Urinary System

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created 10 years ago by sammiellama
updated 10 years ago by sammiellama
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Summarized, these are a few functions of the urinary system:

1. excretes waste
2. regulates blood ion composition
3. regulates blood pH
4. regulates blood volume
5. regulates blood pressure
6. regulates blood osmolarity
7. secretes hormones (Calcitriol and Erythropoietin)
8. helps regulate blood glucose


What are the organs of the urinary system?

Kidneys (filtering organs), ureters (connect kidney and bladder), urinary bladder (storage), and urethra (connects bladder and outside exit)


Define: retroperitoneal

in terms of the kidneys; posterior to parietal peritoneum


What are the 3 layers of the kidneys (from inside to outside)?

1. renal capsule (covers the organ itself)
2. adipose capsule (covers it, anchoring it towards the back)
3. renal fascia (another set of fibrous tissue that attaches it and covers it)


Renal medulla: consists of,

-renal pyramid, apex of which is called renal papilla
- pyramids are called Renal columns
RENAL LOBE = renal pyramid + renal cortex + 1/2 renal column
PARENCHYMA = renal cortex + renal pyramids


What is the functional unit of the kidney?



A urinalysis is an indirect way of doing what?

a blood test! All of your blood was filtered out to become urine



Once things hit the minor calyx, it gets filtered out


Blood supply:
Renal arteries come directly off of?

abdominal aorta


Blood supply:
Renal veins connect directly with?

inferior vena cava


Nephrons, functional units of the kidneys:

Start in cortex, loops down the medulla and back up the cortex
-80-85% of nephrons are cortical (short loop)
-15-20% of neprons are juxtamedullary (long)


What is the "main sewer" of the kidney?

the collecting duct/tubule


The longer the loop of Henle is,

(think camels)

the less likely you are to become dehydrated (more chances for water to be returned to the body)


Purse analogy

Purse = bloodstream
garbage can = minor and major calyx

(cleaning out purse, as you go through the process, the important things are returned first, like glucose and sodium, then you go through the other think-about items one by one determining if you should throw them out.) once the garbage guy (minor calyx) picks it up, you won't get anything returned!


Cortical versus Juxtamedullary Loop of Henle:

Cortical: enter only outer medulla. blood supply-> peritubular capillaries from efferent arteriole

Juxtamedullary: to deep medulla. blood supply-> peritubular capillaries from efferent arteriole and vasa recta (instead of vasa vasorum)from efferent arteriole

**don't confuse the two "vasa"s!


Structure of renal corpuscle

card image

Bowman's capsule surrounds capsular space
-podocytes cover capillaries to form visceral layer
-simple squamous cells form parietal layer

Glomerular capillaries arise from afferent arteriole and form a ball before emptying into efferent arteriole


Histology of renal tubule & collecting duct:

-Proximal convoluted tubule has simple cuboidal with brush border of microvilli that increase surface area
-Descending limb of loop of Henle has simple squamous
-Ascending limb loop of Henle has simple cuboidal to low columnar; forms juxtaglomerular apparatus where makes contact with afferent arteriole, macula densa is a special part of ascending limb
-Distal convoluted & collected ducts have simple cuboidal composed of principal & intercalated cells which have microvilli


Number of nephrons:

What you're born with is what you have.
If injured -- no replacement occurs.

*Dysfunction is not evident until function declines by 25% of normal
**removal of one kidney causes enlargement of the remaining until it can filter at 80% of normal rate of 2 kidneys (remaining kidney overcompensates)


Overview of renal physiology:

Glomerular filtration of plasma, tubular reabsorption, and tubular secretion

(don't confuse reabsorbtion and secretion)
**recall purse analogy, if we put it back in the purse it is reabsorbed. if it is already in the purse and we decide we don't need it anymore, it is secreted and returned to the table where you decide to throw it away)


Glomerular filtration:

-blood pressure produces glomerular filtrate.

-filtration fraction is 20% of plasma.

-48 gallons/day filtrate reabsorbed to 1-2 qt. urine.


Filtering capacity enhanced by?

thinness of membrane & large surface area of glomerular capillaries


What does the filtration membrane do?

1. stops all cells and platelets
2. stops large plasma proteins
3. stops medium-sized proteins, not small ones




card image

NFP = total pressure that promotes filtration

NFP = GBHP - (CHP + BCOP) = 10mm Hg

[GBHP is glomerular blood hydrostatic pressure]
[CHP is capsular hydrostatic pressure]
[BCOP is blood colloid osmotic pressure]


What is the average adult male GFR?

125 mL/min


What are the three mechanisms of how GFR can be balanced?

renal autoregulation, neural autoregulation, and hormonal regulation


What is renal autoregulation?

myogenic mechanism: uses smooth muscle contraction to reduce diameter of afferent arteriole to return the GFR to it's previous level in SECONDS!

tubuloglomerular feedback: elevated BP raises GFR so that fluid flows too fast for water to be reabsorbed... afferent arterioles constrict and reduce GFR


what is the neural regulation?

with extreme stimulus from sympathetic nervous system (exercise of hemorrhage), vasoconstriction of afferent arterioles reduces GFR
-lowers urine output and permits blood flow to other tissues


what is the hormonal regulation?

-atrial natriuretic peptide (ANP) increases GFP when there's too much going into the atrium... i.e. too much blood volume or hypertension

-angiotensin reduces GFR when pressure is too low (kinda the opposite of ANP)


movement of water will always be described as:




the lining of the cells cannot reabsorb glucose fast enough if the blood glucose level is above normal. (glucosuria literally means glucose remaining in the urine)

**common cause is diabetes mellitis b/c insulin activity is deficient and blood sugar is too high


reabsorbption in the PCT (first half does all the important stuff!)

most components (i.e. glucose, amino acids, lactic acid, vitamins and nutrients) are completely reabsorbed in the first half of the proximal convoluted tubule


Also in the PCT, we absorb:

acids and bases;bicarbonates (Na+ and H+ ions) acts as an important buffering system to balance the acid/base in the body,

**for every H+ secreted, one filtered bicarbonate will eventually return to the blood


passive reabsorbption in the second half of PCT:

(sodium in the first half, chloride in the second half)

chloride will leave and water soon follows which promotes osmosis in the PCT (they named the pores where water can pass through AQUAPORINS)


Symporters in the loop of Henle:

1st part lined by simple, 2nd part lined by columnar. water prefers to go through osmosis in the thinner membrane.

**countercurrent mechanism happens here

ascending's main responsibility is the passing of sodium

descending's main responsibility is the passing of chloride (remember that water leaves the descending, thus its name: countercurrent)


Reabsorption in the DCT

parathyroid hormone makes sure you absorb calcium at the DCT

**by the end of DCT, 95% of sulutes & water have been reabsorbed and returned to the bloodstream


In the collecting duct,

cells here make final adjustments;
PRINCIPAL CELLS (bald) can still suck sodium back {recall purse decision analogy}... but if sodium is sucked back, potassium must be released (bartering)

ALDOSTERONE makes sure all the sodium will be returned

INTERCALATED CELLS (rebel that still has the mohawk): if they see too much potassium being dumped, they can return them back to their place, and secrete hydrogen to regulate pH of body fluids


Hormonal regulation (MUST STUDY TABLE 26.4 on page 967 in the book)

angiotensin II and aldosterone, and atrial natriuretic peptide


SUMMARY of H2O reabsorption

most responsibility is in the PCT (65%)
loop of Henle (15%)
DCT (10-15%)
collecting duct (5-10%) with ADH


Formation of dilute urine:

dilute = having fewer solutes than plasma
**diabetes insipidus


Formation of concentrated urine:

urine can be up to FOUR TIMES greater osmolarity than plasma

**cells in the collecting ducts reabsorb more water & urea when ADH is increased


Countercurrent mechanism influenced by?

vasa rectus


Anatomy of ureters

-10-12 inches long, diameter of 1-10mm
-extends from renal pelvis to bladder
-enters posterior wall of bladder
-has a physiological valve only
-bladder wall compresses arterial opening as it expands during filling
-flow results from peristalsis, gravity & hydrostatic pressure


Histology of ureters:

mucus is in the urine if the urine is too acidic to prevent damage to cells from the urine


Anatomy of the urinary bladder

hollow, distensible muscular organ with capacity of 700-800ml

-trigone (triangular and makes your pee gone!) is smooth flat area bordered by 2 ureteral openings and one urethral openings


Histology of urinary bladder:

very similar to ureters, but the muscle layer is shifted a little bit (detrusor muscle!)


what is the micturition reflex?

the act of urinating

(DONT mix this up with deglutition!!)


Females and males urethra:

females is a length of 1.5 inches, males is longer and the tube passes through prostate


another word for a kidney stone is?

renal calculi


types of UTI

urethritis (inflammation of urethra)
cystitis (inflammation of urinary bladder)
pyelonephritis (inflammation of kidneys)
pyelitis (inflammation of renal pelvis and its calyces)

**ALWAYS will be inflammation


Glomerulonephritis (Bright's disease)

inflammation of the glomeruli...
most common cause is an allergic reaction to toxins given by streptococcoal bacteria that recently infected a part of the body, especially the throat (this can be a beginning symptom of Lupus)

**the glomeruli may be permanently damaged, leading to some sort of renal failure