Urinary System DYK Questions

Question 1

What is the composition of the filtrate in the Bowman’s capsular space

Answer 1

Similar to plasma, only no proteins

Question 2

Why don’t plasma proteins pass into the Bowman’s capsular space under normal circumstances?

Answer 2

Glomerular filtration membrane pores are too small

Question 3

What part of the nephron is involved with obligatory water, ion, and organic nutrient reabsorption?

Answer 3

PCT

Question 4

An obstruction of a ureter by a kidney stone limits the flow of urine between which two points?

Answer 4

Renal pelvis and urinary bladder

Question 5

The ability to consciously control the micturition reflex depends on the ability to control which muscle?

Answer 5

External urethra; sphincter

Question 6

James goes out for a morning run. His mean arterial pressure (BP) increases to 115mmHg, thus increasing his GFR. To maintain GFR, do you vasodilate or vasoconstrict his afferent arteriole?

Answer 6

Vasoconstrict. By vasoconstricting the afferent arteriole, you have returned James GFR to normal

Question 7

While James is reading the Sunday paper the dog starts barking. James goes to investigate. His BP increases to 88mg.His GFR increases slightly too. To maintain GFR, do you vasodilate or vasoconstrict his afferent arteriole?

Answer 7

By slightly vasoconstricting James afferent arteriole, you have counteracted his slight increase in BP. James GFR normalises (back to homeostasis)

Question 8

James is napping with his dog. His BP decreases to 80mm Hg and his GFR decreases too. To maintain GFR, do you vasodilate or vasoconstrict his afferent arteriole.

Answer 8

By vasodilating the afferent arteriole, you have returned James GFR to normal.

Question 9

James is experiencing chest pain. His BP plummets to 70mmHg, causing a major decrease in GFR. To maintain GFR, do you vasodilate or vasoconstrict for afferent arteriole.

Answer 9

If you answered vasodilate then …OUCH! You have increased the blood flow to the kidney at the expense of other organs. James is going into shock due to a heart attack. This is an emergency, and the extrinsic controls will take over to shunt the blood to other vital organs when BP falls below 80mmHg.

Question 10

What effect does renin have on the glomerular filtration rate (GFR)

Answer 10

It will increase the GFR and vasoconstrict the efferent arteriole

Question 11

Mr. Petit has been prescribed a drug to lower his blood pressure that inhibits angiotensin-converting enzyme (ACE). What effect will this have on his body?

Answer 11

It will inhibit the conversion of angiotensin I to angiotensin II

Question 12

Can you list the main functions of the urinary system?

Answer 12

Excretion
Removal of metabolic wastes from body fluids
Elimination
Discharge of these wastes from body
Homeostatic regulation
Regulating blood volume and blood pressure
Regulating plasma ion concentrations
Helping to stabilise blood pH
Conserving valuable nutrients
Assisting liver

Question 13

Can you describe the structures of the nephron and their functions? (hint: renal corpuscle, renal tubule (includes PCT, Loop of Henle, DCT and collecting ducts and also the JGC)

Answer 13

• Structural and functional unit of kidney
  - 1 million per kidney
  - Performs the processes to filter blood plasma and form urine
  - Consists of
  ○ Renal corpuscle
  - consists of 2 parts
  ○ Bowman’s capsule
  ○ Glomerulus

			○ Renal tubule
				○ Renal tubule has 3 main parts
					- Proximal convoluted tubule (PCT)
					- Nephron loop (loop of Henle)
Distal convoluted tubule (DCT)

Question 14

Can you follow the movement of fluid through the kidney? (Hint: start with blood, then follow in the form of filtrate)

Answer 14

Glomerular filtration
a. Makes a protein-free filtrate that contains water, ions, nutrients and waste products
Tubular reabsorption
a. Selective movement of valuable wanted substances from filtrate back into blood (via peritubular capillaries)
b. Glucose, amino acids, 99% of water, salt (NaCL)
Tubular secretion
Selective movement of some unwanted substances from blood (peritubular capillaries) back into filtrate

Question 15

Can you describe the reabsorption in the PCT, DCT and CD as well as secretion at DCT?

Answer 15

Reabsorption at the PCT

		- PCT cells normally reabsorb 60-70% of filtrate produced in glomerulus/renal corpuscle
		- Substances for reabsorption diffuse out of tubular into adjacent peritubular blood capillaries
		- Four functions of the PCT
			1. Reabsorption of organic nutrients (eg. 100% of filtered glucose)
			2. Reabsorption of ions
			3. Reabsorption of water

	Reabsorption along the nephron loop
		- Mainly reabsorption of water and Na2+ and Cl- ions
		- Further reabsorption of water (descending limb)
		-  reabsorption  of Na+ and K+ and Cl- ions (ascending limb)
	Sets up a concentration gradient so water can be reabsorbed and at same time makes concentrated urine 

	reabsorption in the DCT

		- Hormonally regulated by aldosterone, and parathyroid hormone (PTH)
		- Variable reabsorption of water, Na+ and Ca+2 under hormonal control
		- DCT cells reabsorb tubular sodium Na+ (by aldosterone and water follows)
		- DCT cells reabsorb calcium Ca2+ (by PTH)

Question 16

What is the usual composition of the filtrate and urine?

Answer 16

• Usually clear, and pale to dark yellow
  ○ Should be no glucose or amino acids (normal reabsorbed in PCT), also no protein (never filtered at glomerulus)
  ○ Variations could indicate pathology
  ○ 95% water
  5% solutes (in decreasing order of concentration)

Question 17

Can you describe the extrinsic long term hormonal and neural response (initiated by Angiotensin II) to decreasing blood flow to the kidneys (Hint: activation of RAAS)

Answer 17

Summary on how angiotensin II works in 3 ways
1. At the adrenal gland: angiotensin II stimulates aldosterone secretion > increases Na+ reabsorption by DCT and CD cells > water follows sodium back into blood > increases blood volume > increases BP > GFR restored
2. At the nephron: angiotensin II release > selectively causes vasoconstriction of efferent arterioles > decreases blood flow out of the glomerulus > increases the glomerular hydrostatic pressure > leads to an increase in GFR > restores GFR homeostasis. Also causes vasoconstriction of systemic veins directly > increases BP > increases GFR > GFR restored
In the CNS: angiotensin II stimulates increased production of antidiuretic hormone (ADH) from brain > acts on DCT and CD to reabsorb more water from filtrate back into blood > increases BV > increases BP > GFR restored