Urinary System Physiology

2. The goal of urine production:
1. maintain homeostasis
2. by regulating volume and composition of blood
3. including excretion of metabolic waste products
a) Urea
a) Breakdown product of proteins and amino acids
b) Creatinine
a) Breakdown product of creatine (involved in muscle
contraction)
c) Uric acid
Uric acid is a product of the metabolic breakdown
of purine nucleotides. G and A
High blood concentrations of uric acid can lead to gout and are associated with other medical
conditions including diabetes and the formation of ammonium acid urate kidney stones.

3. • a pair of muscular tubes
• Extend from kidneys to urinary
bladder
• Ureteral openings are slit-like rather
than rounded, helps prevent
backflow of urine.
• Uretal valve – also stops backflow

4. • Is a hollow, muscular organ
• Functions as temporary reservoir urine storage
• Full bladder can contain 1 liter of urine

5. 1. Lining the urinary bladder has folds (rugae):
that disappear as bladder fills.
2. Transitional Cell Epithelium

6. – Smooth muscle.
– contraction compresses urinary bladder and expels urine

7. The Trigone of the Urinary Bladder
• Acts as a funnel:
– channels urine from bladder into urethra
• Is a triangular area bounded by:
– openings of ureters
– entrance to urethra

8. • Extends from neck of urinary bladder
• To the exterior of the body

9. • Is very short (3–5 cm)
• Extends from bladder External urethral
orifice is near anterior wall of vagina

10. • Longer than the female urethra
• Portion is surrounded by the male prostate gland.
The prostate secretes fluid that nourishes and protects sperm.

11. 4. Spongy urethra
(penile urethra):
extends from urogenital
diaphragm
to external urethral orifice
1. Pre-Prostatic urethra:
2. Prostatic Urethra:
– passes through center of prostate gland
3. Membranous urethra:
– short segment that
penetrates the urogenital
diaphragm

13. Clinical urine tests are examinations of the physical and
chemical properties of urine and its microscopic
appearance to aid in medical diagnosis.

15. Acidity (pH). The pH level indicates the amount of acid in urine.
Abnormal pH levels may indicate a kidney or urinary tract
disorder.

16. Concentration. A urine specific gravity test compares the
density of urine with the density of water. It allows doctors to
see the concentration of particles present in urine.

17. Protein. Low levels of protein in urine are normal. If there is a
problem with your kidneys, protein can leak into your urine.
While a small amount is normal, a large amount of protein in
urine may indicate kidney disease.

18. Sugar. Normally the amount of sugar (glucose) in urine is too
low to be detected. If a random urine sample shows more
than 0.25mg/ml, this is considered glycosuria and can be
caused by too high blood glucose levels, a problem with your
kidney filters, or both. Any detection of sugar on this test
usually calls for follow-up testing for diabetes.

19. Ketones. If your cells don't get enough glucose, your body
burns fat for energy instead. This produces a substance called
ketones, which can show up in your blood and urine. High
ketone levels in urine may indicate diabetic ketoacidosis (DKA),
a complication of diabetes that can lead to a coma or even death

20. Bilirubin. Bilirubin is a product of red blood cell breakdown.
Normally, bilirubin is carried in the blood and passes into your
liver, where it's removed and becomes part of bile. Bilirubin in
your urine may indicate liver damage or disease (hepatitis).

21. White Blood Cells. If either nitrites or leukocyte esterase —
a product of white blood cells — is detected in your urine, it
may be a sign of a urinary tract infection.

22. Blood. Hematuria - Blood in your urine requires additional
testing — it may be a sign of kidney damage, infection,
kidney or bladder stones, kidney or bladder cancer, or blood
disorders.

23. As the bladder fills with urine:
1. Detrusor muscle stretch receptors (>500 ml):
• stimulate pelvic nerve
2. Stimulus travels from pelvic nerves
to the Pons: Pontine micturition
center (PMC, also known
as Barrington's nucleus)
3. Signal then delivers sensation to
cerebral cortex
4. Normally the brain send an
inhibitory signal to the pons to
inhibit the bladder from contracting
until a bathroom is found.
Micturation = urination

24. Infants
• Lack voluntary control over urination
• Corticospinal connections are not established

25. Age-Related Changes in Urinary System
• Decline in number of functional nephrons
• Reduced sensitivity to ADH
Incontinence - Is the inability to control urination voluntarily
(allows reabsorption of water)

26. 1. Sphincter muscles lose tone:
– leading to incontinence

27. 2. Brain Damage:
– a stroke
– Alzheimer’s disease
– CNS problems
affecting cerebral
cortex or
hypothalamus

28. 3. In males, urinary retention may develop
if enlarged prostate gland compresses
the urethra and restricts urine flow
The prostate secretes fluid that nourishes and protects sperm

29. Kidney stones form when there is a decrease in urine volume
and/or an excess of stone-forming substances in the urine.

30. a genetic disorder in which abnormal
cysts develop and grow in the kidneys

31. suprarenal glands
Produce hormones that help regulate your metabolism,
immune system, blood pressure, response to stress and
other essential functions.

32. The adrenal cortex produces hormones that:
1. controls sex (androgens, estrogens),
2. salt balance in the blood (aldosterone), and
3. sugar balance (cortisol).
The adrenal medulla produces hormones involved in the fight-
or-flight response (catecholamines, or adrenaline type
hormones such as epinephrine and norepinephrine).

33. A steroid hormone secreted by adrenal glands.
Its main role is to regulate salt and water in the body, thus
having an effect on blood pressure.
(allows reabsorption of salt)

34. Produced in the hypothalamus.
helps regulate the amount of water in your body. It works to
control the amount of water your kidneys reabsorb as they filter
out waste from your blood.
(allows reabsorption of water)

35. Released by muscle cells in the atria in response to high
blood pressure.
Exerts a vasodilator effect on the kidney and also reduces
tubular reabsorption of sodium. Both actions result
in increased urinary elimination of salt and water and tend to
restore atrial pressure toward the normal..
(allows for salt and water loss)