The Urinary System

Function1. Remove nitrogenous wastes2. Maintain electrolyte, acid-base,

and fluid balance of blood3. Homeostatic organ4. Acts as blood filter5. Release hormones: calcitriol &

erythropoietin

Kidneys as Filters

• Diuretic- loose water; coffee, alcohol• Antidiuretic- retain water; ADH• Aldosterone- sodium & water reabsorption,

and K+ excretion• GFR= 180 liters (50 gal) of blood/day• 178-179 liters are reabsorbed back into

blood• Excrete a protein free filtrate

Organs of the

Urinary System

Organs of the

Urinary System

kidneys

ureters

urinary bladderurethra

A KidneyBlood and waste enter through renal artery

Filtered blood leaves through renal vein

Excess water and toxic waste leaves through ureter as urine

The Urinary System

General Functioning of the KidneyGeneral Functioning of the Kidney

Nitrogenous Wastes

Proteins

Amino acids

COOH -NH2

Ammonia Urea Uric Acid

ureter

Kidney AnatomyKidney Anatomy

renal cortex

renal pelvisrenal medulla

renal pyramids

renal capsule

nephron

renal cortex

renal medulla

Each kidney contains over 1 million nephrons and thousands of collecting ducts

Collecting duct

Loop of Henle

PCT

DCTGlomerulus

Glomerulus

To renal pelvis

Peritubular capillaries

Collecting duct

PCT

Loop of Henle

DCT

Glomerular FiltrationGlomerular Filtrationafferent arteriole glomerulus

efferent arteriole

Bowman’s capsule

Filters blood; proteins can’t pass through

Composition of Glomerular Filtrate• WaterWater• Small Soluble Organic Small Soluble Organic

MoleculesMolecules• Mineral IonsMineral Ions

Proximal Convoluted Tubule

Reabsorbs: water, glucose, Reabsorbs: water, glucose, amino acids, and sodium.amino acids, and sodium.

•65% of Na+ is reabsorbed•65% of H2O is reabsorbed

•90% of filtered bicarbonate (HCO3-)

•50% of Cl- and K+

Loop of Henle

Creates a gradient of increasing Creates a gradient of increasing sodium ion concentration towards sodium ion concentration towards the end of the loop within the the end of the loop within the interstitial fluid of the renal pyramid.interstitial fluid of the renal pyramid.

•25% Na+ is reabsorbed in the loop•15% water is reabsorbed in the loop•40% K is reabsorbed in the loop

Distal Convoluted Tubule

Under the influence of the hormone Under the influence of the hormone aldosterone, reabsorbs sodium and aldosterone, reabsorbs sodium and secretes potassium. Also regulates secretes potassium. Also regulates pH by secreting hydrogen ion when pH by secreting hydrogen ion when pH of the plasma is low.pH of the plasma is low.

• only 10% of the filtered NaCl and 20% of water remains

Collecting Duct

Allows for the osmotic Allows for the osmotic reabsorption of water.reabsorption of water.

ADH (antidiuretic hormone)- makes collecting ducts more permeable to water-- produce concentrated urine

From the original 1800 g NaCl, only 10 g appears in the urine

UrineWater- 95%Nitrogenous waste:

• urea• uric acid• creatinine

Ions:• sodium• potassium• sulfate• phosphate

Urinary BladderUrinary Bladder

ureters

internal sphincters

external sphincters

urethra

When bladder fills with 200 ml of urine, stretch receptors transmit impulses to the CNS and produce a reflex contraction of the bladder (PNS)

Diuresis (Micturition)

When is incontinence normal?

Why do doctors ask for a urine sample?       

Urinalysis

characteristics:• smell- ammonia-like• pH- 4.5-8, ave 6.0• specific gravity– more than 1.0;

~1.001-1.030 • color- affected by what we eat: salty

foods, vitamins

odor- normal is ammonia-like

diabetes mellitus- smells fruity or acetone like due to elevated ketone levels

diabetes insupidus- yucky

asparagus---

Odor

Color- pigment is urochromeYellow color due to metabolic breakdown of hemoglobin (by bile or bile pigments)

Beets or rhubarb- might give a urine pink or smoky color

Vitamins- vitamin C- bright yellowbright yellow

Infection- cloudy

Color

Water: s.g. = 1g/liter; Urine: s.g. ~ 1.001 to 1.030

Specific Gravity

When urine has high s.g.; form kidney stones

Diabetes insipidus- urine has low s.g.; drinks excessive water; injury or tumor in pituitary

pH- range 4.5-8 ave 6.0

vegetarian diet- urine is alkaline

protein rich and wheat diet- urine is acidic

Normal Constitutes of Urine

Normal Constitutes of Urine

 Glucose

Indicative of:• Excessive carbohydrate intake• Stress• Diabetes mellitus

Abnormal Constitutes of Urine

Albumin

Abnormal Constitutes of Urine

• Ketone

• RBC

• Hemoglobin

• Bile

• WBC

• Casts

Abnormal Constitutes of Urine

INQUIRY1. List several functions of the kidneys.2. What does the glomerulus do?3. What are several constitutes you should not

find in urine?4. What is specific gravity?5. What two hormones effect fluid volume and

sodium concentration in the urine?6. Where are the pyramids located in the

kidney?7. What vessel directs blood into the

glomerulus?8. Where does most selective reabsorption occur

in the nephron?

Moment of Zen