Kidney capillary network
- highly specialises, v different
- runs parallel to LOH and blood flow in OPPO direction
- this is called VASA RECTA
- allows supply of O2 adn nutrients deep into medulla
- creates an osmotic gradient
What is fluid like in DCT
HYPO osmotic - v dilute
Hypothalamus and pituitary
- brain base
- under = bright red cherry pituitary
- important endocrine, releases lots of hormones
- posterior pit
- anterior pit
Posterior pituitary
• Bit of brain tissue embedded in P gland
• Nerves continuous with P hold chemical substances, neuroendocrine.
• ADH MADE in brain, travels to P pituitary where released
• ADH =
i. Small peptide, released pp
ADH
• ADH affects number of aquaporins in CD = affects permeability of CD to water
• ADH synthesized in brain, released from PP into BLOOD
• Receptors downstream activate 2nd messengers – APorins inserted in CD membrane so water moves down conc gradient
• Greater ability of water to leave filtrate and get absorbed
• Drink lots = no ADH
- No water drunk = inc ADH = inc permeability of CD to water
Calcium in kidney
what is it important for?
- important: second messenger, muscle contraction and many other
- 50% protein bound so only free Ca goes through into PCT
- in PCT 70% reabsorbed
- There is selective reabsorption of calcium in DCT and CD under hormone control
- Normally only 1-2% filtered Ca is excreted
Phosphorus in kidney
- Inorganic phosphate 100% filtered
- Reabsorption in PCT by Na+ cotransport under hormone control
- Not reabsorbed in DCT and CD
- Eat a lot (cell membranes) so dietary XS is excreted in via kids
How does body respond to decreased conc Ca2+ in blood?
• PARATHYROID hormone is released in response
o Decreases reabsorption of phosphate in proximal tubule
o Increases reabsorption Ca2+ in ascending loop of Henle, distal tubule and collecting duct
…. by time filtrate has entered DCT what has happened to Na
- 100% filtered approx. 90% reabsorbed -most in PCT some in LoH
Principle cells allow what in terms of Na and K
reabsorption of Na and secretion of potassium
by time filtrate has entered DCT what has happened to K
- 100% filtered
- 100% reabsorbed
- more reabsorbed in PCT than LOH
By the time the filtrate has entered DCT what ahs happened to bicarbonate? HCO3-
- Freely filtered
- 100% reabsorbed
- 80-90% reabsorbed in PCT
- 10-20% in LoH
By the time the filtrate has entered DCT what ahs happened to H+
- Freely filtered
- Unregulated secretion into PCT via secretion of NH4
- Unregulated secretion into PCT via secretion of H+
