Lecture 9: Urinary System

Question 1

What 3 processes are involved in the production of urine & adjustment of blood composition

Answer 1

1. glomerular filtration
2. Tubular Reabsorption
3. Tubular Secretion

Question 2

How many times per day does renal system filter plasma volume

Answer 2

more than 60 times per day

- 180L fluid per day

Question 3

how much fluid does renal system excrete per day

Answer 3

~ 0.5 - 2.0L per day leaving 178 - 179.5 L to be reabsorbed

-99% of water that is filtered out of glomerular blood per day is reabsorbed into tubular blood

Question 4

The process of filtration

Answer 4

• created from blood

- passive and non selective: substances (liquids, solutes) are pushed through the mebrane by hydrostatic pressure

Question 5

What is a key feature of filtration

Answer 5

glomerular capillaries are long and have high pressure for efficient filtration
-the membrane of filtration is very permeable to H2O and solutes

Question 6

what ensures elevated pressure in filtration membrane

Answer 6

-inferior diameter in the efferent capillaries compared to the afferent capillaries ensure elevated pressure

Question 7

How does hydrostatic pressure of glomerular capillaries (blood pressure) work in filtration

Answer 7

Push H2O and solutes out of blood and through the filtration membrane

Question 8

How does osmotic pressure of glomerular capillaries work in filtration

Answer 8

Due to plasma protein

Question 9

How does hydrostatic pressure of capsular space work in filtration

Answer 9

Exerted by the liquids of the capsular space

Question 10

How does movement work.in reabsorption

Answer 10

From filtrate to blood

- process is done actively and passively depending on substances that are being reabsorbed

Question 11

How does reabsorption work in kidney

Answer 11

• let’s H2O and solutes EXIT from blood

- filtrate then reabsorbs (into blood) useful elements leaving behind (into filtrate) elements to EXCRETE

Question 12

What is trascellular route of reabsorption

Answer 12

• Apical membrane -> cytosine-> basolateral membrane (can involve lateral intracellular space) -> interstitial fluid -> capillary

Question 13

What is the paracellular route of reabsorption

Answer 13

Movement through leaky tight junction (especially proximal convoluted tubule)

Question 14

What is proximal convoluted tubule (PCT)

Answer 14

Principal site of reabsorption

• other structures: help to adjust the blood composition to maintain homeostasis via secretion
• Control: changes in osmotic pressure (blood) in peritubular & vasa recta capillaries, H2O reabsorbed passively (osmosis) from filtrate

Question 15

What happens in the loop

Answer 15

• permeability changes
• H2O (osmosis) in descending limb
• symport Na+, Cl- in ascending limb

Question 16

What happens in Distal Convoluted Tubule (DCT)

Answer 16

• controlled via hormones: ADH & aldosterone

- symport Na+, Cl-

Question 17

What happens in collecting duct (CD)

Answer 17

• hormone (ADH & aldosterone)
• Na+ channels (aldosterone used to reabsorb sodium)
• K+ channels: (aldosterone used for its reabsorption)
• H2O (ADH for its reabsorption)
• H+, HCO3 (according to blood pH, urea with or without ADH)

Question 18

What are the 2 types of counter current mechanisms that concentrate urine

Answer 18

1. Countercurrent multiplier
   - ascending & descending limbs of long loop of juxtamedullary nephron
2. Countercurrent exchanger
   - ascending & descending portions of vista recta

Question 19

What osmotic gradient do the kidneys need to maintain

Answer 19

~ 300 mmol/ kg

Question 20

What us the vasa recta

Answer 20

• all permeable to H2O and solutes
• with countercurrent exchanges btw the vasa recta & the interstitial fluid allows the blood remain to isomotic to surrounding (maintains the osmotic gradient )

Question 21

What is the urine composition

Answer 21

95% water
Dissolved substances:
- nitrogen wastes 
- electrolytes
- toxins
- pigments
- hormones
- abnormal constituents

Question 22

What is pyelonephritis

Answer 22

• infection & inflammation of entire kidney
• leads to edema, formation abscesses, accumulation of pus
• tx: antibiotic

Question 23

What is pyelitis

Answer 23

• infection of the pelvis and calyces
• ascending urinary tract infection
• antibiotic therapy

Question 24

What is anuria

Answer 24

• abnormally weak urinary flow
• cause: glomerular arterial pressure too low to undertake filtration
• ex: brought about via a crushing wound or an acute nephritis

Question 25

What is cystitis

Answer 25

• inflammation of the bladder

- caused by bacteria; painful & frequent micturition

Question 26

What is Urethritis

Answer 26

• inflammation of urethra

Question 27

What is incontinence

Answer 27

• inability to control voluntarily micturition

- causes: emotional problems, physical pressure (pregnancy), troubles with NS, age ex. Baby or elderly

Question 28

What is Enuresis

Answer 28

• inability to control micturition during sleep (toddler/ elderly)

Question 29

What is diabetes insipidus

Answer 29

• state where a large quantity of dilute urine is eliminated (polyuria) & thus get also an intense thirst (polydipsia)
• lack / insufficient quantity of ADH
• tx: hormone

Question 30

What is addison’s disease

Answer 30

• excrete large quantities of Na+, Cl-, H2O
• cause: lack/ insufficient quantities of aldosterone (& also cortisol)
• must maintain liquids / salts