1. Urinary System 9-15

2. Nephron types (8)
Cortical nephrons – 85% of nephrons located in the renal cortex
Juxtamedullary nephrons – located at the cortex-medulla junction
Loops of Henle deeply invade the medulla
Extensive thin segments produce highly concentrated urine

3. Nephron functional unit of the kidney

4. The 2 Capillary beds of the nephron (9)
Glomerular capillaries – inside glomerulus, fed by afferent arterioles, then exits glomerulus via efferent arterioles; efferent arteriole divides again into another capillary network:
Peritubular capillaries – network that surrounds the PCT & DCT & ultimately the loop of Henle as vasa recta

6. Vasa recta (10)
After the efferent arterioles descend into the medulla they divide into long thin STRAIGHT capillaries called the vasa recta (Latin for straight vessels)

8. Urine formation (11) The 3 big-picture processes
Glomerular filtration – Tubular absorption + Tubular secretion = Excretion

9. 3 levels of filtration – makeup of filters & filtrate (what is filtered) (12) & (9) Pressure differences of vessels
Glomerular filtration
Tubular reabsorption
Tubular secretion

10. Glomerular filtration (13)
Separates plasma fluid and small solutes from larger proteins and blood cells
High blood pressure in glomerular capillaries forces fluid through capillary walls into Bowman’s capsule

11. Tubular reabsorption (14)
Returns filtered water and nearly all major nutrients to the blood
Primary active transport of Na+ across cell membrane drives diffusion of Cl- and water; provides energy for reabsorption by secondary active transport or passive diffusion of other substances

12. Tubular secretion (15) Removes harmful or excess substances from blood
Substances move by active transport or passive diffusion from capillaries into the tubule

13. Filtrate contents (13) glomerular filtrate
Contains all plasma components except protein
Loses water, nutrients, and essential ions to become urine
The urine contains metabolic wastes and unneeded substances

14. Countercurrent mechanism (14)Tubes that interact to make the excretory process work.
Involves sodium pumps that create an area of high sodium concentration deep in the medulla, near the collecting duct
This allows the kidneys to produce dilute or concentrated urine depending on your body’s needs
Interaction between the flow of filtrate through the loop of Henle (countercurrent multiplier) and the flow of blood through the vasa recta blood vessels (countercurrent exchanger) allow this process to work