Week 9 (renal system)

Question 1

Why do we need kidneys?

Answer 1

For the maintenance of water and solutes in the internal environment.
For waster removal.

Question 2

What must surround body cells in order for them to function properly?

Answer 2

An extra-cellular fluid which is relatively constant with regard to osmolality.

Question 3

What do the kidneys (along with the neural and endocrine system) regulate?

Answer 3

The volume and osmolality of the ECF by altering the amount of electrolytes and water excreted.

Question 4

What are kidneys?

Answer 4

2 bean shaped organs lying in the retroperitoneal space and next to the bones and muscles on the back.

Question 5

Name and explain the key sections of a kidney

Answer 5

Gerota’s fascia: a thin, fibrous tissue on the outside of the kidney. Below Gerota’s fascia is a thin layer of fat.
Renal capsule: layer of fibrous tissue that surrounds the body of the kidneys inside the layer of fat.
Cortex: tissue just under the renal capsule.
Medulla: inner part of the kidney.
Renal pelvis: a hollow area in the centre of each kidney where urine collects.
Renal artery: brings blood to the kidney.
Renal vein: takes blood back to the body after it has passed through the kidney.
Renal hilum: area where the renal artery, renal vein and ureter enter the kidney.
Nephrons: millions of small tubes inside each kidney.

Question 6

What are the basic functions of the kidney?

Answer 6

Controls blood composition.
Controls blood volume.
Controls blood pressure.

Question 7

Explain how the kidneys maintain the composition and volume of body fluids.

Answer 7

The kidneys excrete variable quantities of water and solutes resulting in the regulation of body fluid volume, osmolality, electrolyte content/concentration and the excretion of metabolic end products and foreign substances.

Question 8

How do the autonomic nerve fibres, ganglia and sympathetic vasomotor fibres control the kidney and ureter?

Answer 8

Decrease the rate of blood flow to the glomerulus through contraction of precapillary sphincters.
Sympathetic nervous system is stimulated by renin, which is released by the kidney.
Causes changes in water and sodium reabsorption by the nephron.

Question 9

What is the nephron?

Answer 9

The functional unit of the kidney.
Responsible for blood processing.
Change in the type of cells along the length of the nephron to enable it to perform its function.

Question 10

Name the 3 main areas of the nephron

Answer 10

Renal corpuscule
Renal tubule
Collecting duct

Question 11

What 4 principles are key to kidney function and urine production?

Answer 11

Filtration
Reabsorption
Secretion
Excretion

Question 12

Define filtration

Answer 12

Movement of fluid from glomerus into lumen of Bowman’s capsule and then the proximal convoluted tubule.

Question 13

Define reabsorption

Answer 13

Fluid in the tubule lumen is now ‘external’ to the body unless it is reabsorbed and returned into system via peritubular capillaries, lymph and vasa recta.

Question 14

Define secretion

Answer 14

Removes molecules from blood and secretes them into lumen

Question 15

Define excretion

Answer 15

Urine (which contains waste products like urea, creatine, excess salts and other unwanted substances), is collected in the collecting ducts and are transported by the ureters (muscular tubes) from the kidneys to the bladder to be emptied out of the body.

Question 16

Describe glomerular filtration

Answer 16

Occurs at the renal corpuscle.
Plasma moves from the blood vessels of the glomerulus into the lumen of the Bowmans capsule.

Question 17

What happens to 20% of the plasma?

Answer 17

Moves into Bowmans capsule and most of this is then reabsorbed further along the nephron.

Question 18

What happens to 80% of the plasma?

Answer 18

Proceeds to the peritubular capillaries, where secretion of desired solutes into the nephron lumen occurs, ready for excretion.

Question 19

What increases the permeability of the glomerulus?

Answer 19

Fenestrated endothelium (pores)

Question 20

What is the plasma that moves into the Bowman’s space dependent on?

Answer 20

Hydrostatic pressure
Colloid osmotic pressure
Hydrostatic fluid pressure

Question 21

What controls glomerular filtration rate?

Answer 21

Net filtration: changes in renal blood flow and blood pressure.
Filtration coefficient: changes in diameters of the afferent and efferent arterioles to alter the GFR.

Question 22

What actions the changes in the control of glomerular filtration rate?

Answer 22

Hormones: angiotensin II and prostaglandins.
Nervous: sympathetic nerves release noradrenaline resulting in arteriole constriction.
Autoregulation: myogenic response and tubuloglomerular feedback.

Question 23

What makes up filtrate?

Answer 23

Plasma
Glucose
Amino acids
Most hormones
Urea
Uric acid
Creatine
Ions
Water

Question 24

What isn’t filtered into filtrate?

Answer 24

Red blood cells
Platelets
Plasma proteins

Question 25

What is the glomerular filtration rate?

Answer 25

The amount of filtrate the kidneys produce per minute.

Question 26

How much filtrate is produced by the kidneys:
1. per minute
2. per day

Answer 26

1. 125ml
2. 180l

Question 27

How much urine is produced per day.

Answer 27

1 litre

Question 28

How much filtrate is reabsorbed?

Answer 28

99%

Question 29

Describe the process of tubular reabsorption

Answer 29

The process by which substances in the renal tubules are transferred back into the bloodstream.
Most reabsorption takes place in the proximal convoluted tubule.
Highly selective process.
More important than secretion for must nutrients and ions.
Allows for easy tuning of ions and water balance.

Question 30

What happens during tubular reabsorption?

Answer 30

Nutrients are reabsorbed first, then ions such as sodium. This then generates a concentration gradient so that water is reabsorbed by osmosis.

Question 31

Describe the descending and ascending limb of the loop of Henle

Answer 31

Descending limb = thin walls
Ascending limb = thin walls then thick walls

Question 32

What does the Loop of Henle reabsorb?

Answer 32

Half the remaining water.
2/3 of remaining ions.

Question 33

What system does the loop of Henle use?

Answer 33

Counter-current multiplication

Question 34

Describe the counter-current multiplication process

Answer 34

1. Na and Cl are pumped out of the ascending limb.
2. Increase in Na and Cl concentration outside.
3. Water leaves descending limb by osmosis.
4. High concentration of Na and Cl in ascending limb.

Question 35

Why use the counter-current system?

Answer 35

It is an efficient way of reabsorbing solutes and water.
It establishes a concentration gradient which allows reabsorption in the collecting system

Question 36

What does angiotensin II do?

Answer 36

Constrict arterioles closing down capillary beds.
Stimulate proximal tubules to reabsorb sodium.
Stimulate adrenal cortex to release aldosterone from adrenal gland.
Increase strength of heartbeat.
Stimulates pituitary to release antidiuretic hormone.

Question 37

What does ADH (anti-diuretic hormone) do?

Answer 37

Controls water reabsorption in DCT and collecting system.
Creates water channels increasing permeability.
Stimulates water reabsorption and controls blood volume.