1. Urinary System

2. Overall Functions Excretion – remove nitrogenous wastes from blood
Osmoregulation – maintain proper balance of ions
Volume regulation – maintain proper balance of water
Regulation of pH
Detoxify superoxides, free radicals and some types of drugs.

3. Why are nitrogenous wastes a problem?
Ammonia is a moderately strong base (elevates blood pH).
Urea is a weaker base made from ammonia and carbon dioxide in the liver – less toxic than ammonia (NH3)
Uric Acid is a waste produced from the metabolism of nucleic acids
Creatinine is a waste product from creatine metabolism.

4. The kidneys only comprise about
0.5% of the total body weight, but
they receive 1,200 mL of blood
per minute; about 20% of the
Total cardiac output.
Kidneys are constantly cleaning,
balancing ions and water, and adjusting the
pH of the blood.

5. Inferior Vena Cava
Aorta
Renal Artery
Renal Vein
Kidney
Ureter
Urinary Bladder
Urethra

6. Tubule system
(produces urine)
Calyx
(funnel-like
Structure that
Collects urine from
Tubules)
Pelvis of the
Kidney
Cortex
Medulla
ureter

7. The Nephron is the Functional Unit of the Kidney
Proximal Convoluted tubule
Bowman’s Capsule
Glomerulus
Afferent
Arteriole
Collecting Duct
Efferent
Arteriole
Distal
Convoluted
Tubule
Urine is carried to Calyx,
Pelvis and then the Ureter
Loop of Henle

8. Functions of the Nephron 1. Filtration
The glomerulus is made of “fenestrated
capillaries” that are unusually permeable.
All of the following substances can easily filter out of the glomerulus and into Bowman’s capsule.
water
glucose (and other sugars)
amino acids
small organic molecules
ammonia, urea, uric acid
salts, H+, HCO3
The only substances that are not usually filtered out are blood cells, proteins and larger organic molecules.
Notice that several important nutrients are filtered out of the blood during
the filtration process.

9. Functions of the Nephron 2. Reabsorption
Reabsorption is a process that
1. Utilizes active transport pumps
2. Occurs in the proximal and distal tubules
3. Reclaims nutrients that were lost
during the filtration process.
4. Returns the nutrients to the blood
Examples of reabsorbed substances
1. glucose
2. amino acids
3. NaCl
NOTE: water is reabsorbed passively by osmosis.

10. Functions of the Nephron 3. Tubular secretion
Secretion is a process that
1. Utilizes active transport pumps
2. Occurs in the proximal and distal tubules
3. Adds wastes from the blood that were not
effectively filtered at the glomerulus.
4. Increases the concentration of wastes in
the urine
Examples of secreted substances
1. Ammonia, H+ (smaller ionic)
2. histamine, creatinine (larger, organic)
3. penicillin

11. Glomerular Filtration Rate
The two kidneys produce nearly 45 gallons (180 liters) of filtrate per day.
Glomerular Filtration Rate (GFR) depends almost completely on hydrostatic pressure in the glomerulus.
* dilation or constriction of
afferent and efferent arterioles.
* overall blood pressure
What happens in exercise when blood pressure may increase up to 200 mm Hg or more?
During exercise, the sympathetic nervous system comes into play. Symp. Nerves stimulate the afferent arteriole and it constricts.

12. Regulation of Na+ Reabsorption
If blood pressure is low for an extended period of time, the kidney reacts by releasing an enzyme called renin.
Renin is involved in a series of reactions that ultimately lead to the release of a hormone called Aldosterone from the adrenal gland.
Aldosterone is a steroid that acts on the distal convoluted tubule and increases the rate of NaCl reabsorption.
As the concentration of NaCl increases in the blood, water is reabsorbed at a faster rate (osmosis).
With more salt and water in the blood, the volume of blood goes up and blood pressure goes up.
Impact of diet and strenuous exercise

13. Regulation of Urine Volume coordinate function of Loop of Henle and the Collecting Duct
Four Times Saltier
Than the Blood