Lecture Exam- Urinary System Flashcards
Urinary System
rids the body of waste products
closely associated with the reproductive system
Shared embryonic development and adult anatomical relationship
Collectively called the urogenital (UG) system
kidneys
play important roles in blood volume, pressure, and composition
parts of the Urinary System
- consists of six organs: two kidneys, two ureters, urinary bladder, and urethra
Functions of the Urinary System
Filter blood and excrete toxic metabolic wastes
Regulate blood volume, pressure, and osmolarity by regulating water output
Regulate electrolyte and acid-base balance of body fluids
Secrete erythropoietin stimulating production of RBcs
Regulate calcium homeostasis and bone metabolism by calcitriol
Clear hormones and drugs form blood limiting action
Detoxify free radicals
In starvation, synthesize glucose from amino acids.
Nitrogenous Wastes
are nitrogen containing compounds consist of urea, uric acid, creatine,
what are the three nitrogen wastes and how are they made
Urea formation 50% Proteins-amino acids-NH2 removed-forms ammonia, Liver converts ammonia to urea Uric acid Product of nucleic acid catabolism Creatinine Product of creatine phosphate catabolism
azotemia
Blood urea nitrogen (BUN)—level of nitrogenous waste in blood
Azotemia: elevated BUN- May indicate renal insufficiency
uremia
Uremia: syndrome of diarrhea, vomiting, dyspnea, and cardiac arrhythmia stemming from the toxicity of nitrogenous waste
Treatment—hemodialysis or organ transplant
four body systems carry out excretion
Respiratory system- CO2, water
Integumentary system- water, inorganic salts, lactate, and urea
Digestive system- eliminates food residue, excretes water, salt, CO2, lipids, bile pigments, cholesterole
Urinary system-excretes metabolic wastes, toxins, drugs, hormones, salts, hydrogen ions, and water
Nephrons what are they what are they composed of?
Each kidney has about 1.2 million nephrons
Each composed of two principal parts renal corpuscle and renal tubule
Renal corpuscle:
simple squamous. Glomerular filtrate collects in capsular space, flows into proximal convoluted tubule. Note the vascular and urinary poles. Note the afferent arteriole is larger than the efferent arteriole. .filters the blood plasma
consists of the glomerulus and a two-layered glomerular capsule that encloses glomerulus
Renal tubule:
long, coiled tube that converts the filtrate into urine
Name and describe the three parts of the glomerular capsule
Parietal (outer) layer of glomerular capsule is simple squamous epithelium
Visceral (inner) layer of glomerular capsule consists of elaborate cells called podocytes that wrap around the capillaries of the glomerulus
Capsular space separates the two layers of glomerular capsule
Cortical nephrons
85% of all nephrons
Short nephron loops
Efferent arterioles branch into peritubular capillaries around PCT and DCT
Juxta medullary nephrons
15% of all nephrons
Very long nephron loops, maintain salinity gradient in the medulla and help conserve water
Efferent arterioles branch into vasa recta around long nephron loop
Vascular pole
—the side of the corpuscle where the afferent arterial enters the corpuscle and the efferent arteriole leaves
Urinary pole
the opposite side of the corpuscle where the renal tubule begins
Renal (uriniferous) tubule
—duct leading away from the glomerular capsule and ending at the tip of the medullary pyramid
Divided into four regions
Proximal convoluted tubule, nephron loop, distal convoluted tubule: parts of one nephron
Collecting duct
receives fluid from many nephrons.
receives fluid from the DCTs of several nephrons as it passes back into the medulla
Numerous collecting ducts converge toward the tip of the medullary pyramid
. Osmolarity of extracellular fluid 4x as high in lower medulla than cortex, medullary portion is more permeable to water than solutes as it goes down increasingly hypertonic leaving tubule by osmosis while other wastes stay behind
Proximal convoluted tubule (PCT)
—arises from glomerular capsule
Longest and most coiled region
Simple cuboidal epithelium with prominent microvilli for majority of absorption
Nephron loop
long U-shaped portion of renal tubule. found mostly in medulla begins where PCT straightens and dips toward or into medulla
Descending limb and ascending limb
Thick segments have simple cuboidal epithelium
Initial part of descending limb and part or all of ascending limb
Heavily engaged in the active transport of salts and have many mitochondria
Thin segment has simple squamous epithelium
Forms lower part of descending limb
Cells very permeable to water
Distal convoluted tubule (DCT)—
begins shortly after the ascending limb reenters the cortex
Shorter and less coiled than PCT
Cuboidal epithelium without microvilli
DCT is the end of the nephron
Papillary duct:
formed by merger of several collecting ducts
30 papillary ducts end in the tip of each papilla end in pores at tip of papilal w/ urine draining into minor calyx that encloses it
Collecting and papillary ducts lined with simple cuboidal epithelium
Filtration Membrane what is it and what passes through what doesn’t and how do these pass through?
Filtration Membrane: Almost any molecule smaller than 3 nm can pass freely through the filtration membrane. Water, rest electrolytes, glucose, fatty acids, amino acids, nitrogenous wastes, and vitamins
Some substances of low molecular weight are bound to the plasma proteins and cannot get through the membrane
Most calcium, iron, and thyroid hormone
Unbound fraction passes freely into the filtrate
In what cases would the filtration membrane allow larger molecules?
W/ kidney disease presence of proteins, albumin or hematuria (blood in urine) present in blood w/ distance runner and swimmers having temporary reducing perfusion of kidneys deteriorating glomerulus under prolonged hypoxia leaking protein and blood into filtrate.
Glomerular Filtration
forms urine using capillary exchanges w/ water and solutes and blood plasma pass through capillaries in glomerular space.
Forces Involved in Glomerular Function
High BP in glomerulus makes kidneys vulnerable to hypertension
It can lead to rupture of glomerular capillaries, produce scarring of the kidneys (nephrosclerosis), and atherosclerosis of renal blood vessels, ultimately leading to renal failure by blockage.
Stage 2: Tubular ReabsorptionTwo routes of reabsorption
process of reclaiming water and solutes from tubular fluid and returning them to blood.
transcellular and paraclleular route
Transcellular route
Substances pass through cytoplasm of PCT epithelial cells and out their base
Paracellular route
Substances pass between PCT cells
Junctions between epithelial cells are leaky and allow significant amounts of water to pass through
Solvent drag—water carries a variety of dissolved solutes with it
Reabsorbed fluid is ultimately taken up by peritubular capillaries
How is Sodium reabsorption created.
Two types of transports proteins in apical cell surface responsible for sodium uptake.
Creates osmotic and electrical gradients that absorb water and other solutes, sodium is most abundant in filtrate w/ steep concentration gradients favoring diffusion into epithelial cells.
symports and antiport
Symport
that simultaneously bind sodium and another solute such as glucose, amino acids or lactate
antiport
Sodium hydrogen anti-port that pulls sodium into cell while pumping out hydrogen into tubular fluid.
Sodium is prevented from accumulating
in epithelial cells by sodium potassium pump in basal surface of epithelium. Pumping sodium out to extracellular fluid too much doesn’t build up.
Sodium is picking up by peritubular capillaries and returned to blood
Chloride movement in urine
Negative chloride ions follow positive sodium ions by electrical attraction w/ various antiports in apical cell membrane absorbing chloride in exchange for other anions they eject into tubular fluid w/ potassium and chloride symport.
other ions movement in urine
Potassium, magnesium, and phosphate ions diffuse through the paracellular route with water
Phosphate is also cotransported into the epithelial cells with Na+
Some calcium is reabsorbed through the paracellular route in the PCT, but most Ca2+reabsorption occurs later in the nephron
Glucose transported
Glucose is cotransported w/ Na+ by sodium-glucose transport (SGLT) proteins normally all glucose is reabsorbed
Nitrogenous wastes excretion
Nephron reabsorbs about half of urea in tubular fluid
Concentration remaining in blood is safe
PCT reabsorbs uric acid, but later portions of the nephron secrete it
Creatinine is not reabsorbed – it is passed in urine
Kidneys produce how much urine and how is this done?
kidneys produce 180 L of filtrate everyday that is condensed to 1-2 L of urine. 2/3 of water in filtrate reabsorbed in PCT reabsorbed solutes and solutions makes it hypertonic to tubule fluid as water follows solute by osmosis PCT reabsorbed at constant rate aka obligatory water reabsorption.
Tubular Secretion
takes chemicals from capillary blood and secretes them into tubular fluid
Purposes of secretion in PCT and nephron loop include
acid-base balance
waste removal
clearance of drugs and contaminants
Acid–base balance
Secretion of varying proportions of hydrogen and bicarbonate ions helps regulate pH of body fluids
Waste removal
Urea, uric acid, bile acids, ammonia, and a little creatinine are secreted into the tubule secreted into tubule
Clearance of drugs and contaminants
Examples include: morphine, penicillin, and aspirin
Some drugs must be taken multiple times per day to keep up with renal clearance .
Water Conservation
The kidney eliminates metabolic wastes from the body, but prevents excessive water loss
As the kidney returns water to the tissue fluid and bloodstream, the fluid remaining in the renal tubules passes as urine, and becomes more concentrated
How is control of water loss maintained
How concentrated the urine becomes depends on body’s state of hydration
Water diuresis—drinking large volumes of water will produce a large volume of hypotonic urine w/
Cortical portion of CD reabsorbs NaCl, but it is impermeable to water
Salt is removed from the urine but water stays in
Urine concentration may be as low as 50 mOsm/L
Hypertonic urine w/ hydration absorbing more overall of salts and water flowing more slowly through tubes w/ more time for reabsorption
what happens if GFR is too high?
Fluid flows through renal tubules too rapidly for them to reabsorb the usual amount of water and solutes
Urine output rises
Chance of dehydration and electrolyte depletion
what happens if GFR is too low
Wastes are reabsorbed
Azotemia may occur
renal auto regulation
the ability of the nephrons to adjust their own blood flow and GFR without external (nervous or hormonal) control. Have rate and waste management
Enables kidney to maintain a relatively stable GFR in spite of changes in systemic blood pressure
Two methods of autoregulation: myogenic mechanism and tubuloglomerular feedback
Sympathetic nerve fibers
richly innervate the renal blood vessels
Sympathetic nervous system and adrenal epinephrine constrict the afferent arterioles in strenuous exercise or acute conditions like circulatory shock.
Reduces GFR and urine output
Redirects blood from the kidneys to the heart, brain, and skeletal muscles
GFR may be as low as a few milliliters per minute
urinalysis
examination of physical and chemical properties of urine
appearance
varies from clear to deep amber depending on state of hydration
odor
bacteria degrade urea to ammonia, some foods and diseases impart particular aromas
specific gravity
compares urine sample’s density to that of distilled water
Density of urine ranges from 1.001 to1.028 g/mL
osmolarity
Osmolarity(blood = 300 mOsm/L)
Ranges from 50 mOsm/L to 1,200 mOsm/L in dehydrated person
pH
pH—range: 4.5 to 8.2, usually 6.0 (mildly acidic)
chemical composiiton
95% water, 5% solutes
Normalto find: urea, NaCl, KCl, creatinine, uric acid, phosphates, sulfates, traces of calcium, magnesium, and sometimes bicarbonate, urochrome, and a trace of bilirubin
Abnormalto find: glucose, free hemoglobin, albumin, ketones, bile pigments
volume
Normalvolume for average adult—1 to 2 L/day
Polyuria—output in excess of 2 L/day
Oliguria—output of less than 500 mL/day
Anuria—0 to 100 mL/day
Yellow color urine
due to urochrome pigment from breakdown of hemoglobin (RBCs)
Cloudiness or blood
could suggest urinary tract infection, trauma, or stones; or might just be contamination with other fluids
Pyuria:
pus in the urine
Hematuria:
blood in urine due to urinary tract infection, trauma, or kidney stones
anuria causes
Low output from kidney disease, dehydration, circulatory shock, prostate enlargement
Low urine output of less than 400 mL/day, the body cannot maintain a safe, low concentration of waste in the plasma (leads to azotemia)
Diabetes—
any metabolic disorder resulting in chronic polyuria
At least four forms of diabetes
Diabetes mellitus type 1,type 2,and gestational diabetes
Diabetes in urine
High concentration of glucose in renal tubule
Glucose opposes the osmotic reabsorption of water
More water passes in urine (osmotic diuresis)
Glycosuria—glucose in the urine
Diabetesinsipidus
ADHhyposecretioncauses not enough water to be reabsorbed in the collecting duct
More water passes in urine
Diuretics
any chemical that increases urine volume. Impairs countercurrent stopping stuff from entering renal medulla.Reducing body’s fluid volume and blood pressure
Some act on nephron loop (loop diuretic): inhibit Na+–K+–Cl−symport
Impairs countercurrent multiplier reducing the osmotic gradient in the renal medulla
Collecting duct unable to reabsorb as much water as usual
cafeeine
Some increase GFR: Caffeine dilates the afferent arteriole
Some reduce tubular reabsorption of water:
alcohol
Alcohol inhibits ADH secretion
diurhetics are used to treat
Diuretics are commonly used to treat hypertension and congestive heart failure by reducing the body’s fluid volume and blood pressure
Renal Function Tests
Tests for diagnosing kidney disease- Evaluating their severity Monitoring their progress Determining renal clearance Determining glomerular filtration rate
Renal Clearance
the volume of blood plasma from which a particular waste is completely removed in one minute important for understanding how your kidneys are functioning determined by glomerular filtration, tubular secretion, tubular reabsorption. . Urea influences clearance w/ renal clearance used for other things and urinalysis.
Glomerular Filtration rate
Often need to measure GFR to assess kidney disease
Cannot use clearance rate of urea, because reabsorption and secretion of urea influence its clearance
Need a substance that is not secreted nor reabsorbed at all so that all of it in the urine gets there by glomerular filtration
Kidneys convert blood plasma to urine in four stages what are they and briefly describe each stage
Glomerular filtration- plasma-like filtrate water and some solutes but no protein in blood pass through capillaries of glomerulus into capsular space of nephron.
Tubular reabsorption- removes useful solutes from filtrate, returns them to blood
Tubular secretion-removes additional wastes from blood, adds them to the filtrate
Water conservation- removes water from urine and returns it to blood; concentrates waste
Glomerular filtrate—
the fluid in the capsular space, Similar to blood plasma except that it has almost no protein
Tubular fluid—
fluid from the proximal convoluted tubule through the distal convoluted tubule
Substances have been removed or added by tubular cells
Urine—
fluid that enters the collecting duct
Undergoes little alteration beyond this point except for changes in water content.
Renal calculus (kidney stone)
—hard granule of calcium phosphate, calcium oxalate, uric acid, or a magnesium salt called struvite
Form in the renal pelvis can block passage from calyxes to ureter or can block ureter can cause infections further up in kidneys. w/ lots of innervation causing great pain. Not a lot of smooth muscle for innervation to push out.
Usually small enough to pass unnoticed in the urine flow
Large stones might block renal pelvis or ureter and can cause pressure buildup in kidney which destroys nephrons. Usually passing blood as well.
Passage of large jagged stones is excruciatingly painful and may damage ureter causing hematuria
Urinary tract Infection (UTI) what are the three things it can cause?
Cystitis—infection of the urinary bladder
Especially common in females due to short urethra
Frequently triggered by sexual intercourse
Can spread up the ureter causing pyelitis
Pyelitis—infection of the renal pelvis
Pyelonephritis—infection that reaches the cortex and the nephrons
Can result from blood-borne bacteria
Voiding Urine-
sympathetic activity post-ganglionic to detrusor muscles to internal common iliac to be excited to close so urine doesn’t pass through.
Between acts of urination, the bladder fills
Detrusor muscle relaxes
Urethral sphincters are tightly closed
Sympathetic activity in upper lumbar spinal cord stimulates postganglionic fibers to the detrusor muscle (relax it) allowing for internal urethral sphincter (excite it)
Somatic motor fibers from upper sacral spinal cord travel through pudendalnerve to supply the external sphincter to allow voluntary control
Micturition
—the act of urinating
Micturition reflex—
involuntary spinal reflex that partly controls urination (steps 1–4)
Stretch receptors detect filing of bladder, transmit afferent signals to the spinal cord
Signals return to bladder from spinal cord (S2 or S3) via parasympathetic fibers in the pelvic nerve
Efferent signals excite detrusor muscl
Efferent signals relax internal urethral sphincter (male); urine is involuntary voided if not inhibited by the brain
Voluntary control of micturition
(steps 5–8)
For voluntary control, the micturition center in the pons receives signals from stretch receptors
If it is timely to urinate, the pons returns signals to spinal interneurons that excite detrusor and relax internal urethral sphincter(male); urine is voided
If it is untimely to urinate, signals from the pons excite spinal interneurons that keep external urethral sphincter contracted; urine is retained in the bladder
If it is timely to urinate, signals from the pons cease, and external urethral sphincter relaxes; urine is voided
There are times when the bladder is not full enough to trigger the micturition reflex but one wishes to “go” anyway
Valsalva maneuver used to compress bladder
Excites stretch receptors early to get the reflex starteD
Renal insufficiency
—a state in which the kidneys cannot maintain homeostasis due to extensive destruction of their nephrons. nephrons work overtime to compensate for kdineyfunction cant do for too long.
Causes of nephron destruction
Hypertension, chronic kidney infections, trauma, prolonged ischemia and hypoxia, poisoning by heavy metals or solvents, blockage of renal tubules in transfusion reaction, atherosclerosis, or glomerulonephritis
What happens during renal insufficiency for compensation?
Nephrons can regenerate and restore kidney function after short-term injuries
Other nephrons work overtime to compensate for kidney function but they cannot do this for too long. Can survive with one-third of one kidney
When 75% of nephrons are lost, urine output of 30 mL/hr is insufficient (normal 50 to 60 mL/hr) to maintain homeostasis
Causes azotemia, acidosis, and uremia develops, also anemia
Hemodialysis—
procedure for artificially clearing wastes from the blood
Wastes leave bloodstream and enter dialysis fluid as blood flows through a semipermeable cellophane tube; also removes excess body water
Urine Storage and Elimination.
Urine is produced continually
Does not drain continually from the body
Urination is episodic—occurring when we allow it
Made possible by storage apparatus and neural controls for timely release
