cog-teeth, in the subpulmonary conus just proximal to the pulmonary valves. Here we show that these cog-teeth act in the estuarine crocodile Crocodylus porosus (Fig. 1) as a valve that regulates the flow of… Expand
Is our heart a well-designed pump? The heart along animal evolution.
The circulatory pumping systems used in the different classes of animals, their advantages and failures, and the way they have been modified with evolution are described. Expand
Physiological Society Symposium ‐ Vagal Control: From Axolotl to Man
There is increasing evidence for a close regulation of the three unique structures in the crocodilian cardiovascular system and their importance for the normal function of the crocodiliadreptile circulation. Expand
Delayed depolarization of the cog-wheel valve and pulmonary-to-systemic shunting in alligators.
Evidence is provided that phasic contraction of the cog-wheel valve muscle controls shunting, that nervous and cholinergic stimulation can alter the delay and strength of valve depolarization and that this can affect the propensity to shunt. Expand
Does the left aorta provide proton-rich blood to the gut when crocodilians digest a meal?
The findings do not support the hypothesis that a R–L shunt serves to deliver CO2 for the gastrointestinal system after feeding in crocodilians, and blood in the left aorta of American alligators does not contain elevated PCO2 levels during digestion. Expand
Prenatal cardiovascular shunts in amniotic vertebrates
This review examines and compares the embryonic shunts available for fetal mammals and embryonic reptiles, including lizards, crocodilians, and birds, and finds that mammals and reptiles have either a single ductus arteriosus (mammals) or paired ducts arteriosi that provide a right-to-left shunt of right ventricular output away from the unventilated lungs. Expand
Contribution of active atrial contraction to cardiac output in anesthetized American alligators (Alligator mississippiensis)
It is suggested that the atria are non-essential (i.e. redundant) for ventricular filling in alligators, at least under anesthesia, but may serve as important volume reservoirs. Expand
Cardiovascular function in ectotherm sauropsids
The results support the idea that pulmonary bypass may improve digestive function by supporting gastric acid secretion and buffering the postprandial alkaline tide rather than being an adaptation to extended diving periods in crocodiles. Expand
Surgical removal of right-to-left cardiac shunt in the American alligator (Alligator mississippiensis) causes ventricular enlargement but does not alter apnoea or metabolism during diving
While surgical removal of R–L shunt in American alligators causes considerable changes in cardiac morphology similar to aortic banding in mammals, its removal does not affect the respiratory pattern or metabolism of alligators, and it appears probable that the low metabolic rate of reptiles allows for normal aerobic dives. Expand
Morphology of the embryonic and hatchling american alligator ductus arteriosi and implications for embryonic cardiovascular shunting
It is proposed that the paired DA of the embryonic alligator have a reduced role in the embryonic right‐to‐left shunt of blood from the right ventricle when compared with the avian DA. Expand
Non-dimensional physics of pulsatile cardiovascular networks and energy efficiency
A complete network-independent non-dimensional formulation that incorporates pulsatile flow regimes is developed andSimulations demonstrate that the proposed non- dimensional indices are independent of body size for healthy conditions, but are sensitive to deviations caused by off-design disease states that alter the energetic load. Expand


It is clear from the present work that low systemic blood pressure is a factor of crucial importance in establishing left aortic flow. Expand
The cardiovascular hemodynamics of Crocodilia.
Physiologic studies of the central circulation of Alligator mississipiensis were carried out, utilizing direct intracardiac pressure measurements, selective angiocardiography and indicator dilution curves, and it was shown that virtually all right ventricular blood was ejected into the pulmonary artery rather than into the left aorta. Expand
Functional anatomy of the heart of reptiles.
  • F. White
  • Medicine, Biology
  • American zoologist
  • 1968
Intravascular pressures, distributions of blood oxygen, dye-dilution curves, cineradiography, and electromagnetic flowmeters in major vessels suggest a highly directional flow oE systemic andExpand
Dynamic anatomical study of cardiac shunting in crocodiles using high-resolution angioscopy
It is found that the left aortic valves were unable to cover the foramen of Panizza during any part of the cardiac cycle, supporting the reversed foramen flow hypothesis and ensuring a supply of blood to the coronary and cephalic circulation during a complete shut-down of the left side of the heart, such as might occur during prolonged submergence. Expand
Comparative cardiac anatomy of the reptilia. III. The heart of crocodilians and an hypothesis on the completion of the interventricular septum of crocodilians and birds
  • G. Webb
  • Biology, Medicine
  • Journal of morphology
  • 1979
The crocodilian heart is compared with, and seen as an advancement of, the heart of non‐crocodilian reptiles, and the varanid ventricle is re‐examined, as it appeared to contain many crocodilian features, along with the ophidian characteristics described previously. Expand
The mitogenic effect of platelet-derived growth factor in human hepatic stellate cells requires calcium influx.
The results suggest that 1) spatial and time dynamics of PDGF-induced [Ca2+]i increase are dependent on cell density and 2) PD GF-induced mitogenesis requires extracellular Ca2+ influx. Expand