The efferent arteriole then forms a second capillary network around the tubule, called the peritubular capillaries. For juxtamedullary nephrons, the portion of the capillary that follows the loop of Henle deep into the medulla is called the vasa recta. As the glomerular filtrate progresses through the tubule, these capillary networks recover most of the solutes and water, and return them to the circulation. Since a capillary bed the glomerulus drains into a vessel that in turn forms a second capillary bed, this is another example of a portal system also seen in hypothalamus-pituitary axis and hepatic portion of the digestive system.
Visit this link to view an interactive tutorial of the flow of blood through the kidney. As discussed earlier, the renal corpuscle consists the glomerulus and the glomerular capsule. The glomerulus is a high pressured, fenestrated capillary with large holes fenestrations between the endothelial cells. The glomerular capsule captures the filtrate created by the glomerulus and directs this filtrate to the PCT.
The outermost part of glomerular capsule is a simple squamous epithelium. It transitions over the glomerulus as uniquely shaped cells podocytes with finger-like arms pedicels that cover the glomerular capillaries Figure A thin basement membrane lies between the glomerular endothelium and the podocytes. The pedicels interdigitate to form filtration slits , leaving small gaps that form a sieve. As blood passes through the glomerulus, 10 to 20 percent of the plasma filters out of the fenestrations, through the basement membrane and between these sieve-like fingers to be captured by the glomerular capsule and funneled to the PCT.
These features comprise the filtration membrane. The filtration membrane prevents passage of blood cells, large proteins, and most negatively charged particles but allows most other constituents through. These substances cross readily if they are less than 4 nm in size and most pass freely up to 8 nm in size. The lumen of the ureter is covered by transitional epithelium also called urothelium.
Recall from the Laboratory on Epithelia that the transitional epithelium is unique to the conducting passages of the urinary system. Its ability to stretch allows the dilation of the conducting passages when necessary. The ureter connects the kidney and the urinary bladder. The ureter empties the urine into the bladder. The transitional epithelium continues over the surface of this organ. The thickened muscular layers become interwoven and cannot be clearly identified at this point.
The urethra carries the urine away from the bladder to the outside of the body. In the male, it is joined by the genital system. The epithelium changes from transitional to stratified or pseudostratified columnar in the urethra, and to stratified squamous in the distal end of the urethra.
Answer: Podocyte: Foot processes assist in filtration barrier function by repelling negatively-charged molecules. Mesangial Cell: Provides structure support and regulate diameter of capillaries. Macula Densa: Senses blood pressure, regulates blood flow in afferent arteriole to maintain the glomerular filtration rate and stimulates release of renin. Juxtaglomerular Complex: synthesize, store and release renin.
Answer: The ureter and bladder have a transitional epithelium. The initial segment of the urethra has a stratified epithelium, and the final segment has a stratified squamous epithelium. Slides Please select whether to view the slides in study mode or quiz mode. In study mode, the images will contain labels and a description.
In quiz mode, labels and description will be hidden. Study Mode. Virtual Microscope Slides Kidney Begin by identifying roughly where the renal cortex and renal medulla are located. Ureters are tubes that propel urine from the kidneys to the urinary bladder.
This last part of the nephron connects with and empties its filtrate into collecting ducts that line the medullary pyramids. The collecting ducts amass contents from multiple nephrons, fusing together as they enter the papillae of the renal medulla. Urine leaves the medullary collecting ducts through the renal papillae, emptying into the renal calyces, the renal pelvis, and finally into the bladder via the ureter.
Learning Objectives Explain the role of the nephron as the functional unit of the kidney. Your kidneys, ureters, and bladder are part of your urinary tract. Your kidneys remove wastes and extra fluid from your body. Your kidneys also remove acid that is produced by the cells of your body and maintain a healthy balance of water, salts, and minerals—such as sodium , calcium , phosphorus , and potassium —in your blood. Watch a video about what the kidneys do.
Each of your kidneys is made up of about a million filtering units called nephrons. Each nephron includes a filter, called the glomerulus , and a tubule. The nephrons work through a two-step process: the glomerulus filters your blood, and the tubule returns needed substances to your blood and removes wastes.
As blood flows into each nephron, it enters a cluster of tiny blood vessels—the glomerulus. The thin walls of the glomerulus allow smaller molecules, wastes, and fluid—mostly water—to pass into the tubule. Larger molecules, such as proteins and blood cells, stay in the blood vessel. A blood vessel runs alongside the tubule.
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