Renal an intro to kidneys and body fluids

Question 1

What equilibrium must the ICF and ECF be in?

Answer 1

The ICF and ECF must be in osmotic
equilibrium

Question 2

What will a change in solute concentration in either ICF or ECF generate?

Answer 2

Change in solute concentration in either ICF or ECF will generate osmotic gradient, resulting in shifts of water between compartments

Question 3

Why is osmolarity of the ECF regulated to avoid?

Answer 3

Osmolarity of the ECF is regulated to avoid
osmotic shifts of water between ICF and ECF
volumes

Question 4

What is the normal range of osmolarity?

Answer 4

Normal range 280-300 mOsm/L

Question 5

What is osmoregulation?

Answer 5

Osmoregulation is the physiological
process that maintains constant
ECF osmolarity
-control of salt concentration in the ECF by adjusting
the amount of pure water in the body

Question 6

What is the ECF compartment subdivided into?

Answer 6

• Interstitial (or extravascular) compartment (about 75% of ECF)
• Plasma (or vascular) compartment (about 25% of ECF)

Question 7

What is volume regulation?

Answer 7

Volume regulation is control of the ECF volume to ensure appropriate plasma volume and blood pressure

Question 8

What does maintaining salt and water balance require?

Answer 8

Maintaining salt and water balance requires
integration of osmoregulation and volume
regulation

Question 9

What is volume regulation?

Answer 9

control of the amount of salt and water in the ECF
and hence, ECF volume

Question 10

What is the central funciton of the kidney and what is its by-product?

Answer 10

Homeostasis is the central
function of the kidney
-Production of urine is the by-product

Question 11

what do renal functions include?

Answer 11

• Osmoregulation
• Volume regulation
• Acid-base balance
• Regulation of electrolyte balance (eg potassium, calcium, phosphate)
• Removal of metabolic waste products from blood
• Removal of foreign chemicals in the blood (e.g. drugs)
• Regulation of red blood cell production (erythropoietin)

Question 12

What is the nephron?

Answer 12

The nephron is the functional unit of the kidney

Question 13

What does the nephron consist of?

Answer 13

The nephron consists of special
blood vessels and elaborate
tubules

Question 14

Structural organization of the nephron: renal tubule

Answer 14

Look at slides for structure

Question 15

Structural organization of the nephron: blood
vessels

Answer 15

Look at slides for structure

Question 16

What are the 4 basic processes of renal function?

Answer 16

• Glomerular Filtration
• Tubular Reabsorption
• Tubular Secretion
• Excretion of water and solutes in
  the urine

Question 17

What are the steps involved in glomerulara filtration?

Answer 17

• Balance of Starling forces drive water and solute across the capillary membrane
• Small molecules pass readily – large ones (proteins) and cells cannot pass
• This leads to a plasma ultrafiltrate in the Bowman’s capsule, the first step in the production of urine

Question 18

What is glomerular filtration rate(GFR)/

Answer 18

The amount of filtrate produced by the kidneys each minute

Question 19

What is the average GFR?

Answer 19

Averages 125 ml/min (approx 20% of renal plasma flow)

Question 20

When is GFR reduced?

Answer 20

Very important clinical indicator (reduced in renal failure)

Question 21

What can be used as an index of GFR?

Answer 21

Plasma creatinine can be used as an index of GFR

Question 22

What are the steps involved in tubular reabsorption?

Answer 22

Many substances are filtered and then reabsorbed from the tubular lumen into the peritubular capillaries
About 70% of filtered salt and water reabsorbed from proximal tubule
20-25% from loop of Henle
Variable fraction of remaining 5-10% is reabsorbed from distal tubule and collecting duct

Question 23

What are the steps involved in tubular secretion?

Answer 23

Tubular secretion is important for disposing of substances beyond their level in the filtrate
Eliminating toxins and metabolic by-products

Question 24

In tubular secretion, where is excess K+ secreted?

Answer 24

Potassium balance: excess K+ secreted in DT and CD

Question 25

In tubular secretion, what does acid-base balacne rely on?

Answer 25

Acid-base balance relies on H+ secretion in DT and CD

Question 26

What are the steps involved in excretions of water and solutes in urine?

Answer 26

The tubular fluid remaining after filtration, reabsorption and secretion is excreted as urine.

Question 27

How can amount excreted in urine be measured?

Answer 27

Amount filtered-amount absorbed+amount secreted

Question 28

Why can you estimate GFR from plasma concentration?

Answer 28

creatinine is filtered but not reabsorbed; can estimate GFR from plasma concentration

Question 29

What are the physiological response to water restriction?

Answer 29

Loss of water (skin, lungs)
* Plasma osmolality rises
Response is
* Increased thirst
* Increased secretion of hormone, vasopressin (also called antidiuretic hormone, ADH)

Question 30

What does ADH increase and how?

Answer 30

ADH increases renal water reabsorption
* Decreased urine volume
* Increased urine osmolality

Question 31

What are physiological repsonse to increase in water intake?

Answer 31

Increase in water absorption through GIT
* Plasma osmolality falls
Response is
* Decreased thirst
* Reduced secretion of ADH
Results in
* Urine volume increases
* Urine osmolality decreases

Question 32

What is ECF volume determined by?

Answer 32

ECF volume is determined by the amount of sodium in this
compartment

Question 33

Where are the main volume sensors for ECF?

Answer 33

Main volume sensors are in the cardiovascular system

Question 34

What is a fall in blood volume opposed by?

Answer 34

A fall in blood volume is opposed by hormonal signals promoting
sodium retention; water follows osmotically, restoring volume

Question 35

Why must sodium intake and secretion be balaned?

Answer 35

Sodium intake and excretion must be balanced to maintain constant
ECF volume

Question 36

What does RAAS do in sodium balance?

Answer 36

• Increases renal Na reabsorption
• Increases ECF volume

Question 37

What does cardiac natriuretic peptides do in sodium balance?

Answer 37

• Decreases renal Na reabsorption
• Decreases ECF volume