Kidney Structure

1
Kidney Structure
Outer cortex, inner medulla, and renal pelvis
Cortex contains NEPHRON filtering
units. Nephron Bowman's capsule containing
Glomerulus (capillary bed) ---gt tubules of
nephron.
2
Kidney Structure
Bowman's capsule --gt proximal convoluted tubule
--gt Loop of Henle --gt distal convoluted tubule
--gt collecting duct --gt The urine then drains
down the ureter --gt urinary bladder (storage
area). Passes out of the body through the
urethra.
Note There are thousands of nephrons in each
kidney.
3
Make note of location of Cortex Medulla- now
locate the Nephron in relation to these 2
structures
4
Nephron Function

• 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.

5
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.

6
Nephron Function

• C) filtrate moves to the Loop of Henle
• Descending part of the loop --gt water flows out
  of the
• filtrate thus concentrating filtrate, by
  absorbing water back
• into circulatory system --gt medulla tissue
  becomes more
• salty
• salty medulla --gt causes a lot of water absorbed
  by adjacent
• capillaries.
• Ascending loop --gt sodium pumped out (keeps
  medulla
• salty) --gt water leaves descending loop.
• Note much of the sodium is absorbed by the
  descending part, through a countercurrent
  exchange of salt.

7
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

8
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

9
4
5
2
1
Use numbers To trace flow of Filtrate
through nephron.
3
Detail of Nephron structure
10
Read Step by step process of filtration of
blood brought to nephron
11
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 --gt signals posterior pituitary to
  release
• ADH when
  dehydration detected e.g if
• you eat too
  much salt
• .
• ADH --gt 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).