Week 6: Kidney Review

the function of the urinary system

filter blood and eliminate toxic waste products

the outer _____________ houses the nephron, while the inner __________ contains the collection of tubules

cortex, medulla

drainage from renal filtration enters the renal ___________

pelvis

which part of the nephron is responsible for absorption, acidification, and secretion?

proximal tubule

the ______________ tubules empty into the renal pelvis

collecting

how much blood flow does the kidney receive?

1200 mL/min

an average daily volume of _______ glomerular filtrate is converted into ultrafiltrate

180 L

what is the final urine volume?

600 - 1800 mL

what are the principle solutes excreted in urine?

• urea

• Cl-

• Na+

• K+

what are lesser solutes excreted in urine?

• phosphates

• sulfates

• creatinine

• uric acid

glucose and amino acids should be completely _____________ from ultrafiltrate

reabsorbed

clearance tests require ________ urine specimens

24 hour

the reabsorption of water is controlled by which hormone?

ADH

what is tubular reabsorption?

transfer from the tubular lumen to capillary plasma

what is tubular secretion?

transfer from capillary plasma to tubular lumen

glomerular filtration has a _______ permeability for water and ions, and a ____ permeability for plasma proteins

high, low

glomerular filtration rate

volume of liquid filtered through the glomerular capillaries into the bowman’s capsule per unit of time

blood constituents that DO pass through the glomerular membrane are called what?

glomerular filtrate

what are the following considered?

• glucose

• amino acids

• urea

• LMW substances

glomerular filtrate

the proximal convoluted tubule utilizes active transport through what mechanism?

Na/K ATPase pump

the _____________ tubule actively reabsorbs 100% of glucose, amino acids, and proteins

proximal

the ___________ tubule absorbs bicarbonate, phosphate, sulfate, calcium, magnesium, and uric acid

proximal

water and chloride are reabsorbed ____________ through ____________ in the proximal tubule

passively, diffusion

renal threshold

when the plasma conc. of a substance is too high, and exceeds the max tubular reabsorption capacity → substance appears in the urine

renal threshold of glucose

serum: 160-180 mg/dL

what molecules are secreted in the tubules to maintain acid-base balance?

• H+

• phosphate

• organic acids

tubular secretion is primarily an _________ process

active

function of the descending loop of Henle

loses both water and Na+ (permeable to water)

function of the ascending loop of Henle

loses Na+ and Cl- through active and passive transport WITHOUT water (impermeable to water)

under the control of aldosterone, Na+ is ____________ and K+ is ____________

reabsorbed, secreted

aldosterone works upon the __________ tubule

distal

the distal tubule also secretes what into the glomerular filtrate?

H+ and NH4+

what is the main function of the collecting tubules?

final pH adjustment, osmolality, and electrolyte content

______ of glomerular filtrate is reabsorbed by the time it reaches the distal convoluted tubule

90%

ADH influences the _________________ to stimulate water reabsorption

collecting ducts

ADH is secreted by what?

posterior pituitary

when the body is ________________, ADH is secreted and the walls of the distal tubules and collecting ducts become more permeable to water to increase reabsorption

dehydrated

increased body hydration → ____________ ADH → increased urine volume

decreased

decreased body hydration → ____________ ADH → decreased urine volume

increased

there is more ___________ in the cortex and more _______ in the medulla

cortex, medulla

the loop of Henle creates an increasing solute concentration gradient where _________ can be recovered in the collecting ducts

water

the ____________ loop reabsorbs water and salts while the ___________ reabsorbs electrolytes

descending, ascending

which part of the nephron is responsible for the following?

• reabsorption of sodium ions and water (ADH)

• secretion of acids, ammonia, and drugs

distal tubule

which part of the nephron is responsible for the following?

• reabsorption of sodium ions and water (ADH)

• secretion of H+

collecting duct

which substances are almost completely reabsorbed by the renal tubules?

• glucose

• Na+

• Cl-

• amino acids

• K+

• creatinine

• ascorbic acid

urine is _____% water and _____% dissolved substances

95, 5

what are the major nitrogenous waste products in urine?

• urea (50%)

• uric acid

• creatinine

what are the 3 parts of urinalysis?

1. physical examination

2. chemical analysis

3. microscopic examination

normal range of RBCs in microscopic urinalysis

0-2/hpf

normal range of WBCs in microscopic urinalysis

0-5/hpf

examples of epithelial cells that can be seen in microscopic urinalysis

• squamous

• renal

• transitional

what are casts?

clumping of cells or other material within a protein matrix

examples of casts

• RBC

• WBC

• hyaline

• granular

• waxy

• fatty

casts indicate what?

renal disease

crystals appear after a urine _______, and most have little clinical significance

stand

examples of acid crystals

• uric acid

• calcium oxalate

• amorphous urates

• sodium urates

• hippuric acid

examples of alkaline crystals

• triple phosphates

• amorphous phosphates

• calcium carbonate

• calcium phosphate

• ammonium biurate

examples of abnormal crystals

• cysteine

• tyrosine

• leucine

• cholesterol

• sulfate

• bilirubin

a significant number of bacteria indicates what?

UTI

yeast in microscopic urinalysis indicates what?

vaginal contamination

casts are cylindrical structures which form in the lumen of what?

distal convoluted tubule or collecting ducts

renal tubules secrete a mucoprotein called ______________________ which is the basic structure of casts

tamm-horsefall protein

what are some causes of cast formation?

• urinary stasis

• acid pH

• high solute concentration

• presence of the abnormal protein constituent tamm-horsefall protein

normal functions of tamm-horsefall protein

• binds pathogens to prevent infections

• inhibits crystallization of calcium → prevents kidney stones

• regulates ion transport, blood pressure, and fluid balance in nephron

as the cast makes it way through the kidney, ______________ changes occur that are associated with renal stasis

degenerative

what factors help identify crystals?

• morphology, color, refraction

• solubility

• pH of urine