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47 Cards in this Set

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List the three main processes involved in urine production and the locations where they occur.
Filtration occurs at the filtration membrane.
Reabsorption occurs in both the distal and proximal tubules, as well as in the loop of Henle.
Secretion also occurs throughout the nephron.
the condition that exists when red blood cells are found in the urine
What are the three different pressure components that constitute the filtration capillary pressure?
Glomerular pressure forces blood into the lumen of Bowman's capsule (50mm Hg); Capsule pressure forces blood back into the glomerulus (10mm Hg); Blood Colloid Osmotic Pressure results pulls blood back into the glomerulus (30mm Hg)
Why is the glomerular capillary pressure higher than the pressure in other similar areas of the body?
Resistance. The resistance of blood flow in the afferent arterioles and the glomerular capillaries is low, but as the vessel diameter decreases at the efferent arteriole, resistance increases, resulting in decreased flow and greater pressure in the glomerulus.
What active process is largely responsible for the movement of most solutes across the apical membrane of the nephron?
Na+ is actively transported out of the epithelial cells of the nephron by a Na+/K+ pump. As this occurs, the conc. of Na+ inside those cells is low, this allows for cotransport of Na+ with other solute particles to occur across the apical membrane by carrier molecules.
Renal capsule
a layer of fibrous connective tissue that surrounds each kidney
Perirenal fat
a dense layer of fat that surrounds the renal capsule
Renal fascia
a connective tissue layer that surrounds the perirenal fat and anchors the kidney and associated fat layers to the abdominal wall
the functional unit of the kidney; consists of the renal corpuscle (glomerulus and Bowman's capsule), the proximal tubule, the loop of Henle, the distal tubule, and the collecting duct
Juxtamedullary nephron
one of two types of nephrons; consists of long loops of Henle that extend deep into the medulla; plays an important role in maintaining the medullary concentration gradient
Cortical nephrons
one of two types of nephrons; contains shorter loops of Henle than juxtamedullary nephrons
Juxtaglomerular cells
a layer of smooth muscle cells that form a cufflike arrangement around the arteriole
Macula densa
a group of cells that lie between the afferent and efferent arterioles adjacent to the renal corpuscle and composing portion of the distal tubule wall; closely associated with the juxtaglomerular cells
Juxtaglomerular apparatus
composed of the juxtaglomerular cells and macula densa; secretes renin and plays an important role in the autoregulation of filtrate formation
one of the three processes that is involved in the production of urine; occurs in the renal capsule as the blood is filtered through the filtration barrier (fenestrae, basement membrane, filtration slits); about 180L filtered daily
the movement of substances from the filtrate back into the blood, occurs in the tubules of the nephron
the active transport of solutes into the nephron; occurs mostly in the collecting ducts and the ascending limb of the loop of Henle
Renal fraction
the part of the total cardiac output that passes through the kidneys; varies from 12%-30% of the cardiac output in a healthy resting adult (average 21%)
Renal plasma flow rate
plasma that flows through the kidney each minute; calculated as the product of the renal blood flow rate multiplied by the portion of the blood that is made of plasma (about 55%)
Renal blood flow rate
the rate of total blood flow through the kidneys; about 1176 mL/min
Filtration fraction
the part of the plasma flowing through the filtration membranes into the lumen of Bowman's capsules to become filtrate; averages 19% of the plasma flowing through the kidney
Glomerular filtration rate (GFR)
the amount of filtrate produced each minute; approximately 180 L daily or 125 mL each minute
Filtration pressure
a pressure gradient which forces fluid from the glomerular capillary across the filtation membrane into the lumen of Bowman's capsule; results from the sum of the forces that move fluid out of and into the lumen of Bowman's capsule
Glomerular capillary pressure (GCP)
the blood pressure inside the capillary that moves fluid out of the capillary into Bowman's capsule; averages 50mmHg; a value that is considerably higher than the pressure in other capillaries
Capsule pressure (CP)
a pressure that moves fluid from Bowman's capsule to the gomeruli which is caused by the pressure of the filtrate already inside Bowman's capsule; approximately 10mmHg
Blood colloid osmotic pressure (BCOP)
the osmotic pressure that acts on the filtrate in Bowman's capsule as a result of the proteins and cells that remain in the glomeruli because they are too large to pass through the filtration barrier; approximately 30 mmHg
Approximately what size of particles will fit through the filtration barrier?
Particles smaller than 7nm in diameter will fit through the filtration barrier
At which limb of the loop of Henle is water impermeable and how does that characteristic contribute to the medullary concentration gradient?
the ascending limb of the loop of Henle is impermeable to water but permeable to solutes such as Na+, K+, and Cl-; diffusion of these solutes out of the nephron contribute to the medullary concentration gradient
What countercurrent exchange system exists in the urinary system?
the vasa recta runs countercurrent to the flow of filtrate in the loop of Henle; this helps to maintain the high concentration of solutes found in the medulla
Osmoreceptors located in the supraoptic nuclei control urine volume and conctration in what way?
these osmoreceptors are involved in the formation of urine by stimulating the release of ADH from the posterior pituitary in response to osmolality changes in the interstitual fluid of the supraoptic nuclei; osmolality increases leads to ADH release, osmolality decreases leads to inhibition of ADH release
Why does alcohol dehydrate you?
ethyl alcohol interferes with the release of ADH from the posterior pituitary gland; a lower concentration of ADH results in a decreased permeability of the collecting ducts and distal tubules to the reabsorption of water, leading to increased urine volume
Cells of the juxtaglomerular apparatus release renin in response to what stimuli?
-if blood pressure in the afferent arteriole decreases, renin secretion increases
-if the Na+ conc. of the filtrate decreases as it passes by the macula densa cells, renin secretion increases
a plasma protein produced by the liver and found in the general circulation; converted to angiotensin I by renin
Angiotensin-converting enzyme (ACE)
a proteolytic enzyme found in the capillary beds of organs such as the lungs; converts angiotensin I into angiotesin II
Angiotensin II
a potent vasoconstricting substance the increases the peripheral resistance resulting in an increase in blood pressure; increases the rate of aldosterone secretion, thirst, salt appetite, and ADH secretion; formed from angiotensin I by the action of ACE
a steroid hormone secreted by the cortical cells of the adrenal gland; bind to receptors inside the cells of the distal tubules and collecting ducts causing increased production of Na+ transport channels, thereby increasing the concentration of Na+ that is reabsorbed
Atrial Natriuretic hormone (ANH)
a hormone secreted from cardiac muscle cells in the right atrium of the heart in response to increased blood volume (and, therefore, pressure) in the right atrium; inhibits Na+ reabsorption in the kidneys and inhibits the secretion of ADH from the posterior pituitary; also dilates arteries and veins
the maintenance within the kidneys of a relatively stable glomerular filtrate rate (GFR) over a wide range of system blood pressures;
What branch of the nervous system regulates kidney blood flow?
sympathetic ennervation and neural stimulation with norepinephrine act to contsrict small arteries and afferent arterioles, thereby restricting renal blood flow and filtrate formation
Plasma clearance (mL/min) = quantity of urine (mL/min) x (conc. of substance in urine/conc. of subsatnce in plasma); can be used to estimate GFR and renal plasma flow using appropriate substances, such as inulin and p-aminohippuric acid, respectively
Tubular load
the total amount of a substance that passes through the filtration membrane into the nephrons each minute
Tubular maximum
the maximum rate at which a substance can be actively reabsorbed; unique for each substance; determined by the number of active transport molecules and the rate at which they are able to transport the substance
What happens if the tubular load surpasses the tubular maximum?
in this case, the substance will begin to appear in the urine at appreciable conc.; for example, someone suffering from diabetes mellitus may experiencce high levels of glucose in the blood, when the tubular load exceeds the nephron's ability to reabsorb the glucose, it will be foudn in the urine
How is urine moved down the ureters? (Hint...its not through gravity alone - what if you are laying down - or standing on your head?)
Peristaltic waves occur from the renal pelvis to the urinary bladder once every few seconds to a couple minutes; parasympathetic stimulation increases the frequency of peristalsis; sympathetic stimulation decreases the frequency of peristalsis
the eliminatino of urine from the urinary bladder through the urethra
Micturition reflex
a reflex that results in the initiation of micturition; results from sensory stretch receptors in the urinary bladder that propogate action potentials to the sacral regions of the spinal cord which in turn results in parasympathetic stimulation of the internal urinary sphincter; this reflex can be controlled by the motor cortex in the cerebrum and areas in the pons
What are the major mechanisms that create and maintain the high solute conc. in the renal medulla?
1) the active transport of Na+ and cotransport of other ions out of the thick portion of the ascending loop of Henle;
2) the impermeability of the ascending limb of the loop of Henle to water;
3) the vasa recta supply of blood and removal of excess water and solutes without affecting the conc.;
4) active transport of ions from the collecting ducts to the interstitial fluid;
5) the passive diffusion of urea from the collecting ducts into the interstitial fluid