Urinary System Flashcards
What are the major functions of the urinary system?
Elimination
Excretion
Homeostatic Regulation of blood plasma
What structures contribute to the elimination role of the urinary system?
Ureters
Bladder
Urethra
What is elimination?
Discharge of waste products out of the body
What structure contributes to the excretion role of the urinary system?
The kidney
What is excretion?
Removal of organic waste products from body fluids, that produce urine
What structure contributes to the homeostatic regulation of blood plasma role of the urinary system?
The kidney
How does the kidney maintain homeostatic regulation of blood plasma?
- Regulates BV and BP
- Regulates plasma ion concentrations
- Stabilizing blood pH
- Conserves nutrients
The kidneys produce urine from: A. liquids directly transported to kidneys after swallowing B. Products filtered from blood C. Water in digestive tract D. Excess fluids in the body E. Extracellular fluid
B. Products filtered from blood
Everytime your heart beats, what percent of cardiac output goes to the kidneys?
25%
If your BV goes up, you
have higher BP
Larger amount of urine
If your BC goes down, you
Have lower BP
Absorb more water
Smaller and more concentrated amount of urine
Smooth muscle ____ force urine toward the urinary bladder
Peristaltic contractions
What is a ureter?
12 inch tube of smooth muscle where urine is sent following filtration
What division of the ANS controls urination?
Parasympathetic stimulation
What muscle is responsible for emptying the bladder?
Detrusor muscle
Which urinary sphincter is involuntary: internal or external?
Internal
Right before ejaculation, the _____ closes tightly to prevent semen and urine from mixing
Internal urinary sphincter
After childbirth, women have more leakage because _____ is beat up after the baby leaves your body
the external urinary sphincter
You gain control of the external urinary sphincter between ______ and _____ years old because synapses need time to form
2 and 3 years old
Define urination (voiding)
Expelling urine from the urinary bladder through the urethra
Urination is coordinated by the ________
micturition reflex
What is the micturition reflex?
When your urinary bladder becomes stretched, you consciously sense bladder distentsion, and signals go to ANS to cause relflexive contraction of detrusor muscle
What does the micturition reflex occur in response to?
Stretched bladder
Parasympathetic input
Urination requires coupling the _____ with the _____
Micturition reflex
Relaxation of internal and external urethral sphincters
After overriding the signal to urinate, why does it take a second to finally urinate instead of immediately happening?
When you finally go to urinate, you have to relax the external urinary sphincter, and it takes a second for your body to understand that it is now open and to relax the internal urinary sphincter
The coupling of the micturition reflex refers to
The relaxation of both the internal and external urinary sphincters in order to urinate
Define incontinence
Inability to voluntarily prevent the release of urine
Incontinence is most common
among females
especially after childbirth
Define urinary retention
Inability to voluntarily release urine
Urinary retention is most common
among males
due to an enlarged prostate
Why does an enlarged prostate lead to urinary retention?
As the prostate grows, it pushes on the urethra so not as much urine can be expelled from the bladder, increasing the sensation of needing to urinate but being unable to
What are the two types of UTI’s?
Urethritis
Cystitis (inflammation of the bladder)
UTI’s can occur anywhere along the urinary tract, but are most commonly found in
the urethra
Why are UTI’s more common in females?
Shorter urethra
Closer to vagina so easily exposed to pathogens during intercourse
What is the body’s natural way of getting rid of UTI’s?
Urination (flushes bacteria out)
The kidney contains how many nephrons and what is the nephron’s job?
1.25 million
To make urine
The renal medulla consists of collecting ducts that drain urine from
neprhron to calyces
Calyces drain urine into the
central renal pelvis
The renal pelvis drains urine into the
ureter
What three structures focus mainly on getting urine out of the body?
Ureters
Bladder
Urethra
What structures make urine?
Kidneys
Describe the general overview of the urine making process
25% of cardiac output comes into the renal artery, and blood travels up to the nephrons. Collectingducts take the urine and drain into the calyxes which then drain into the ureter.
Following the urine making process, cleaned up blood leaves through ___ and extra waste leaves through ____
renal vein
ureter
The renal corpuscle is composed of
Bowman’s capsule and the glomerulus capillary bed
The renal tubule consists of
PCT
Loop of Henle
DCT
What is filtrate?
Fluid pushed from glomerulus into capsular space
The renal corpuscle is responsible for
the production of filtrate from blood
The renal tubules are responsible for
- Reabsorption of organic nutrients and water and ions from filtrate into blood stream
- Secretion of waste products into filtrate
____ arterioles supply blood to the capillary bed of the glomerulus in the renal corpuscles
Afferent
____ arterioles collect blood leaving the glomerulus capillary bed
Efferent
______ capillaries surround the renal tubules
Peritubular
Peritubular capillaries are responsible for
Collecting nutrients, water, and ions reabsorbed out of filtrate
The glomerular capillary bed is unique because
It does not possess any venules
Because the glomerulus does not possess any venules, it is not a capillary bed that exists for ____
Oxygen delivery
The main goal of the glomerulus is for
Fluid to be pushed out to make filtrate
Trace the pathway of blood through glomerulus and peritubular capillaries
Oxygenated blood comes through afferent arteriole
Filtrate is formed
Oxygenated blood leaves through efferent arteriole
Oxygenated blood travels through peritubular capillary where item exchange occurs
Deoxygenated blood leaves via renal vein
What are the two types of nephrons?
Cortical nephrons and juxtamedullary nephrons
What type of nephrons make up the majority of all nephrons
Cortical nephrons
Compare cortical and juxtamedullary nephrons
Cortical: loop of henle are shorter; located in cortex
Juxtamedullary: Loop of henle longer; located in renal pyramids
Which type of nephron produces more concentrated urine?
Juxtamedullary nephrons
What causes water and solutes to move out of glomerular capillaries and into renal tubules?
Blood pressure
What is reabsorption?
The removal of water and solutes from filtrate into peritublar fluid
What is peritubular fluid?
Interstitial fluid surrounding renal tubule andperitubular capillaries
What is secretion?
Transport of solutes form the peritubular fluid into the filtrate
Blood pressure has to be ____ than factors that pull blood out of the nephron loop in order to make filtrate
greater than
Something that is reabsorbed travels through ____
peritubular fluid first then to peritubular capillary bed
Reabsorption and secretion occur via ________ across epithelial cells forming the wall of renal tubule
Epithelial cells
What are the three types of carrier mediated transport?
Facilitated diffusion
Active transport
Cotransport
The main type of transport used in reabsorption and secretion is
facilitated diffusion
Glucose is reabsorbed into the peritubular capillaries by hitching a ride with
Sodium
What are the characteristics of carrier proteins?
- Specific for a particular molecule
- Transport only in one direction
- Distribution of carrier proteins vary
- Can be controlled by hormones
Almost all of your glucose is reabsorbed in the_____
Proximal convoluted tubule
What is the transport maximum?
Carrier proteins have a renal threshold for reabsorption of substances in tubular fluid
When carrier proteins reach transport maximum what happens?
You have made all of the carrier proteins you can make and any excess that can no longer be reabsorbed is “lost” in urine
Protein creation is controlled by hormones in the
Distal convoluted tubule
If sodium levels drop what horomone is secreted to tell the kidneys to reabsorb more sodium?
Aldosterone
Presence of aldosterone tells your body to
Transcribe a sodium channel which is put in the membrane and sodium becomes reabsorbed in the blood
Diabetes means what for the kidneys?
High glucose exceeds transport maximum so it is lost in urine
Higher osmotic potential is present within the nephron so you secrete more water from the blood
Why don’t plasma proteins and large molecules cross the glomerulus?
3 layers of glomerular filtration prevent them from crossing the barrier
What are the three layers of the glomerulus?
Capillary endothelium
Lamina densa
Podocytes
What is the function of podocytes?
Cover lamina densa of capillaries and produce filtration slits
Renal corpuscles have fenestrated capillary beds to
allow for easy exchange of materials
Materials are transferred from blood to nephron via
Filtration slits
The net filtration pressure is the sum of
opposing forces ( Blood pressure, Capsular Hydrostatic pressure, Blood osmotic pressure)
What is the equation for filtration pressure?
FP= BHP-CsHP-BOP
What is the blood pressure at the glomerulus and is it constant? What direction does it push fluid?
50 mmHg
yes
Pushes fluid out of glomerulus
What is the pressure of CHP? Is it constant? What direction does it push fluid?
15 mmHg
yes
Pushes fluid into glomerulus
What is the pressure of BOP? Is it constant? What direction does it push fluid?
25 mmHg
yes
Pushes fluid into glomerulus
What is the normal filtration pressure that the kidneys work to maintain?
10 mmHg
The kidneys produce how much filtrate per day?
180 L/day
Glomerular filtration rate is
The rate at which fluid is pushed out of glomerulus and filtered
GFR is effected by
- changes in blood pressure
- changes in blood osmotic pressure
- changes in fluid movement in renal tubules causing a build up of pressure in renal capsule
- blockage of filtration slits in glomerulus
Anything that alters the filtration pressure will alter
the GFR
When the GFR is effected by factors that alter net filtration pressure also cause changes in urine
output and composition
Low blood pressure will _____ filtration
Decrease
If you’re dehydrated and your bp drops to 40 mmHg, what happens to GFR?
It falls to zero
What is glomerulonephritis?
Blockage of filtration slits by antigen- antibody complexes in the blood
What are the implications of glomerulonephritis?
Fluids cannot move out of capillaries
GFR decreases
Urine production falls
What is nephritis?
Inflammation of the kidney
What are the implications of nephritis?
Swelling causes increased capsular pressure so filtration rate slows
When the glomerulus is damaged
capillaries become very permeable
Plasma proteins and RBC’s enter filtrate
Less net BOP pulling water into blood
Increase GFR and urine production
What is proteinuria
Plasma proteins appear in urine
What is hematuria
Blood cells appear in urine
What are the controlling factors of the GFR?
- Autoregulation
- Sympathetic ANS
- Renin-angiotensin
What hormones influence kidney reabsorption and secretion?
- PTH and Calcitonin
- Aldosterone
- Anti-diuretic hormone
The kidneys ________ afferent and efferent arteriole diameters in order to keep GFR constant despite changes in systemic BP
autoregulate
If BP decreases, how do the kidneys accomodate the drop in pressure?
- Dilate afferent arteriole
- Dilate glomerular capillaries
- Constrict efferent arteriole
If BP increases, how do kidneys accomodate the rise in pressure?
Constrict the afferent arteriole
What type of regulation can over-ride autoregulation of the kidneys?
Sympathetic ANS regulation
What effective does hypotensive (hemorrhaging) stress produce on the GFR?
strong vasoconstriction of afferent arteriole, reduced blood flow to glomerulus
What effect does overheating and exercise stress produce on the GFR?
- Blood is diverted away from kidney by vasodilation of arterioles in skin and skeletal muscles
Renin is released by the juxtaglomerular complex to stimulate a drop in filtration pressure which in turn
- Increases blood volume and BP
- Triggers formation of angiotensin II
Trace the pathway of how Renin triggers the release of angiotensin II
Renin converts angiotensinogen to angiotensin I
Angiotensin I moves through lungs, meets ACE (enzyme)
ACE converts angiotensin I to angiotensin II
Angiotensin II increases blood volume and pressure
Nitrogenous wastes are made when we break down
proteins
Almost all of our ammonia is converted to
Urea
If urea is present in the body
Kidneys go into overdrive to put out as much urine as possible to get all of the urea out
What is the normal range of pH
4.5-8 (Avg 6)
What percent of normal urine is water?
93-97%
Proximal convoluted tubule’s function is to
reabsorb nutrients and ions by carrier mediated transport
The PCT reabsorbs what percent of filtrate?
60-70%
The function of the descending limb of nephron loop is to
absorb water via osmosis
Impermeable to solutes
Which limb is thicker?
Ascending
The ascending limb of nephron loop functions to
Reabsorb Na+ and Cl-
Impermeable to water
What is the function of distal convoluted tubule and collecting ducts?
Depends on the levels of hormones
What is the function of the glomerulus?
To produce filtrate
Most reabsorption of nutrients at the PCT is done through
Carrier mediated transport
____ ions might be secreted out of blood if blood is too acidic to maintain normal pH
H+ ions
Increased osmolarity from NaCl transport from ascending limb results in increased movement of _______ from the descending limb
water
pH of blood is controlled by the varying amounts of _____ secreted or _____ reabsorbed
H+ secreted
HCO3- reabsorbed
The presence of parathyroid hormone causes
Active reabsorption of Ca2+ ions to raise calcium levels
Presence of Calcitonin causes
Active secretion of Ca 2+ ions to lower calcium levels
Presence of Aldosterone causes
Active reabsorption of Na+ and Cl- in exchange for K+
Presence of ADH causes
Reabsorption of water
Aldosterone is released in response to
High K+
Low Na+
low BP
Aldosterone increases the synthesis of
Transport proteins for absorption of Na+ and secretion of K+
In the absence of aldosterone
Na+ reabsorption and K+ secretion is minimal in DCT and collecting ducts
ADH characteristics include
- Facultative water reabsorption
- Creates water channels in the membrane to move water from DCT into blood
In the absence of ADH
water reabsorption is low in DCT and collecting ducts
Normal levels of ADH is enough to reabsorb ______ liters of the 27 L/day entering the DCT
25-26
ADH regulation is controlled primarily by
Osmoreceptors in hypothalamus
High levels of ADH are released in response to
high blood osmolarity
Low water content
Low BP
Low BV
Less ADH is released in response to
High water content in blood
Low osmolarity
High BP
High BV
Release of ADH can also effect the baroreceptors in the heart that respond to
blood pressure
If you are taking an ACE inhibitor or drink alcohol
you will supress ADH and excrete a low concentrated urine
What are the problems that result from micturition reflex
Incontinence
Urinary retention
Urinary retention occurs as a result of
prostate gland hypertrophy (enlargement)
Incontinence is common after
childbirth
Kidney stones can be made of
Calcium, magnesium, or uric acid crystals
As we age, we lose functional nephrons and have a reduced sensitivity to
ADH
Reduced sensitivity of ADH leads to
incontinence because you aren’t absorbing any water
One method of treating large kidney stones is
Shock wave lithotripsy
