Chapter 26: Renal Function(Exam 4)

What are the main functions of the kidneys?

Maintain fluid and electrolyte balance and remove water-soluble wastes

What is the functional unit of the kidney?

Nephron

How many nephrons are in each kidney?

About 1 million

How much fluid do kidneys filter per hour?

More than 7 liters

What percentage of filtered fluid is reabsorbed?

About 99%

At what nephron loss does serious renal impairment occur?

75–90% loss

Why is chronic kidney disease often diagnosed late?

Symptoms do not appear until significant nephron loss

Where are the kidneys located?

Retroperitoneal space under the diaphragm

Which kidney is lower and why?

Right kidney due to the liver

What is the hilum of the kidney?

Entry/exit site for vessels, nerves, and lymphatics

What are the three parts of the renal parenchyma?

Cortex, medulla, pelvis

What is the function of the cortex?

Contains glomeruli and nephron tubules

What is the function of the medulla?

Contains renal pyramids

What is the function of the renal pelvis?

Collects urine via calyces

What are the three main functions of the nephron?

Filtration, reabsorption, secretion

What structure performs filtration in the nephron?

Glomerulus

What are the parts of the renal tubule?

Proximal tubule, loop of Henle, distal tubule

What does the proximal tubule reabsorb?

2/3 of water/electrolytes and all glucose, amino acids, vitamins

What is the descending loop of Henle permeable to?

Water

What is the ascending loop of Henle permeable to?

Ions (Na+, K+, Cl−) but not water

What hormone increases sodium and water reabsorption in distal tubule?

Aldosterone

What hormone increases water reabsorption in collecting duct?

Antidiuretic hormone (ADH)

What cells regulate acid-base balance in the collecting duct?

Intercalated cells

What determines glomerular filtration rate (GFR)?

Filtration pressure and membrane permeability

What pressures favor filtration?

Capillary hydrostatic and Bowman capsule oncotic pressure

What pressures oppose filtration?

Plasma oncotic and Bowman capsule hydrostatic pressure

How does increased blood volume affect GFR?

Increases GFR

How does decreased blood volume affect GFR?

Decreases GFR

What is autoregulation in the kidney?

Maintains stable GFR despite blood pressure changes

What do mesangial cells do when they contract?

Decrease GFR

What do mesangial cells do when they relax?

Increase GFR

What is the juxtaglomerular apparatus?

Structure that regulates GFR and releases renin

What happens when afferent arteriole constricts?

GFR decreases

What happens when afferent arteriole dilates?

GFR increases

What is transcellular transport?

Movement through tubular cells via transporters

What is paracellular transport?

Movement between cells through tight junctions

Where is glucose reabsorbed in the nephron?

Proximal tubule

What happens when glucose exceeds renal threshold?

Glycosuria (glucose in urine)

How do kidneys regulate acid-base balance?

Excrete H+ and reabsorb bicarbonate

What enzyme helps convert carbonic acid in the kidney?

Carbonic anhydrase

What hormone promotes potassium secretion?

Aldosterone

What is the role of ADH?

Increases water reabsorption and decreases osmolality

What hormones increase blood volume?

Aldosterone and angiotensin II

What hormones decrease sodium reabsorption?

Natriuretic peptides and urodilatin

What are diuretics?

Drugs that increase urine output

What do osmotic diuretics do?

Increase filtrate osmolality to retain water in tubule

What hormone stimulates red blood cell production?

Erythropoietin

When is erythropoietin released?

During hypoxia or low RBC count

What is the role of active vitamin D from kidneys?

Helps calcium absorption

What happens in chronic kidney failure regarding hormones?

Anemia and bone disease occur