urinary system3

7/30/2019 Urinary System3

1/10

Regulation of Urine Volume and Concentration

Is already diluted ; hypo-osmolar

(compared to plasma osmolarity).Urine is 100 mOsm while plasma (and

also glomerular filtrate) is 300 mOsm

- Depends on our water-bodily needs

- Water is needed reabsorption occur produce highly concentrated urine

- Water is not needed let go into renal

pelvis produce more diluted urine

- But how to produce the already diluted

(hypo-osmolar) urine?

Through the countercurrent mechanism


2/10

- The countercurrent

mechanism establish an

osmotic gradient

extending from cortex tomedulla

- With this organization the:

a) Concentration of urine

that are formed arereadily hypo-

osmolar/diluted and

b) Blood osmolarity is

maintained at 300

mOsm in and out renal

How does the

osmotic gradient is

achieved ???

?? Hypo-

osmolar

urine

Thru

c/currentmechanism

Create

osmotic

gradient


3/10

thru the Countercurrent Multiplier & Exchanger

- The term

countercurrent

means something

flows opposite

directions through

adjacent channels

- Countercurrent

mechanism

contributes the

interactionbetween:

1) Countercurrent

multiplier tubular

component-loop of

Henle

2) Countercurrent

exchangervascular

component-vasa

recta


4/10

The Countercurrent Multiplier

Fn: Establish osmotic gradient

1)Descending loop > permeable to water, permeable to NaCl but not to

water

3)Collecting duct permeable to urea, contributeto gradient concentration


5/10

The Countercurrent Exchanger

Fn: Maintain osmotic gradient

- Flow is sluggish (slow) to make passive exchanges of water & NaCl with

surrounding ISF thus made equilibrium


6/10

Formation of diluted or concentrated urine..??? by ADH

Diluted urine Concentrated urine


7/10


8/10

Urine and Urination (Micturition)

Composition of urine

- water, urea, chloride, potassium, sodium, creatinine, phosphates, sulfates

and uric acid

Physical properties of urine

- pH from 5.0-8.0, slightly acidic (eat meat pH 5-6, vegetarian pH 7-8)

- Translucent (clear not cloudy)changed color by substances like antibiotic,

blood

- Specific gravity: 1.00-1.035 (compare to distilled water)

- Aroma : unpleasant odor ; stale urine produce harsh, stale smell


9/10

Urination (Micturition)

- Is the emptying of the urinary bladder.

- Governed by micturition reflex, but is

also under voluntary control


10/10

Volume reached 250 400 mL will

stimulate stretch receptors

Afferent input to spinal cord stimulates

parasympathetic output to cause muscular

wall to contract

send

Internal sphincter opens allowing

bladder emptying urine is released out

of body

- but, emptying of bladder can be

postpone voluntarily at individual

convenience external sphincter

- 500-600 mL emptying irresistible

whether one wills or not

urinary system3

Documents