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
Upon leaving the glomerular capillaries, the filtrate enters the first portion of the tubule, Bowman’s capsule. The glomerulus is pushed into Bowman’s capsule, much like a fist pushed into a balloon or a catcher’s mitt. From Bowman’s capsule, the filtrate passes through the proximal tubule, which is also located in the cortex of the kidney. The next segment of the tubule is the Loop of Henle. This portion of the tubule is found in the medulla of the kidney. The descending limb dips into the medulla and the ascending limb returns toward the cortex. From the Loop of Henle, the filtrate passes through the distal tubule in the cortex of the kidney. Finally, up to eight distal tubules empty into a collecting duct. The collecting ducts run downward through the medulla. Any filtrate remaining within the tubule at the end of the collecting duct drains through the renal pelvis to the ureters and is excreted as urine.
Upper Urinary Tract Obstruction
Anthony R. Mundy, John M. Fitzpatrick, David E. Neal, Nicholas J. R. George in The Scientific Basis of Urology, 2010
The collecting duct normally receives hypotonic filtrate from the distal tubule and acts to vary the concentration of the final urine by modifying free water reabsorption. This system is tightly controlled by changes in baroreceptor and osmoreceptor firing in response to changes in blood pressure and osmololality. A decreased circulatory volume or increased plasma osmolality excites magnocellular and parvocellular neurosecretory cells of the hypothalamus to release arginine vasopressin (AVP) into the circulation from their axon terminals in the neuro-hypophysis. Interaction of AVP with V2 receptors in the collecting duct leads to cyclic adenosine-monophosphate (cAMP) generation, protein kinase A activation and the stimulation of both the expression and apical membrane localization of aquaporin-2 (AQP2) water channels.
Interpretation of abnormal results
Alistair Burns, Michael A Horan, John E Clague, Gillian McLean in Geriatric Medicine for Old-Age Psychiatrists, 2005
Sodium is the major extracellular cati�n: 80-90% is located in the extracel- lular compartment. There does not seem to be a control mechanism that regulates sodium intake. Thus, to maintain a constant body sodium content, intake must be balanced by output. Small amounts of sodium are lost in sweat and faeces, but the major excretory route is via the kidney. About 70% of filtered sodium is reabsorbed in the proximal convoluted tubule. Because of concurrent water absorption, the tubular fluid remains iso-osmotic with the plasma. Some 20-30% of the filtered sodium is reabsorbed in the loop of Henl�. This sodium is trapped in the renal interstitium and, along with urea, contributes to the medullary osmotic gradient, which is needed for concentration of the uri�e. In addition, 5-10% of the filtered sodium is reabsorbed in the distal convoluted tubule, which also secretes potassium into the tubular fluid. The reabsorption of sodium and loss of potassium is modulated by the adrenal cortical hormone, aldosterone. Aldosterone also regulates sodium absorption in the collecting ducts. Atrial natriuretic pep- tides and brain natriuretic peptides also reg�late sodium reabsorption/loss. Thus, the major factors regulating renal sodium handling are:
Regenerating the kidney using human pluripotent stem cells and renal progenitors
Published in Expert Opinion on Biological Therapy, 2018
Francesca Becherucci, Benedetta Mazzinghi, Marco Allinovi, Maria Lucia Angelotti, Paola Romagnani
Pluripotent SC-derived organoids have provided interesting information about the capability of self-organization in similar-kidney structures. Notwithstanding this, this strategy could be inefficient in generating a sufficient number of cells for kidney regeneration purposes. Therefore, alternative solutions have been set up. In this view, ‘re-cellularization’ of biologic or artificial scaffolds with appropriate combinations of specific renal cell types is an attractive hypothesis. These cells can be either isolated from pluripotent SC-derived organoids that are separated and expanded in culture or differentiated in vitro from their specific tissue/cell of origin [62,63]. Scaffolds can be made of purified silk, 3D-printed polymer arrays, decellularized kidneys, and extracellular matrix [63]. Independently on the kind of scaffold, this approach requires the appropriate setup of vascular structures (here including the correct development and localization of endothelial, smooth muscle and pericytes cells, as well as interstitial cells) to allow the scaffolds to be served by blood flow and the structures to be consequently functional [64,65]. Finally, these newly generated structures should be communicate with collecting ducts to allow the urine stream to flow and kidney to fulfill all its functions [66]. The ultimate goal is to obtain synthetic kidneys that can be transplanted to a host [62].
Therapeutic role of Azadirachta indica leaves ethanolic extract against diabetic nephropathy in rats neonatally induced by streptozotocin
Published in Ultrastructural Pathology, 2021
Abd El-Fattah B. M. El-Beltagy, Amira M.B. Saleh, Amany Attaallah , Reham A. Gahnem
The renal sections from control (Figure 2A&A1) and neem supplemented (Figure 2B&B1) rats appeared with normal histological architecture whereas it is differentiated into outer cortex and inner medulla. The renal cortex displayed well-organized renal corpuscles and tubules. The renal corpuscle consists of glomerulus that is surrounded by Bowman’s space and intact Bowman’s capsule that lined with simple squamous epithelium. The renal tubules represented by proximal tubules (PT), distal tubules (DT) and collecting ducts (CD). The PT is characterized by its star-shaped lumen that is lined with brush bordered cubical epithelium. Moreover, the DT has relatively rounded lumen that lined by cubical epithelium with little microvilli. The CD lined with short cubical epithelium and has a relatively wider lumen than the PT and DT. The renal medulla displayed well-organized collecting ducts and Henel,s loops.
Effects of caffeic acid phenethyl ester use and inhibition of p42/44 MAP kinase signal pathway on caveolin 1 gene expression and antioxidant system in chronic renal failure model of rats
Published in Drug and Chemical Toxicology, 2023
Yilmaz Cigremis, Hasan Ozen, Merve Durhan, Selahattin Tunc, Evren Kose
Phospho-p42/44 MAPK immunoreactivity was observed only in the collecting ducts of renal tissue in the control group (Figure 4(a)). Comparably fewer collecting ducts with immunoreactivity were seen in the renal cortex than that of the medulla. Not all collecting ducts in medulla were also immunopositive for phospho-p42/44 MAPK and severity of the staining in epithelia showed differences in a given duct. Phospho-p42/44 MAPK immunoreactivity was mostly nuclear but some cytoplasmic staining was also seen. In general, no immunoreactivity was observed in glomerulia, proximal and distal tubules, however occasional proximal tubules showed some signs of immunopositivity. Compared to the control group, phospho-p42/p44 MAPK immunoreactivity was higher in the CsA group (p < 0.05) (Figure 4(b)). The number of immunostained ducts especially in the medulla and the density of immunostaining was higher in the CsA group. Immunostaining pattern in the renal cortex was however similar to that of the control group. In CsA + PD (Figure 4(c)), CsA + PD + CAPE (Figure 4(d)), and CsA + CAPE (Figure 4(e)) groups, phospho-p42/44 MAPK immunoreactivity pattern was similar to that of the control group (p > 0.05), though with slightly less immunoreactivity and fewer number of collecting ducts. CsA-V (Figure 4(f)), CAPE-V (Figure 4(g)) and PD-V (Figure 4(h)) groups also showed similar phospho-p42/44 MAPK immunoreactivity pattern to that of control group (p > 0.05).
Related Knowledge Centers
- Nephron
- Renal Corpuscle
- Vasopressin
- Kidney
- Renal Calyx
- Renal Pelvis
- Electrolyte
- Fluid Balance
- Hormone
- Aldosterone