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Nephrons have two lengths with different urine-concentrating capacities: long juxtamedullary nephrons and short cortical nephrons. The four mechanisms used to create and process the filtrate (the result of which is to convert blood to urine) are filtration, reabsorption, secretion and excretion.
The collecting duct system of the kidney consists of a series of tubules and ducts that physically connect nephrons to a minor calyx or directly to the renal pelvis.The collecting duct participates in electrolyte and fluid balance through reabsorption and excretion, processes regulated by the hormones aldosterone and vasopressin (antidiuretic hormone).
Nephrons, the urine-producing functional structures of the kidney, span the cortex and medulla. The initial filtering portion of a nephron is the renal corpuscle , which is located in the cortex. This is followed by a renal tubule that passes from the cortex deep into the medullary pyramids.
Conditions involving low output of urine are oliguria (< 400 mL/day) and anuria (< 100 mL/day). The first step in urine formation is the filtration of blood in the kidneys. In a healthy human, the kidney receives between 12 and 30% of cardiac output, but it averages about 20% or about 1.25 L/min.
The nephrons of the mammalian kidneys have loops of Henle, which are the most efficient way to reabsorb water and produce concentrated urine to conserve water in the body. [12] The mammalian kidneys combine both nephrons with a short and nephrons with a long loop of Henle. [77] The medulla is divided into outer and inner regions.
For example, mountain beavers have only nephrons with a short loop, and, accordingly, there is no inner medulla in the kidneys and their ability to concentrate urine is low. Dogs and cats , on the other hand, have only long-loop nephrons with an average ability to concentrate urine.
Bowman's capsule (or the Bowman capsule, capsula glomeruli, or glomerular capsule) is a cup-like sac at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form urine. A glomerulus is enclosed in the sac. Fluids from blood in the glomerulus are collected in the ...
The pyramids appear striped because they are formed by straight parallel segments of nephrons' Loops of Henle and collecting ducts. The base of each pyramid originates at the corticomedullary border and the apex terminates in a papilla, which lies within a minor calyx, made of parallel bundles of urine collecting tubules.