formation of urine

Question 1

what processes in the nephron form urine

Answer 1

glomerular filtration
tubular reabsorption
tubular secretion

Question 2

filtrate contains

Answer 2

same concentration of all substances except for proteins and blood cells

Question 3

urine

Answer 3

waste that leaves the body.
- contains urea, creatinine, uric acid
- metabolic waste including
sodium, potassium, chloride and excess water.

Question 4

where does glomerular filtration occur?

Answer 4

renal corpuscle

Question 5

glomerular filtration is a…

Answer 5

passive process where hydrostatic pressure forces fluids and solutes through the membrane

Question 6

glomerular filtration produces filtrate that:

Answer 6

includes: water, glucose, amino acids and nitrogenous wastes.
excludes: proteins and RBC

Question 7

endothelium of filtration membrane includes:

Answer 7

1st layer.pores, 2nd layer. basement membrane and 3rd layer. membrane of glomerular capsule.

Question 7

what wraps around the capillaries to form the filtration membrane

Answer 7

fenestrations or pores and podocytes

Question 8

pores allows passage of..

Answer 8

plasma components excluding BCs and proteins

Question 9

basement membrane restricts..

Answer 9

all but small protiens, and allows other solids to pass

Question 10

membrane of glomerular capsule is made up of ____ and has __________ between their processes

Answer 10

podocytes, filtration slits

Question 11

forces that drive fluid and solutes out of blood across glomerular capillary membrane

Answer 11

hydrostatic pressure favours filtration as efferent arteriole is smaller than afferent –> feeds into glomerular space

opposing filtration
capsular hydrostatic pressure and blood colloid osmotic pressure.

Question 12

tubular reabsorption occurs

Answer 12

predominantly in the PCT loop of Henle and DCT

Question 13

what is the net filtration of glomerular filtration

Answer 13

10+ millimetres of mercury mmHg

Question 14

PCT - tubular reabsorption

Answer 14

PTC cells are most active reabsorbers.
reabsorb glucose amino acid sodium potassium and water via osmosis.
PTC cells absorb nearly all uric acid and half of the urea, these waste products are later secreted back into filtrate

Question 14

what is reabsorbed back into the blood stream?

Answer 14

99% of water, glucose, amino acids, sodium and chloride ions,

Question 14

tubular reabsorption occurs as…

Answer 14

filtrate traveling through renal tubule is reabsorbed back into blood stream via peritubular capillaries

Question 15

the reabsorption of sodium creates an osmotic gradient across the tubule which drives..

Answer 15

water absorption through aquaporins.
WATER REABSORPTION IS DEPENDANT ON SODIUM REABSORPTION

Question 15

DCT and collecting duct - tubular reabsorption

Answer 15

fine tuning of electrolyte reabsorption
- 10% sodium and 20% of water remain in tubules.
- ADH controls water reabsorption–> makes collecting ducts more permeable to water via aquaporins
- aldosterone controls fine tuning of sodium and potassium
- ANP inhibits sodium reabsorption at collecting ducrts = reduces blood sodium conc. =decrease bp and volume
- PTH acts on DCT fine tuning of calcium and phosphate ions

Question 16

loop of henle- tubular reabsorption

Answer 16

produces highly concentrated or very dilute urine.
descending –> concentrates filtrate by removing water to peritubular blood via osmosis (impermeable to solutes)
ascending–> impermeable to water no aquaporins, removes solutes like sodium and chloride.

Question 17

sodium reabsorption provides the energy for..

Answer 17

for the reabsorption of most other solutes ect. glucose, amino acids, vitamins

Question 18

substances are not reabsorbed if..

Answer 18

• lack carriers or channels
• are not lipid soluble
• too large to pass through membrane pores
• urea, creatinine and uric acid most important non reabsorbed substances

Question 19

micturition

Answer 19

prices of emptying urine from the bladder, also known as urination

Question 20

micturition process

Answer 20

kidney produce urine, collected by renal pelvis, travels to ureter, bladder then released by ureters

Question 21

bladder has three layers:

Answer 21

mucosa- inner, detrusor -middle and adventitia- outer

Question 22

three things must happen simultaneously for micturition to occur

Answer 22

contraction of detrusor muscle (autonomic)
internal urethral sphincter (smooth muscle) involuntary must OPEN (autonomic involuntarily)
external urethral sphincter (skeletal muscle ) must open (voluntary)

Question 23

Steps of micturition reflex (children no voluntary control

Answer 23

1. Bladder wall distends as urine accumulates
   
   2. Stretch receptors are activated
   3. Sends signals to sacral region of spinal cord, stimulates parasympathetic neurons, causing detrusor muscle contraction
   4. Internal urethral sphincter will open, inhibits the sympathetic neurons to the internal urethra sphincter which helps it to open

Question 24

Within the brain–> pons, two centres participate in the control of micturition:

Answer 24

PONSTINE STORAGE CENTRE –> inhibits
PONTINE MICTURITION CENTRE –> promotes reflex

Question 25

PONTINE STORAGE

Answer 25

1. Neural fibres from stretch receptors in bladder get relayed to pons and higher brain centres (provide consciousness of full bladder)
   2. Small bladder activates pontine storage centre
   3. Inhibits urination= SUPRESSES PARASYMPATHETIC and ENHANCES SYMPATHETIC output to bladder.
   4. Person chooses to not void/empty bladder
   5. Bladder contraction subside temporarily
   6. Bladder fills
   7. External urethra sphincter is VOLUNTARY we choose to keep it closed

Question 26

PONTINE MICRUITION

Answer 26

2. Urine added to bladder, stretch receptors activate pontine micturition
   
   3. Parasympathetic activity is promoted and sympathetic activity decreased
   4. Open internal urethral sphincter.
   5. Decreased somatic activity to the external urethral sphincter, opening it.
      Urine exits.