Urinary System - Mod. 3 Flashcards
What percentage of urine is water? and what substances make up remaining percent of urine?
95% water, 5% are products of metabolism, urea, ammonia, bilirubin, and uric acid.
What ions does the urinary system regulate in the blood?
Sodium, potassium, calcium, chloride, and phosphate ions.
How do the kidneys maintain blood osmolarity?
Regulating the total number of particles dissolved per liter of solution.
How does the urinary system regulate blood pH?
Excreting hydrogen ions and altering the concentration of bicarbonate ions.
How does the urinary system regulate blood pressure?
Through the secretion of renin, increase in renin concentration raises blood pressure.
What hormones are produced by the kidneys?
renin, erythropoietin, and calcitriol.
What is the function of renin?
Regulates blood pressure.
What is the function of erythropoietin?
Stimulates the production of red blood cells.
What is the function of calcitriol?
Enhances the absorption of calcium and phosphorus from food, and increases the amount circulating in the blood.
How does the urinary system regulate blood glucose?
When blood glucose levels fall, the kidneys metabolize glutamine to synthesize new glucose molecules, via gluconeogenesis, causing the blood glucose levels to rise.
What is the shape, color, and length of the kidneys?
Bean shaped, reddish-brown in color, and about 11cm long.
What is the function of the hilum in the kidneys?
The hilum is the entry and exit point for the renal vessels and the renal pelvis.
Where do the renal arteries arise from?
Directly from the abdominal aorta, suppyling the kidneys.
What do most renal nerves regulate?
The volume of blood flowing through the kidneys by affecting the vasoconstriction or vasodilation of the arterioles.
What nervous system are the renal nerves apart of?
The autonomic nervous system.
What are the functional units of urinary system?
Nephrons
What does the renal corpuscle contain?
It contains a compact network of capillaries, called glomerules, which is surrounded by the glomerular capsule (bowmans capsule)
What is the function of nephrons?
Filter the blood to produce urine, removing waste or unwanted substances from the body, while retaining nutrients and other important substances.
What are the two types of nephrons?
85% are cortical nephrons, and the other 15% are juxtamedullary type.
What are the two major portions of nephrons?
Renal tubule and renal corpuscle.
Where does glomerular filtration occur?
In the renal corpuscle, when blood in the glomerulus is under pressure.
What happens during glomerular filtration?
The blood if filtered, and water and solutes move out, forming a fluid called glomerular filtrate (tubular fluid)
What is tubular reabsorption?
Water and solutes are reabsorbed from the tubular fluid and move back into the blood.
What percent of water filtered into the glomerular capsule is reabsorbed into the bloodstream?
Approximately 99%
What is tubular secretion?
It removes harmful or unwanted substances out of the blood and tubular cells and into the renal tubular fluid (filtrate).
What is excretion?
The process of removing the waste products from metabolism.
What is secretion?
The process of moving materials that have a purpose within the body
How can the rate of excretion be calculated?
Excretion = Filtration - Reabsorption + Secretion
What is the mean daily volume of glomerular filtrate in males?
180 liters
What is the mean daily volume of glomerular filtrate in females?
150 liters
What prevents cells and large molecules from entering the glomerular capsule?
The filtration membrane.
What does the filtration membrane separate?
It separates the glomerulus and the glomerular capsule.
What are the three layers of the filtration membrane?
A layer of endolithium, a basal lamina, and a visceral layer.
They prevent the passage of progressively smaller substances.
What is the key determinant of the rate of fluid filtration in the kidneys?
Pressure
What is net filtration pressure?
The pressure promoting the movement of fluid from the glomerular capillaries through filtration membrane and into the capsular space.
What is glomerular blood hydrostatic pressure (GBHP)?
It promotes filtration in the kidneys, and acts to force liquid through the filtration membrane.
What is blood colloid osmotic pressure (BCOP)?
It opposes filtration in the kidneys, and is caused by the presence on large proteins that cannot easily pass through the filtration membrane, preventing the passage of liquid through the filtration membrane.
What is capsular hydrostatic pressure (CHP)?
It opposes filtration in the kidneys, and is caused by the presence of fluid already inside the capsular space and the renal tubule, preventing the passage of liquid through the filtration membrane.
What is the daily volume of urine produced?
Generally less than 2 liters (depending on fluid intake)
What substances are reabsorbed during tubular reabsorption?
- Water (typically 99% of filtered water is reabsorbed)
- Ions (Na+, K+, Ca2+, Cl-, HCO3-, and HPO42-)
- Molecules (glucose, amino acids, and urea)
What are the two routes that reabsorption can take place?
Paracellular and transcellular.
What is paracellular reabsorption?
The process of moving solutes and water through the tight junctions between cells in the renal tubules, it is a passive process and occurs by simple diffusion.
What substances are involved in paracellular reabsorption?
Water and some small ions
What is transcellular reabsorption?
The process in which substances pass from the tubular fluid, through the tubular cells, and into the peritubular capillaries, occurs along the length of the nephron.
What substances are involved in transcellular reabsorption?
Water, ions, and molecules.
What determines the distinct mechanism of how a substance is reabsorbed transcellularly?
Whether they require ATP (active transport) or not (passive diffusion), whether a specific transporter protein is required, and the specific ion transported.
What are the three types of passive transport in transcellular reabsorption?
- simple diffusion
- facilitated diffusion
- osmosis
How do substances move in simple diffusion?
They move unassisted from the tubular fluid, across the plasma membrane, into the tubule cells.
How do substances move in facilitated diffusion?
They are assisted in their movement across the plasma membrane of the tubule epithelial cells, either by leakage channels or carrier proteins.
What happens during osmosis?
Movement of water across a selectively permeable membrane, down its concentration gradient, from areas of high water concentration (low solute concentration) to areas of low water concentration (high solute concentration).
What are the two types of active transport in transcellular reabsorption?
- Primary active transport
- Secondary active transport (cotransport)
What happens during primary active transport?
Carrier proteins (pumps) use ATP to move various solutes across the plasma membrane against their concentration gradient.
What happens during secondary active transport?
The movement of a substance across a plasma membrane, against its electrochemical gradient.
What is the function of symporters in secondary active transport?
It transports two or more functions in the same direction.
What proteins are used in secondary active transport?
Symporters and antiporters
What is the function of antiporters in secondary active transport?
It transports two or more substances in the opposite directions
What substances are secreted into tubular filtrate during tubular secreted?
Ions, creatinine and urea, and some hormones and drugs.
What processes determine the volume and composition of urine?
Glomerular filtration, tubular reabsorption, and tubular secretion.
What is glomerular filtration rate (GFR)?
The speed at which fluid passes out of the blood and into the glomerular capsule.
How is glomerular filtration rate measured?
As the amount of glomerular filtrate produced per minute.
How is blood flow into and out of the glomeruli regulated? and how does it affect glomerular filtration rate (GFR)?
Constriction of the afferent arterioles decrease the flow of blood, decreasing GFR.
Dilation of the afferent arterioles increases the flow of blood, increasing GFR.
How does surface area of glomerular capillaries affect GFR?
Filtration occurs more efficiently over a larger surface area. Therefore, if the surface area of the glomerular capillaries is increased, GFR will also increase, and vice versa.
What does GFR stand for?
Glomerular filtration rate.
What are the two ways GFR is regulated?
Intrinsically (within the kidneys) and extrinsically (through hormones).
What are the two main hormones that regulate GFR extrinsically?
Angiotensin II and atrial natriuretic peptide (ANP).
How does angiotensin II affect GFR?
It causes vasoconstriction of systemic arterioles, increasing systemic mean arteriole blood pressure, decreasing GFR. However, the efferent arteriole vasoconstricts more than the afferent arteriole, resulting in an increased glomerular pressure, increasing GFR.
How does atrial natriuretic peptide (ANP) affect GFR?
It dilates the afferent arterioles, constricts the efferent arterioles, and increases glomerular capillary surface area, thus increasing GFR.
How does the nephron respond to dehydration?
It increases water reabsorption to minimize water loss in urine.
How does the nephron respond to excess fluid intake?
It rapidly forms a large volume of urine to remove excess fluid.
What five hormones regulate absorption and secretion in the nephron?
Angiotensin II, aldosterone, atrial natriuretic peptide, parathyroid hormone, antidiuretic hormone.
How does angiotensin II and aldosterone affect the nephron?
They regulate GFR and increase reabsorption and secretion in the nephron.
How does atrial natriuretic peptide affect the nephron?
It decreases reabsorption or Na+ and water, and the secretion of aldosterone and ADH.
How does parathyroid hormone regulate ions?
Affects the reabsorption of HPO42- and Ca2+
What is the function of antidiuretic hormone (ADH)?
It increases water reabsorption, helps the kidneys control the amount of water and salt in the body by reducing urine output and increasing urine concentration.
What is the loop of henle?
A part of the kidneys nephron that uses a countercurrent multiplier system to concentrate urine.
What are the three factors that cause countercurrent multiplication?
- The permeability of the ascending limb of the loop of henle
- The permeability of the descending limb of the loop of henle
- Urea recycling.
What is dilute urine?
Urine that is less concentrated than blood plasma, produced when water intake is high or water loss it low, due to the absence of ADH, leading to less water reabsorption.
What is concentrated urine?
Urine that is more concentrated than blood plasma, produced when water intake is low or water loss is high, due to increased ADH, leading to more water reabsorption.
Where does urine go after it is formed in the kidneys?
It flows down the ureters and into the bladder.
What is the function of the bladder?
It is a muscular structure that stores urine until it is eliminated from the body.
What is micturition? how is it controlled?
The removal of urine from the bladder, controlled by nervous impulses that trigger a change in the tone of both voluntary and involuntary muscles.
What are the ureters?
Two tubes that drain urine from the renal pelvis into the urinary bladder.
What is the thick wall of smooth muscle in the bladder called?
The detrusor muscle.
What triggers urination?
When the bladder is filled with 250-300mL of urine, sensory impulses trigger a reflex contraction of the bladder and relaxation of the urethral sphincters.
What are the two urethral sphincters? how are they controlled?
- Internal sphincter - involuntary control (smooth muscle)
- External sphincter - voluntary control (skeletal muscle)
How long is the female urethra?
4 cm long
What is the function of the female urethra?
It expels urine from the body
How long is the male urethra?
18-20 cm long
What are the four portions of the male urethra?
- Preprostatic part
- Prostatic part
- Membranous part
- Spongy part
What are the functions of the male urethra?
Expels urine from the urinary system, and expels seminal fluid from the reproductive system.
How is micturition controlled in adults?
By involuntary muscle contractions of the detrusor muscle and the internal urethral sphincter, and the voluntary muscle contraction of the external urethral sphincter.
How is micturition controlled in young infants?
By a spinal reflex, causing involuntary urination when the bladder is full.
What is urinalysis?
The analysis of the physical and chemical properties of the urine.
What is the blood urea nitrogen (BUN) test?
A test that measures the amount of nitrogen related to urea, resulting from the deamination and catabolism of amino acids.
What is the plasma creatinine test?
A test that measures the amount of creatinine in the blood, resulting from the catabolism of creatine phosphate.
What is renal plasma clearance?
The volume of plasma cleared of a certain substance per minute.
What does high plasma clearance indicate?
A substance is removed from the blood efficiently
What does low plasma clearance indicate?
Low excretory efficiency of a substance.
