Urinary System Review – Nephron, Filtration, and GFR Regulation

A set of study flashcards covering kidney anatomy, nephron structure, filtration processes, tubular reabsorption/secretion, GFR, and hormonal regulation of renal function.

What are the organs of the urinary system?

Kidneys, ureters, urinary bladder, and urethra.

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

Filter blood to remove waste, regulate pH, and maintain fluid and electrolyte balance; also produce hormones like EPO and calcitriol.

Which hormones do the kidneys produce and what are their roles?

Erythropoietin (stimulates red blood cell production) and calcitriol (active vitamin D, increases intestinal calcium absorption).

What is the nephron?

The functional unit of the kidney.

What are the two main parts of the nephron?

The Glomerulus (filtration site) and the tubular system (reabsorption and secretion).

What is the order of filtrate flow through the nephron?

Bowman's capsule → proximal convoluted tubule → Loop of Henle (descending and ascending limbs) → distal convoluted tubule → collecting duct.

What is glomerular filtration?

The process by which blood plasma is filtered from glomerular capillaries into Bowman's capsule to form filtrate.

What forces drive glomerular filtration?

Glomerular hydrostatic pressure pushes fluid into Bowman's capsule; capsular hydrostatic pressure and blood colloid osmotic pressure oppose filtration.

What is tubular reabsorption?

Movement of water, glucose, amino acids, and ions from the tubular fluid back into the blood.

What is tubular secretion?

Movement of waste products (e.g., H+, K+) from blood into the tubular fluid to be excreted; helps regulate pH.

What does GFR stand for and what does it measure?

Glomerular Filtration Rate; the volume of filtrate produced per minute.

What happens if GFR is too low or too high?

Too low: waste products build up; too high: nutrients and wastes may be lost in urine.

What is renal autoregulation of GFR?

Local mechanisms (myogenic and metabolic) that keep GFR relatively constant despite BP changes.

How does Angiotensin II affect GFR?

Constricts the efferent arteriole to maintain GFR when blood pressure is low.

How does ANP (atrial natriuretic peptide) affect GFR?

Dilates the afferent arteriole and constricts the efferent arteriole to increase GFR and promote fluid excretion.

How does sympathetic stimulation affect GFR?

Constricts the afferent arteriole, lowering GFR during stress or blood loss.

What is the role of calcitriol in calcium absorption?

Calcitriol (active vitamin D) increases intestinal calcium absorption.

Which structures transport urine from the kidneys to the bladder?

Ureters.

What is the function of the urinary bladder?

Stores urine until it is voided.

What is the role of the urethra?

Excretes urine from the bladder to the outside of the body.

What is the impact of plasma proteins on filtration?

Plasma protein–generated oncotic (osmotic) pressure opposes filtration by pulling fluid back into the capillaries.