The<unk>  can be divided into four parts: *Thin descending limb of<unk>  :The thin descending limb has low permeability to ions and urea while being highly permeable to water. The<unk>  has a sharp bend in the renal medulla going from descending to ascending thin limb. *Thin ascending limb of<unk>  :The thin ascending limb is impermeable to water, but it is permeable to ions. *Ascending limb of<unk>  :Sodium (Na+), potassium (K+) and chloride (Cl−) ions are reabsorbed from the urine by secondary active transport by a Na-K-Cl cotransporter (NKCC2). The electrical and concentration gradient drives more reabsorption of Na+, as well as other cations such as magnesium (Mg2+) and calcium (Ca2+). *Cortical thick ascending limb :The cortical thick ascending limb drains urine into the distal convoluted tubule. The tissue type of the<unk>  is simple squamous epithelium. The "thick" and "thin" terminology does not refer to the size of the lumen, but to the size of the epithelial cells. The<unk>  is also sometimes called the Nephron<unk> . Blood supply Counter current multiplier diagram The<unk>  is supplied by blood in a series of straight capillaries descending from the cortical efferent arterioles. These capillaries (called the vasa recta; recta is from the Latin for "straight") also have a countercurrent multiplier mechanism that prevents washout of solutes from the medulla, thereby maintaining the medullary concentration. As water is osmotically driven from the descending limb into the interstitium, it readily enters the capillaries. The low bloodflow through the vasa recta allows time for osmotic equilibration, and can be altered by changing the resistance of the vessels' efferent arterioles. As well, blood in the vasa recta still has large proteins and ions which were not filtered through the glomerulus. This provides an oncotic pressure for ions to enter the vasa recta from the interstitium. The main function of the<unk>  is to set up a concentration gradient.
Loop of Henle
Crypts of Henle
Glomerular basement membrane
Adrenal cortex
Bowman's capsule
Reticuloendothelial system
Reticular membrane
Node of Ranvier