STRUCTURAL AND FUNCTIONAL ORGANIZATION OF THE URINARY SYSTEM Flashcards
What consists of two kidneys, two ureters, one urinary bladder, and one urethra?
The urinary system
After the kidneys filter the blood, they return most of the water and many solutes to the bloodstream, what does the remaining water and solute constitute?
Urine
What is the scientific study of anatomy, physiology, and disorders of the kidneys?
Nephrology
What is the branch of medicine that deals with the male and female urinary system, and the male reproductive system?
Urology
What are these functions of?
- Regulation of ion levels in the blood
- Regulation of blood volume and blood pressure
- Regulation of blood pH
- Production of hormones
- Excretion of wastes
Functions of the kidneys
The kidneys help regulate blood levels of several ions, most importantly what?
- Sodium ion (Na+)
- Potassium ions (K+)
- Calcium ions (Ca2+)
- Chloride ions (Cl-)
- Phosphate ions (HPO)
True or False
The kidneys adjust the volume of blood in the body by returning water to the blood or eliminating it in the urine
True
The kidneys help regulate blood pressure by secreting what enzyme?
Renin
The enzyme renin activates what pathway, by adjusting blood flow into and out of the kidneys, and by adjusting blood volume?
Renin-angiotensin-aldosterone pathway
How do the kidneys regulate blood pH?
Regulating the concentration of H+ in the blood and conservation of the blood bicarbonate ions (HCO3-), an important buffer of H+
What two hormones do the kidneys produce?
- Calcitrol
a. active form of vitamin D, regulates calcium homeostasis - Erythropoietin
a. stimulates RBC production
What are some wastes excreted in the urine?
- Ammonia and urea (breakdown of amino acids)
- Bilirubin (breakdown of hemoglobin)
- Creatinine (breakdown of creatine phosphate in muscle fibers)
- Uric acid (breakdown of nucleic acids)
- Drugs and environmental toxins
What organs lie at the level of the 12th thoracic and first three lumbar vertebrae?
Kidneys
True or False
The right kidney is slightly lower than the left because the liver occupies a large area above the kidney on the right side
True
What is the indentation alone the medial border of the kidney through which the ureter leaves the kidney and blood vessels, lymphatic vessels, and nerves enter and exit?
Renal Hilum
What surrounds each kidney, is a smooth connective tissue sheath that helps maintain the shape of the kidney and serves as a barrier against trauma?
Transparent renal capsule
What surrounds the renal capsule and serves as a cushion for the kidney, and anchors the kidney to the posterior abdominal wall?
Adipose (fatty) tissue
What are the two main internal regions of the kidneys?
- Renal cortex, outer light-red region
2. Renal medulla, inner, darker red-brown region
Within the renal medulla are several cone-shaped renal pyramids; extensions of the renal cortex, called _____, fill the spaces between renal pyramids.
Renal columns
Urine formed in the kidney passes from thousands of papillary ducts within the renal pyramids into cuplike structures called minor calyces; each kidney has how many minor calyces?
8-12
After leaving the minor calyces, urine next flows into how many major calyces, and then into the urinary bladder for storage and elimination from the body?
2-3 major calyces
Collecting ducts –>papillary ducts (in pyramids) –>minor calyces –>major calyces –> renal pelvis –>ureter–> where ?
urinary bladder –> urethra –>external
About how much of the resting cardiac output flows into the kidneys through the right and left renal arteries?
20-25% (1200mL a minute)
Within each kidney, the renal artery divides into smaller and smaller vessels (segmental, interlobar, arcuate, interlobular arteries) that eventually deliver blood to what?
Afferent arterioles
What does each afferent arteriole divide into?
Glomerulus
The capillaries of the glomerulus reunite to for what kind of arteriole?
Efferent arteriole
After leaving the glomerulus, each efferent arteriole divides to form a network of capillaries around the what?
Kidney tubules
True or False
Peritubular capillaries eventually reunite to form peritubular veins, which merge into interlobular, arcuate, and interlobar veins
True
What is the functional unit of the kidney?
Nephron
About how many nephrons are in each kidney?
1 million
What are the two parts of a nephron?
- Renal corpuscle
a. blood plasma is filtered here - Renal tubule
a. where glomerular filtrate passes
What are the two parts that make up a renal corpuscle?
- Glomerulus
2. Glomerular (Bowman’s) capsule
What is a double-walled cup of epithelial cells that surrounds the glomerular capillaries?
Bowman’s capsule
Glomerular filtrate first enters the glomerular capsule and then passes into the what?
Renal tubule
What are the three main sections of the renal tubule and in what order does fluid pass through them?
- Proximal convoluted tubule
- Loop of Henle
- Distal Convoluted tubule
The renal corpuscle and both convoluted tubules lie within the what? The loop of Henle extends into where?
- Renal cortex
2. Renal medulla
True or False
The distal convoluted tubules of several nephrons empty into a common collecting duct and several collecting ducts merge to form a papillary duct, which leads to a minor calyx and a major calyx, renal pelvis and ureter
True
To produce urine, nephrons and collecting ducts perform three basic processes which include what?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
What is the first step in urine production?
Glomerular filtration
What occurs as filtered fluid flows along the renal tubule and through the collecting duct?
Tubular reabsorption
Tubule and Duct cells return about how much of the filtered water and many useful solutes to the blood flowing through the peritubular capillaries?
99%
What also takes place as fluid flows along the tubule and through the collecting duct?
Tubular secretion
By the time the filtered fluid has undergone tubular reabsorption and tubular secretion and enters the minor and major calyx it is called what?
Urine
True or False
As nephrons perform their functions, they help maintain homeostasis of the blood’s volume and composition
True
The space between the renal corpuscle and the glomerular capsule is what?
Capsular space
What cells make up the inner wall of the glomerular capsule and adhere closely to the endothelial cells of the glomerulus?
Podocytes
Together, Podocytes and glomerular endothelium form a what that permits passage of water and solutes from the blood into the capsular space?
filtration membrane
What is the pressure that causes filtration in the glomerular capillaries?
Glomerular capillary blood pressure
What are the two other pressure that oppose glomerular filtration?
- Blood colloid osmotic pressure
2. Glomerular capsule pressure
What happens when either blood colloid osmotic pressure or glomerular capsule pressure increases?
glomerular filtration decreases
Net Filtration Pressure
Normally blood pressure is greater than the two opposing pressures producing a net filtration pressure of what?
10mmHg
Net filtration pressure forces a large volume of fluid into the capsular space, about how much in males a day and how much in females a day?
- Males: 180 liters
2. Females: 150 liters
How do you get Net Filtration Pressure?
Net Filtration Pressure = glomerular capillary blood pressure – (blood colloidal osmotic pressure + glomerular capsule pressure)
True or False
When the blood pressure increases slightly or decreases slightly, changes in the diameters of the afferent and efferent arterioles can actually keep net filtration pressure steady to maintain normal glomerular filtration
True
True or False
Constriction of the afferent arteriole decreases blood flow into the glomerulus, which decreases net filtration pressure
True
True or False
Constriction of the efferent arteriole slows outflow of blood and increases net filtration pressure
True
What is the amount of filtrate that forms in both kidneys every minute called?
Glomerular Filtration Rate (GFR)
What is the normal GFR for Males?
125mL/min
What is the normal GFR for Females?
105mL/min
What happens if the bodies GFR is to high?
needed substances are unable to be reabsorbed by the body
What happens if the bodies GFR is to low?
waste products are not properly excreted
What is a hormone that promotes loss of sodium ions and water in the urine in part because it increases GFR?
Atrial Natriuretic Peptide (ANP)
Cell in what organ secrete more ANP in response to it being stretched, that occurs when blood volume increases?
Heart
With greater sympathetic stimulation (exercise, hemorrhage, etc.) the afferent arterioles are constricted more then the efferent arterioles, resulting in blood flow in the glomerular capillaries being greatyl reduced, net filtration dropping, and what else?
GFR decreasing
What is the second basic function of the nephrons and collecting ducts?
Tubular reabsorption
Returning most of the filtered water and many of the filtered solutes to the blood
Typically 99% of the filtered water is reabsorbed and only 1% of the water in glomerular filtrate actually leaves the body in urine, the fluid then drains into the what?
Renal Pelvis
What along the renal tubules and collecting ducts carry out tubular reabsorption?
Epithelial cells
What cells make the largest contribution to reabsorption?
Proximal convoluted tubule cells
True or False
The movement of solutes into the peritubular capillaries decreases the solute concentration of the tubular fluid but increases the solute concentration in the peritubular capillaries
True
What cells fine-tune reabsorption to maintain homeostatic balances of water and selected ions?
cells located distal to the proximal tubule.
Tubular secretions help eliminate what substances from the body?
- Hydrogen ions (H+)
- Potassium (K+)
- Ammonia (NH3)
- Urea
- Creatine
- Certain drugs
What is a poisonous waste that is produced when amino groups are removed from amino acids?
Ammonia
What do liver cells convert most ammonia to?
Urea
Urea and ammonia in the blood are both filtered at the glomerulus and secreted by the what?
Proximal convoluted tubule cells into the tubular fluid
What is the normal range for blood pH?
7.35-7.45
To help eliminate some acids, the cells of the renal tubules secrete what into the tubular fluid to be expelled in urine?
Hydrogen (H+)
What are the most important hormonal regulators of ion reabsorption and secretion?
- angiotensin II
2. aldosterone
What is found in the proximal convoluted tubules and enhances the reabsorption of Na+ and Cl-?
angiotensin II
Angiotensin II stimulates the adrenal cortex to release what?
Aldosterone
What hormone stimulates the tubule cells in the last part of the distal convoluted tubules and throughout the collecting ducts to reabsorb more Na+ and Cl- and secrete more K+?
Aldosterone
What is the major regulator of blood K+ level?
Aldosterone
Can an elevated level of K+ in the blood plasma cause serious disturbances in cardiac rhythm or even cardiac arrest?
You bet your sweet bippy
By increasing the GFR, what hormone plays a minor role in inhibiting the reabsorption of Na+ (and Cl- and water) by renal tubules?
Atrial natriuretic peptide (ANP)
As the GFR increases and Na+ and Cl- and water reabsorption decrease, more water and salt are lost in the urine, giving what final effect?
Lower blood volume
What is the major hormone that regulates water reabsorption?
Antidiuretic hormone (ADH) operates via negative feedback loop
When the concentration of the water in the blood decreases by as little as 1% osmoreceptors in the hypothalamus stimulate release of ADH from where?
Posterior pituitary
Can things like decreased blood volume in cases of severe bleeding and dehydration causes the secretion of ADH?
Yes
ADH acts on tubule cells in the last part of the _____ and throughout the collecting ducts.
distal convoluted tubules
The kidneys can produce as little as how much very concentrated urine when ADH concentration is maximal, such as during dehydration?
400-500mL
Lower than normal levels of Ca2+ in the blood stimulates the parathyroid glands to release what hormone?
Parathyroid hormone (PTH)
PTH stimulates cells in the what to reabsorb more Ca2+ into the blood?
distal convoluted tubules
PTH inhibits reabsorption of what in the proximal convoluted tubules, promoting phosphate excretion?
HPO42- (phosphate)
What is the normal adult volume of urine eliminated per day?
1-2 liters (about 1-2 quarts)
Water accounts for about how much of the total volume of urine?
95%
Each of the two ureters transports urine from where in the kidneys to the urinary bladder?
Renal pelvis
If the physiological valve in the bladder that stops backflow of urine into the ureters isn’t operating what can occur?
Cystitis that may develop into a kidney infection
What are the three layers of the wall of a ureter?
- Inner layer: mucosa (transitional epithelium, underlying areolar connective tissue)
- Middle layer: smooth muscle
- Outer layer: areolar connective tissue (blood vessels, lymphatic vessels, and nerves)
What is a hollow muscular organ situated in the pelvic cavity behind the pubic symphysis?
Urinary bladder
What is the normal urinary bladder capacity averages?
700-800mL
What holds the urinary bladder in position?
folds of the peritoneum
Like ureters, the mucosa of the urinary bladder contains what?
transitional epithelium
The muscular layer of urinary bladder wall consists of three layers of smooth muscle called the what?
Detrusor muscle
True or False
The peritoneum, which covers the superior surface of the urinary bladder, forms a serous outer coat; the rest of the urinary bladder has a fibrous outer coating
True
What is the terminal portion of the urinary system and is a small tube leading from the floor of the urinary bladder to the exterior of the body?
The urethra
Where does the urethra pass through in males?
Vertically through the prostate, deep perineal muscles, and the penis
Is the internal urethral sphincter composed of smooth muscle?
Yes (involuntary)
The external sphincter is composed of skeletal muscle, and is under voluntary or involuntary control?
Voluntary
The urinary bladder stores urine prior to its elimination and then expels urine into the urethra by an act called what?
Micturition (urination)
When volume of urine in the bladder exceeds what, pressure within the bladder increases and stretch receptors in its walls transmit nerve impulses into the spinal cord?
200-400mL
In the micturation reflex, what kind of impulses from the spinal cord cause contraction of the detrusor muscle and relaxation of the internal urethral sphincter muscle?
Parasympathetic
Simultaneously with the parasympathetic impulses of the micturation relfex, the spinal cord inhibits what kind of motor neurons, causing relaxation of skeletal muscle in the external urethral sphincter?
Somatic motor neurons
In lean adults, the body fluids make up between 55% and 60% of what?
total body mass
About two-thirds of body fluid is what?
Intracellular fluid (ICF) or cytosol, fluid within the cells
What is extracellular fluid (ECF)?
fluid outside of the cells
About 80% of the ECF is what?
Interstitial fluid
What percentage of the ECF does blood plasma constitute?
20%
What two barriers separate intercellular fluid, interstitial fluid, and blood plasma?
- Plasma membrane
2. Blood vessel walls
What is the primary means of water movement between intracellular fluid and interstitial fluid?
Osmosis
Most solutes in body fluids are what?
Electrolytes
What are the main contributors to the osmotic movement of water?
Electrolytes
Fluid balance depends primarily on what?
Electrolyte balance
The main sources of body water are ingested liquids (1600mL) and moist foods (700mL) absorbed from the GI tract, which totals about how many mL per day?
2300mL per day
Metabolic water gain accounts for about how mL per day?
200mL
What is the daily total water gain?
2500mL
Each day the kidneys excrete about ____mL in urine, about ___mL evaporates from the skin surface, the lungs exhale about ___mL as water vapor, and the GI tract eliminates about ___mL in feces?
- 1500ml in urine
- 600ml from skin surface
- 300ml from lungs
- 100ml from feces
What area of the brain governs the urge to drink?
area in the hypothalamus called the thirst center
When water loss is greater than water gain what stimulates thirst?
Dehydration
a decrease in volume and increase in osmotic pressure of body fluids
Osmoreceptors in the hypothalamus and increased ____ in the blood both stimulate the thirst center in the hypothalamus.
Angiotensin II
What is the main factor that determines body fluid volume?
The extent of urinary salt (NaCl) loss
What are the three hormones that regulate the extent of renal Na+ and Cl- reabsorption (and how much is lost in the urine)?
- Atrial natriuretic peptide (ANP)
- Angiotensin II
- Aldosterone
After a salty meal you may have an increase in the total blod volume, becasue of this increase in volume the artria stretches more and promotes the release of what?
ANP
What promotes natriuresis, elevated urinary loss of Na+ (and Cl-) and water, which decreases blood volume?
ANP
The initial increase in blood volume also slows release of renin from the kidneys; as renin levels decreases, less what is formed?
Angiotensin II
With less angiotensin II, the kidney tubules reabsorbs less Na+, Cl-, and water; less angiotensin II leads to less what further slowing reabsorption?
Aldosterone
What is the major hormone that regulates water loss?
Antidiuretic Hormone (ADH)
An increase in the osmotic pressure of body fluids (a decrease in the water concentration of the fluids) stimulates the release of what?
ADH
What promotes the insertion of water channels into the plasma membranes of cells in the collecting ducts of the kidneys?
ADH
An increase in the osmotic pressure of interstitial fluid draws water out of cells and what happens?
They shrink
Does a decrease in the osmotic pressure of interstitial fluid cause cells to swell?
Yes
Changes in osmotic pressure most often result from changes in the concentration of what?
Na+
A decrease in the osmotic pressure of interstitial fluid inhibits the secretion of what?
ADH
What are the most abundant EXTRACELLULAR ions, representing 90% of extracellular cations?
Sodium ions (Na+)
What plays a pivotal role in fluid and electrolyte balance because it accounts for almost half of the osmostic pressure of extracellular fluid?
Na+
True or False
Na+ is necessary for the generation and conduction of action potentials in neurons and muscle fibers
True
What are the most prevalent ANIONS in extracellular fluid?
Chloride ions (Cl-)
What are the most abundant CATIONS in intracellular fluid?
Potassium ions (K+)
When K+ moves in or out of cells what is it exchanged for to regulate the pH of body fluids?
H+
The level of K+ in blood plasma is controlled mainly by what?
Aldosterone
True or False
About 98% of the calcium in adults is in the skeleton and teeth
True
What are the two main regulators of Ca2+ level in the blood plasma?
- Parathyroid Hormone (PTH)
2. Calcitrol (form of vitamin D that acts as a hormone)
In body fluids, calcium is mainly what?
Extracellular cation
A low plasma Ca2+ level promotes release of more PTH, which increases bone
resorption by stimulating ______ in bone tissue to release Ca2+ (and phosphate) from mineral salts of bone matrix.
Osteoclasts
What also enhances reabsorption of Ca2+ from glomerular filtrate back into blood and increases production of calcitriol?
PTH
What are the four general functions in the body when ions are formed when electrolytes break apart?
- Ions control the osmosis of water between fluid compartments
- Ions help maintain the acid-base balance required for normal cellular activities
- Ions carry electrical current, which allows production of action potentials
- Several ions serve as cofactors needed for optimal activity of enzymes
What is the difference between blood plasma and interstitial fluid?
Blood plasma has more protein anions
What is the difference in osmotic pressure between blood plasma and interstitial fluid called?
Blood Colloid Osmotic Pressure
The difference in protein concentration is largely responsible for what?
blood colloid osmotic pressure
What is the normal pH of a healthy persons blood?
7.35-7.45
The removal of H+ from body fluids and its subsequent elimination from the body depend on what three major mechanisms?
- Buffer systems
- Exhalation of CO2
- Kidney excretion of H+ into the urine
What are substances that act quickly to temporarily bind H+, removing the highly reactive, excess H+ from the solution but not the body?
Buffers
What prevents rapid, drastic changes in the pH of a body fluid?
Buffers
What are the principal buffer systems of the body fluids?
- Protein buffer system
- Carbonic-acid bicarbonate buffer system
- Phosphate buffer system
What is the most abundant buffer in intracellular fluid and plasma?
Protein buffer system
What are composed of amino acids, organic molecules that contain at least one carboxyl group (-COOH) and at least one amino group (-NH2)?
Proteins
What buffer system is based on the bicarbonate ion (HCO3-), which can act as a weak base and carbonic acid (H2CO3), which can act as a weak base?
Carbonic acid-bicarbonate buffer system
What is a significant anion in both intracellular and extracellular fluids?
HCO3- (bicarbonate)
H+ (hydrogen ion) + HCO3- (bicarbonate ion) = ?
H2CO3 (carbonic acid)
What are the components of the phosphate buffer system?
- Dihydrogen Phosphate (H2PO4-)
2. Mono-hydrogen phosphate (HPO4^2)
Which component of the phosphate buffer system acts as a weak acid?
Dihydrogen phosphate
Which component of the phosphate buffer system acts as a weak base?
Mono-hydrogen phosphate
The phosphate buffer system is an important regulator of pH in the cytosol, meaning the concentration of phosphates is highest where?
Intracellular fluid
An increase in the CO2 concentration of body fluids does what?
- increases H+ concentration
- lowers pH
Body fluids become more acidic
A decrease in the CO2 concentration of the body fluids does what?
- H+ concentration falls
- Blood pH rises
body fluids become more alkaline
If ventilation is slower than normal, the less CO2 is exhaled, and what happens to the blood pH?
blood pH falls
True or False
When the blood acidity increases, the decrease in pH (increase in concentration of H+) is detected by chemoreceptors in the medulla oblongata and in the aortic and carotid bodies, both of which stimulate the inspiratory area in the medulla oblongata.
True
What is the slowest mechanism for removal of acids, but is also the only way to eliminate most acids that form in the body?
Urination (kidney excretion of H+)
If the systemic arterial blood pH falls below what, depression of the nervous system is so severe that the individual can become disoriented, comatose, and may die?
7
Arterial blood pH higher than 7.45 is considered what and can lead to over-excitability in both the central nervous system and peripheral nerves?
Alkalosis
A change in blood pH that leads to acidosis and alkalosis may be encountered by what?
compensation
What is the term for when a person has an altered blood pH due to a metabolic cause and hyper or hypoventilation brings the blood pH back toward the normal range?
Respiratory compensation
occurs within minutes, reaches max within hours
True or False
If a person has altered blood pH due to respiratory causes, then renal compensation, changes in secretion of H+ and reabsorption of HCO3- by the kidney tubules—can help reverse the change. Renal compensation may begin in minutes, but it takes days to reach maximum effectiveness.
True
