The Urinary System Why how is urine used

The Urinary System

Why / how is urine used to determine if individuals have various disorders?

The Kidneys • Kidneys play a key role in removing waste, balancing blood p. H and maintaining water balance.

Metabolic Wastes Waste Origin of Waste Organ of Excretion Ammonia Deamination of a. a. by liver Urea Uric Acid Two ammonia combine with CO 2 Byproduct of nucleic acid breakdown (e. g. , DNA) kidneys

The Kidneys… • Each kidney has a mass of 150 g and are the size of your fist. • They hold 25% of the body’s blood. • They filter 200 L of fluid each day!

The Urinary System • Wastes filtered by the kidneys travel along the ureters to the urinary bladder. • A urinary sphincter is found at the base of the bladder. – Upon relaxation, urine enters the urethra and it is voided.

The Urinary System

Bladder Capacity • 200 ml: stretch receptors send impulses to the brain; urge to urinate. • 400 ml: more receptors activated & higher frequency of impulses; feeling of urination more urgent. • 600 ml: voluntary control is lost; micturition reflex occurs.

The 3 Regions of the Kidney • Renal Cortex • Renal Medulla • Renal Pelvis

Nephrons • Over 1 million per kidney. • The smallest functional units of the kidneys.

Nephrons • Afferent arterioles from the renal artery branch into a capillary bed (glomerulus). – Supplies the nephrons with blood. • Blood leaves via efferent arterioles that form the peritubular capillaries that wrap around the nephron.

Nephrons • Bowman’s capsule surrounds the glomerulus. • Water and other solutes filter into the Bowman’s capsule.

Nephrons • The capsule tapers off into the proximal tubule. • Carries the filtrate to the loop of Henle. • Filtrate passes through the distal tubule and then the collecting ducts. • The collecting ducts collect urine from many nephrons, which merge in the renal pelvis.