1. Urinary System

2. Kidney Functions Kidneys filter the blood and create urine
They filter ~200 liters of fluid from the bloodstream every day
Excess water, toxins, metabolic wastes and excess ions normally make up urine

3. Renal arteries deliver
Renal arteries deliver .25 of the total cardiac output to the kidneys each minute

4. Kidney Functions Regulate the volume and chemical makeup of the blood
Maintain balance of
water and salts
acids and bases

5. Kidney Functions Gluconeogenesis
Glycerol and amino acids are converted to glucose when glucose reserves have been depleted
Produce the enzyme renin which helps regulate blood pressure

6. Kidney Functions
Produce the hormone erythropoietin which stimulates red blood cell production
Metabolizes dietary Vitamin D to its active form that can be used by the body

7. Other Urinary Organs
Ureters – tubes that lead from the kidneys to the bladder
Bladder – muscular sac that holds urine prior to leaving the body
Urethra – tube that carries urine out of the body

8. Kidney Anatomy ~size of a large bar of soap
A kidney has 3 distinct regions
Cortex – most external region (glomeruli of nephrons found here)
Medulla – middle region (loop of Henle & collecting duct found here)
Pelvis – most internal region (urine collected here)

10. Nephrons Filtering units of the kidneys
Each kidney contains > 1 million

11. Multiple nephrons attach to one collecting duct

12. Parts of the Nephron
Glomerulus – a ball of capillaries held in Bowman’s capsule
The site of filtration
The filtrate is collected in Bowman’s capsule and travels through the proximal convoluted tubule (PCT) the Loop of Henle and the distal convoluted tubule (DCT)

13. Kidney Physiology: Urine Formation
Step 1 – Glomerular Filtration
The kidneys process about 180 L of blood derived fluid (filtrate) daily
Filtrate contains everything found in plasma except the proteins
Blood cells remain in blood

15. Between Podocytes are spaces called filtration slits where filtrate moves through

16. Kidney Physiology: Urine Formation
Step 2 – Tubular Reabsorption
Reabsorption may be passive (no energy required) or active (energy required) depending on the substance.

17. Kidney Physiology: Urine Formation
Substances that are reabsorbed are Na+, K+, Mg2+, Ca2+, Cl-, HCO3-, Glucose, Amino acids, Vitamins, Water, Urea, and fat-soluble substances

18. Kidney Physiology: Urine Formation
Nonreabsorbed substances creatinine and uric acid
Incompletely reabsorbed - urea

19. Kidney Physiology: Urine Formation
Step 3 – Tubular Secretion -
substances are secreted from peritubular capillaries into the filtrate
Secreted substances include certain drugs, urea, uric acid, K+, Na+, and H+

20. Kidney Physiology: Urine Formation
Only about 1.8 L of filtrate leaves the body as urine
Urine normally contains mostly water, urea, uric acid, creatinine, Na+, K+, PO43-, SO42-, Ca2+, Mg2+, and HCO3-