1. Urinary System

2. Functions of Urinary System
Secrete waste
Regulate blood volume and composition
Ph, excrete H+, conserve bicarbonate ions
Ions like Na, K, Ca, Cl, and phosphate
Help regulate blood pressure
Synthesize glucose
Release erythropoietin
Participate in vitamin D synthesis
Gets rid of urine

3. KIDNEYS AND NEPHRONS

4. NEPHRON

5. Nephrons
2 main structures – glomerulus=knot of capillaries and a renal tubule
The renal tubule surrounds the glomerulus
This portion of the tubule is called the glomerular or bowman’s capsule
Podocytes make up the inner layer of the capsule. They have long branching processes that intertwine and cling to the glomerulus
They produce a porous membrane around the glomerulus

7. Collecting Ducts
Proximal convoluted tubule, loop of Henle, distal convoluted tubule
Lumen of proximal contains microvilli for SA

9. Nephrons continued
Most nephrons are called “cortical” because they are located in the cortex
Some are denoted “juxtamedullary nephrons” b/c they are situated between the cortex/medulla junction
Collecting ducts run from the pyramids which give the kidney its striped appearance
They deliver final urine product into calyces and renal pelvis

10. Figure 3. Kidney tubules, transverse section (2) (Formalin, H&E, Bar = 16.7 µm). 1. first proximal tubule; 2. second proximal tubule; 3. intermediate tubule segment; 4. distal tubule; 5. collecting duct; 6. brush border; 7. mitotic epithelial cell; 8. melanomacrophage; 9. red blood cells.

11. Nephron capillaries
Each nephron has a glomerulus and a peritubular capillary bed
Fed (afferent arteriole) and drained (efferent arteriole) by arterioles

13. Glomerulus capillary bed
Specialized for filtration
Fed and drained by arterioles (high resistance vessels) blood pressure is high
The high pressure forces fluid and solutes out of the blood into glomerular capsule

15. Peritubular Capillary Bed
Arises from efferent arteriole that drains the glomerulus
Low pressure and porous for absorption
Found clinging to length of renal tubules where they can receive solutes and water
These peritubular capillaries drain into interlobular veins leaving the cortex

16. Blood Supply
The kidneys continuously cleanse the blood (1/4 of total blood supply passes through the kidney per minute)
Arterial blood supply
Renal hilus divides into segmental arteriesin pelvis break up into lobar arteriesinterlobar arteries which travel through the renal columns to reach the cortex

17. Artery branching continued
@ medulla-cortex junction, interlobar arteries give off arcuate arteries
Curve over medullary pyramids
Interlobular arteries branch off the arcuate arteries and run outward to supply the cortex tissue

18. Venous system in the kidney
Venous blood drains from the kidney in the same pattern as the arterial blood flow but in the opposite direction
Interlobular veinsarcuate veinsinterlobar veinsrenal vein which emerges at the hilus
NOTICE: no lobar or segmental veins