1. The Urinary System: Anatomy and Physiology
Components
Kidneys
Ureters
Urinary bladder
Urethra

2. Organs of the Urinary System
Kidneys
Ureters
Urinary bladder
Urethra

3. Function Remove nitrogenous wastes (urine)
Maintain electrolyte, acid-base, and fluid balance of blood
Homeostatic organ
Acts as blood filter
Release hormones: calcitriol & erythropoietin
Calcitriol increases the level of calcium (Ca2+) in the blood by increasing the uptake of calcium from the gut into the blood, and possibly increasing the release of calcium into the blood from bone

4. The Urinary System: Anatomy and Physiology
Kidneys are supplied with blood from renal arteries
Located Retroperitoneally
Lateral to T 12 – L 3 Vertebra

5. Relationship of Kidneys to Vertebra and Ribs

6. Nephrons About 1 million nephrons are in a kidney.
They are the functioning unit of the kidney

7. Nephrons Consists of a renal corpuscle and a renal tubule.
Glomerulus is a tangled cluster of blood capillaries that makes up a renal corpuscle
Renal tubule leads away from the glomerulus

8. PARTS OF NEPHRON

9. Formation of Urine Glomerular filtration initiates urine formation.
Plasma is filtered by the glomerular capillaries.
Most of this fluid is reabsorbed into the bloodstream.

10. Formation of Urine Urine formation summary: Glomerular filtration
Reabsorption of substances
Secretion of substances

11. General Functioning of the NEPHRON
blood
General Functioning of the NEPHRON
filtration
tubular reabsorption and secretion
urine
“refreshed” blood

12. Formation of Urine Renin also controls the filtration rate.
Responds to three types of stimuli:
Drop in blood pressure
Sympathetic stimulation
Decrease in chloride, potassium, and sodium ions

13. Formation of Urine
Renin reacts with angiotensinogen to form angiotensin I.
Angiotensin-converting enzyme converts to angiotensin II
Helps maintain sodium and water balance
Vasoconstricts the efferent arteriole
Helps decrease glomerular filtration rate
Stimulates kidneys to secrete aldosterone

14. Formation of Urine
Atrial natriuretic peptide(ANP) increases sodium excretion by increasing the glomerular filtration rate.

15. Formation of Urine Urea is a result of amino acid catabolism.
Uric acid is a result of the metabolism of certain organic bases in nucleic acids.
Urine is about 95% water.
Contains urea and uric acid

16. Formation of Urine Ureter drains into the urinary bladder
Bladder empties to the outside of the body through the urethra
1.5 to 2 L of urine is extracted every day.

17. Sphincter Muscles on Bladder
Internal urethral sphincter:
Smooth muscle
Involuntary control
More superiorly located
External Urethral sphincter:
Skeletal muscle
Voluntary control
Posteriorly located