Renal System

What are the three main functions of the excretory (renal) system?

Regulating electrolyte levels, regulating body water, and ridding the body of waste.

What are non-renal excretory organs in humans?

The skin (sweat with salts and urea) and the liver (waste processing and bilirubin excretion).

What are the main anatomical structures of the renal system?

Kidneys, renal artery and vein, ureter, urinary bladder, and urethra.

What are the three internal regions of the kidney?

Renal cortex, renal medulla, and renal pelvis.

What is a nephron?

The functional unit of the vertebrate kidney containing long convoluted tubes that extend through the cortex and medulla.

What are the four key excretory processes?

Filtration, reabsorption, secretion, and excretion.

What are the two major structural areas of a nephron?

Renal corpuscle and renal tubule.

What is the renal corpuscle?

The glomerulus surrounded by Bowman's capsule; the site of filtration.

What brings blood to the glomerulus?

Afferent arteriole.

What takes blood away from the glomerulus?

Efferent arteriole.

What are the three layers of the filtration membrane in the renal corpuscle?

Glomerulus cell walls, basement membrane, and podocytes.

What is the major limiting factor in filtration?

Size (larger molecules like proteins and blood cells cannot enter tubules; small molecules like water, electrolytes, glucose, and amino acids pass into filtrate).

What is filtrate?

The fluid and substances that pass the filtration membrane and enter the renal tubules.

What are the four anatomic segments of the renal tubule?

Proximal Convoluted Tubule (PCT), Loop of Henle, Distal Convoluted Tubule (DCT), and Collecting Duct.

What occurs in the Proximal Convoluted Tubule (PCT)?

Reabsorption of various ions, water, glucose, and amino acids; secretion of drugs, toxins, and urea.

What is the permeability of the descending loop of Henle?

Only permeable to water (reabsorbed via aquaporins, increasing filtrate concentration).

What is the permeability of the ascending loop of Henle?

Only permeable to salt (sodium and chloride are reabsorbed, decreasing filtrate concentration).

What is the vasa recta?

A network of blood vessels running alongside the loop of Henle that helps return substances back to the bloodstream.

What is the function of the Distal Convoluted Tubule (DCT)?

Further adjusts filtrate concentration via ion and water reabsorption and ion secretion.

What does the sodium-chloride cotransporter do in the DCT?

Moves sodium and chloride ions out of the tubule back into the blood; water follows.

What is the collecting duct?

The final segment of the nephron where reabsorption and secretion depend on hormone activity, leading to renal calyces.

What is the renal osmolarity gradient?

The concentration of salt in kidney tissues surrounding the nephron increases with depth (cortex is least concentrated, inner medulla is most concentrated).

What is the pathway of fluid leaving the kidney?

Renal cortex -> renal medulla -> renal calyx -> renal pelvis -> ureter -> bladder -> urethra.

What does Antidiuretic Hormone (ADH) / Vasopressin do?

Increases water reabsorption by inserting aquaporins into the DCT and collecting duct.

What does aldosterone do?

Increases sodium reabsorption in the DCT and collecting duct, leading to water retention, increased blood volume, and increased blood pressure.

What is the juxtaglomerular apparatus (JGA)?

Specialized kidney cells comprised of the macula densa and juxtaglomerular cells that monitor and adjust blood pressure and volume.

What does the macula densa monitor?

Sodium chloride concentration within the DCT tubule.

What do juxtaglomerular cells release when blood pressure is low?

Renin.

What is the Renin-Angiotensin-Aldosterone System (RAAS)?

A hormone cascade pathway regulating blood pressure and volume by increasing water and sodium reabsorption.

How do marine fish osmoregulate?

They live in hypertonic environments, constantly lose water, drink water to compensate, and rarely urinate.

How do freshwater fish osmoregulate?

They live in hypotonic environments, water constantly enters cells, they rarely drink, and they constantly urinate dilute urine.