Nephro- A&P

What is the functional unit of the kidney?

Nephron

What does the nephron consist of?

Renal corpuscle (glomerulus & bowman’s capsule) & a renal tubule

What does a renal tubule consist of?

Proximal convoluted tubule, loop of henle (ascending limb & descending limb), distal convoluted tubule (drains into collecting duct)

How do the kidneys help regulate blood pH?

Excrete H+ into urine & conserve HCO3

How do the kidneys regulate blood volume?

Conserving or eliminating water in the urine

How does an increase in blood volume affect blood pressure?

Increase

How does a decrease in blood volume affect blood pressure?

Decrease

How do kidneys help regulate BP?

Secreting renin which activates renin-angiotensin-aldosterone pathway

How does an increase in renin affect BP?

Increase

How do the kidneys maintain blood osmolarity?

Separately regulating loss of water & loss of solutes in urine; maintain relatively constant blood osmolarity ~ 300 milliosmoles/L

What 2 hormones do the kidneys produce?

Calcitriol (active form of vit D) to regulate Ca homeostasis

Erythropoietin which stimulates production of RBCs

How do the kidneys help regulate blood glucose?

Use glutamine in gluconeogenesis & release glucose into blood

What wastes do the kidneys secrete?

Ammonia, urea, bilirubin, creatinine, uric acid

What are the 3 basic processes the nephrons & collecting ducts perform to produce urine?

Glomerular filtration, tubular reabsorption, tubular secretion

What is the first step of urine production?

Glomerular filtration: Water & most solutes in blood plasma move across walls of glom capillaries → glomerular capsule → renal tubule

What process?

• 2nd step of urine production

• Filtered fluid flows along renal tubule & through collecting duct & tubule cells reabsorb 90% of filtered water & solutes

• water & solutes return to blood & flow through peritubular capillaries & vasa recta

Tubular reabsorption

What process?

• 3rd step of urine production

• As fluid flows along renal tubule & collecting duct, tubule & duct secrete other materials such as wastes, drugs, excess ions into fluid

Tubular secretion

What is urine mainly made of?

Water

What is a normal adult urine volume?

1-2 L in 24 hr period

What are the 3 components of the juxtaglomerular apparatus (JGA)?

Juxtaglomerulus cells: afferent arteriole, baroreceptors

Macula densa; DCT, chemoreceptors sensing solute load

Lacis cells: vasoconstriction/dilation w/in mesangium

What is fluid that enters the capsular space?

Glomerular filtrate

Over 99% of glom filtrate is reabsorbed into blood stream, how much is excreted as urine?

1-2 L

What are the 3 phases that glomerular filtration depends on?

GBHP: 55mmHg, promotes filtration of water/solutes

CHP: 15mmHg, opposes filtration

BCOP: 30mmHg, opposes filtration

*net filtration pressure 10mmHg

What is a normal GFR?

100-120 ml/min

What are the 2 main GFR regulation mechanisms?

Control of BF by changing diameter of afferent/efferent arterioles

Control of glom SA via contraction/relaxation of mesangial cells

What is the best overall index of kidney function?

GFR

What hormone is released by the posterior pituitary in response to increased plasma oncotic pressure, LA distention, exercise, & emotional states?

ADH (vasopressin)

Where does ADH act?

Collecting tubules to promote resorption of free water

What deficiency results in the kidneys not being able to concentrate fine, leading to symptoms of polyuria & polydipsia?

ADH insufficiency / DI

What condition is an excess of ADH that results in excessive resorption of free water, hyponatremia, cerebral edema, and neurological dysfunction?

SIADH

RAAS BP control

woohoo