Urinary System Flashcards
Describe the structure of the kidney
Located retroperitoneally in perirenal capsul
What are the functions of the urinary system
Dispose of metabolic waste and excess substances through formation of urine + filters the blood: gets rid of nitrogenous waste ammonia etc. salts glucose vitamins.
Regulate fluid electrolyte balance. Regulate acid-base balance in blood. Produce hormone erythropoietin
What are the three regions of the kidney
Cortex, medulla and pelvis
What is the cortex of the kidney
Outer region. Lightly colored and granular
Describe the medulla
Darker, reddish brown. Contains cone shaped renal pyramids that are striated. Composed of parallel bundles of urine collecting tubules. The renal pyramid and surrounding cortical tissue constitutes a lobe
Describe the pelvis of the kidney
Flat, funnel shaped tube continuous with ureter and exits out the hilium
What are the major calyces
Large branches of the renal pelvis that are subdivided into several minor calyces. Collect urine draining from papilla of each renal pyramid. Empty urine into the renal pelvis
How does the urine flow through the pelvis and ureters to the bladder
By peristalsis
What are ureters
Tubes connecting the renal pelvis to the bladder. Ureters enter bladder at an oblique angle and when bladder is full shape changes and pinches off ureters to prevent backflow of urine
What are the three tissue layers that the wall of the ureter is composed of
It are mucosal layer is transitional epithelium. Middle layer is smooth muscle. Outer layer is fibrous
Describe the urinary bladder
Stores urine until a limitation. Stretching of wall makes it thinner and more susceptible to rupture. Stretch receptors trigger contractions. Involuntary sphincter control is urine flow into urethra.
Describe the urethra
Tube connecting bladder to outside of body. Typically longer in males but not true and cats.
What does the urethra carry in females
Urine
What does the urethra carry in males
Urine and semen
Describe kidney filtration
Kidneys receive one fourth of aortas blood at any given time. All of body’s blood is filtered every five minutes. 25% of blood plasma enters the nephron as filtrate. All but one percent of filtrate is reabsorbed back into the blood by capillories surrounding the nephron that are called peritubular capillaries. Remaining filtrate enters calyces as urine.
Describe blood flow to and from kidneys
Aorta ➡️ renal artery➡️afferent arteriole ➡️glomerulus ➡️peritubular capillaries ➡️renal vein ➡️inferior vena cava
How is the kidney capillary bed and the regular capillary bed different
This capillary bed is different because it is forced movement not by concentration gradient.
What is the renal corpuscle
The glomerulus and the Bowmans capsule
What is a nephron
Structural and functional renal unit. Forms urine
What does the nephron consist of
Glomerulus
Bowmans capsule
Renal tubule
Describe the glomerulus
Capillary bed. Blood enters under high-pressure. Endothelium is fenestrated. Filtration of blood is selective only by size. Filtrate enters the renal tubule after the glomerulus
What can pass through the glomerulus
Plasma + dissolved solutes
What shouldn’t pass through the glomerulus
Proteins, cells. Too large to be re absorbed and will Be thus present in urine
Describe the Bowmans capsule
Surrounds glomerulus and is continuous with the renal tubule. Odor parietal layer is simple squamous epithelium. Inner visceral layer consists of podocytes that cling to basement membrane. Filtrate passes through fenestrations between the feet in the capsule
Where are the pct and dct located
The cortex
Where are the loop of henle and the collecting ducts
Medulla
Describe the proximal convoluted tubule
Simple cuboidal epithelium with microvilli brush border. Reabsorbs water and solids from filtrate and returns to blood via peritubular capillaries. Secrete substances into filtrate.
Describe the loop of Henle
Loop of the renal tubule that dips into the medulla.
What are the two portions of the loop of Henle
The descending limb and the ascending limb
Describe the descending limb of the loop of Henle
Proximal part has cells similar to proximal convoluted tubule then becomes narrow and has simple squamous cells freely permeable to water
Describe the ascending limb of the loop of henle
Tube widens again epithelium is cuboidal and columnar and inpermeable to water
Describe the distal convoluted tubule
Cuboidal cells without microvilli. Not as twisted as proximal convoluted tubule. Functions more in secretion than reabsorption. Empty into collecting ducts.
Describe the collecting ducts
Receive filtrate from numerous distal convoluted tubule’s. Deliver filtrate to renal pelvis. Composed of two cuboidal cell types. Principal cells maintain water and potassium balance and intercalcated cells maintain acid-base balance and have microvilli
Describe the glomerulus capillary bed
Fed by afferent arteriole, drained by efferent arteriole. Produces filtrate
Describe the peritubular capillaries
Site of reabsorption and secretes. Site of gas exchange. Merge to form renal vein
What are the three major processes in urine formation and adjustment of blood composition
Glomerulus filtration
Tubular reabsorption
Tubular secretion
Describe filtration
Occurs at glomerulus, size selective only
Describe reabsorption
Tubule➡️peritubular capillaries. Good stuff lost at glomerulus is returned to blood unless in excess. All of glucose and amino acids should be reabsorbed
Describe secretion
️peritubular capillaries ➡️ tubules. Bad stuff not filtered in glomerulus transported to tubule for excretion
Where should reabsorbed and secreted substances also pass through
Institial space between vessels and nephron. Transport may be passive (diffusion) or active (ATP). Osmotic gradient in medulla affects transport
How does urine volume regulation work
Amount of water reabsorbed by dct and collecting ducts is variable.
What is urine volume influence by
Influenced by adh and aldersterone. Also influenced by pathologies such as diabetes mellitis
What does adh do to the urine
Affects water transport proteins in dct and collecting tubules.
What is diabetes insipidus
Pu/pd: caused by inadequate adh release from posteur petuitary (central DI) or non responsive tubule cells (nephrogenic DI)
What happen when no ADH is present
Collecting duct is not permeable to water and a large volume of urine is produced
What happens when no adh is present
Collecting duct is permeable to water and a small volume of urine is produced
What does aldersterone do
Acts on DcT and collecting duct cells. Increases reabsorption of NA+ which causes water to follow if adh is present
What is the renal threshold of glucose
Limited amount of glucose can be reabsorbed by pct into blood. Excess remains in filtrate/urine
What is BUN
Urea in blood
What does high glucose in filtrate cause
Increased water secretion➡️ increased urine volume ➡️ dehydration and pu/pd
What is the dogs renal threshold
180mg/dl
What is the cats renal threshold
240mg/dl
What is urination called
Mucturation and uresis
What is normal urine output
1-2 ml/kg/hr.
What can urine output show
Can provide info about renal function. Affected by other fluid losses (vomiting) and fluid input (iv).
What is the best way to measure urine output
With an indwelling urinary catheter
What is the glomerulus filtration rate
Volume of blood filtered by glomerulus and entering Bowmans capsule per unit of time. Affected by blood pressure and blood volume. Want a relatively steady rate of GFR
What can high GFR show
Not enough time for all substances to be filtered, secreted and reabsorbed
What is low GFR
Too much time for reabsorption, substances that should have been excreted and reabsorbed
What can GFR be used to measure
Renal function
How do you measure kidney function?
Serum creatinine concentration test
Plasma clearance of substance
What is the serum creatinine concentration test
Creatinine is a waste product of muscle cells which travels in blood and is excreted in urine. Amount produced and excreted depends on muscle mass but is relatively constant in an individual. Measure amount of creatinine in urine. If elevated, may indicate renal dysfunction.
What is the advantage to the serum creatinine concentration test
Cheap and easy
What is the disadvantage to the serum creatinine concentration test
Not really sensitive. GFR needs to be 75% less than normal for a change to be detected.
What is the plasma clearance of substance
Inject a substance Into the blood, measure the amount of time it takes for the blood to be cleared of the substance: need to take blood samples at regular intervals. Want to use a substance that is not normally present in the blood and one that will not be reabsorbed into blood or secreted back into tubules or metabolized. Test blood samples for presence of substance
What is renal dysfunction
Kidneys are unable to remove waste from blood, nitrogen waste builds up in blood and is measurable.
What is azotemia
Abnormally high levels of nitrogen waste in blood but no symptoms in individual
What is item is
Abnormally high level of nitrogen waste in blood that now produces symptoms
How do you test for renal dysfunction
Measure bun
What is prerenal uremia
Kidney fx normally but decreases blood flow to kidneys so they cannot remove waste properly. Due to dehydration etc
What is renal uremia
Damage to nephrons due to toxins; acute or chronic
What is post renal uremia
Due to blockage after kidney can lead to renal uremia
What is dialysis
Diffusion of substances through a semi permeable membrane
What is hemodialysis
Blood is removed from animal and filtered into a machine : 4-6hrs
What is continuous renal replacement therapy
Similar to hemodialysis but slower; takes 12hrs
What is peritoneal dialysis
Fluid introduced into peritoneal cavity then flushed out
What is bacterial cystitis
Bladder infection, most common in dogs, usually due to bacteria travelling up from urethra
What are the signs of bacterial cystitis in Dogs
Pollakiuria, hematuria, Dysuria, cloudy urine, frequent licking of urethra
How do you test for bacterial cystitis in dogs and what is the treatment
Urinalysis and the treatment is antibiotics
What can cystitis also be caused by
Stones, tumors or be idiopathic
What is feline lower urinary tract disease
Collection of disorders affecting bladder and urethra. Can be caused by presence of uroliths, infection, tumor or can be idiopathic.
What are the signs of feline lower urinary tract disease
Stranguria, Dysuria, hematuria, frequent licking, innapropriate urination
What is the treatment of flutd
Depends on the cause. UA can help in diagnosis
What is urethral obstruction
Most common in male cats due to caudal location of penis. Urethra curves and narrows near penis. Can be fatal in 36-48hrs.
What are the signs of urinary obstruction
Anuria, Dysuria, stranguria, hematuria, rigid bladder, innapropriate urination
What is the treatment for urethral obstruction
Catheterization, cystotomy to remove calculi, or perineal urethrostomy to widen the urethra
What urolithiasis
Formation of uroliths in urinary tract. Symptoms are dependant on location and size. Some animals are asymptomatic. tx involves surgery and dietary changes
Why do urolithiasis form
Normally substances in Urine remains dissolved but will precipitate and forms crystals and under certain conditions. Composed mainly of minerals. Removed surgically or using lithotripsy
What is urethral duplication
Extra urethras
What is uranalysis
Tests to evaluate physical and chemical properties of urine.
What are the urine collecting methods
Free catch, catheterization, and cystocentesis
How do you do urine specimen processing
Collect in clear container without additives. Ideally analyze sample immediately after collection. Refrigerate up to four hours. Reduces bacteria growth but may cause crystallization. Allow sample to warm to rt before testing.
What are the physical properties of urine processing
Color, transparency and specific gravity
What is specific gravity
Amount of dissolved solutes in urine
What are the chemical properties of urine specimen processing
Use dip stick for color change.
What is microscopic urine analysis
Centrifuge sample, examine sediment looking for presence of cells and casts
What are casts
Cylindrical aggregation of substances
What is crystalluria
Crystals in urine
What are struvites
Can be caused by more alkaline ph. Most common crystals in cats and dogs.
What is calcium oxalate stones
Can be caused by more acidic ph. Common in cats
