E3.1 - Water balance, ECF, ICF, renal functions and anatomy

Renal functions

regulate RBC production by secreting erythropoietin. Production of activated form of vitamin D (calcitrol). Synthesize glucose de novo = gluconeogenesis

Peritubular capillaries

surround the tubules of the nephron and re-collect substances the body needs.

Blood supply to kidney:

kidneys see 22% of cardiac output. Vessels enter and exit the kidney through the Hilum.

Afferent and Efferent Arterioles

work together to regulate filtration pressure and pressure in peritubular capillaries.

Loop of Henle:

Thin descending segments

Loop of Henle:

Thick ascending segments

Urine Formation

Urea, creatinine, and uric acid all dissolved in H2O.

Glomerular filtration

everything in blood is filtered except plasma proteins. Albumin is repelled from pores due to its negative charge.

Glomerular filtration rate: GFR

= Kf * Net filtration pressure.
Kf= Permeability * filtering surface area OR GFR/Net filtration pressure.
Often 400x that of typical blood capillaries

Effect of changing afferent arteriole resistance

Pressure decreases, GFR decreases, and renal blood flow decreases

Effect of changing efferent arteriole resistance

Constricting the efferent arteriole will cause the pressure to go up, the GFR to increase temporarily, and the renal blood flow to decrease.

Control of GFR

Angiotensin II= makes sure GFR does not drop
Norepinephrine, epinephrine, and endothelin = Decrease GFR
Endothelial-derived nitric oxide and prostaglandins = Increase GFR

Tubuloglomerular feedback and autoregulation of GFR

1. Distal tubule senses decreased NaCl and dilates the afferent arterioles.
2. Renin release from the juxtaglomerular cells and angiotensin II constricts the efferent arterioles