Nephron Tubules

The tubular portion of a nephron consists of a glomerular capsule, a proximal convoluted tubule, a descending limb of the loop of Henle, an ascending limb of the loop of Henle, and a distal convoluted tubule (fig. 17.5).

The glomerular (Bowman's) capsule surrounds the glomerulus. The glomerular capsule and its associated glomerulus are located in the cortex of the kidney and together constitute the renal corpuscle. The glomerular capsule contains an inner visceral layer of epithelium around the glomeru-lar capillaries and an outer parietal layer. The space between these two layers is continuous with the lumen of the tubule and receives the glomerular filtrate, as will be described in the next section.

Filtrate that enters the glomerular capsule passes into the lumen of the proximal convoluted tubule. The wall of the proximal convoluted tubule consists of a single layer of cuboidal cells containing millions of microvilli; these microvilli increase the surface area for reabsorption. In the process of reabsorption, salt, water, and other molecules needed by the body are transported from the lumen, through the tubular cells and into the surrounding peritubular capillaries.

The glomerulus, glomerular capsule, and convoluted tubule are located in the renal cortex. Fluid passes from the proximal convoluted tubule to the loop of Henle. This fluid is carried into the medulla in the descending limb of the loop and returns to the cortex in the ascending limb of the loop. Back in the cortex, the tubule again becomes coiled and is called the distal convoluted tubule. The distal convoluted tubule is shorter than the proximal tubule and has relatively few mi-crovilli. The distal convoluted tubule terminates as it empties into a collecting duct.

The two principal types of nephrons are classified according to their position in the kidney and the lengths of their loops of Henle. Nephrons that originate in the inner one-third of the cortex—called juxtamedullary nephrons because they are

Physiology of the Kidneys

Physiology of the Kidneys

Venous Drainage Renal Cortex

Ureter

Interlobular artery and vein

Renal cortex

Arcuate artery and vein

Renal medulla

Interlobar artery and vein

Renal artery

Renal pelvis

Renal vein

Ureter

Interlobular artery and vein

Electron Micrographs Ureter

■ Figure 17.4 The vascular structure of the kidneys. (a) An illustration of the major arterial supply and (b) a scanning electron micrograph of a glomerulus (300x),

Glomerulus Glomerular capsule

Efferent arteriole Afferent arteriole

Peritubular capillaries

Distal convoluted tubule

Peritubular capillaries

Distal convoluted tubule

Nephrons Efferent And Afferent

Interlobular vein

Collecting duct

Interlobar artery and vein

Interlobar artery and vein

Interlobular vein

Collecting duct

■ Figure 17.5 The nephron tubules and associated blood vessels. In this simplified illustration, the blood flow from a glomerulus to an efferent arteriole, to the peritubular capillaries, and to the venous drainage of the kidneys is indicated with arrows. The names for the different regions of the nephron tubules are indicated with boldface type.

528 Chapter Seventeen

Glomerular Capillaries Nephron Tubules

■ Figure 17.6 The contents of a renal pyramid. (a) The position of cortical and juxtamedullary nephrons is shown within the renal pyramid of the kidney. (b) The direction of blood flow in the vessels of the nephron is indicated with arrows.

next to the medulla—have longer loops of Henle than the more numerous cortical nephrons, which originate in the outer two-thirds of the cortex (fig. 17.6). The juxtamedullary nephrons play an important role in the ability of the kidney to produce a concentrated urine.

A collecting duct receives fluid from the distal convoluted tubules of several nephrons. Fluid is then drained by the collecting duct from the cortex to the medulla as the collecting duct passes through a renal pyramid. This fluid, now called urine, passes into a minor calyx. Urine is then funneled through the renal pelvis and out of the kidney in the ureter.

Polycystic kidney disease is a condition inherited as an autosomal dominant trait (see chapter 20) that affects 1 in every 600 to 1,000 people. This disease is thus more common than sickle-cell anemia, cystic fibrosis, or muscular dystrophy, which are also genetic diseases. In 50% of the people who inherit the defective gene (located on the short arm of chromosome 16), progressive renal failure develops during middle age to the point that dialysis or kidney transplants are required. The cysts that develop are expanded portions of the renal tubule. Cysts that originate in the proximal tubule contain fluid that resembles glomerular filtrate and plasma. Cysts that originate in the distal tubule contain fluid with a lower NaCl concentration and a higher potassium and urea concentration than plasma as a result of the transport processes that occur during the passage of fluid through the tubules.

Test Yourself Before You Continue

1. Describe the "theme" of kidney function in a single sentence. List the components of this functional theme.

2. Trace the course of blood flow through the kidney from the renal artery to the renal vein.

3. Trace the course of tubular fluid from the glomerular capsules to the ureter.

4. Draw a diagram of the tubular component of a nephron. Label the segments and indicate which parts are in the cortex and which are in the medulla.

Physiology of the Kidneys

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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Responses

  • tanja
    What is the function of the afferent arteriole?
    6 years ago
  • Mewael
    Where are the interlobar artery interlobar vein in the nephron?
    6 years ago
  • johanna
    What are the 2 types of tubules in nephron?
    6 years ago
  • martyna
    Where is the arcuate artery and the arcuate vein located in the nephron of the kidney?
    6 years ago
  • BISRAT
    Why pct dominant in renal cortex?
    6 years ago
  • BERND
    What are nephrons called in the cortex?
    6 years ago
  • elaine
    What is the kidney duct that receives fluid from nephrons?
    6 years ago
  • Aatifa
    Is the glomerulus a descending nephron?
    5 years ago
  • camelia smallburrow
    Where is the renal vein located in a nephron?
    5 years ago
  • Everard
    Which fluid passes proximal convoluted tubule?
    5 years ago
  • napoleone
    What capillaries surround the tubules of the nephron?
    5 years ago
  • Mike
    What are the capillaries around the nephron tubules called?
    5 years ago
  • Paul Moeller
    Where is the interlobular artery located on structure?
    5 years ago
  • Birgit
    What are the blood vessels around the renal tubules?
    5 years ago
  • uwe
    Are interlobular arteries smaller than interlobar?
    5 years ago
  • AGATA
    What color are the capillaries in the peritubular?
    5 years ago
  • SUSANNA
    What portion of the renal tubule lies between the glomerular capsule and loop of Henle?
    5 years ago
  • ville-veik kauniainen
    Where are glomerular capilliaries?
    5 years ago
  • emory
    How renal tubule and collecting docts produce concentrated urine?
    5 years ago
  • Sienna
    Where is the cortical nephron?
    5 years ago
  • hietam
    What three structures are located in the renal pyramids?
    5 years ago
  • monika
    Where is the distal convoluted tubule located?
    5 years ago
  • peter
    Where In The Kidney Are Nephrons cortex?
    5 years ago
  • Manfredo
    Why are blood vessels twisted around proximal tubule?
    5 years ago
  • semolina
    Are peritubular capillaries located in the glomerular capsule?
    5 years ago
  • senay
    Which organ receives fluid from several nephrons?
    5 years ago
  • winta
    What are the capillaries that surround the tubule portion of the nephron?
    5 years ago
  • SAKU
    WHAT SURROUNDS THE TUBULAR PORTION OF THE NEPHRON?
    5 years ago
  • chilimanzar
    Where is the nephron loop located?
    5 years ago
  • violante
    What are the blood vessels of a nephron?
    5 years ago
  • rocco milano
    What are the capillaries that surround the proximal tubules?
    5 years ago
  • RUBY RUMBLE
    What is the effect of nephron tubules inability to concentrate urine?
    5 years ago
  • leroy
    WHAT CAPILLARIES SURROUND THE CORTICAL NEPHRON?
    4 years ago
  • kirstie
    WHERE IS THE PROXIMAL CONVOLUTED TUBULE LOCATED?
    4 years ago
  • Elanor
    What nephron surrounds glomerulus?
    4 years ago
  • Welde
    What blood vessels surround the renal tubule?
    4 years ago
  • ELEN
    What is the order of fluid flow through a juxtamedullary nephron.?
    4 years ago
  • Victoria
    Are peritubular capillaries around the nephron loop?
    4 years ago
  • Wegahta
    What is the physiology of the renal tubule?
    4 years ago
  • paula
    What are the principal portions of the nephon?
    4 years ago
  • Luke
    What surrounds the tubules of a nephron?
    4 years ago
  • kristian
    Do interlobar arteries surround the cortical nephron?
    4 years ago
  • scudamor
    Where are glomeruli and nephron tubules located?
    3 years ago
  • kristel
    What surrounds the distal convoluted.tubule?
    3 years ago
  • abraham
    Do peritubular capillaries surround the distal convoluted tubule?
    3 years ago
  • Fedro
    Is the glomerular capsule located within the renal medulla or the renal cortex?
    3 years ago
  • GOLDILOCKS
    Is the ascending nephron loop in the renal cortex or renal medulla?
    3 years ago
  • gustava
    What area recieves fluid from multiple tubules in the nephron?
    3 years ago
  • FRE-QALSI
    What is the fluid in the glomerular capsule and renal tubules is called?
    2 years ago
  • Semere
    What capillaries surround the proximal convoluted tubule?
    2 years ago
  • Daisy
    How is the fluid passes through of the glomerulus to the collecting duct?
    2 years ago
  • Yonas
    How is the course of tubular fluid from the glomerular capsule to the ureter?
    2 years ago
  • julia
    What surround and protect the renal tubules?
    2 years ago
  • fatima
    What is the function of blood capillaries surrounding the nephron?
    2 months ago

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