Kidney Structure and Function

Question 1

Nephrons

Answer 1

Situated in cortex of the kidney. Responsible primarily for removal of waste products and reabsorption of nutrients.

Question 2

Juxtamedullary nephrons

Answer 2

Have longer loops of Henle that extend deep into the medulla of the kidney, their function is concentration of the urine.

Question 3

Kidney Clearance and Water Balance are controlled by what functions?

Answer 3

The ability of the kidneys to clear waste products selectively from the blood and simultaneously to maintain the body’s essential water and electrolyte balances is controlled in the nephron by the following renal functions:

1. Renal blood flow
2. Glomerular filtration
3. Tubular reabsorption
4. Tubular secretion

Question 4

Normal Glomerular Clearance Rate

Answer 4

Every minute approximately two to three million glomeruli filter approximately 120 mL of water-containing low-molecular-weight substances.

Question 5

Difference Between Filtrate and Plasma

Answer 5

Difference between the compositions of the filtrate and the plasma is the absence of plasma protein, any protein-bound substances, and cells.

Question 6

Location of Water/Essential Nutrient Reabsorption

Answer 6

When the plasma ultrafiltrate enters the proximal convoluted tubule, the nephrons, through cellular transport mechanisms, begin reabsorbing essential substances and water

Question 7

Active Transport, Substances Transported and Where

Answer 7

Substance to be reabsorbed must combine with a carrier protein contained in the membranes of the renal tubular epithelial cells. Substances reabsorbed include: glucose, amino acids, and salts in the proximal convoluted tubule, chloride in the ascending loop of Henle, and sodium in the distal convoluted tubule.

• more than two-thirds of the filtered sodium is accompanied by the passive reabsorption of an equal amount of water, and accompanies the active transport of chloride in the ascending loop.

Question 8

Passive Transport, Substance Transported and Where

Answer 8

The movement of molecules across a membrane as a result of differences in their concentration or electrical potential on opposite sides of the membrane.

Water is passively reabsorbed everywhere but the ascending loop of Henle.

Urea is passively reabsorbed in the proximal convoluted tubule and the ascending loop of Henle,

Question 9

Tubular Concentration

Answer 9

Water is removed by osmosis in the descending loop of Henle, and sodium and chloride are reabsorbed in the ascending loop.

Question 10

Collecting Duct Concentration

Answer 10

In the presence or absence of ADH, renders the walls of the distal convoluted tubule and collecting duct permeable or impermeable to water.

Question 11

Acid-Base Balance within the Kidney

Answer 11

The buffering capacity of the blood depends on bicarbonate (HCO3 –) ions, which are readily filtered by the glomerulus and must be expediently returned to the blood to maintain the proper pH. The secretion of hydrogen ions (H+) by the renal tubular cells into the filtrate prevents the filtered bicarbonate from being excreted in the urine and causes the return of a bicarbonate ion to the plasma.

Question 12

Urine pH in Respiratory/Metabolic Acidosis/Alkalosis

Answer 12

In respiratory or metabolic acidosis not related to renal function disorders, the urine is acidic, conversely if respiratory or metabolic alkalosis is present, the urine is alkaline

Question 13

Renal Tubular Acidosis

Answer 13

The inability to produce acid urine in the presence of metabolic acidosis, resulting from impaired tubular secretion of hydrogen ions associated with the proximal convoluted tubule defects and ammonia secretion associated with the distal convoluted tubule

Question 14

Polyuria

Answer 14

Excess urine secretion (>2000mL/day)

Question 15

Renin Secretion Stimulation

Answer 15

Stimulated by Macula Densa cells