PHSC1122 Physio II - Chapter 26 Renal System (26.5)

Passive

Is filtration at the renal corpuscle active or passive?

Metabolic wastes, excess ions, glucose, free fatty acids, amino acids, and vitamins

solutes entering the capsular space at the renal corpuscle during filtration

Reabsorbing useful organic nutrients in filtrate, reabsorbing more than 90% of water in filtrate, and secreting any wastes that did not enter filtrate at glomerulus

3 functions of the renal tubule

Reabsorption and secretion

two processes that occur in every segment of renal tubule and in collecting system

Reabsorption

process that recovers useful materials from tubular fluid and returns them to blood; 99 percent of filtrate is reabsorbed in renal tubules

Secretion

process that adds substances from blood to tubular fluid

From tubular fluid to blood

Where do materials go in reabsorption in the renal tubule system?

From blood to tubular fluid

Where do substances get added in secretion in the renal tubule system?

99

percent of filtrate reabsorbed in the renal tubules

Diffusion, Osmosis, Leak channels, and Carrier-mediated transport

4 things reabsorption and secretion by kidneys involve (think transport/diffusion)

Facilitated diffusion, Active transport, Cotransport, Countertransport

4 types of carrier-mediated transport

Renal threshold

plasma concentration at which a specific compound or ion begins to appear in urine; varies with substance involved

Specific compound or ion begins to appear in urine

What happens once the plasma concentration reaches the renal threshold?

Glucosuria

glucose in urine

Aminoaciduria

amino acids in urine

180 mg/dL

renal threshold for glucose

65 mg/dL

renal threshold for amino acids

After protein rich meal

When are amino acids commonly found in urine?

60-70

percent of filtrate volume produced in renal corpuscle normally absorbed by PCT cells

Enter peritubular fluid and diffuse into peritubular capillaries

Where do PCT reabsorbed materials go?

About 1/2 of remaining water and 2/3 of remaining sodium and chloride ions

What does the nephron loop reabsorb?

Freely permeable

The descending limb of nephron loop is _____________________(freely permeable/impermeable) to water but not to solutes

impermeable

The ascending limb of nephron loop is _____________________(freely permeable/impermeable) to water but not to solutes

Descending limb of nephron loop

freely permeable to water but not to solutes

Ascending limb of nephron loop

impermeable to water; passively and actively removes sodium and chloride ions from tubular fluid; very long in juxtamedullary nephrons, creating high solute concentrations in peritubular fluid

15-20

percent of the initial filtrate volume that reaches DCT

Na+ and Cl-

What is actively transported out of tubular fluid at the DCT?

Along distal regions

Where at the DCT do tubular cells contain ion pumps that reabsorb Na+ in exchange for another cation (usually K+)?

Aldosterone

hormone produced by adrenal cortex that stimulates synthesis and incorporation of Na+ pumps and channels in plasma membranes along DCT and collecting duct; reduces Na+ lost in urine

Adrenal cortex

What produces aldosterone hormone?

Sodium pumps and channels along DCT and collecting duct to reduce loss in urine

What does aldosterone stimulate synthesis and incorporation of, and why?

Hypokalemia

a dangerous reduction in plasma K+ concentration; produced by prolonged aldosterone stimulation

Prolonged aldosterone stimulation

What hormone can produce hypokalemia?

Atrial natriuretic peptide (ANP)

opposes secretion of aldosterone and its actions on DCT and collecting system

Parathyroid hormone

regulates calcium ion reabsorption at DCT

Calcium reabsorption at DCT

What does parathyroid hormone regulate?

Toward renal sinus

Where do collecting ducts carry the tubular fluid received from nephrons?

ADH

controls permeability to water; secretion is suppressed by ANP

Aldosterone actions and ADH secretion

What does ANP suppress?

Sodium, bicarbonate, and urea

3 materials reabsorbed in the collecting system

Potassium

What is sodium exchanged for in the collecting system when reabsorbed?

Chloride

What is bicarbonate exchanged for in the collecting system when reabsorbed?

By diffusion

How is urea reabsorbed in the collecting system?

pH of body fluids

What does secretion in the collecting system control?

Carrier proteins pump H+ into tubular fluid and reabsorb bicarbonate ions into peritubular fluid

What does secretion cause if there is low pH in peritubular fluid?

Collecting system secretes bicarbonate ions and pumps H+ into peritubular fluid

What does secretion cause if there is high pH in peritubular fluid? (uncommon)

High pH

Is low or high pH in peritubular fluid uncommon?