Characteristics of Urine & Micturition

Question 1

How much blood is filtered through the kidneys in 24hrs, and how much of this is collected for urine? (2)

Answer 1

150-180L per 24hrs

1.5-1.8L per 24hrs

Question 2

Differentiate between filtrate and urine. (2)

Answer 2

1. Filtrate - contains everything that blood plasma has (except protein), but by the time it reaches the collecting ducts, most of the H2O has been lost and so it contains mostly nutrients and specific ions
2. Urine - contains nitrogenous wastes and unneeded substances

Question 3

What colour range is urine normally and what is the colour due to?

Answer 3

1. Freshly voided urine = clear and pale to deep yellow in colour
2. Colour is due to urochrome → a pigment that results from the body’s destruction of hemoglobin

Question 4

How does the urine colour change with an increase of solutes?

Answer 4

Deeper yellow

Question 5

What other, healthy way may urine change in colour other than the level of solutes?

Answer 5

Eating certain foods (beets = red)

Question 6

Why does urine change in odour when left to stand and what kind of odour does it take on? (2)

Answer 6

1. Action of bacteria on urine solutes

2. Ammonia odour

Question 7

List 3 things that change the smell of urine. (3)

Answer 7

1. Drugs
2. Vegetables (esp asparagus)
3. Diseases (diabetic urine → sweet)

Question 8

What pH is urine usually?

Answer 8

pH 6

Question 9

What do you call foods that make urine more acidic?

Answer 9

Acid-ash foods

Question 10

What kind of diets would make urine more alkaline?

Answer 10

Vegetarian diets

Question 11

What sickness may also make urine more alkaline?

Answer 11

Urinary tract infections (UTI)

Question 12

Does urine weight more or less than diluted water and why? (2)

Answer 12

1. Urine weighs more than diluted water

2. Urine = water + solutes

Question 13

What is specific gravity (SG)?

Answer 13

A form of measurement used to describe how much heavier or lighter something is compared to distilled water

Question 14

What is the SG of distilled water?

Answer 14

SG of distilled water = 1.0

Question 15

What is the range in SG for urine?

Answer 15

Urine SG ranges from 1.001-1.035

Question 16

Define: micturition (voiding)

Answer 16

Emptying of the bladder

Question 17

Name the 2 sphincters that control the flow of urine from the bladder. (2)

Answer 17

1. Internal urethral sphincter (most superior)

2. External urethral sphincter (most inferior)

Question 18

At what point does the stretching of the bladder wall activate the stretch receptors?

Answer 18

After the bladder has collected about 200mL of urine

Question 19

How do nerve impulses travel to the bladder for contractions? (3)

Answer 19

1. Impulses are transmitted to the sacral region of the spinal cord
2. Impulses go back to the bladder via the pelvic splanchnic nerves
3. This causes the bladder to go into reflex contractions

Question 20

What happens as the reflex contractions grow stronger? (2)

Answer 20

1. Stored urine is forced past the internal urethral sphincter into the upper part of the urethra
2. This gives the urge to void

Question 21

When does micturition reflex occur?

Answer 21

After 200-300mL of urine has been collected by the bladder

Question 22

When does incontinence occur?

Answer 22

When one is unable to voluntarily control the external sphincter

Question 23

What population is incontinence naturally common in and why? (2)

Answer 23

1. Usual in children 2yrs old or younger

2. They have yet to gain control of their voluntary sphincter

Question 24

What is urine retention?

Answer 24

The opposite of incontinence; the bladder is unable to expel urine

Question 25

Who is urine retention common in and why? (2)

Answer 25

1. Patients who had been administered general anesthesia

2. It takes longer for the smooth muscles to regain their activities

Question 26

Define: hyperplasia

Answer 26

Hyperplasia: enlargement of the prostate gland which surrounds the neck of the bladder

Question 27

Why is urinary retention relatively common in older men?

Answer 27

Hyperplasia means that the prostate gland is enlarged, and this often results in the bladder being pressured by the increased size of the prostate