Chapter 12: Filtering Out the Junk: The Urinary System Summary

The Urinary System

The urinary system filters harmful substances like urea creatinine and uric acid from blood plasma and excretes them from the body. It removes excess substances present in the blood.

The urinary system also maintains the normal osmotic pressure by removing water when the tissue level concentration is very high.

The kidney

The kidneys filter about 1.2 liters of blood within a minute. Humans have two kidneys located in the lumbar region. The left kidney looks larger than the right kidney.

Kidneys are posterior to the peritoneum hence are referred to as retroperitoneal. The renal capsule has collagen fibers that extend outwards to attach the kidney to the nearby structures.

Kidneys are bean-shaped. The medial border is the region of the bean that folds in and a concave depression called the hilum (hilus) is formed.

The renal sinus is the fat-filled area where the hilus opens which contains blood vessels, renal pelvis, nerves, and fat.

The renal cortex is found beneath the renal capsule and below the cortex is the medulla which then folds to form renal pyramids.

The renal papillae are the renal pyramid tips. The papillae empty into the minor calyx. Urine moves into the major calyx from the minor calyx then into the ureter and finally the bladder.

Filtration in the kidney

Filtration takes place across the glomerular filtrate by the action of hydrostatic pressure.

Selective reabsorption occurs when water and other important materials are absorbed back to the blood and the filtered materials move through the nephrons.

The kidneys also produce renin enzymes that convert angiotensinogen to angiotensin 1 (peptides produced in the liver). The antidiuretic hormone from the pituitary gland also regulates urine production by inducing water retention in kidneys and high blood pressure.

Removing the filtered wastes from kidneys

• The ureter:  It is a thin muscular canal through which accumulated wastes move. Ureters are retroperitoneal and their inner walls are covered with a mucous membrane
  • The urine moves within ureters in minute portions while it is forced down by muscular contractions.
• Bladder ballooning: The bladder is located behind the pubis bones in the pelvis. The bladder contains contain three openings, two are located on the sides where ureters enter while the front one opens into the urethra. The urethra is the channel through which urine is transported to outside the body.
  • The inner surface of the bladder contains elastic epithelium. When full, the lining of the bladder is stretched. The elevated pressure activates stretch receptors in the organ and induces someone to urinate.

The female and male urethra

The female urethra is approximately 1.5 inches long and is located near the anterior wall of the vagina. The external sphincter is located at the exit point in the urethra.

• The male urethra is approximately 8 inches and is named according to the region it passes.
  • The prostatic urethra has an internal sphincter and travels within the prostate gland.
  • The membranous urethra moves through the pelvic floor and has external sphincters.
  • The cavernous urethra (spongy urethra) travels along the penis length and within the corpus spongiosum at the penis end.

Urination

Urination is the emptying of the bladder through the urethra. Urine is stored in the bladder before releasing it outside.

The bladder’s mucous membrane produces mucus which protects the bladder against alkaline or acidic effects of urine.

The spinal cord transmits afferent signals and efferent signals move back to the bladder. These produce reflex arcs that relax the internal sphincters and contract the bladder muscles which force urine out of the bladder.

Revision

What is the purpose of the kidneys?
act as a filter for blood and get rid of any “junk” or excess material
Filters for:
-Volume: take out anything (water) excess and get rid of it.
-Solutes: take out toxins, drugs, solids and gets rid of it.
-pH: close to 7.4 and blood is too acidic or basic the kidneys will get it back to normal pH

There are 4 main organs of the urinary system (or 6, since two of those types are paired). What are they?
Kidneys -2
Ureter-2
Urinary bladder -1
Urethra -1

The left and right kidneys differ in size and position. What are these differences?
-Right kidney is farther down (inferior) compared to the left kidney.
-Right kidney is slightly smaller than the left.
Room for liver above it
-Positioned in the back of the body.

What is the renal hilum?
area of the kidney where any tubes go into the kidney or out of the kidney

How do we define the renal cortex and medulla?
renal cortex: outer layer of kidney
medulla: inner portion of kidney

What kidney structures are in the medulla?
Name and describe each structure.
Renal pyramids: red triangles located where the urine is initially created

Renal papilla: tip of each pyramid, urine goes out of the papilla

Renal columns: Urine does NOT go through renal columns. Columns are the tissues that separate the pyramids

Calyx: Tubes inside the kidney
2 types:
Minor calyces-tubes that receive urine from renal papilla. They will merge together into major calyces
Major calyces-multiple minor calyces merge to make major calyces

Renal pelvis:All major calyces merge to the renal pelvis, which is a tube

Renal hilum: area of the kidney where any tubes go into the kidney or out of the kidney. Ureter comes out of the hilum as well as the blood vessels

Trace the flow of urine, starting at renal pyramids and ending at the urethra.
Renal pyramids
Renal papilla
Minor calyces
Major calyces
Renal pelvis
Ureter
Urinary bladder
Urethra

Trace the flow of blood into the kidneys, from the renal arteries to the afferent arterioles.
Renal artery
Segmental arteries
Lobar arteries
Interlobar arteries
Arcuate arteries
Interlobular arteries
Afferent arterioles

Which blood vessel enters the hilum?
Which blood vessel is in the renal columns?
Which blood vessels are over the base of the pyramids?
hilum: Renal artery
renal columns: Interlobular arteries
pyramids:Arcuate arteries (around the corners of the pyramids “arching over”

What is the smooth muscle in the urinary bladder called?
smooth muscle tissue

What are the medical implications of the female urethra being shorter than the male urethra?
-Females: more prone to UTI’s because of the shorter urethra
-Females: Urethra is in front of the vagina to emphasize the urinary and reproductive system are completely separate,
-Males the urethra joins up with the two tubes called ejaculatory ducts, which are part of the reproductive system so the urethra is both part of the urinary and reproductive system.

What part of the urinary bladder does the urethra exit from?
trigone: bottom of the urinary bladder

Remember that two ducts of the reproductive system, the ejaculatory ducts, merge with the male urethra, and so the male urethra is used for both urine and sperm. The female urethra is not part of the reproductive system.
-Females: Urethra is in front of the vagina to emphasize the urinary and reproductive system are completely separate,
-Males the urethra joins up with the two tubes called ejaculatory ducts, which are part of the reproductive system so the urethra is both part of the urinary and reproductive system.

What is micturition?
urination

Explain the countercurrent multiplier system.
Move sodium and chloride and those 2 components will be reabsorbed. (activities with the tubules). The purpose is to keep water in the body.

Explain the countercurrent exchange system.
1)Sodium and chloride go into vasa recta
2)Water follows sodium and goes into the vasa recta
The purpose is to keep water in the body.
3)Sodium will leave vasa recta and will go back into the renal medella because Bloodflow in vasa recta is SLOW. The purpse of this is to keep the sodium ion concentration high in the renal medulla, this helps to pull out lots of water in the loop of henle to help us keep lots of water in the body.

Which substances are reabsorbed and secreted in the descending Henle loop?
Is this transport active or passive?
Water is being reabsorbed
*passively (no energy-water follows sodium)

Which substances are reabsorbed in the ascending Henle loop?
Is this transport active or passive?
Sodium and chloride ions are being reabsorbed
*actively (using energy)

Which substances are secreted in the distal convoluted tubule and collecting duct?
DCT & CD will reabsorb sodium, water, and urea

How does antidiuretic hormone (ADH) affect tubular secretion?
helps to keep water in the body by going to the DCT & CD causing the appearance of more Aquaporins in the tubules so more water gets reabsorbed creating hypertonic urine.
effects urine volume

How does aldosterone affect the distal convoluted tubule and collecting duct?
1)Aldosterone causes reabsorption of sodium ions meaning water will follow sodium.

2)Aldosterone causes the secretion of potassium ions and hydrogen ions.
effects urine volume

How does atrial natriuretic hormone (ANH) affect tubular secretion?
More sodium when be in urine, water following sodium therefore increasing urine volume

Both tubuloglomerular feedback and the myogenic mechanism can affect urine volume.
Explain each mechanism.
regulate urine volume by regulating the GFR, trying to keep it constant

tubuloglomerular feedback: -effects the efferent arterioles, will regulate more/less blood to go out.
-dependent on the juxtaglomerular apparatus, and the reninangiotensin-aldosterone system (RAAS)

myogenic mechanism: effects the afferent arteriole smooth muscle directly.

What are some common wastes excreted by urine?
1)Nitrogenous wastes:
ammonia, creatinine, uric acid, urea
2) Electrolytes:
sodium, ammonia, chloride, bicarbonate, phosphate, sulfate
3)Toxins:
during disease, bacterial poisons leaving the body

What are urochromes?
pigments in urine (makes it yellow)

What are some abnormal things sometimes found in urine?
chemicals from food, drugs, blood, albumin, casts, and calculi, high level of hormones, toxins

What is renal hypertension?
high blood pressure caused by stenosis (narrow blood vessel) of the renal artery.

What are some causes of renal obstructive disorders?
renal obstructive disorders-any kind of blockage of urine flow.
ex: calculi, tumors

What are renal calculi?
kidney stones–> crystallized minerals

What are the four kinds of urinary tract infections?
Where does each happen?
1)urethritis: urethra
2)cystitis: bladder
3)nephritis: kidney
4)pyelonephritis: renal pelvis

What are glomerular disorders?
glomerulonephritis: problem with glomerulus
nephrotic syndrome: symptoms associated with kidney disorders such as; protein in urine, swelling of kidney tissues

What is kidney failure?
What is dialysis?
kidney failure: failure of the kidney to filter blood and make urine

dialysis: mechanical method to filter the blood artifically.
1)blood from artery into machine
2)blood pumped through tubes in machine surrounded by fluid
3)material from the blood goes into the dialysis fluid to filter the blood like the kidneys would
4)once the blood has been processed and cleaned it’s pumped back into the body

What is the range of fluid content of the human body?
45%-75% of human body weight is water

Describe how age, sex, and body fat % can affect the % of human body water.
Body fat: more body fat = less of their body is made of water

Age: as people age, less of ones body is made of water. Older you are = less water

Sex: females have a lower % of their bodies made of water

What are the extracellular and intracellular fluids?
intracellular fluid: fluid inside cells

extracellular fluid: fluid outside cells

What fluid compartments make up the extracellular fluid?
Plasma and interstitial fluid
Plasma: blood fluid
Interstitial fluid: fluid in tissues or between cells

Roughly, what proportion/% of body fluid is the intracellular fluid?
66%
most body water is inside cells

What are the main chemical differences between the intracellular and extracellular fluid?
ECF: more sodium, less potassium, more chloride, less proteins
-vs-
ICF: less sodium, more potassium, less chloride, more proteins,

How does blood composition differ from the interstitial fluid?
Plasma: slightly more ions and has more protein
-vs-
IF: less ions and less protein

Protein: ICF (most)
Plasma (2nd)
IF (almost 0)

What are the 3 ways to qualify the concentration of solutes in fluid?
How are they different?
1)mg%: used when creating solutions (IV sol). Pour out electrolytes into a container and measure their mass. mg of solute in 100ml of solution.

2)molarity/ osmolarity: accounts for mass, but also accounts for dissolving, when you dissolve a molecule it may break up into multiple parts. Has more info than mg% because it accounts for the dissolve and breakdown.

3)milliequivalent (mEq): accounts for mass and dissolving and the charge of electrolytes (+/-) MOST EXACT MEASUREMENT

What is the main way by which water enters the body?
What are the 4 main ways by which water leaves the body?
Water enters the body via the digestive tract

1)As urine through the kidneys (MOST)
2)As water is expired air through the lungs-exhaling
3)As sweat through the skin
4)As feces from the intestines

Remember, that to maintain homeostasis, water going in much equal water going out.
Water in=Water out

What parts of the brain are responsible for regulating fluid intake? Remember that these brain parts can both cause a feeling of thirst and release ADH if body fluids are low.
Thirst center
-hypothalamus
-subfornical organ

*osmoreceptors-receptors that detect the balance of fluid and electrolytes
IF THERE IS AN IMBALANCE then osmoreceptors communicate with the thirst center and makes you feel thirsty then the thirst center produces antidiuretic hormone (ADH) and it fixes the problem

How do ADH, aldosterone and atrial natriuretic hormone affect urine volume?
atrial natriuretic hormone (ANH):
2 triggers:
1)high amount of sodium ions.
2)Too much sodium
ANH gets released, a high plasma volume may also trigger ANH release. This causes increased filtration rate.

ADH: two main triggers.
1)low plasma vol.
2)high plasma osmolarity: high sodium ions
When ADH gets released we will reabsorb water back into the body from the nephron and you get a higher plasma volume and sodium ions are diluted which fix the 2 problems. ADH will cause increased thirst which will also fix the problem.

Aldosterone: Triggered by
1)low sodium ions
2)low plasma vol.
Detected by the juxtaglomerular apparatus resulting in releasing the hormone Renin (released from kidneys) and Renin converts angiotensinogen into angiotensin I, then angiotensin II, then angiotensin II (leads to increased thirst) goes to adrenal cortex and causes release of aldosterone and the aldosterone causes sodium ion reabsorption then leads to water reabsorption. This takes care of the low sodium and low plasma problems.

For the 3 hormones in the above question, what are the conditions that can trigger each hormone to release?
atrial natriuretic hormone (ANH):
2 triggers:
1)high amount of sodium ions.
2)Too much sodium
ANH gets released, a high plasma volume may also trigger ANH release. This causes increased filtration rate.

ADH: two main triggers.
1)low plasma vol.
2)high plasma osmolarity: high sodium ions
When ADH gets released we will reabsorb water back into the body from the nephron and you get a higher plasma volume and sodium ions are diluted which fix the 2 problems. ADH will cause increased thirst which will also fix the problem.

Aldosterone: Triggered by
1)low sodium ions
2)low plasma vol.
Detected by the juxtaglomerular apparatus resulting in releasing the hormone Renin (released from kidneys) and Renin converts angiotensinogen into angiotensin I, then angiotensin II, then angiotensin II (leads to increased thirst) goes to adrenal cortex and causes release of aldosterone and the aldosterone causes sodium ion reabsorption then leads to water reabsorption. This takes care of the low sodium and low plasma problems.

Explain the renin-angiotensis-aldosterone system.
atrial natriuretic hormone (ANH):
2 triggers:
1)high amount of sodium ions.
2)Too much sodium
ANH gets released, a high plasma volume may also trigger ANH release. This causes increased filtration rate.

ADH: two main triggers.
1)low plasma vol.
2)high plasma osmolarity: high sodium ions
When ADH gets released we will reabsorb water back into the body from the nephron and you get a higher plasma volume and sodium ions are diluted which fix the 2 problems. ADH will cause increased thirst which will also fix the problem.

Aldosterone: Triggered by
1)low sodium ions
2)low plasma vol.
Detected by the juxtaglomerular apparatus resulting in releasing the hormone Renin (released from kidneys) and Renin converts angiotensinogen into angiotensin I, then angiotensin II, then angiotensin II (leads to increased thirst) goes to adrenal cortex and causes release of aldosterone and the aldosterone causes sodium ion reabsorption then leads to water reabsorption. This takes care of the low sodium and low plasma problems.

Starling’s law of capillaries defines 4 forces that determine filtration from a capillary.
Define each of these forces, including noting if they promote filtration or reabsorption.
Determines which way the fluid moves and how much fluid moves. Driven by pressure

1)Blood hydrostatic pressure (BHP):pressure in blood pushing fluid from blood to interstital fluid
strongest

2)Blood colloid osmotic pressure (BCOP):pulls interstitial fluid into blood
stronger

3)Interstitial fluid hydrostatic pressure (IFHP):pressure pushing fluid from interstitial fluid into blood

4)Interstitial fluid colloid osmotic pressure (IFCOP) on the other side: pulls blood into interstitial fluid

*If the forces pushing out of blood and forces pulling into blood then nothing changes.
*For fluid to get filtered the force of blood pushing out has to be greater than the forces pulling fluid back in
(BHP+IFCOP)>(IFHP+BCOP)
*If the forces moving fluid out of blood are weaker than the forces moving fluid back into blood we get reabsorption
(BHP+IFCOP)<(IFHP+BCOP)

What main organic compound is responsible for the high value of blood colloid osmotic pressure?
solutes (proteins and electrolytes)

What is edema?
How can changes in the forces of Starling’s law cause edema?
Edema-condition where there is too much fluid in tissues. Too much interstitial fluid.

*Retention of electrolytes in the ECF-High IFCOP

*Increased capillary blood pressure-High Blood hydrostatic pressure

*Decreased concentration of plasma proteins normally retained in the blood. Low BCOP

Is hydrostatic pressure or colloid osmotic pressure the main regulator of transfer of fluids between interstitial fluid and intracellular fluid?
colloid osmotic pressure will normally change

How do ADH, aldosterone, and ANH regulate electrolyte balance?
aldosterone: sodium ions reabs; potassium and hydrogen ions get secreted

ANH: less sodium reabsorption (more sodium loss in urine)

ADH: water reabsorption–> dilute ions/electrolytes that are already in the body

Chloride ions generally follow potassium ions

What are hypokalemia and hyperkalemia?
What are causes of hypokalemia?
Electrolyte imbalances
kalemia: potassium

hypokalemia: not enough potassium in the body
Cause: too much water in your body

hyperkalemia: too much potassium in the body
Cause: physical injury

What are hyponatremia and hypernatremia?
What are causes of hyponatremia?
Natremia=sodium

hyponatremia: not enough sodium in the body
Cause: too much water in your body

hypernatremia: too much sodium in the body
Cause: ingesting too much sodium or being dehyrdrated

What are hypovolemia and hypervolemia?
What are causes of hypovolemia?
Fluid imbalances
volemia=water in the body

hypovolemia: not enough water in the body
Cause: not drinking enough water

hypervolemia: too much water in the body
Cause: drinking too much water

Why is hypervolemia bad?
If you drink too much water in too short of a time, the water will dilute the potassium and sodium in the body. It can also lead to edema everywhere in your body, including in your brain and your brain can be crushed in your skull from too much water in your body

Hydration can be estimated via tenting.
What is tenting?
Tenting-squeezing your skin and if you are properly hydrated your skin should go back to normal quickly. If you are dehydrated your skin will stay deformed for a few seconds because your skin is not very elastic due to the lack of water.

If hydrogen ion concentration changes, how does pH change?
as the pH goes down acids have more hydrogen ions than water and as you go up they have less hydrogen ions than water.

The closer to 0 & 14 the more harmful it is.

If pH changes by one unit, how much does the hydrogen ion concentration change?
What is pH changes by two units?
changes by one unit-hydrogen ions change 10 times

changes by two units-hydrogen ions change 100 times

What is neutral pH?
What is blood pH?
neutral pH=7 (water)
blood pH-7.4

How do we define an acid and a base?
acid: pH less than 7.35
base: pH greater than 7.45

What are some chemicals that can change the pH of body fluids?
carbonic acid: aerobic glucose metabolism

lactic acid: anaerobic glucose metabolism

sulfuric acid: produced by oxidation of sulfur-containing amino acids

phosphoric acid: accumulates when certain phosphoproteins and ribonucleotides are broken down

acidic ketone bodies: accumulate during incomplete breakdown of fats, when your body is breaking down more fats than normal by decreased carbs

acid-forming/base forming minerals: through diet (orange=citric acid)

The pH can be controlled by both chemical and physiological mechanisms.
Which is fastest?
chemical buffers are the fastest

The chemical methods are buffers.
What is a buffer?
Chemical Buffers are immediate in their action. FASTEST

buffers are chemicals floating in blood and if there is too much hydrogen ions the buffers will tie up the hydrogen ions, meaning the chemicals will grab the hydrogen ions and bind the hydrogen with chemicals so the hydrogen ions cannot do anything.
If there are too few hydrogen ions the buffers can release hydrogen ions until we have a normal pH.

What are the two physiological mechanisms for controlling blood pH?
1)Breathing-changes in the rate and depth of breathing
next fastest:1-2 minutes

2)Kidneys-kidney excretion of acids and bases
slowest: up to 24 hrs

What is the major buffering system found in blood?
Aside from this, what are some other buffers found in blood?
Buffers are pairs of chemical.

1)weak acid w/basic salt
2)bicarbonate pairs
Main buffer system in the body
3)plasma protein pairs
4)hemaglobin pairs and phosphate buffer pairs

If there is a strong base the buffer will transform it into a weak base

If there is a strong acid the buffer will transform it into a weak acid

What is the chloride shift?
HCO3- ions move out of red blood cells into the plasma down a concentration gradient. To maintain the electrical balance, Cl- ions take their place.

How does the respiratory system influence blood pH?
If there is more CO2 in the body, there will be more hydrogen ions and will have a lower pH (acidic).

If there is a low amt of CO2 in the body there will be less hydrogen ions and pH will go up (basic/alkaline)

*we have to monitor CO2 closely by chemoreceptors (detect chemicals in blood, including CO2)
**Peripheral= aorta/ carotic artery (blood)
**Central= medulla (brain)
Based on what the chemoreceptors detect can cause changes in breathing

*can be either a solution or a cause of problems

Does acidosis trigger hyperventilation or hypoventilation?
Answer the same question for alkalosis.
acidosis triggers hyperventilation, increased breathing causes exhaling more CO2 and lose more CO2 and hydrogen ions go down fixing the acidosis problem.
*Prolonged hyperventilation may increase the blood pH enough to produce alkalosis

alkalosis triggers hypoventilation, decreasing breathing causes you to keep CO2 and hydrogen ions go up fixing the alkalosis problem.
*Prolonged hypoventilation may decrease the blood pH enough to produce acidosis

***If there is a pH problem 1st, breathing changes can fix the problem
***If there is a breathing problem 1st, that breathing problem can lead to a pH problem

What are two mechanisms the urinary system uses to get rid of excess hydrogen ions?
Distal tubules/collecting ducts secrete hydrogen ions and reabsorb basic ions to control pH, when the positive charge goes to tubule then a positive charged ion goes back into the blood to create balance.

What are some causes of metabolic acidosis?
What are some causes of metabolic alkalosis?
metabolic acidosis: metabolism is causing the pH to become acidic.
Causes: anything making your body produce ketones (DM or starving), diarrhea-losing fluid from intestines which is basic which means the fluid left in your body is more acidic

metabolic alkalosis: fewer hydrogen ions
Causes: antacids, vomiting-expelling stomach acid so there is less acid in your body which means the fluid left in your body is more basic

What are some causes of respiratory acidosis?
What are some causes of respiratory alkalosis?
respiratory acidosis: decreased breathing you are keeping CO2 in the body therefore the number of hydrogen ions go up and decreases pH, which is acidosis
Causes: pneumonia, emphysema, drugs

respiratory alkalosis: increased breathing you are losing CO2 in the body therefore the number of hydrogen ions go down and increases pH, which is alkalosis.
Causes: hyperventilation, fever, mental stress