Excretory System and Nephron Quiz

The Excretory System

• Aims to maintain osmotic balance and remove metabolic wastes.
• Includes skin, liver, and lungs – but the main focus is on the kidneys.
• Kidneys filter blood and produce urine, which is waste products.
• Key organs of the urinary system: kidneys (2), bladder (1), ureters (2), urethra (1).

The Nephron

• Functional unit of the kidney.
• Contains a glomerulus (cluster of capillaries) surrounded by Bowman's capsule.
• Blood pressure forces fluid (filtrate) from glomerulus into Bowman's capsule.
• Filtrate contains water, glucose, amino acids, salts, ions, medications, vitamins, and urea.

Nephron Process

• Filtrate travels through the nephron, undergoing reabsorption and secretion.
• Reabsorption: substances move from filtrate back to interstitial fluid (surrounding the nephron).
• Secretion: substances move from interstitial fluid into the filtrate.
• Transport modes: diffusion, facilitated diffusion (passive, no ATP), and active transport (requires ATP).

Proximal Tubule

• Nearest the glomerulus.
• Reabsorption: NaCl, water, glucose, amino acids, potassium (K+), bicarbonate (HCO3-).
• Secretion: H+ ions and ammonium ions (NH4+).
• Important for pH regulation.

Loop of Henle

• Descending limb: aquaporins allow water reabsorption, NaCl remains in filtrate, solute concentration in filtrate increases.
• Ascending limb: thin segment – NaCl diffuses out, thick segment – NaCl actively transported out, filtrate becomes dilute.

Distal Convoluted Tubule

• Reabsorption: NaCl, water, bicarbonate.
• Secretion: H+, ammonium, potassium.
• Contributes to pH regulation.

Collecting Duct

• Filtrate becomes urine.
• NaCl and water reabsorption, regulated by hormones.
• Urea reabsorption by diffusion.
• Filtrate becomes concentrated, urine composition influenced by hydration levels.

Urine Excretion

• Urine from nephrons travels through ureters to the bladder, where it is stored.
• Urine is expelled from the body through the urethra.

Kidney Function and Conditions

• Kidneys play a critical role in maintaining osmotic balance and waste removal.
• Diuretics, medications that act on nephron osmoregulation, can be prescribed for high blood pressure, congestive heart failure, and other conditions.
• Kidney failure can require dialysis (hemodialysis or peritoneal dialysis) to filter blood and support osmoregulation.
• Nephrology is a specialized field focusing on kidney health and diseases.

Further Exploration

• Exploring the specific transport mechanisms used in the nephron.
• Learning about the hormonal control regulating nephron function and urine composition.

Test your knowledge on the excretory system and the nephron, the functional unit of the kidneys. This quiz covers the roles of the kidneys, the structure of the nephron, and the processes of reabsorption and secretion. Gain a better understanding of how the body maintains osmotic balance and eliminates waste.