The nephron consists of the renal corpuscle and a tubule system
As stated above, the renal corpuscle represents the beginning of the nephron. It consists of the glomerulus, a tuft of capillaries composed of 10 to 20 capillary loops, surrounded by a double-layered epithelial cup, the renal or Bowman's capsule. Bowman's capsule is the initial portion of the nephron where blood flowing through the glomerular capillaries undergoes filtration to produce the glomerular ultrafiltrate. The glomerular capillaries are supplied by an afferent arteriole and are drained by an efferent arteriole that then branches, forming a new capillary network to supply the kidney tubules. The site where the afferent and efferent arterioles penetrate and exit from the parietal layer of Bowman's capsule is called the vascular pole. Opposite this site is the urinary pole of the renal corpuscle, where the proximal convoluted tubule begins (see Fig. 19.6).
Continuing from Bowman's capsule, the remaining parts of the nephron (the tubular parts) are
• Proximal thick segment, consisting of the proximal convoluted tubule (pars convoluta) and the proximal straight tubule (pars recta)
• Thin segment, which constitutes the thin part of the loop of Henle
• Distal thick segment, consisting of the distal straight tubule (pars recta) and the distal convoluted tubule (pars convoluta)
The distal convoluted tubule connects to the collecting tubule, often through a connecting tubule, thus forming the uriniferous tubule, i.e., the nephron plus collecting tubule (see Fig. 19.3).
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