Urinary System Flashcards
Name all the structures of the urinary system
Kidneys
Ureters
Urinary bladder
Urethra
What is the function of the urinary system
To regulate and excrete organic wastes, salts, and water to control plasma composition
What is the major organic waste that is excreted in urine
Urea
True or false
The urinary system has a minor role in waste product removal im the body compared to other systems
FALSE
it is the most important route of waste excretion removing nearly all soluble waste products from the blood
What are the 4 main functions of the kidney
Urine production Maintaining homeostasis Acid base balance Fluid and electrolyte balance Hormone production
How does the kidney maintain homeostasis
Through altering plasma composition by filtering plasma contents from the blood and reabsorbing or secreting certain components as needed
How does the urinary system maintain the acid base balance
By removing hydrogen and bicarbonate ions from the urine
The urinary system maintains a tight control of water and electrolytes by removing them from the blood at a ___ rate as they’re put in
Equal
Diuresis
Excess water = more urine formed
Urinating more than usual
Oliguria
Insufficient water = less urine formed
Urinating less than usual
Anuria
Deficiency of water = no urine formed
No urination
Fluid and electrolyte balance is mainly under hormonal control by which 2 hormones
Antidiuretic hormone
Aldosterone
What 3 hormones does the kidney produce and what do they do
Renin: increases BP through the renin-angiotensin system
Erythropoietin: increase RBC production with hypoxia
Prostaglandins: helps maintain renal perfusion (autacoid)
What is the functional unit of the kidney
The nephron
Describe the nephron
A microscopic epithelial structure that consists of a filtration unit attached to a long tube for absorption and secretion of urine as its end product
Where are the kidneys located
In the abdominal cavity on each side of the midline
They are retroperitoneal
True or false
The right kidney is more cranial than the left kidney
True
What is the thick layer of fat that surrounds and protects the kidney called
Perirenal fat
What does the perirenal fat allow for on xrays
They give contrast to the kidney for better visualization
What color and shape are the kidneys often compared to
Kidney beans
What are the two animals that are exceptions to the typical shape of the kidney
Horse: heart shaped
Cattle: lobulated appearance
What are the 5 components of the kidney
Capsule Hilus Renal pelvis Renal cortex Renal medulla Renal crest
What is the capsule
A thin connective tissue layer that surrounds the kidney
What is the hilus
An area in the depression of the kidney where the renal artery and nerves enter and the renal vein, ureter and lymphatic vessels leave the kidney
What is the renal pelvis
The expanded part of the ureter just inside the hilus, this receives urine from the collecting ducts in the kidney
Where is the renal cortex
Immediately under the capsule
Where is the renal medulla
The inner layer that appears striated due to the collecting ducts and loops of henle
What is the renal crest
The ridge that projects into the renal pelvis (collecting tubules of the medulla empty here)
The bovine kidneys are lobulated, what do they lack
Renal pelvis and renal crest
How does the ureter work in a bovine kidney
The ureter branches into each lobe and forms Calyces (calyx) which acts as a funnel that individual medullary pyramids project into and direct the fluid into the ureter
Describe the porcine kidney
Also has calyces which funnel into the renal pelvis
Where does the kidney recieve most of its nerve supply from
The sympathetic nervous system of the autonomic NS
Sympathetic stimulation ____ renal blood flow
Decreases
True or false
The kidney relys 100% on the sympathetic NS for stimulation
FALSE
Can rely on other control mechanisms
How much of the cardiac output does the kidney recieve and how much is converted to urine
1/4 of the cardiac output
1 thousandth of this volume
The renal artery enters the hilus and divides into smaller and smaller branches until it becomes the
Afferent glomerular arterioles
The afferent glomerular arterioles branch to form the cappilary network of the
Glomerulus
What do the glomerular capillaries do
Filter out some of the plasma from the blood
True or false
The capillary system in the glomerulus is the only capillary network where blood enters and leaves oxygenated
TRUE
Once the capillaries leave the glomerulus and surround the rest of the nephron what are they called
Efferent glomerular arterioles
These efferent callilaries reform as ____ until they become the renal ____ and leave the kidney at the hilus and join the caudal vena cava
Veins
Renal vein
When blood is within the capillary network of the nephron, ____ and ____ are removed from the blood and go into the nephron
Waste and excesses
Water and useful components are _____ from the filtrate of the nephron into the blood
Reabsorbed
What is the ureter
Muscular tube that propels urine forward with peristalsis from the kidney to the bladder
Where does the ureter exit the kidney and enter the bladder
Exits the kidney at the hilus
Enters the bladder near the neck
The ureter enters the bladder at an ____ angle
Oblique angle
Why does the ureter enter the bladder at an onlique angle
When the bladder becomes full it occludes the ureter to prevent back flow of urine
True or false
Even if the ureter is occluded/collapsed, urine can still Move forward due to peristalsis
True
What are the 3 layers of the ureter
Outer fibrous layer
Middle smooth muscle
Inner transitional epithelium (to allow stretching as urine passes)
Describe the bladder
A hollow muscular organ capable of stretching (transitional epithelium)
What does size and position of the bladder depend on
Fullness of the bladder
Describe the bladder when it is empty
Will be inside the pelvis, and will have think walls
Describe the bladder when it is filling/full
Pear shaped, extends cranially from the pelvis, has thin walls
At the neck of the bladder there is a sphincter of skeletal muscle to allow
Voluntary control of urination
What is the useful landmark of the bladder
The trigone: area between the urethra and uretal openings in the bladder
What is the function of the bladder
Collects, stores and releases urine
The kidneys constantly produce urine, without the bladder what would you see
The animal would be constantly dribbling urine as kidneys produce it
What is the definition of urination and what are 2 other words that mean the same thing
Expulsion of urine from the body
Micturition and uresis
What are the 3 steps of urination, describe each of them
- Accumulation of urine (when the bladder reaches a critical point stretch receptors are activated)
- Muscle contraction: the spinal cord reflex activates and causes contraction of smooth muscle and creates the sensation of fullness
- Sphincter control: voluntary release of skeletal muscle at the sphincter
What is urinary incontinence
Loss of voluntary control of the bladder
Inability to urine when desired
A full bladder is very prone to___
Rupture
What is the urethra
A continuation of the neck of the bladder made of transitional epithelium that carries urine from the bladder to the outside of the body
Describe a urethra in females
Short and straight, opens onto the floor of the vestibule
Describe the urethra in males
Long and curved, runs down the center of the penis
The urethra carries urine from the bladder to the ourside of the body, what does it also carry for males
Semen during ejaculation (also surrounded by urethral muscle)
What are the 4 main parts of the nephron in order
Renal corpuscle
Proximal convoluted tubule
Loop of henle
Distal convoluted tubule
What is the renal corpuscle composed of, describe these parts
Glomerulus: tiny capillary network
Bowman’s Capsule: double walled capsule surrounding the glomerulus (inner layer lines the capillaries, outer layer surrounds it, space between is an extension of the PCT)
What is the function of the renal corpuscle
Glomerulus filters blood through capillaries and creates glomerular filtrate, and collectings filtrate in the bowman’s capsule
What is the proximal convoluted tubule
Highly coiled tubule in the renal cortex continuous with the bowman’s capsule
What type of epithelium lined the proximal convoluted tubule and why is this beneficial
Cuboidal epithelium with microvilli
Increases surface area for reabsorption
What is the function of the proximal convoluted tubule
Reabsorption and secretion
Describe the percentages of molecules and water that are reabsorbed in the proximal convoluted tubule
65% of total reabsorption
80% of all water/sodium/chloride/bicarb
100% of glucose and amino acids
Describe the loop of Henle
U-shaped tube that extend from the cortex into the medulla and loops back into the cortex
Has ascending and descending limbs
Has a smaller diameter than the rest of the renal tubules
What is the function of the Loop of Henle
Reabsorption
Sodium exchange for other ions
Describe the distal convoluted tubule
A coiled tubule In the cortex, that joins with the collecting ducts along with other nephrons
What is the function of the distal convoluted tubule
Reabsorption
Sodium exchnage for other ions
Nephrons join to common collecting ducts which extend into the
Renal papilla
Collecting ducts are important for
Potassium levels
Secretion of hydrogen and ammonia
Acid and base balance
Antidiuretic hormone has great effect on the
Collecting ducts
Where does filtration of blood occur
Renal corpuscle
What are 3 ways renal capillaries are different from normal capillaries
Connect 2 arterioles
Have small pores to increase fluid leakage/filtration
Under high pressure
True or false
Pores in renal capillaries are large enough to allow proteins and blood cells to be filtered out
FALSE
Protein in urine indicates damage to the ____ which can be seen on urinalysis
Glomerulus
What creates the high pressure in renal capillaries
The afferent arterioles are larger than the efferent arterioles which causes presssure to build up in the glomerulus
What does the high pressure of renal capillaries do
Forces the glomerular filtrate out to collect in the bowman’s capsule
What is GFR and what is it measured in
Glomerular filtration rate: how fast plasma is filtered depending in the rate of blood flow to the kidneys
Measured in ml/minute
Blood pressure is critical for maintaining GFR, how is this accomplished
Through the renin-angiotensin system
Renin is secreted by the juxtaglomerular apparatus
Golmerular filtrate contains many substances needed to maintain balance of nutrients/minerals/electrolytes/acid base balance. What are some of these key substances
Sodium Potassium Calcium Magnesium Glucose Amino acids Chloride Bicarbonate Water
True or false
Only about 50% of water is reabsorbed
False
About 99% is
Reabsorption mainly occurs in the
Proximal convoluted tubule
Describe how substances move during reabsorption
By passive diffusion or active transport
From the tubular lumen, to the interstitial space, into the peritubular capillaries
Describe sodium cotransport
Active transport of sodium out of the tubular epithelium by a carrier protein on the basement cell membrane uses energy
Cotransport of sodium with glucose and amino acid occurs to maintain those levels
What is the renal threshold
The limit on how much glucose can be reabsorbed
What happens if blood glucose levels exceed the renal threshold
Glucose will remain in the urine
Causing diabetes mellitus, polyuria, polydipsia and other conditions causing high blood glucose
How does reabsorption in the loop of henle and the distal convoluted tubule occur
Controlled by aldoesterone (mineralocorticoid from the adrenal cortex)
Sodium is reabsorbed in exchange for hydrogen, ammonium or potassium
True or false
Potassium is reabsorbed by diffusion in most parts of the renal tubules
True
Calcium is reabsorbed in most parts of the renal tubules
What 3 things does absorption of calcium involve
Vitamin D (convert to calcitriol)
Parathyroid hormone (increases absorption of calcium)
Calcitonin (decreases absorption)
Describe how kidneys are related to vitamin D
The kidneys release the active form of Vitamin D calcitriol which increases calcium absorption in the GIT
True or false
Magnesium is reabsorbed in most parts of the renal tubule
True
When sodium is pumped out of the tubular lumen, and electrical charge is created (positive outside the lumen and negative inside)
What restores the neutrality of the lumen
Chloride ions diffusing out of the lumen
What is the effect of osmotic diuresis due to glucosuria
Prevents proper reabsorption of water
Where does secretion occur in the kidneys
PCT: for histamine, uric acid, creatinine and hydrogen
DCT: for hydrogen, potassium and ammonia
Aldosterone helps promote secretion of ___ and reabsorption of ____ in the DCT
Secretion of potassium
Absorption of sodium
What does easy secretion of drugs like penicillin and sulfonamides help in
When treating UTIs, these drugs can easily reach very high levels in the urine and animals are often sensitive to these drugs
Describe the movement of substances during secretion
Substances move from the peritubular capillaries, through the interstitial fluid, and into the tubular lumen
secretion is important for things that are inadequately filtered out in the ___
Glomerulus
What is urine volune primarily controlled by
Antidiuretic hormone (posterior pituitary) and aldosterone (adrenal cortex)
What does antidiuretic hormone do
Increases water absorption from the DCT and collecting ducts (increases number of water pores in cells)
What happens if there is inadequate amounts of ADH
Inadequate reabsorption of water
This causes a high volume of urine and increased drinking to compensate for water loss (PU/PD)
Low specific gravity
Diabetes insipidus
What does aldosterone do
Increases sodium reabsorption in the DCT and collecting ducts
Results in chloride and water following sodium
Creates a osmotic imbalance
Water intake is regulated by a thirst center in the hypothalamus that responds to
Blood pressure and water concentration in the blood
Explain the renin-angiotensin system when responding to low blood pressure or salt concentrations
When there is decreased blood flow to the kidneys, or when the macula densa senses low NaCl concentrations, renin is released by the juxtaglomerular apparatus (in the glomerulus)
Renin catalyzes the conversion of angiotensinogen into angiotensin 1
Angiotensin 1 is then converted to angiotensin 2
Angiotensin 2 acts on the adrenal glands to stimulate the release of aldosterone
Aldoesterone stimulates salt and water reabsorption and causes vasoconstriction to increase blood pressure
What is renal failure
The inability of the kidneys to perform their normal functions
What is uremia or azotemia
The accumulation of urea in the blood due to renal failure
What normally identifies uremia
Blood tests
What normally accompanies uremia
Accumulation of creatinine (a waste product of muscle metabolism)
What is prerenal uremia
The problem is occuring before the kidneys
Decreased blood flow to the kidneys due to dehydration, congestive heart failure or shock
What is renal uremia
The problem is within the kidneys
Damaged nephrone due to toxins/infections/inflammation
Damaged nephrons cannot filter blood and leads to toxin accumulation
Describe how kidneys have a great capacity to compensate when there is kidney damage
You need a loss of 2/3 to 3/4 of nephron fucntion to see clinical signs
This leaves the need for only at least 1/3 to 1/4 of normal function
What is postrenal uremia
Problem is occuring after the kidneys
Usually due to urethral obstruction (stones, mucus plugs, clots or tumors)
If postrenal uremia is severe enough what occurs
Urine backs up into the kidneys and damages or destroys the nephrons
Causing renal uremia
What is acute renal failure
A recent loss of kidney function
Usually due to trauma, obstruction, shock, viruses or poisoning (heavy metals, antifreeze)
True or false
It is easy to distinguish between acute and chronic renal failure
FALSE
it is very difficult
In acute renal failure, loss of function can be corrected if
The cause can be discovered and corrected
What aids in the treatment of any kidney damage
Kidneys having a lot of regenerative power
What are the signs of acute renal failure
Vomiting, diarrhea, Depression, dehydration, anorexia and anuria
Describe copper toxicity in sheep
Causes hemolysis and acute renal disease following chronic ingestion of copper due to hemoglobin precipitating out in the kidneys
Describe chronic renal failure
Loss of function developed over an extended amount of time
Usually seen when much of the kidney is already damaged
Little hope in being corrected
What are the signs of chronic renal failure
The same as acute renal failure but include
Polyuria/polydipsia
Weight loss
Anemia
Why would you see anemia with chronic renal failure
Because kidneys make erythropoietin, a hormone that stimulates RBCs production
On an ultrasound, how does a kidney look with chronic vs actute renal failure
Chronic: shrunken
Acute: swollen
What is cystitis
Inflammation of the bladder
Why are female more prone to cystitis
Because the urethra is shorter, wider and opens up to the vagina
What are the signs of cystitis
Frequent small volume urination with cloudy urine
Cloudy from WBCs and/or RBCs
Some waste products in urine may precipitate out and clump together to form solid crystals or stones called
Uroliths
Urinary stones
Urinary calculi
What animals are uroliths common in, which ones are they not common in
Common: dogs, cats, cattle, sheep, goats
Uncommon: horses
Composition of uroliths vary and can be identified through
Microscopic examination
What is the most common urolith called (magnesium ammonium phophate hexahydrate)
Struvite
Where does formation of uroliths mainly occur
In the bladder
What does the formation of uroliths depend on
Urine pH Diet UTIs Urinary volume Frequency of urination
Why do urinary tract infections predispose animals to struvite uroliths
UTIs raise pH and help precipitate crystals
Why are dehydrated animals, or animals not frequently allowed to urinate predisposed for uroliths
Because decreased urine flow increases risk of urolith formation
Where can uroliths also form besides the bladder
Renal pelvis (kidney stones)
Ureters
Urethra
Why is urethral obstruction more common in males
Because of the small diameter, long length and curvature of the male urethra
Why may unilateral ureteral obstructions not be clincally recognized even if it destroys the associated kidney
Because the other kidney will take over
What is the treatment for uroliths/obstructions of the urinary tract
Surgical removal
Diets to dissolve them or prevent them
Antibiotics (if there is an associated UTI)
Surgical bypass using a urethrostomy
What breeds is canine urolithiasis most seen in
Minature shnauzer Dachshund Dalmatian Pug Bull dog Basset hound Beagles
(Metabolic differences)
When is ruminant urolithiasis or “water belly” most seen
In the winter when water intake in decreased
When water sources have high mineral content (minor)
When a high grain content diet is fed (low calcium high phosphate diets) (feedlots)
Occlusion of the urethra by calculi leads to
Rupture of the urethra or the bladder
What are the clinical signs of ruminant urolithiasis
Failure to pass urine
Dribbling urine
Painful abdomen
What is Feline Lower Urinary Tract Disease (FLUTD)
AKA Feline Urological Syndrome (FUS)
When cats get sand-like crystals (often struvite or calcium oxalate crystals) Which produce mucus-like matrix that combines with the crystals to form a gelatinous plug which obstructs the urethra
Usually due to high dietary magnesium and calcium, genetic factors, dry food diets, lower water intakes
What are the signs or FLUTD/FUS
Very painful
Increased use of litter box
With complete obstruction in males they will lick their penis a lot
What is the treatment and prevention of FLUTD/FUS
Anesthetization to allow catheterization to relieve obstruction
Diets to minimize poorly soluble substances that cause uroliths
Diet to maintain low pH
Antibiotics
What are the main poorly soluble substances seen to cause uroliths
Calcium
Magnesium
Phosphorus
True or false
With an obstructed ureter, urination is often not affected unlike with obstructed urethras
True
True or false
Uremia is often seen with obstructed urethras unlike obstructed ureters
True
Why are cats fed dry diets at higher risk for uroliths
Cats on dry food diets have lower water intake and produce more concentrated urine than cats on wet food
Define polyuria
Increased urine volume
Define pollakiuria
Increased frequency of urination
define hematuria
Blood in urine
Define glucosuria
Glucose in urine
Define dysuria
Difficulty urinating (straining)
Define stranguria
Painful urination
Define anemia
Lack of hemoglobin in blood
What is the trigone
Land mark in the bladder between the ureters and urethra
