Renal Physiology Flashcards Kidneys I

Flashcards about Renal Physiology Lecture

Kidney Function

Extracellular fluid volume & blood pressure control, regulation of ions, regulation of plasma pH, regulation of blood composition, control of waste removal, production of urine, and production of hormones.

Filtration

Fluid moves from the blood into the glomerulus at the Bowman’s capsule. The fluid that enters the lumen of the nephron is called the filtrate.

Reabsorption

Movement of substances from the filtrate back into the blood.

Secretion

Highly selective movement of molecules from the blood, across the tubule epithelium, assisted by cell membrane proteins.

Glomerular Filtration Rate (GFR)

Bowman’s capsule fluid filtered over time, approximately 125 mL/min or 180 L/day.

Filtration Fraction (FF)

The fraction of plasma volume that filters into the tubule, approximately 20% (GFR / RPF = FF, 125 / 650 = ~20%).

Renal Plasma Flow

approximately 650 mL/min

Venules carry blood…

away from the nephrons to join the renal vein.

Blood flows from the efferent arteriole away

from the glomerulus

towards a second capillary bed – the

peritubular capillaries

Kidney’s receive how much cardiac output

20% , 1L/min

How much of the plasma filtered through

the kidney must be reabsorbed

Most of it

Key processes of the nephron

1) Filtration, 2) Reabsorption, 3) Secretion

Filtration

Fluid moves from the blood into the glomerulus at the Bowman’s capsule

Filtrate

The fluid that enters the lumen of the nephron

Reabsorption

Movement of substances from the filtrate

back into the blood

Micturition

The process of excreting urine

Secretion

Highly selective movement of molecules from the blood, across the tubule epithelium, assisted by cell membrane proteins

Filtration barriers

Fenestrated capillary endothelium, Basal lamina (basement membrane), Epithelium of Bowman’s capsule

Bowman’s capsule

The epithelial lining forms part of the filtration barrier for fluid moving into the tubule of the nephron from the blood

Glomerular capillary bundle

The capillary lining cells (endothelium) and basement membrane surrounding the capillary prevent cells and larger blood components from entering the Bowman’s space between the capillaries and the epithelium of the capsule

Capillary pressure

Drives filtration, Capillary pressure (+55 mmHg) + capillary colloid osmotic pressure (-15 mmHg) + capsule fluid pressure (-30 mmHg) = net inward nephron force (10 mmHg)