The Renal System Quiz

Primary Functions of the Kidneys

• Main role is to filter blood and reclaim most water and solutes for the body.
• Kidneys also produce hormones but this is secondary to their filtering capacity.

Urinary Structures

• Ureter carries urine from the kidneys to the bladder.
• Urethra dispels urine from the bladder to the outside.

Anatomy of the Kidney

• Kidneys are bean-shaped and approximately the size of a fist (around 11 cm long).
• Located behind the peritoneum on the posterior abdominal wall.

Internal Anatomy of the Kidney

• Medulla contains cone-shaped structures known as renal pyramids.
• Renal pelvis functions to drain urine from the kidney into the ureter.

Nephron

• The nephron is the kidney's structural and functional unit.
• Renal corpuscle within the nephron is responsible for the filtration of plasma.
• 85% of nephrons in the kidneys are classified as cortical nephrons.
• Renal tubules handle reabsorption and secretion processes.

Hormonal Functions of the Kidneys

• Erythropoietin, produced by the kidneys, stimulates the formation of red blood cells (hemopoiesis).
• Average Glomerular Filtration Rate (GFR) is about 125 ml/min.
• Calcitriol, a hormone, aids in calcium reabsorption in the kidneys.

Micturition Reflex

• Stretch receptors in the bladder wall are activated by urine filling the bladder.
• The pons and cerebrum increase conscious awareness of the need to urinate.
• External urethral sphincter is controlled by skeletal muscle, allowing voluntary control over urination.

Glomerular Filtration Rate

• High GFR can lead to loss of beneficial substances due to rapid fluid passage through nephrons.
• GFR is kept constant through autoregulation via the juxtaglomerular apparatus.

Tubular Reabsorption

• Around 99.5% of the nephron filtrate is reabsorbed back into the body.
• Proximal convoluted tubule (PCT) is primarily responsible for reabsorption operations.
• ADH (antidiuretic hormone) regulates water reabsorption in the distal convoluted tubule (DCT).

Tubular Secretion

• The distal convoluted tubule (DCT) is most active in the secretion process.
• Secretion of H+ ions helps to control blood pH in the nephron.

Loop of Henle

• The Loop of Henle establishes a salt gradient in the medulla, crucial for concentrating urine.
• Juxtamedullary nephrons feature long Loops of Henle facilitating this gradient.

Juxtaglomerular Apparatus (JGA)

• Juxtaglomerular cells monitor blood pressure, playing a key role in renal regulation.
• Macula densa cells detect changes in filtrate flow, adjusting nephron function accordingly.

Collecting Duct

• Aldosterone controls Na+ reabsorption in the collecting duct, influencing blood pressure and volume.
• Collecting ducts empty urine into papillary ducts, leading toward the urinary bladder.

Miscellaneous Functions

• The renal capsule surrounds and protects the kidneys, providing vital structural support.