1. Excretory System
Urinary System

2. Kidney Filters 200 liters of fluid from the blood stream every day
Eliminates toxins, excess ions, and metabolic wastes
Returns needed substances to the blood

3. Other renal (kidney) functions:
Regulates blood pressure (renin enzyme)
Stimulates RBC production
Metabolizes vitamin D to its active form

4. Renal Blood Flow
Renal arteries take oxygenated blood to each kidney (1/4 of total cardiac output each minute)
Renal veins: return blood from each kidney (low oxygen and high carbon dioxide) to the inferior vena cava

5. Renal Anatomy Renal capsule: outer covering
Adipose capsule: fatty mass for cushioning blows
Renal fascia: outer layer of dense fibrous CT that anchors the kidney to surrounding structures

7. Internal Renal Anatomy
Renal cortex: light outer layer
Renal medulla: darker middle layer
Renal pyramids: in medulla
Renal columns: separate pyramids
Renal pelvis: flat, funneled tube
Calyces: cups to collect urine

8. Nephron: Functional unit of the kidney
Each kidney contains over 1 million of these tiny, blood- processing units

9. Kidney Physiology:3 Easy Steps
Step 1: Glomerular Filtration
Passive, Filtration
Proteins and blood cells are too large to pass – would indicate filtration problems

10. Step 2: Tubular Reabsorption
Most of tubule contents are reabsorbed to the blood
Can be active or passive
Almost all organic nutrients (glucose and amino acids) are reabsorbed to maintain plasma concentrations
Reabsorption of water is constantly regulated.
Also sodium, ions, nutrients are reabsorbed
Urea, creatinine, and uric acid

11. Step 3: Tubular Secretion
Helps dispose of substances not already in the filtrate – some drugs
Eliminating urea and uric acid
Getting rid of excess K+
Controls blood pH

12. Ureters
Convey urine to the bladder
Continuous with the renal pelvis

13. Urinary Bladder
Storage tank for urine

14. Urethra Thin walled muscular tube
Drains urine from the bladder (micturition)