Properties of the Arterial Wall
Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos in McDonald's Blood Flow in Arteries, 2022
The function of the systemic arterial system is to deliver blood at high pressure and in a continuous stream to peripheral vascular beds. From a simplistic perspective, it can be separated into three anatomical regions to serve the left ventricle as a pulsatile pump and the tissues that need a supply of blood. Each region has a distinct and separate function: (1) The large arteries, especially the elastic arteries (aorta, brachiocephalic, carotid, etc.), serve predominately as a cushioning reservoir, or “Windkessel,” that stores blood during systole and expels it to the tissue during diastole. (2) The long muscular arteries act predominately as conduits, distributing blood to the extremities; these arteries also actively modify wave propagation by changing smooth muscle tone and diameter with little change in mean arterial blood pressure. (3) The arterioles, by changing their caliber, alter peripheral resistance and therefore aid in the maintenance of mean arterial blood pressure, as well as the delivery of a steady or continuous flow of blood to the organs and tissues according to their need. Major changes in the central elastic arteries occur over long periods of time, while acute alterations in wall properties (e.g. with rise or fall in dis-tending pressure) are passive (Nichols and Edwards, 2001; Giannattasio and Mancia, 2002). Changes in the muscular arteries and arterioles most often occur acutely, and alterations in wall properties are active (Boutouyrie et al., 2000; Nichols and Edwards, 2001; Safar et al., 2003).
Cardiovascular System and Muscle
George W. Casarett in Radiation Histopathology: Volume II, 2019
The elastic arteries are conducting arteries in which the elastic tissue expands to absorb some of the pulse beat of the heart and temporarily store some of the energy involved. In the return of the stretched walls during refilling of the heart, the elastic tissue releases kinetic energy and maintains a more constant pressure and a smoother, less interruptive flow of blood. The muscular arteries are distributing arteries which, under the nervous control of their muscular medial layers, can regulate the quantities of blood brought to various organs and tissues according to need by contracting or dilating. The arterioles, with their relatively thick muscular walls and narrow lumen, play a prime role in controlling the local flow of blood in tissues and in controlling systemic blood pressure, being responsible for most of the fall in blood pressure within tissues and organs.
Coronary arterial anatomy: Normal, variants, and well-described collaterals
Debabrata Mukherjee, Eric R. Bates, Marco Roffi, Richard A. Lange, David J. Moliterno, Nadia M. Whitehead in Cardiovascular Catheterization and Intervention, 2017
The final component is the network of intramural arterioles, which have diameters less than 100 pm. The arteriole wall consists of an endothelial layer facing the blood surrounded by a layer of circumferentially oriented smooth muscle cells. These are encased by connective tissue containing a rich plexus of sympathetic and parasympathetic fibers. The smooth muscle cells are able to constrict the lumen of an arteriole and frequently do under physiologic and pathologic stimuli. Their role is to regulate myocardial blood supply to match myocardial oxygen consumption. This function is especially marked at their junction with the capillaries, thus blood passage into the capillaries is care- fully controlled. The arterioles have a high resting tone and dilate in response to metabolites released by the myocar- dium at times of increased oxygen demand.[25] Blood flow can increase by 200% or more over resting values in many capillary beds by the relaxation of the arteriolar constric- tors. Therefore, by regulating the resistances in the prearterioles and arterioles, blood flow is matched with oxygen requirements in the coronary circulation.[26]
Dynamic Changes in Retinal Vessel Diameters and Arteriovenous Ratio within 10 Days of Birth
Published in Current Eye Research, 2023
Previous studies in adults have shown that the retinal artery’s diameter decreases with the onset of diabetes while the retinal vein’s diameter widens.3 In addition, when systemic blood pressure continues to rise, self-regulating vessels narrow the arterioles.4 Moreover, retinal vascular morphological changes may predict age-related cognitive decline,5 and a low AVR may indicate adverse pregnancy outcomes.6 Similarly, newborns experience parturition from inside to outside in the neonatal period. Whole-body microcirculation is influenced by sudden changes in the environment, the gradual establishment of pulmonary circulation, and changes in blood oxygen content. These changes may theoretically lead to severe relaxation and contraction of the retinal blood vessels shortly after birth. With the development of fundus photography systems and semi-automatic measurement software for newborns, the diameter of the retinal vessels in newborns can also be quantitatively analyzed. Kandasamy et al. measured the retinal blood vessels of 20 full-term newborns within 7 days of birth using digital software and found that the average AVR was 0.66. However, there are no studies on early changes in the retinal vessel diameter and AVR with age in full-term newborns.
TULP1 related retinal dystrophy: report of rare and novel variants with a previously undescribed phenotype in two cases
Published in Ophthalmic Genetics, 2022
H. Al-Hindi, M. Z. Chauhan, R. Sanders, H. Samarah, M. DeBenedictis, E. Traboulsi, S. H. Uwaydat
A four-year-old female patient with a prior ocular clinical diagnosis of pattern dystrophy presented with poor vision and difficulty navigating in dark environments. Otherwise, she was generally healthy with no perinatal or developmental problems. On presentation, best corrected visual acuity was 20/300 OD and 20/250 OS, with a refractive error of −2.00 OU. Anterior segment examination was normal, and patient was orthophoric at near and disctance with no nystagmus. Ophthalmoscopy showed a large central area of RPE atrophy in a bull’s eye pattern and peripheral fundus pigmentary changes, as well as hyper-FAF along the retinal vessels in both eyes (Figure 2a, b). In addition, there was notable arteriolar narrowing. Electroretinography (UTAS SunBurst TM, LKC Technologies, Gaithersburg, Maryland, USA) revealed that the photopic white responses and 30 Hz flicker cone responses were markedly reduced.
Uric acid as a cardiorenal mediator: pathogenesis and mechanistic insights
Published in Expert Review of Cardiovascular Therapy, 2021
Asma Gulab, Ricardo Torres, Jerald Pelayo, Kevin Bryan Lo, Anum Shahzad, Supriya Pradhan, Janani Rangaswami
Uric acid has also been associated with vascular smooth muscle proliferation by different signaling mechanisms such as stimulation of platelet derived growth factor-A (PDGF-A) and cyclooxygenase 2 (COX-2) mediated generation of thromboxane [29,30]. Hyperuricemia models in rats have shown thickening of preglomerular vessels due to increased number of vascular smooth muscle cells and transmural macrophagic infiltration [30]. These changes potentially produce obliteration of afferent arterioles with decreased renal plasma flow and ischemia in post-glomerular regions [31]. UA also induced glycocalyx shedding (endothelial covering against injury) with resultant increased vascular permeability, increased ROS generation and reduced NO [32]. Podocyte injury by ROS has also been described in animal models which develop albuminuria after exposure to high levels of UA[33].