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Unformatted text preview: Overview of Kidneys and Renal Physiology Overview of the Kidneys and Renal Physiology The kidneys are located in a retroperitoneal position in the abdominal cavity at the level of the T12 to L3 vertebrae. The hilum of the left kidney is located on the transpyloric plane, whereas the right kidney is located 2-3 cm more inferiorly because of the presence of the liver. From the perspective of the back, the superior pole of the kidney underlies the 11 th and 12 th ribs. The inferior pole of the right kidney is 1 finger’s breadth above the iliac crest. They are embedded in two layers of fat that are separated by a layer of renal fascia. The perirenal fat lies on the inside of the renal fascia, whereas the pararenal fat lies on the outside. The perirenal and pararenal fat, renal fascia, blood vessels, and ureters hold the kidneys in place. In fact, should the amount of fat diminish as occurs in severe states of starvation, the kidneys may prolapse resulting in kinking of the ureter and subsequent hydronephrosis. The renal hilum contains the renal artery, vein and pelvis. The renal artery branches directly from the abdominal artery at the level of the L1-L2 intervertebral disc just inferior to the superior mesenteric artery. The renal arteries are posterior to the respective renal veins which drain into the IVC. The internal structure of the kidney contains a cortex on the outside that surrounds the medulla. The medulla contains renal (medullary) pyramids with renal columns (cortical tissue) between them. The apex of the renal pyramids is the renal papilla that points toward the renal hilum. At the hilar side of the kidney is a space known as the renal sinus. It contains minor and major calyces, renal pelvis, and vessels and nerves. Urine flows from the renal papilla into the minor calyx, then the major calyx, and finally to the renal pelvis which is the proximal, dilated part of the ureter. Referred pain from the kidney travels via the least splanchnic nerve to the level of the T11 to L2 spinal cord. Thus, pain is referred to the T11-L2 dermatomes. It may extend to the proximal thigh and external genitalia via the genitofemoral nerve (L1, L2/L3). Sometimes there is a horseshoe shaped kidney in which the inferior poles of the right and left kidneys are fused. Ectopic kidneys that lie in the pelvic cavity due to failure to ascend into the abdominal cavity also occur. Kidney Physiology Prior to describing renal physiology it is necessary to understand functional renal anatomy, i.e. the anatomy of the nephron, collecting ducts and associated arterioles. There are 2 types of nephrons: 1) superficial, and 2) juxtamedullary. The juxtamedullary nephron has several unique traits such as a longer loop of Henle, larger glomerulus, lower renin content, and different tubular permeability. It has a higher glomerular filtration rate and plays a more significant role in the regulation of fluid and electrolytes. The nephron begins with the renal corpuscle which is a combination of the...
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This note was uploaded on 02/17/2012 for the course MPAS PA 602 taught by Professor Dr.laird during the Fall '10 term at Chatham University.
- Fall '10