Introduction to the Kidneys and Body Fluids

Question 1

What 2 sub-compartments does the ECF contain?

Answer 1

Plasma (3L)
Interstitial fluid (11L)

Question 2

Which forces determine fluid and solute movement between plasma and interstitial fluid?

Answer 2

Starling forces

Question 3

What must be kept the same in the ICF and ECF and why?

Answer 3

Osmolarity must be kept the same to avoid excess shifts of water between ECF and ICF

Question 4

What differs between the ECF and ICF

Answer 4

Solute composition

Question 5

What is the principal electrolyte of the ECF and therefore what does it determine?

Answer 5

Sodium is the principal electrolyte of the ECF and therefore it determines ECF osmolarity

Question 6

Why is the control of body fluids important?

Answer 6

For cell structure and function

Tissue perfusion

Question 7

What causes disruption to tissue structure and function?

Answer 7

Large shifts between the volume of ECF and ICF

Question 8

What does tissue perfusion depend on?

Answer 8

The balance between circulating (plasma) volume and interstitial volume

Question 9

What two key processes does the balance of salt and water depend on?

Answer 9

Osmoregulation and volume regulation

Question 10

What is osmoregulation?

Answer 10

The maintenance of osmotic equilibrium between the volume of ECF and ICF

Question 11

What is volume regulation?

Answer 11

The maintenance of adequate ECF volume to support plasma volume

Question 12

What can plasma osmolarity be estimated by and what is the typical value?

Answer 12

2[Na] + 2[K] + [glucose] + [urea]

Typically 288mOsm/L

Question 13

Why does Na have a bigger impact on osmolarity than any other electrolyte?

Answer 13

As other electrolytes are present in much lower concentrations and can be neglected as a contributor to osmolarity

Question 14

What are the two ways of changing the osmolarity of a solution?

Answer 14

Add/remove solute

Add/remove water

Question 15

How does the body accomplish osmoregulation?

Answer 15

By adding/removing water, not sodium

Question 16

What does it mean when plasma osmolarity rises and what happens as a response to this?

Answer 16

Means more water is needed

Kidneys produce a small volume of concentrated urine= water retention

Question 17

What does it mean when plasma osmolarity falls and what happens as a response to this?

Answer 17

Means there is too much water in the body

Kidneys produce a large volume of dilute urine= water excretion

Question 18

What are changes in plasma volume detected by?

Answer 18

Stretch and pressure receptors in the cardiovascular system

Question 19

What is a fall in blood volume opposed by and what happens as a result of this?

Answer 19

Opposed by sodium retention

Causes water to follow osmotically and restores the volume

Question 20

What is the main function of the kidneys?

Answer 20

Homeostasis

Question 21

What is a by-product of kidney function?

Answer 21

Urine

Question 22

What is the urinary tract important for?

Answer 22

Temporary storage and removal of urine

Question 23

What are the other functions of the kidney?

Answer 23

• Osmoregulation
• Volume regulation
• Acid-base balance
• Regulation of electrolytes
• Removal of metabolic waste from blood
• Removal of foreign chemicals in bloof
• Regulation of red blood cell production

Question 24

What is the functional unit of the kidney?

Answer 24

The nephron

Question 25

What does the nephron consist of?

Answer 25

Special blood vessels and elaborate tubules

Question 26

Where does urine production begin?

Answer 26

In the nephron

Question 27

What major structures are found in each nephron?

Answer 27

Blood vessels, the golemrulus, Bowman's capsule and the renal tubule

Question 28

Which artery supplies the kidney?

Answer 28

The renal artery

Question 29

What supplies the nephron?

Answer 29

Subdivisions of the renal artery= the afferent arteriole

Question 30

Which vein drains the kidneys?

Answer 30

The renal vein

Question 31

What are the four basic processes of renal function?

Answer 31

- Glomerular filtration - Tubular reabsorption - Tubular secretion - Excretion of water and solutes in the urine

Question 32

What is the Glomerular Filtration Rate?

Answer 32

The amount of filtrate produced by the kidneys each minute

Question 33

What reduces the GFR?

Answer 33

Renal failure

Question 34

What can be used as an index of GFR?

Answer 34

Plasma creatinine

Question 35

What is the process of Glomerular filtration?

Answer 35

- Hydrostatic pressure forces fluids and solutes through the glomerular capillary membrane - Small molecules pass readily, larger molecules can't pass - Leads to a plasma ultra filtrate in the Bowman's capsule

Question 36

What is the process of reabsorption?

Answer 36

Many substances are filtered and then reabsorbed from the tubular lumen into the peritubular capillaries

Question 37

What is secretion important for?

Answer 37

- Disposing of substances not already in the filtrate - Eliminating undesirable substances eg urea and uric acid - Ridding the body of excess K+ - Controlling blood pH

Question 38

What is the equation for total body water balance?

Answer 38

Balance= input - output

Question 39

What should the total body water balace be and why?

Answer 39

Should be 0, or otherwise there will be a change in osmolality

Question 40

What is the result of water restriction?

Answer 40

- Plasma osmolality rises - Causes increased secretion of ADH - Results in decreased urine volume and increased urine osmolality

Question 41

What is the result of an increase in water intake?

Answer 41

- Increase in water absorption through GIT - Plasma osmolality falls - Reduced secretion of ADH - Results in increased urine volume and decreased urine osmolality

Question 42

What is [Total body Na+] equal to?

Answer 42

Intake - elimination

Question 43

How is Na+ lost from the body?

Answer 43

Sweat, diarrhoea and vomit

Question 44

Which major hormone system is important in retaining sodium?

Answer 44

The Renin-angiotensin-aldosterone system (RAAS)

Question 45

Which major hormone system is important in eliminating sodium?

Answer 45

Cardiac natriuretic peptides (ANP)