Download ppt. lecture

Kidney Structure
[Outer cortex, inner medulla, and renal pelvis]
Cortex contains NEPHRON filtering units.
Nephron = Bowman's capsule containing Glomerulus
(capillary bed) ---> tubules of nephron.
Kidney Structure
Bowman's capsule --> proximal convoluted tubule --> Loop
of Henle --> distal convoluted tubule --> collecting duct -->
The urine then drains down the ureter --> urinary bladder
(storage area). Passes out of the body through the urethra.
Note: There are thousands of nephrons in each kidney.
Make note of location
of Cortex & Medulla- now
locate the Nephron in relation
to these 2 structures
Nephron Function
A) Bowman's capsule:
• blood enters under very high pressure
• arrives directly from the aorta
• blood forced into glomerulus & Water, salts, glucose,
urea, & amino acids forced out into the nephron - forms
crude filtrate.
• Up to 95% water & salts resorbed.
Nephron Function
B) filtrate travels to the proximal convoluted tubule
• majority water & salt resorption occurs
• water moves from tubule to blood via steep
osmotic gradient
• sodium/potassium exchange pump brings sodium back in
• glucose & chlorine ions resorbed.
Nephron Function
C) filtrate moves to the Loop of Henle
• Descending part of the loop --> water flows out of the
filtrate [thus concentrating filtrate, by absorbing water back
into circulatory system] --> medulla tissue becomes more
salty
• salty medulla --> causes a lot of water absorbed by adjacent
capillaries.
• Ascending loop --> sodium pumped out (keeps medulla
salty) --> water leaves descending loop.
Note: much of the sodium is absorbed by the descending
part, through a countercurrent exchange of salt.
Nephron Function
D) Distal convoluted tubule:
• sodium & chlorine ions actively transported out
• water "follows" and is resorbed by cappilaries of
juxtaglomerular complex.
• Tubular secretion formed:
Ammonia, urea, H+ ions pass out of tubule as
waste products contained within the filtrate.
Note: ammonia is by product of protein digestion
Nephron Function
E) Collecting tubule:
• sodium ions & water move out of filtrate
• other wastes move in
• countercurrent exchange of urea
• final filtrate forms in duct = URINE
4
5
2
1
Use numbers
To trace flow of
Filtrate through
nephron.
3
Detail of Nephron structure
Read: Step by step process of filtration of blood brought to nephron
Control of Nephron Function
Antidiuretic Hormone (ADH): controls water absorbtion
• Recall, main function of nephron is to help maintain osmotic
balance of your body
• Hypothalamus --> signals posterior pituitary to release
ADH when dehydration detected [e.g if
you eat too much salt]
.
• ADH --> targets cells within collecting ducts
• Function: increases cellular permeability to water.
• As more water is resorbed, the osmolarity of the blood
returns to "normal" and the hypothalamus switches off the
production of ADH (Negative Feedback Loop).