Lecture 1: Function and Structure of Renal System

The renal system act as __, removing metabolic products and toxins from the __ and excreting them through the __.

filters; blood; urine

What does the renal system regulate? (3)

• body’s fluid status

• electrolyte balance

• acid-base balance

The renal system maintains body stores and concentrations of Na+, K+, H+, H2O, etc in such a way that the __ and __ of intra- & extracellular compartments are regulated.

volumes; compositions

ex: controls plasma blood volume → blood pressure regulation

The renal system produces or activates __ that are involved in erythrogenesis, Ca2+ metabolism, and the regulation of blood pressure and blood flow.

hormones

What makes up the kidneys and urinary system?

• kidney

• ureter

• bladder

• urethra

The kidneys __ 18L of fluid/day.

filter

The kidneys __ 1-3L of fluid/day.

excrete

The kidney make up <0.5% of __

body weight

The kidneys receive 20% of __

cardiac output

Once filtrate reaches the ureter, it will not __ contents as it will travel through bladder and urethra.

change

How is the aorta connected to the kidney?

aorta → renal artery → kidney → renal vein → IVC

The __ is 180L/day, 60 times/day compared to __, which has a filter rate of 4L/day and 1.3 times/day.

GFR (glomerular filtration rate); capillaries

• demonstrates importance of reabsorption and filtration in renal system

• measures amount of plasma that filters from glomerulus

There are millions of __ sitting in the cortical section of the kidney.

nephrons (functional unit of kidney, responsible for filtering blood and producing urine)

The cortical section of the kidney is __, and the renal medulla is __.

isoosmotic; hyperosmotic

• cortex has proximal tubule

• medulla has loop of henle

The glomerulus is a network of capillaries within the __

renal corpuscle

20% of volume is pushed out in the __, and 80% return and are picked up by __ to re-enter circulation.

glomerulus; renal capillaries

2/3 of reabsorption occurs in the __

proximal tubule

There is no loop of Henle in the __

cortical nephron (located in cortex/outer layer of kidney)

How does osmosis change in the loop of henle?

hyperosmotic in descending limb, hypoosmotic in ascending limb

• meaning: water reabsorption in descending limb, and solute reabsorption in ascending limb

Describe the route from the glomerulus to the renal pelvis.

100% of __ are reabsorbed in the proximal tube.

amino acids

Different cells have different __ controls for different __.

regulatory; ions

Filtrate comes through the __ with high [Na+]. [Na+] and other ions are transported into the __ and pushed back into the __ to return into circulation.

tubular lumen; tubular epithelial cell; peritubular capillary

Filtrate → capillaries = __

capillaries → filtrate = __

reabsorption; secretion

What 4 things does the kidney regulate?

1. water

2. acid-base balance

3. electrolytes (Na+)

4. nitrogenous waste excretion

How does the glomerulus work?

plasma enters afferent arteriole → glomerulus capillaries, where filtrate passes into the Bowman’s capsule

• → filtrate channels to proximal tubule

• → remaining blood leaves through efferent arteriole

The proximal tubule has a low intracellular __ concentration due to:

Na; Na/K pump

In the proximal tubule, there is a __ to make ATP to maintain a low Na concentration.

mitochondrial network

The __ reabsorbs 65% of glomerular filtrate.

proximal tubule

Fluid reabsorbed in the proximal tubule has the same __ as filtrate.

osmolality

• isoosmotic since ion flow causes fluid to follow

What is reabsorbed exclusively in the proximal tubule? (3)

glucose, amino acids, certain organic acids (usually completely reabsorbed)

• body wants to maintain these in blood

What is exclusively secreted in the proximal tubule?

other classes of organic acids and bases

What is the goal of the descending limb of the loop of henle?

generate higher osmolarity (absorb more water)

The descending limb has no regulatory control. It is __

passive

The thin limbs of the loop of henle are __ and __ epithelia without __.

thin; flat; mitochondria

What does this image show?

thin limbs of loop of henle

How do the thin limbs maintain the environment of the interstitium? How does this contribute to the counter-current multiplier

• descending limb = permeable to water but not solutes → water reabsorbed passively by high osmolarity of interstitial fluid & water passively leaves filtrate, making it more concentrated

  • hyperosmotic

• ascending limb = impermeable to water but permeable to solutes → sodium and chloride passively transported out of filtrate into interstitial space

  • hypoosmotic

• → maintains osmotic gradient in kidneys interstitium

  • crucial for countercurrent multiplier system → enables kidney to produce concentrated urine when needed (during dehydration)

  • collecting ducts can efficiently function by allowing water to move out of collecting duct and into interstitium

What vasoconstrictors are found in the glomeurulus and JGA (juxtaglomerular apparatus)?

• sympathetic nerves (catecholamines)

• angiotensin II

• endothelin

What vasodilators are in the glomerulus and JGA? (6)

• PGE2

• PGI2

• nitric oxide

• bradykinin

• dopamine

• ANP (atrial natriuretic peptide)

There are a lot of __ in the thick ascending limb.

mitochondria

The thick ascending limb reabsorbs 25% of __

salt (sodium escapes but not water)

The thick ascending limb reabsorbs little __, so fluid remaining is __. Why?

H2O; dilute

• sets stage for regulatory control in collecting duct

The thick ascending limb provides __ to glomerulus at __.

regulatory feedback; macula densa (T-G feedback)

The thick ascending limb sets up the __

counter-current multiplier

The early distule tubule has __

mitochondria

The __ reabsorbs 5% of filtered salt.

distal tubule

Like the thick ascending limb, the __reabsorbs little H2O, so fluid remaning is diluted even more.

distal tubule

• no aquaporins

The early distal tubule is similar to the thick ascending limb except they have different __.

transporters

The early distal tubule regulates hormonal __

Ca2+

In the collecting tubule, there are 2 __ with different regulatory controls. What are they?

cell types (principal cell, a-intercalated cell)

What is the function of principal cells? (3)

• adjust amounts of Na+ and H2O reabsorbed into body

• adjusts amount of K+ secreted

• hormonal control: aldosterone & ADH

What is the function of a-intercalated cells?

• adjust amounts of K+ reabsorbed

• acid-base regulation: H+ secretion