Exam 4 Physio: Renal 1

Front 1

EXAM 4 PHYSIO: RENAL 1

Back 1

EXAM 4 PHYSIO: RENAL 1

Front 2

Major functions of the kidneys?

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1. regulate water vol
2. regulate bal of iorganic ions
3. regulate body pH
4. excretion of metabolic wastes
5. produce hormones/enzymes
6. reg blood pressure

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Normal osmolarity of body fluids:

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300 mOsm

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What hormones do the kidneys synthesize?

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1. Erythropoietin
2. 1,25- Dydroxyvitamin D3 (Calcitrol)
3. Renin (not a hormone though)

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1, 25-Dihydroxyvitamin D3

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Increases absorption of Ca & PO4 from the GI tract.

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Function of renin?

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Hydrolyzes Angiotensinogen to Angiotensin I

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Function of AII?

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1. aldosterone secretion (Na retention in kidney)
2. Stimulates thirst (increased water ingestion)

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What are the two kinds of nephrons?

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1. cortical nephron
2. juxtamedullary nephron

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What is the mOsm value in the deepest portion of medulla?

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1200 mOsm

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What are some commonalities between the cortex and medulla?

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1. two arteriole (afferent, efferent)
2. two capillary beds (glomerular--filtration and peritubular/vasa recta)

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Cortical Nephrons

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1. peritubular capillaries (90% of renal blood flow).

Remove reabsorbed solutes and H2O.

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Juxtamedullary nephrons

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Vasa recta
10% renal blood flow

Helps maintain osmotic gradient.

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Principles of the nephron

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1. filters plasma
2. reabsorb the substances body needs.
3. secrete what body doesn't need.
4. excrete what is left (urine)

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Area of nephron where filtration takes place?

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Renal corpuscle

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Reabsorption and secretion occurs where?

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Rest of the tubule

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Loop of Henle

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Reabsorbs NaCl and thus separates Salt and H2O.

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Distal tubule and CD

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Fine tunes ion absorption

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Amount excreted is equal to:

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Amount filtered - Amount reabsorbed + Amount secreted.

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Reabsorption value

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~180L / day

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Excretion value

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1-2L per day

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Renal blood flow

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1L/min

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Renal Plasma flow

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625ml/min (900L/day)

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GFR value

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125ml/min (180 L/ day)

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Pgc

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Glomerular capillary BP

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Conditions leading to decreased GFR:

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1. constriction of afferent arteriole and normal efferent arteriole.
2. decreased Pgc

Condition 2
1. Normal AA
2. Dilated EA
3. Decreased Pgc

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Conditions leading to increased GFR?

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Case 1
1. Constricted EA
2. Inc Pgc

Case 2
1. Dilated AA
2. Increased Pgc

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Extrarenal mechanism in the control of arteriolar resistance:

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Neural and hormonal inputs to AA and EA alter the resistance of both in a similar way.

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Two examples of Intra-renal mechanisms (autoregulation):

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1. myogenic
2. tubuloglomerular feedback

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Myogenic

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AA respond to increased BP--> inc contraction of AA smooth muscles--> inc resistance--> dec Pgc--> dec GFR

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Tubuloglomerular feedback

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Paracrine inputs to AA alter its resistance so Pgc remains constant, therefore GFR remains constant.

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Macula densa

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Senses Na concentration in the distal tubule.

Senses increase in luminal salt load.

Release paracrines that act on smooth muscle cells of AA.

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Inc arterial BP can lead to:

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inc Pgc--> Inc GFR--> inc amount of salt load moved into tubule--> macula densa release paracrines to act on AA--> inc AA resistance--> dec Pgc--> dec GFR.