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Both hormones exert their effects principally on the collecting ducts. Tubular secretion occurs simultaneously during re-absorption of filtrate. Substances, generally produced by body or the by-products of cell metabolism that can become toxic in high concentration, and some drugs (if taken). These all are secreted into the lumen of renal tubule.
The urinary system refers to the structures that produce and transport urine to the point of excretion. In the human urinary system there are two kidneys that are located between the dorsal body wall and parietal peritoneum on both the left and right sides. The formation of urine begins within the functional unit of the kidney, the nephrons.
The kidney participates in whole-body homeostasis, regulating acid–base balance, electrolyte concentrations, extracellular fluid volume, and blood pressure. The kidney accomplishes these homeostatic functions both independently and in concert with other organs, particularly those of the endocrine system.
Mammalian kidneys are susceptible to ischemic injury because mammals lack a renal-portal system, and as a result, vascular vasoconstriction in the glomeruli can lead to decreased blood supply to the entire kidney. The kidneys are susceptible to toxic injury, since toxins are reabsorbed in the tubules along with most of the filtered substances. [47]
The kidney has many functions, which a well-functioning kidney realizes by filtering blood in a process known as glomerular filtration. A major measure of kidney function is the glomerular filtration rate (GFR). The glomerular filtration rate is the flow rate of filtered fluid through the kidney.
The renal arteries are paired arteries that supply the kidneys with blood. Each is directed across the crus of the diaphragm, so as to form nearly a right angle. The renal arteries carry a large portion of total blood flow to the kidneys. Up to a third of total cardiac output can pass through the renal arteries to be filtered by the kidneys.
A partial nephrectomy should be attempted when there is a kidney tumor in a solitary kidney, when there are kidney tumors in both kidneys, or when removing the entire kidney could result in kidney failure and the need for dialysis. Partial nephrectomy is also the standard of care for nearly all patients with small renal masses (<4 cm in size). [22]
The nephron is the functional unit of the kidney. [3] This means that each separate nephron is where the main work of the kidney is performed. A nephron is made of two parts: a renal corpuscle, which is the initial filtering component, and; a renal tubule that processes and carries away the filtered fluid. [4]: 1024