1. Processes
in the Nephron
• Filtration
• Reabsorption
• Secretion

2. Nephron
• 1.25 million nephrons in a kidney
• FILTER blood

3. Parts of the Nephron
• Glomerulus
– Bed of capillaries
– Receives “DIRTY” blood from the renal
ARTERY
• Bowman’s capsule
– CUP-LIKE structure that surrounds the
GLOMERULUS
– “Dirty” blood (FILTRATE) is forced here by
a FILTRATION process

4. Parts of the Nephron
• Renal tubule
– Proximal convoluted tubule
– Loop of Henle
– Distal convoluted tubule
– Walls are PERMEABLE
• Collecting duct
– SURROUND the
renal tubule
– Leads to the ureter

7. Filtration
• General Definition
– Passing liquid or gas through a filter to
remove impurities
• Nephron
– Small particles in the blood are forced out of
the GLOMERULUS into the BOWMAN’S
CAPSULE.
– This solution is now referred to as the
FILTRATE (similar to plasma except that it
does not contain protein.)

8. Filtration
• Materials that ARE filtered include…
– WATER
– MINERAL SALTS
– Nutrients (Glucose & amino acids)
– NITROGENOUS WASTES

9. Filtration
• Materials that ARE NOT filtered
include…
– Proteins
– Large Cells
– Red Blood Cells

11. Two pathways
1. Some materials will flow through the
RENAL TUBULE into the
COLLECTING DUCT and be excreted
as URINE.
2. Some materials will be
REABSORBED into the blood through
CAPILLARIES that surround the renal
tubule.

12. Reabsorption
• Process where a LIQUID is taken back
into a VESSEL
• FILTRATE flows through the RENAL
TUBULE
• Material that the body need is
REABSORBED by surrounding
CAPILLARIES

13. Reabsorption
• Materials reabsorbed by…
– ACTIVE TRANSPORT
• NaCl,nutrients (glucose & amino acids)
– PASSIVE TRANSPORT
• H20 (osmosis)

14. Reabsorption
• 75% of reabsorption occurs in the
PROXIMAL CONVOLUTED TUBULE
• Rest of reabsorption occurs in the
LOOP OF HENLE and the DISTAL
CONVOLUTED TUBULE

15. Reabsorption
• Concentration gradient formation by
ACTIVE TRANSPORT
– Causes blood in capillaries to become
HYPERTONIC, therefore WATER follows
by simple DIFFUSION, (OSMOSIS).

17. Secretion
• Release of specific substances from the
BLOOD (capillaries) back into the
FILTRATE (now known as urine) in the
renal tubule.
– Nitrogenous wastes (passive transport)
– Hydrogen ions (active transport)
• Adjusts the pH of the filtrate (urine) to about 6.
– Potassium ions (active transport)

18. Secretion
• Occurs mostly in the
DISTAL CONVOLUTED TUBULE
• Some in the
PROXIMAL CONVOLUTED TUBULE

20. Collecting duct
• Continues to concentrate the urine by
removing water from the urine

21. Hormones
• Antidiuretic Hormone

22. Antidurietic Hormone (ADH)
• Regulates WATER conservation
• Increases water absorption by making walls of
the collecting ducts MORE PERMEABLE
• Regulated by the BRAIN (PITUITARY GLAND)

23. Feeling thirsty?
What’s happening to your ADH levels
(and the concentration of your urine)?
– ADH levels INCREASE
– MORE water is retained
– Urine is CONCENTRATED

25. Had enough water?
• ADH levels DECREASES
• LESS water is retained
• Urine is NOT concentrated

27. Last stages…
• Urine collects in the COLLECTING DUCTS of
NEPHRONS
• Urine enters the hollow area of the kidney
called the RENAL PELVIS
• Urine passes through the URETERS
• Urine gets stored in the URINARY BLADDER
where the SPHINCTER muscles CONTROL
when urine is expelled through the
URETHRA.