Shape: Bean shaped Hilum Hilus leads into the renal sinus which contains renal artery, vein and renal pelvis. Renal vein anteriorly, Renal artery in middle and Renal pelvis posteriorly Size: Measures cm in length x 6 cm in Width x 3 cm in AP US is the best modality to obtain the size of kidneys Contour Smooth Axis Long axis - directed outwards and laterally Tilted, superior pole closer to mid line Relationship: Anteriorly the right kidney is related to the Liver, duodenum and hepatic flexure of ascending colon Anteriorly the left kidney is related to Stomach, Jejunum, Pancreas, Spleen and descending Colon Adrenal gland is superior and anterior to the Kidneys The kidney is surrounded by a distinct layer of fascia Perirenal fascia that separates the fat surrounding the kidney into the perinephric and paranephric fat.
Kidneys lie in a fatty cushion of perinephric fat Right Kidney is related to the 12th rib posteriorly resting on diaphragm The left kidney rises to as high as the 11th thoracic rib posteriorly, extending from TL3, resting on diaphragm Renal Structure:. Thin capsule Renal cortex Renal cortex consists of glomeruli and renal tubules Normal thickness is 2. The right kidney sits just below the diaphragm and posterior to the liver, the left below the diaphragm and posterior to the spleen.
The kidneys : Human kidneys viewed from behind with the spine removed. Resting on top of each kidney is an adrenal gland adrenal meaning on top of renal , which are involved in some renal system processes despite being a primarily endocrine organ.
The upper parts of the kidneys are partially protected by lower ribs, and each whole kidney and adrenal gland are surrounded by two layers of fat the perirenal and pararenal fat and the renal fascia. The kidneys are located at the rear wall of the abdominal cavity just above the waistline and are protected by the ribcage.
They are considered retroperitoneal, which means that they lie behind the peritoneum, the membrane lining of the abdominal cavity. There are a number of important external structures connecting the kidneys to the rest of the body. The renal artery branches off from the lower part of the aorta and provides the blood supply to the kidneys. Renal veins take blood away from the kidneys into the inferior vena cava. The renal tubule carries urine from the glomerular capsule to the renal pelvis.
The primary function of the kidneys is the excretion of waste products resulting from protein metabolism and muscle contraction. The liver metabolizes dietary proteins to produce energy and produces toxic ammonia as a waste product.
The liver is able to convert most of this ammonia into uric acid and urea, which are less toxic to the body. Meanwhile, the muscles of our body use creatine as an energy source and, in the process, produce the waste product creatinine. Ammonia, uric acid, urea, and creatinine all accumulate in the body over time and need to be removed from circulation to maintain homeostasis.
The glomerulus in the kidneys filter all four of these waste products out of the bloodstream, allowing us to excrete them out of our bodies in urine. Urea in the blood helps to concentrate other more toxic waste products in urine by maintaining the osmotic balance between urine and blood in the renal medulla. The kidneys are able to control the volume of water in the body by changing the reabsorption of water by the tubules of the nephron.
Under normal conditions, the tubule cells of the nephron tubules reabsorb via osmosis nearly all of the water that is filtered into urine by the glomerulus. Water reabsorption leads to very concentrated urine and the conservation of water in the body. ADH stimulates the formation of water channel proteins in the collecting ducts of the nephrons that permit water to pass from urine into the tubule cells and on to the blood.
Hydrogen ions accumulate when proteins are metabolized in the liver and when carbon dioxide in the blood reacts with water to form carbonic acid H2CO3. Carbonic acid is a weak acid that partially dissociates in water to form hydrogen ions and bicarbonate ions. Both ions are filtered out of the blood in the glomerulus of the kidney, but the tubule cells lining the nephron selectively reabsorb bicarbonate ions while leaving hydrogen ions as a waste product in urine.
The tubule cells may also actively secrete additional hydrogen ions into the urine when the blood becomes extremely acidic. The reabsorbed bicarbonate ions enter the bloodstream where they can neutralize hydrogen ions by forming new molecules of carbonic acid. Carbonic acid passing through the capillaries of the lungs dissociates into carbon dioxide and water, allowing us to exhale the carbon dioxide. The kidneys maintain the homeostasis of important electrolytes by controlling their excretion into urine.
The kidneys help to control blood pressure in the body by regulating the excretion of sodium ions and water and by producing the enzyme renin.
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