The Urinary System and Its Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
After the efferent arteriole leaves the glomerular capsule, it branches into secondary capillary plexuses around both the proximal and distal convolutions before finally reaching the renal vein. Through these capillaries, the circulatory system selectively reabsorbs some of the filtrate from the Bowman's capsule. Ions and glucose are reabsorbed early in the proximal convolution, and other nutrients and much of the water are reabsorbed in the distal convolution, converting glomerular filtrate into urine by the time it reaches the collecting tubules for transport to the renal pelvis.
The renal system
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Filtration of the plasma takes place at the glomerulus (i.e., glomerular capillaries), located in the cortical region of the kidney. Water and solutes exit the vascular compartment through these capillaries to be processed by the tubular component of the nephron. Blood is delivered to the glomerulus by the afferent arterioles. The glomerular capillaries then join to form a second arteriole referred to as the efferent arteriole. All cellular elements of the blood (red blood cells, white blood cells and platelets) as well as the unfiltered plasma continue through this vessel. The efferent arterioles then lead to a second set of capillaries, the peritubular capillaries. These capillaries provide nourishment to the renal tissue and return the substances reabsorbed from the tubule to the vascular compartment. Peritubular capillaries are closely associated with all portions of the renal tubules and wrap around them. These capillaries then join to form venules and progressively larger veins that remove the blood from the kidneys.
SBA Answers and Explanations
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury in SBAs for the MRCS Part A, 2018
Angiotensin II preferentially constricts the efferent more than the afferent arteriole. This has the effect of raising glomerular filtration pressure, while reducing renal blood flow. Under the circumstances of decreased arterial blood pressure (when angiotensin II is released) this helps to prevent decreases in GFR (tubuloglomerular feedback method of autoregulation); at the same time by reducing renal blood flow it causes increased reabsorption of sodium and water. In cases of renal artery stenosis, maintenance of the glomerular filtration pressure is dependent on the angiotensin II-dependent vasoconstriction of the efferent arteriole. Administration of ACE inhibitors abolishes the vasoconstriction of the efferent arteriole, resulting in an abrupt fall in the glomerular filtration rate. This explains why ACE inhibitors are contraindicated in renal artery stenosis.
Treatment with human umbilical cord blood serum in a gentamicin-induced nephrotoxicity model in rats
Published in Drug and Chemical Toxicology, 2022
Naser Mirazi, Fatemeh Baharvand, Reza Moghadasali, Alireza Nourian, Abdolkarim Hosseini
Prior to the implementation of eosin and hematoxylin staining, from the kidney tissues, 5 µ-size sections were deparaffinized and rehydrated. The reagents and stains were bought from Sigma (St. Louis, MO, USA). An Olympus BX-50 microscope, with the integration of a color digital camera (Olympus, Japan, DP-72), was utilized for observing the histological sections. Protective effects of hUCBS on kidney were quantitatively assessed by measuring the glomerular surface area (GA), glomerular volume (GV) and number of proximal tubular cell nuclei (PTN). For each group, 20 superficial cortical glomeruli were selected according to the following criteria: 1) presence of afferent or efferent arterioles at the glomerular vascular pole; 2) presence of the beginning of proximal convoluted tubule at the glomerular urinary pole. GA was measured by outlining a perimeter along the glomerular periphery (Gilbert et al.1991) using image analysis software (Image J v1.53). Assuming glomeruli as spheres, we calculated GV using the following formula: GV = 1.2545 × GA (Rangan and Tesch 2007). PTN was counted in 10 proximal convoluted tubular sections close to the renal corpuscles on which the glomerular measurements were performed. The numbers of epithelial cells were calculated as number of nuclei per 100 µm of perimeter of proximal convoluted tubules using Olympus DP2-BSW application software (v2.2). The images were all taken with a magnification of ×400 from H&E-stained renal tissue sections.
Preventing acute kidney injury during transplantation: the application of novel oxygen carriers
Published in Expert Opinion on Investigational Drugs, 2019
Raphael Thuillier, Eric Delpy, Xavier Matillon, Jacques Kaminski, Abdelsalam Kasil, David Soussi, Jerome Danion, Yse Sauvageon, Xavier Rod, Gianluca Donatini, Benoit Barrou, Lionel Badet, Franck Zal, Thierry Hauet
The major function of kidney is to remove waste products and excess fluid from the body to maintain homeostasis. Kidney tissue oxygenation is determined by the presence of oxygen in arterial blood, oxygen consumed by the cells, and arterial-to-venous oxygen shunting [9]. Renal oxygenation is defined as the relationship between renal oxygen delivery (DO2) and renal oxygen consumption (VO2). The anatomy of the nephron and renal microcirculation plays a crucial role in understanding the effect of ischemia on the kidney. In physiological conditions, kidneys receive approximately 20% of cardiac output and this blood flow is channeled to the cortex with blood flow to the medulla predominantly from the vasa recta, a continuation of efferent arterioles of the juxtamedullary glomeruli. In hospital settings, AKI commonly occurs in sepsis, and after procedures associated with temporary cessation of renal perfusion or reduced renal blood flow or oxygen delivery. Such procedures include renal transplantation, cardiac, and other major surgery, resection of renal mass, and reparation of an aneurysm [10]. Blood flow to the kidney is temporarily occluded during surgical procedures such as renal transplantation (cold ischemia), and consequentially, oxygen delivery to the kidney ceases, the kidney becoming hypoxic and anoxic. Hypothermia remains the cornerstone of the methodological approach for organs preservation.
The effect of whole blood viscosity on contrast-induced nephropathy development in patients undergoing percutaneous coronary intervention
Published in Postgraduate Medicine, 2022
Mustafa Kinik, Sencer Çamci, Selma Ari, Hasan Ari, Mehmet Melek, Tahsin Bozat
The relationship between lowness of WBV and CIN can be explained by the tubuloglomerular feedback mechanism in the kidneys. The inability of the glomeruli, which have adapted to the low viscosity environment, to adapt to the sudden increase in viscosity caused by the deformation created by contrast material and contrast on the erythrocytes may cause CIN development [26]. Vasodilation in afferent arterioles and vasoconstriction in efferent arterioles occur to provide the necessary glomerular filtration in a low-viscosity environment. However, in case of a sudden increase in viscosity in the distal tubule, renin- and adenosine-mediated mechanisms cause vasoconstriction in afferent arterioles and the medullary vascular bed, causing a decrease in GFR [26]. This GFR decline is one of the main causes of CIN development. Because of decreased GFR, the removal of the contrast material from the body is delayed, and CIN develops because of this event, causing a vicious circle on the kidneys. Since the WBV values in non-STEMI and STEMI patients were higher than those in elective PCI patients, the tubuloglomerular feedback mechanism adapted to a more viscous environment. Therefore, since the viscosity increase in distal renal tubules in these patients is relatively less, the effectiveness of the feedback mechanism and the GFR decrease are less. The second explanation about the relationship between lowness of WBV and CIN; lower WBV conditions lead to a constricted renal circulation, associated with a condition of decreased NO bioavailability [27]. These may explain that WBV values are not CIN development predictors in these groups.
Related Knowledge Centers
- Blood Pressure
- Nephron
- Plexus
- Renal Cortex
- Renal Medulla
- Capillary
- Blood Vessel
- Urinary System
- Glomerular Filtration Rate
- Mammalian Kidney