Circulation in the Leech, Hirudo Medicinalis L

1988 ◽  
Vol 134 (1) ◽  
pp. 235-246 ◽  
Author(s):  
JAN-PETER HILDEBRANDT
Keyword(s):  
Blood Flow ◽  
Circulatory System ◽  
The Body ◽  
Diastolic Filling ◽  
Dorsal Vessel ◽  
Capillary Networks ◽  
Different Shapes ◽  
Blood Flow Velocities ◽  
Improved Model ◽  
Intravascular Pressure

In the leech, the physiological significance of high-pressure phases (HIP) and lowpressure phases (LOP) of the lateral vessels was studied by intravascular pressure recordings and observation of blood flow in different parts of the circulatory system, and by measurements of the blood flow velocities in the dorsal vessel. Different shapes of the pressure pulses were found in the anterior lateral vessel segments during HIP and LOP phases, according to the different modes of diastolic filling in both phases. Pressure recordings in the lateral abdominal vessels showed the different action of the lateral abdominal sphincters in the HIP and LOP phases of the ipsilateral lateral vessel. The LOP contractions were responsible for the blood supply to the capillary networks of the organs and the body wall, with the possible exception of the intestine. The HIP contractions caused a forward bloodflow within the lateral vessel. In the dorsal vessel, the blood pressure was about 0.9-1.9kPa in different animals. The blood flow was discontinuous with velocities of 0.5-10 mms−1. Average blood flow in the dorsal vessel was 22.9μl min−1. An improved model of the circulation in the leech is presented.

scholarly journals Contractile pericytes determine the direction of blood flow at capillary junctions

2020 ◽  
Vol 117 (43) ◽  
pp. 27022-27033
Author(s):  
Albert L. Gonzales ◽  
Nicholas R. Klug ◽  
Arash Moshkforoush ◽  
Jane C. Lee ◽  
Frank K. Lee ◽  
...  
Keyword(s):  
Blood Flow ◽  
Circulatory System ◽  
The Body ◽  
Capillary Network ◽  
Transitional Region ◽  
Capillary Networks ◽  
Efficiency And Effectiveness ◽  
The Central Nervous System ◽  
Essential Function ◽  
The Brain

The essential function of the circulatory system is to continuously and efficiently supply the O2 and nutrients necessary to meet the metabolic demands of every cell in the body, a function in which vast capillary networks play a key role. Capillary networks serve an additional important function in the central nervous system: acting as a sensory network, they detect neuronal activity in the form of elevated extracellular K+ and initiate a retrograde, propagating, hyperpolarizing signal that dilates upstream arterioles to rapidly increase local blood flow. Yet, little is known about how blood entering this network is distributed on a branch-to-branch basis to reach specific neurons in need. Here, we demonstrate that capillary-enwrapping projections of junctional, contractile pericytes within a postarteriole transitional region differentially constrict to structurally and dynamically determine the morphology of capillary junctions and thereby regulate branch-specific blood flow. We further found that these contractile pericytes are capable of receiving propagating K+-induced hyperpolarizing signals propagating through the capillary network and dynamically channeling red blood cells toward the initiating signal. By controlling blood flow at junctions, contractile pericytes within a functionally distinct postarteriole transitional region maintain the efficiency and effectiveness of the capillary network, enabling optimal perfusion of the brain.

scholarly journals Ideas of V.Z. Golubev - freelance university lecturer of the Kazan Emperor’s university - in modern studies of renal microcirculation

2014 ◽  
Vol 95 (2) ◽  
pp. 161-163
Author(s):  
O A Kaplunova
Keyword(s):  
Blood Flow ◽  
Blood Circulation ◽  
Circulatory System ◽  
Renal Medulla ◽  
Cardiorenal Syndrome ◽  
Scientific Basis ◽  
Kidney Cortex ◽  
Capillary Networks ◽  
Renal Microcirculation ◽  
Vasorenal Hypertension

In 1894 V.Z. Golubev, freelance university lecturer of the Kazan Emperor’s University, presented his thesis «Of the renal blood vessels in mammals and humans». In this work, V.Z. Golubev described the structure of two capillary networks of the renal cortex: glomerular and peritubular. He has identified true straight arterioles, false straight arterioles and direct venules of pyramids as parts of the renal medulla direct vessels. V.Z. Golubev described glomerular capillaries, located along the arcuate arteries of the kidney in the boundary layer and assigned these to the perivascular circulation, as well as noted the important role of the true direct arteriolar blood circulation to the kidneys. According to scientific researches of the second half of the XX century, the structure of the renal circulatory system is subordinated to differentiated renal blood flow in the cortex and medulla, and this is achieved by cortical and juxtamedullary blood flow. Significant increase and the duration of juxtaglomerular bypass cause severe circulatory disorders of the surface layers of kidney cortex and acute renal failure. Modern data on renal blood circulation prepared by researches of V.Z. Golubev, explain the development mechanism of various pathological conditions: acute blood loss, hydronephrosis, vasorenal hypertension, glomerulonephritis, pyelonephritis, cardiogenic shock, cardiorenal syndrome in uncontrolled coronary heart disease, arterial hypertension, sudden cardiac death etc. V.Z. Golubev created a scientific basis for further studies of renal microcirculation. The principles, outlined in his thesis, anticipated later researches of renal juxtamedullary circulation and renal circulation in healthy people and in case of a disease. The thesis of V.Z. Golubev, published 120 years ago, is still of present interest and highlights the problems requiring further research.

scholarly journals Investigation of changes in the skin blood microcirculation when performing the hatha yoga breathing technique

2022 ◽  
Vol 20 (4) ◽  
pp. 33-44
Author(s):  
A. V. Frolov ◽  
Yu. I. Loktionova ◽  
E. V. Zharkikh ◽  
V. V. Sidorov ◽  
A. I. Krupatkin ◽  
...  
Keyword(s):  
Blood Flow ◽  
Laser Doppler Flowmetry ◽  
Circulatory System ◽  
Low Frequency ◽  
Brain Perfusion ◽  
The Body ◽  
Laser Doppler ◽  
Regulatory Mechanisms ◽  
Doppler Flowmetry ◽  
Breathing Exercises

Introduction. Yoga breathing exercises improve the ability to significantly reduce the respiratory rate. A decrease of the minute respiration volume results in compensatory reactions of the microcirculatory bed caused by changes in the gas composition. The reaction of the regulatory mechanisms of the microvascular bed can be evaluated by the optical non-invasive laser Doppler flowmetry method. The aim of the study was to assess the tissue microcirculation parameter changes in people performing yoga breathing exercises. Materials and methods. 25 volunteers performed yoga breathing exercises at a frequency of 3 times per minute, 2 times per minute, 1.5 times per minute, 1 time per minute for 5 minutes, and free breathing for 6 minutes before and after breathing exercises. Parameters aimed to defin the reaction of skin microcirculation in different body areas were simultaneously recorded in six sites by laser Doppler flowmetry using a distributed system of wearable analyzers. The parameters of tissue microcirculation recorded by the method of laser Doppler flowmetry were: the index of microcirculation (Im), nutritive blood flow (Imn), the amplitude of myogenic (Am), neurogenic (An), endothelial (Ae), respiratory (Ar) and cardiac (Ac) regulation circuits. Results. Yoga breathing exercises led to increase of microcirculation index at all breathing frequencies. Breathing at a frequency of 1.5 and 1/minute leads to a significant increase in nutritional blood flow. Low-frequency breathing exercises lead to an increase in blood pressure at the lowest breathing rates – 1.5/minute and 1/minute. The most significant changes were achieved at the lowest respiration rates (1 and 1.5/minute), that could be associated with hypoxic-hypercapnic mechanisms. Conclusion. The absence of significant changes in microcirculation parameters after low-frequency respiration during measurements in the supraorbital arteries in both groups characterizes the work of homeostatic mechanisms for maintaining brain perfusion in stressful situations for the body (low-frequency types of respiration, hypercapnia and hypoxia). When measured in the extremities, a change in the effect of the circulatory system regulatory mechanisms was observed; along with an increase in skin perfusion and the nutritional component, it can characterize the compensatory reaction of the microcirculation to respiration change.

The Circulatory Physiology of Helix Pomatia

1973 ◽  
Vol 59 (2) ◽  
pp. 291-303
Author(s):  
BARBARA A. SOMMERVILLE
Keyword(s):  
Blood Flow ◽  
Helix Pomatia ◽  
Circulatory System ◽  
Mantle Cavity ◽  
Heart Beat ◽  
The Body ◽  
Pericardial Cavity ◽  
Circulatory Physiology ◽  
Pressure Changes ◽  
Characteristic Pressure

1. The pressure changes in the mantle cavity and various parts of the circulatory system of Helix pomatia have been measured. 2. There are characteristic pressure changes associated with the breathing movements, the pattern depending upon the point at which the measurement was made and, in the case of the heart, the position of the body at the time of recording. These pressure changes fail mainly within the range 2-8 cm H2O. 3. The pressure changes associated with contraction of the heart chambers fall within the range 1-2 cm H2O in pulmonary vein and auricle, 10-32 cm H2O in the ventricle, 1-3 cm H2O in the aorta and 1-8 cm H2O in the pericardial cavity. 4. An increased frequency and amplitude of heart beat was associated with an increased rate of blood flow.

scholarly journals Thermal Analysis of Heat Transfer from Catheters and Implantable Devices to the Blood Flow

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 230
Author(s):  
Hossein Zangooei ◽  
Seyed Ali Mirbozorgi ◽  
Seyedabdollah Mirbozorgi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Blood Flow ◽  
Temperature Rise ◽  
Implantable Devices ◽  
The Body ◽  
Transfer Model ◽  
Governing Equations ◽  
Blood Flow Velocities ◽  
Flow Velocities

Implantable devices, ultrasound imaging catheters, and ablation catheters (such as renal denervation catheters) are biomedical instruments that generate heat in the body. The generated heat can be harmful if the body temperature exceeds the limit of almost 315 K. This paper presents a heat-transfer model and analysis, to evaluate the temperature rise in human blood due to the power loss of medical catheters and implantable devices. The dynamic of the heat transfer is modeled for the blood vessel, at different blood flow velocities. The physics and governing equations of the heat transfer from the implanted energy source to the blood and temperature rise are expressed by developing a Non-Newtonian Carreau–Yasuda fluid model. We used a Finite Element method to solve the governing equations of the established model, considering the boundary conditions and average blood flow velocities of 0–1.4 m/s for the flow of the blood passing over the implanted power source. The results revealed a maximum allowable heat flux of 7500 and 15,000 W/m2 for the blood flow velocities of 0 and 1.4 m/s, respectively. The rise of temperature around the implant or tip of the catheter is slower and disappeared gradually with the blood flow, which allows a higher level of heat flux to be generated. The results of this analysis are concluded in the equation/correlation T=310+H3000(1+e−7V), to estimate and predict the temperature changes as a function of heat flux, H, and the blood flow velocity, V, at the implant/catheter location.

The Blood Vascular System of Nephtys (Annelida, Polychaeta)

1956 ◽  
Vol s3-97 (38) ◽  
pp. 235-249
Author(s):  
R. B. CLARK
Keyword(s):  
Body Wall ◽  
Vascular System ◽  
Close Association ◽  
Circulatory System ◽  
Ventral Surface ◽  
Blood Stream ◽  
Neurosecretory Cells ◽  
The Body ◽  
Dorsal Vessel ◽  
The Brain

The four longitudinal vessels of the circulatory system of Nephtys californiensis are dorsal, sub-intestinal, and neural, the latter being paired. There is a complete longitudinal circulation; the dorsal vessel communicates with the sub-intestinal by way of the proboscidial circulation and with the neural by way of the circum-oral vessels. In each middle and posterior segment segmental vessels from each of the longitudinal trunks carry blood to and from the parapodia and body-wall. The segmental circulation is completed by a circum-intestinal vessel connecting the dorsal and subintestinal vessels in each segment and an intersegmental branch connecting the dorsal and sub-intestinal segmental vessels. A trans-septal branch of the neural segmental vessel communicates with the sub-intestinal segmental vessel. This arrangement is modified in anterior segments which house the muscular, eversible pharynx, and no blood-vessels cross the coelom except by running through the body-wall. On anatomical grounds and by comparison with other polychaetes it seems likely that segmental is subordinate to longitudinal circulation. There are no endothelial capillaries such as have been described in some other polychaetes; instead there are numerous blindending vessels the walls of which are composed of the same three layers as other vessels and which are probably contractile. The dorsal vessel, where it is in contact with the ventral surface of the supra-oesophageal ganglion, forms a plexus in close association with a modified part of the brain capsule and a special axonal tract within the ganglion. It is thought that by way of this ‘cerebro-vascular complex’, hormones produced in the neurosecretory cells of the brain pass into the blood-stream.

Heartbeat Control in Leeches. I. Constriction Pattern and Neural Modulation of Blood Pressure in Intact Animals

2004 ◽  
Vol 91 (1) ◽  
pp. 382-396 ◽  
Author(s):  
Angela Wenning ◽  
Gennady S. Cymbalyuk ◽  
Ronald L. Calabrese
Keyword(s):  
Coordination Mode ◽  
Motor Pattern ◽  
Systolic Pressure ◽  
Circulatory System ◽  
The Body ◽  
The Other ◽  
Coordination Modes ◽  
Neural Modulation ◽  
Pressure Profiles ◽  
Intravascular Pressure

Two tubular hearts propel blood through the closed circulatory system of the medicinal leech. The hearts are myogenic but are driven by a centrally generated motor pattern that controls heart rate and intersegmental coordination. In two consecutive papers, we address the question of how the motor pattern is translated into the pattern of diastole and systole of leech hearts. We imaged the constriction patterns of the hearts in quiescent intact animals. In one heart, systole progresses rear-to-front (peristaltic coordination mode), whereas systole occurs nearly simultaneously in the other heart (synchronous coordination mode) with regular switches between these two coordination modes. Intersegmental phase relations between heart segments do not vary with changes in the heartbeat period. The peristaltic heart drives blood forward through itself and then rearward through the other longitudinal vessels. The synchronous heart does not seem to contribute to rearward flow along the body axis and may support segmental circulation instead. Simultaneous monitoring of heart motor neuron discharge and the constriction of the corresponding heart segment in innervated, reduced preparations enabled us later to meld the constriction pattern with the fictive motor pattern described in the following paper. Current injections into one heart modulatory neuron while monitoring intravascular pressure from the corresponding heart showed that these neurons can acutely change diastolic and systolic pressure. However, they do not determine the different systolic pressure profiles associated with the two coordination modes, which appear to result from the constriction pattern.

scholarly journals Мальформации как нарушение фрактальной структуры кровеносной системы организма

2020 ◽  
Vol 90 (9) ◽  
pp. 1506
Author(s):  
В. Антонов ◽  
П. Ефремов
Keyword(s):  
Heat Transfer ◽  
Blood Flow ◽  
Life Support ◽  
Vascular System ◽  
Circulatory System ◽  
Flow Simulation ◽  
Simulation Software ◽  
Heat Fluxes ◽  
The Body ◽  
Model Base

The article contains a description of mathematical models, the bases of which is the representation of the body circulatory system as a multifractal object. As examples, we consider the solution of two problems. The first issue is related to the normal state of the body’s life support system, namely, heat transfer in human skin. The model base is the equations of hydrodynamics and heat transfer. Quantitative results of calculating heat fluxes in three layers of the dermis are presented. The second issue deals with a violation of fractality due to the presence of arteriovenous malformation in the brain vascular system. The SolidWorks 2017 Flow Simulation software product serves as the basis for the implementation of a blood flow model in the presence of malformation. As a result of the simulation, data on the velocities and blood flow in the vessels were obtained for various cases of malformations.

The Hox gene abdominal-A specifies heart cell fate in theDrosophila dorsal vessel

Development ◽  
2002 ◽  
Vol 129 (21) ◽  
pp. 5019-5027 ◽  
Author(s):  
TyAnna L. Lovato ◽  
Thiennga P. Nguyen ◽  
Marco R. Molina ◽  
Richard M. Cripps
Keyword(s):  
Cell Fate ◽  
Hox Genes ◽  
Circulatory System ◽  
The Body ◽  
Heart Cell ◽  
Posterior Chamber ◽  
Dorsal Vessel ◽  
A Cell ◽  
High Level ◽  
First Time

The Drosophila melanogaster dorsal vessel is a linear organ that pumps blood through the body. Blood enters the dorsal vessel in a posterior chamber termed the heart, and is pumped in an anterior direction through a region of the dorsal vessel termed the aorta. Although the genes that specify dorsal vessel cell fate are well understood, there is still much to be learned concerning how cell fate in this linear tube is determined in an anteroposterior manner, either in Drosophila or in any other animal. We demonstrate that the formation of a morphologically and molecularly distinct heart depends crucially upon the homeotic segmentation geneabdominal-A (abd-A). abd-A expression in the dorsal vessel was detected only in the heart, and overexpression of abd-Ainduced heart fate in the aorta in a cell-autonomous manner. Mutation ofabd-A resulted in a loss of heart-specific markers. We also demonstrate that abd-A and sevenup co-expression in cardial cells defined the location of ostia, or inflow tracts. Other genes of theBithorax Complex do not appear to participate in heart specification,although high level expression of Ultrabithorax is capable of inducing a partial heart fate in the aorta. These findings for the first time demonstrate a specific involvement for Hox genes in patterning the muscular circulatory system, and suggest a mechanism of broad relevance for animal heart patterning.

Patterns of Cerebral Blood Flow and Systemic Hemodynamics During Arithmetic Processing

2008 ◽  
Vol 22 (2) ◽  
pp. 81-90 ◽  
Author(s):  
Natalie Werner ◽  
Neval Kapan ◽  
Gustavo A. Reyes del Paso
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Time Course ◽  
Doppler Sonography ◽  
Transcranial Doppler Sonography ◽  
Systemic Hemodynamics ◽  
Heart Period ◽  
Blood Flow Velocities ◽  
Flow Velocities

The present study explored modulations in cerebral blood flow and systemic hemodynamics during the execution of a mental calculation task in 41 healthy subjects. Time course and lateralization of blood flow velocities in the medial cerebral arteries of both hemispheres were assessed using functional transcranial Doppler sonography. Indices of systemic hemodynamics were obtained using continuous blood pressure recordings. Doppler sonography revealed a biphasic left dominant rise in cerebral blood flow velocities during task execution. Systemic blood pressure increased, whereas heart period, heart period variability, and baroreflex sensitivity declined. Blood pressure and heart period proved predictive of the magnitude of the cerebral blood flow response, particularly of its initial component. Various physiological mechanisms may be assumed to be involved in cardiovascular adjustment to cognitive demands. While specific contributions of the sympathetic and parasympathetic systems may account for the observed pattern of systemic hemodynamics, flow metabolism coupling, fast neurogenic vasodilation, and cerebral autoregulation may be involved in mediating cerebral blood flow modulations. Furthermore, during conditions of high cardiovascular reactivity, systemic hemodynamic changes exert a marked influence on cerebral blood perfusion.

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