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Art connection

The kidney is shaped like a kidney bean standing on end. Two layers, the outer renal fascia and an inner capsule, cover the outside of the kidney. The inside of the kidney consists of three layers: the outer cortex, the middle medulla and the inner renal pelvis. The renal pelvis is flush with the concave side of the kidney, and empties into the ureter, a tube that runs down outside the concave side of the kidney. Nine renal pyramids are embedded in the medulla, which is the thickest kidney layer. Each renal pyramid is teardrop-shaped, with the narrow end facing the renal pelvis. The renal artery and renal vein enter the concave part of the kidney, just above the ureter. The renal artery and renal vein branch into arterioles and venuoles, respectively, which extend into the kidney and branch into capillaries in the cortex.
The internal structure of the kidney is shown. (credit: modification of work by NCI)

Which of the following statements about the kidney is false?

  1. The renal pelvis drains into the ureter.
  2. The renal pyramids are in the medulla.
  3. The cortex covers the capsule.
  4. Nephrons are in the renal cortex.

Because the kidney filters blood, its network of blood vessels is an important component of its structure and function. The arteries, veins, and nerves that supply the kidney enter and exit at the renal hilum. Renal blood supply starts with the branching of the aorta into the renal arteries (which are each named based on the region of the kidney they pass through) and ends with the exiting of the renal veins to join the inferior vena cava    . The renal arteries split into several segmental arteries upon entering the kidneys. Each segmental artery splits further into several interlobar arteries and enters the renal columns, which supply the renal lobes. The interlobar arteries split at the junction of the renal cortex and medulla to form the arcuate arteries . The arcuate “bow shaped” arteries form arcs along the base of the medullary pyramids. Cortical radiate arteries , as the name suggests, radiate out from the arcuate arteries. The cortical radiate arteries branch into numerous afferent arterioles, and then enter the capillaries supplying the nephrons. Veins trace the path of the arteries and have similar names, except there are no segmental veins.

As mentioned previously, the functional unit of the kidney is the nephron, illustrated in [link] . Each kidney is made up of over one million nephrons that dot the renal cortex, giving it a granular appearance when sectioned sagittally. There are two types of nephrons— cortical nephrons (85 percent), which are deep in the renal cortex, and juxtamedullary nephrons (15 percent), which lie in the renal cortex close to the renal medulla. A nephron consists of three parts—a renal corpuscle    , a renal tubule    , and the associated capillary network, which originates from the cortical radiate arteries.

Art connection

Illustration shows the nephron, a tube-like structure that begins in the kidney cortex. Here, arterioles converge in a bulb-like structure called the glomerulus, which is partly surrounded by a Bowman’s capsule. Afferent arterioles enter the glomerulus, and efferent arterioles leave. The glomerulus empties into the proximal convoluted tubule. A long loop, called the loop of Henle, extends from the proximal convoluted tubule to the inner medulla of the kidney, and then back out to the cortex. There, the loop of Henle joins a distal convoluted tubule. The distal convoluted tubule joins a collecting duct, which travels from the medulla back into the cortex, toward the center of the kidney. Eventually, the contents of the renal pyramid empty into the renal pelvis, and then the ureter.
The nephron is the functional unit of the kidney. The glomerulus and convoluted tubules are located in the kidney cortex, while collecting ducts are located in the pyramids of the medulla. (credit: modification of work by NIDDK)

Which of the following statements about the nephron is false?

  1. The collecting duct empties into the distal convoluted tubule.
  2. The Bowman’s capsule surrounds the glomerulus.
  3. The loop of Henle is between the proximal and distal convoluted tubules.
  4. The loop of Henle empties into the distal convoluted tubule.

Renal corpuscle

The renal corpuscle, located in the renal cortex, is made up of a network of capillaries known as the glomerulus    and the capsule, a cup-shaped chamber that surrounds it, called the glomerular or Bowman's capsule    .

Renal tubule

The renal tubule is a long and convoluted structure that emerges from the glomerulus and can be divided into three parts based on function. The first part is called the proximal convoluted tubule (PCT)    due to its proximity to the glomerulus; it stays in the renal cortex. The second part is called the loop of Henle    , or nephritic loop, because it forms a loop (with descending and ascending limbs ) that goes through the renal medulla. The third part of the renal tubule is called the distal convoluted tubule (DCT)    and this part is also restricted to the renal cortex. The DCT, which is the last part of the nephron, connects and empties its contents into collecting ducts that line the medullary pyramids. The collecting ducts amass contents from multiple nephrons and fuse together as they enter the papillae of the renal medulla.

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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