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Chapter 14: The Kidneys PART A
Terms in this set (57)
What are the three basic process that lead to the formation of urine?
filtration, reabsorption and secretion.
Does not apply to all substances
What are the five general functions of the kidneys
1. regulate water concentration, ion composition, acidity, and blood volume.
2. remove metabolic waste products from the blood and excrete into urine
3. remove foreign chemicals (drugs, additives, etc) from the blood and excrete into urine
5. Hormone/Enzyme production
pertaining to the kidneys.
Define urea and its source
one of the metabolic wastes excreted by the kidneys made from the catabolism of protein
Define uric acid and its source
one of the metabolic wastes excreted by the kidneys made from the break down of nucleic aids
Define creatinine and its source
one of the metabolic wastes excreted by the kidneys made from the muscle creatine
What gives urine its color?
the end products of the break down of hemoglobin
kidneys can synthesize glucose from amino acids during fasting
What hormones/enzymes do the kidneys secrete?
erythropoietin, vitamin D, renin
What does renin do?
it is an enzyme secreted by the kidneys that is important in control of blood pressure and sodium balance
What are the two components that make up a nephron?
renal corpuscle and a tubule
What is a nephron
the functional unit of the kidney, approximately 1 million per kidney.
What does the renal corpuscle do? What is it made up of?
it is an initial filtering component.
composed of glomerulus and Bowman's capsule
What occurs in the tubule
further filtering and addition of substances
What are the three layers that make up the filtration barrier between the glomerulus and Bowman's capsule?
1. single celled capillary endothelium
2. non cellular proteinaceous layer (basal lamina)
3. single celled epithelial lining of Bowman's capsule
What is the basal lamina
the intermediate layer between the glomerulus and Bowman's capsule, noncellular basement membrane
What are the epithelial cells in the lining of Bowman's capsule called
List in order the parts of the tubule through which filtrate passes
1. proximal tubule
2. descending limb of Loop of Henle
3. thin segment of ascending limb of Loop of Henle
4. thick segment of ascending limb of Loop of Henle
5. Distal convoluted tubule
6. cortical collecting duct
7. medullary collecting duct
What is the kidneys central cavity
the renal pelvis
What occurs in the renal pelvis
multiple corticle collecting ducts merge and urine drains
Describe the vascular around each nephron
There are two sets of capillaries, glomerular and peritubular. there are also two sets of arterioles. these two sets of capillaries are connected by an efferent arteriole by which blood leaves the glomerus. the afferent arteriole supplies blood to the kidneys
What do the peritubular capillaries do
they surround the renal tubules in the cortex of the nephron
What are the two types of nephrons? Percentages of each?
juxtamedullary (15%) and cortical (85%)
What does the afferent arteriole do
supplies blood to the glomerulus
What does the efferent arteriole do
removes the remaining blood away from the glomerulus
Describe juxtamedullary nephrons
renal corpuscle lies in the cortex closest to the cortical medullary junction. Henle's loops are deep in the medulla
What are vasa recta
capillaries that follow the Henle's loops of the juxtamedullary nephrons deep into the medulla
Describe cortical nephrons
renal corpuscles are located in the outer cortex and their Henle's loops do not penetrate deeply. some do not have henle's loops at all.
What is a macula densa
patch of cells in the ascending limb of the loop of Henle combined with the juxtaglomerular cells they compose the juxtaglomerular apparatus
What make up the juxtaglomerular apparatus?
macula densa and juxtaglomerular cells.
What is the function of the juxtaglomerular apparatus
to secrete renin into the blood
What does the amount of any solute excreted equal to?
the amount filtered + the amount secreted - the amount reabsorbed.
What occurs in glomerular filtration
urine formation begins, fluid containing no cells is pushed out of the capillaries and into Bowman's capsule. no blood, no proteins b/c they are too big. solutes, sugar, urea and water leave blood.
What occurs in tubular reabsorption
most of the filtrate is reabsorbed back into the body. solutes, sugar, water, plasma, back into blood
What occurs in tubular secretion
excess quantities of certain substances are excreted from the body.
Compare and contrast plasma and filtrate
filtrate contains all plasma substances in about the same concentrations, except proteins bc they are too big to enter filtrate. filtrate contains no cells
What are the three forces that determine net glomerular filtration pressure? do they favor or oppose filtration
1. Glomerular capillary hydrostatic pressure - favors
2. Hydrostatic pressure from fluid in Bowman's space- opposes
3. osmotic force - opposes
What is the osmotic force
it is a pressure that results in the presence of a protein in the capillary plasma. there is no protein in the filtrate, so this opposes filtration due to osmosis
What is the typical daily glomerular filtration rate for an average person
How do you determine if a substance undergo net secretion or net reabsorption based on amount excreted in the filtered load
if the quantity excreted in urine is less than the filtered load, reabsorption occurred.
if quantity excreted in urine is more than the filtered load, secretion occurred
What are the two methods in which tubular reabsorption occurs
diffusion or mediated transport from the tubular lumen across the epithelium into the interstitial fluid
What is the final step of reabsorption
movement of interstitial fluid into the peritubular capillaries
What causes the movement of interstitial fluid into the peritubular capillaries
bulk flow and diffusion
what are the two pathways for tubular secretion
diffusion or mediated transport
What is tubular secretion
a pathway from the blood into the tubule
What categories of substances are secreted?
choline and creatinine
foreign chemicals - penicillin
Regulation of the number of membrane channels and transporters by hormones, autocrine, and paracrine factors impacts what?
the ability for the tubes to reabsorb and secrete substances
What is renal clearance?
a way of quantifying renal function. the volume of plasma from which that substance is completely removed by the kidneys per unit time. dependent on substance
What is the renal clearance of glucose?
typically zero because it should be reabsorbed
How is renal clearance used to measure renal function
a substance that is normally filtered but not reabsorbed or filtered is infused into the body. the GFR is equal to the clearance of the this substance. (inulin is used to calculate) creatinine clearance is also used to estimate but GFR will be slightly overestimated
How can renal plasma flow be measured
using the clearance of paramino-hippurate which is secreted and completely cleared from the plasma.
urination, ejection of urine
What is the role of the parasympathetic nerves in micturition?
ACT on detrusor muscle (smooth)during filling they are inhibited, during micturition they are stimulated. cause detrusor muscle to contract
What is the role of the sympathetic nerves in micturition?
ACT on internal urethral sphincter (smooth). stimulated during filling (contraction prevents release). inhibited during micturition
What is the role of the somatic nervous system on micturition
ACT on external urethral sphincter (skeletal) stimulated during filling (contraction prevents release). inhibited during micturition. Can override autonomic system
What is incontinence?
involuntary release of urine
what are the two most common types of incontinence?
stress incontinence (sneezing, coughing, exercise)
urge incontinence (desire to urinate)
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