Urinary/Excretory System

• Urinary System

(Excretory System)

Inferior vena cava

Descending aorta

Renal veinRenal artery

Right kidney

Left kidney

Ureter Ureter

Bladder

Urethra

Adrenal gland

Urinary System• Organs

– Kidneys (primary excretory organ)– Ureters– Bladder– Urethra

• Functions– Remove nitrogenous waste product of protein

metabolism and other harmful substances– Eliminates them in the form of ammonia, uric acid or

urea– Eliminates controlled amounts of water and salts to

maintain the internal environment **Function is NOT to make urineFunction is to maintain homeostasis of blood (excrete wastes, absorb

nutrients, maintain electrolytes, pH balance)

Rugae

Sends blood to arterioles

Receives 15-20%of systemic bloodat rest

NephronFunctional Unit of Kidney

Afferentarteriole

Efferentarteriole

Renal Corpuscle

Glomerulus

Renal papilla

Nephron• Up to 1 million in kidney• Functions

– Filtration• removes dissolved substances from glomerulus

(blood supply)• what remains is called the filtrate

– Reabsorption• Substances from filtrate leave nephron• Reabsorb from tubule into blood or interstitial fluid

– Secretion• Releases substances from blood supply or

interstitial fluid into tubule• (opposite direction from reabsorption)

Filtration• Blood pressure forces water and dissolved

substances out of the glomerulus blood into Bowman’s capsule

• Dissolved substances (filtrate): H2O, glucose, amino acids, electrolytes, and wastes (no proteins or cells)

• Averages 125 ml/min for both kidneys (180 liters/day)

• The vast majority of the filtrate (99%) must be taken back to body’s blood supply.

• Urinate (wastes) on avg. 1500 ml/day (0.4 gallons)

Reabsorption

• The return of substances from filtrate in the nephron tubule to the blood or interstitial fluid

• Major Substances:– H2O - osmosis– NaCl - active transport– Glucose, amino acids - active co-transport– Some urea and other salts

• PCT – most reabsorption• Descending loop – reabsorb H2O• Ascending loop & DCT – reabsorbs salt• Collecting duct – reabsorbs H2O

Secretion• The active release of substances INTO the nephron tubule.• Purposes:

– Secreted Substances: toxins and drug residues

– Electrolyte balance: K+ exchanged for Na+– Acid-base balance: H+ , NH3

– Antidiuretic hormone (ADH): produced by posterior pituitary, increases water permeability of the DCT and collecting duct

• Cranberry juice – acidifies urine to help discourage bacteria and some types of kidney stones; decrease UTI by inhibiting bacteria from adhering to urinary tract walls

Osmotic Pressure (Osmolarity)

Urine• Micturation – process of urination

Normal Urine Abnormal Urine

H2O 95% Glucose Recent intake of sugary foods,

Nitrogeneous wastes urea, uric acid,   diabetes melitis (Glycosuria)

  ammonia, creatine Protein Physical exertion, high protein;

Electrolytes Na+, NH4+, K+,  hypertension, glomerulonephritis (Proteinuria)

  Cl-, PO4-3, SO4-2Ketone bodies

Starvation, untreated diabetes mellitus

Toxins bacterial poisonsHemoglobin Hemolytic anemia, severe burns

Pigmentsproducts of breaking down RBC,

Bile pigments

Hepatitis, cirrhosis, bile obstruction

 filtered from food and drugs

Erythrocytes

Bleeding due to trauma, kidney stones,

Hormones     infection, cancer (Hematuria)

    Leukocytes Urinary tract infection

Disorders and Diseases• Pyuria – pus in urine• Dysuria – painful urination• Polyuria – large amounts of urine• Oliguria – very little urine• Anuria – absence of urine• Renal Calculi – crystallized calcium in renal pelvis or calyx

(kidney stones)• Neurogenic bladder – involuntary urine retention, bulging

bladder, burning sensation• Overactive bladder – frequent urination, pain, oliguria• UTI: bacterial infection

– Urethritis: inflammation of urethra; result of gonorrhea and Chlamydia; most common in males

– Cystitis: inflammation of bladder; more common in females due to shorter urethra

– Nephritis: inflammation of kidney• Pyelonephritis – inflammation of renal pelvis

• Renal Failure – kidney failure