Urinary System

Urinary system functions

Eliminates wastes, regulates water/electrolytes/pH, controls blood pressure, helps produce RBCs, activates vitamin D

Nitrogenous wastes

Waste products from protein and nucleic acid breakdown

Mammals excrete

Urea

Birds excrete

Uric acid

Fish excrete

Ammonia

Organs of urinary system

Kidneys, ureters, urinary bladder, urethra

Kidneys location

Retroperitoneal, between T12-L3 vertebrae

Why is right kidney lower?

Because of the liver

Renal cortex

Outer region of kidney

Renal medulla

Inner region of kidney

Renal pelvis

Urine collecting region

Renal capsule

Protective connective tissue covering

Renal hilus

Area where renal artery, vein, and ureter connect

Medullary pyramids

Triangular tissue regions in medulla

Renal columns

Extensions of cortex into medulla

Calyces

Funnel urine toward renal pelvis

Nephron

Structural and functional unit of kidney

Function of nephron

Forms urine

Main nephron structures

Glomerulus and renal tubule

Glomerulus

Specialized capillary bed for filtration

Afferent arteriole

Brings blood into glomerulus

Efferent arteriole

Carries blood away from glomerulus

Why is glomerular pressure high?

Afferent arteriole is wider than efferent arteriole

Glomerular capsule (Bowman’s capsule)

Surrounds glomerulus and collects filtrate

Renal tubule parts

Bowman’s capsule, PCT, Loop of Henle, DCT

Proximal convoluted tubule (PCT)

Site of most reabsorption

Loop of Henle

Helps concentrate urine

Distal convoluted tubule (DCT)

Adjusts ion balance and secretion

Cortical nephrons

Nephrons located mainly in cortex

Juxtamedullary nephrons

Nephrons near cortex-medulla border

Peritubular capillaries

Capillaries surrounding tubules for reabsorption and secretion

Four processes of urine formation

Filtration, reabsorption, secretion, excretion

Filtration

Water and small solutes move from blood into nephron

Where does filtration occur?

Glomerulus

What cannot pass through filtration membrane?

Blood cells and proteins

Filtrate

Fluid collected in Bowman’s capsule

Reabsorption

Movement of substances from tubule back into blood

Most reabsorption occurs where?

Proximal convoluted tubule

Substances reabsorbed

Water, glucose, amino acids, ions

Secretion

Movement of substances from blood into tubule

Substances secreted

Hydrogen ions, potassium ions, creatinine

Excretion

Removal of urine from body

Substances not normally reabsorbed

Urea, uric acid, creatinine, excess water

Normal urine color

Yellow due to urochrome

Normal urine pH

Around 6

Normal urine specific gravity

1.001–1.035

Substances NOT normally found in urine

Blood cells, glucose, large proteins

Ureters

Tubes carrying urine from kidneys to bladder

How do ureters move urine?

Peristalsis

Urinary bladder

Muscular sac that stores urine

Trigone

Three openings in bladder

Trigone openings

Two ureters and one urethra

Detrusor muscle

Smooth muscle of bladder wall

Rugae

Folds in empty bladder

Transitional epithelium

Stretchable bladder lining

Urethra

Tube carrying urine outside body

Internal urethral sphincter

Involuntary sphincter

External urethral sphincter

Voluntary sphincter

Female urethra length

3–4 cm

Male urethra length

About 20 cm

Male urethra function

Carries urine and sperm

Female urethra function

Carries urine only

Micturition

Urination/voiding

What triggers micturition?

Bladder stretching

ADH (antidiuretic hormone)

Hormone that reduces water loss in urine

Aldosterone

Hormone that increases sodium reabsorption

Normal blood pH range

7.35–7.45

Main organ maintaining acid-base balance

Kidneys

Tests of kidney function

Blood electrolytes, creatinine, BUN, GFR, urinalysis

BUN

Blood urea nitrogen

GFR

Glomerular filtration rate

Horseshoe kidney

Kidneys fused during development

Benign prostatic hypertrophy (BPH)

Enlarged prostate causing urinary retention

Stress urinary incontinence

Urine leakage during coughing/laughing

Kidney failure

Loss of kidney function

Oliguria

Low urine output

Anuria

No urine output

Symptoms of kidney failure

Weakness, confusion, edema, arrhythmias

Hemodialysis

Machine filters wastes from blood

Kidney transplant

Surgical replacement of kidney

Polycystic kidney disease

Genetic disorder causing kidney cysts and failure

Pyelonephritis

Bacterial kidney infection

Kidney stones (renal calculi)

Crystals forming in renal pelvis

Lithotripsy

Shock wave treatment to break kidney stones

Cystitis

Bladder infection/UTI

UTI

Urinary tract infection

Urine pathway

Kidney → ureter → bladder → urethra

Nephron pathway

Glomerulus → Bowman’s capsule → PCT → Loop of Henle → DCT