Renal System

• What is the primary function of the kidneys in the urinary system?

  The kidneys do the major work of the urinary system.
• How do the kidneys help in the excretion of wastes?

  By forming urine, the kidneys help excrete wastes from the body.
• What types of wastes are excreted in urine?

  Wastes include nitrogenous wastes like urea and ammonia from amino acid deamination.
• What are some examples of foreign substances excreted in urine?

  Drugs and environmental toxins.
• How do the kidneys regulate blood ionic composition?

  By adjusting the amounts of ions excreted into the urine.
• Which ions are most importantly regulated by the kidneys?

  Sodium ions (Na+), potassium ions (K+), calcium ions (Ca2+), chloride ions (Cl−), and phosphate ions (HPO4 2−).
• What role do the kidneys play in regulating blood pH?

  The kidneys excrete hydrogen ions (H+) and conserve bicarbonate ions (HCO3 −).
• How do the kidneys regulate blood volume?

  By conserving or eliminating water in the urine.
• What effect does an increase in blood volume have on blood pressure?

  An increase in blood volume increases blood pressure.
• How do the kidneys help regulate blood pressure?

  By secreting the enzyme renin.
• What hormone do the kidneys produce to help regulate calcium homeostasis?

  Calcitriol, the active form of vitamin D.
• What is the role of erythropoietin produced by the kidneys?

  It stimulates the production of red blood cells.
• What is the typical size of an adult kidney?

  10–12 cm long, 5–7 cm wide, and 3 cm thick.
• Where does the concave medial border of each kidney face?

  The concave medial border faces the vertebral column.
• What is the indentation called that is located near the center of the concave border of each kidney?

  The renal hilum.
• What are the two distinct regions revealed in a frontal section through the kidney?

  The renal cortex and the renal medulla.
• What shape do the renal pyramids have?

  They are cone-shaped.
• What are the microscopic filtering units of the kidneys called?

  Nephrons.
• What happens to the filtrate formed by the nephrons?

  It drains into large papillary ducts.
• What happens to the filtrate once it enters the calyces?

  It becomes urine because no further reabsorption can occur.
• What percentage of the resting cardiac output do the kidneys receive?

  20–25%.
• What is the renal blood flow in adults?

  About 1200 mL per minute.
• What do segmental arteries supply in the kidneys?

  Different segments (areas) of the kidney.
• What are the interlobar arteries known as at the bases of the renal pyramids?

  Arcuate arteries.
• What do afferent arterioles carry towards in the nephron?

  Toward the glomerulus.
• Why are glomerular capillaries unique among capillaries in the body?

  They are positioned between two arterioles.
• What are the two parts of a nephron?

  A renal corpuscle and a renal tubule.
• What surrounds the glomerular capillaries?

  The glomerular capsule or Bowman’s capsule.
• What are the three main sections of the renal tubule?

  Proximal convoluted tubule (PCT), nephron loop, and distal convoluted tubule (DCT).
• Where do the renal corpuscle and both convoluted tubules lie?

  Within the renal cortex.
• What do collecting ducts converge into?

  Several hundred large papillary ducts.
• What is the second basic function of the nephron and collecting duct?

  Reabsorption, the return of most filtered water and solutes to the bloodstream.
• What percentage of filtered water is normally reabsorbed?

  About 99%.
• Which cells make the largest contribution to reabsorption in the nephron?

  Proximal convoluted tubule cells.
• What solutes are reabsorbed by the nephron?

  Glucose, amino acids, urea, and ions such as Na+, K+, Ca2+, Cl−, HCO3 −, and HPO4 2−.
• What is the largest amount of solute and water reabsorption that occurs in the nephron?

  In the proximal convoluted tubules.
• What percentage of filtered water, Na+, and K+ is reabsorbed in the proximal convoluted tubules?

  65%.
• What substances are secreted by the proximal convoluted tubules?

  Hydrogen ions (H+), ammonium ions (NH4 +), and urea.
• What happens to small proteins and peptides that pass through the filter?

  They are usually reabsorbed via pinocytosis.
• What is tubular secretion?

  The transfer of materials from the blood and tubule cells into glomerular filtrate.