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Urinary System: Ch-24
Terms in this set (101)
Kidneys function in the body related to fluids is?
1.Regulate total water volume in the body;
2.Regulate concentration of solutes in the body; 3.Regulate the concentration of specific IONS in the blood and extracellular fluid;
4.Maintains the acid-base balance;
Other Kidney funstions?
5.Excretes metabolic wastes and foreign substances (e.g. toxins, drugs);
6.Produces erythropoietin and renin;
7.Converts vitamin D to active form;
8.Carries out gluconeogenesis during prolonged fasting.
Kidney anatomy includes?
Ureters- transport urine from the kidneys to the bladder
Urethra- transports urine to the body exterior
Kidneys are located Retroperitoneal, meaning?
located behind the peritoneum
R. kidney lies where?
slightly lower than the left (due to the liver)
Medial surface of kidneys contains the RENAL HILUM, where?
the ureters, blood vessels, nerves, and lymphatics enter/exit the kidney.
Internal anatomy of the kidneys involves 3 regions which include?
CORTEX, MEDULLA, and PELVIS
outer layer of the kidney
consists of RENAL PYRAMIDS, which contain parallel bundles of renal tubules and capillaries.
are separated by extensions of the CORTEX called RENAL COLUMNS
PYRAMID + surrounding COLUMNS?
LOBES (approx. 8 per kidney).
shaped tubes that connect the pyramids to the ureterminor calyces - major calyces - pelvis - ureter. Walls of calyces, pelvis, and ureter contain smooth muscle to propel urine by peristalsis.
infection of the calyces and/or pelvis
infection of the entire kidney
The functional unit of the kidney
Each kidney contains how many nephrons?
> 1 million
The nephron consists of?
one renal corpuscle, and one renal tubule
Renal corpuscles are located in the?
CORTEX; renal tubules start in the cortex, loop down into the medulla, then return back up to the cortex
Consist of the GLOMERULUS + GLOMERULAR CAPSULE (aka Bowman's capsule)
a ball of capillaries
completely surrounds/encases the glomerulus
In the Glomerulus Capillaries are FENESTRATED, allowing passage of?
of large amounts of solute-rich (but protein free) fluid from the blood into the glomerular capsule = FILTRATE (which eventually becomes urine).
GLOMERULAR CAPSULE has 3 layers, which are?
Parietal layer, Capsular space, Visceral layer
forms the outer structure of the capsule
in between the two layers
interfaces with the capillary basement membranes via PODOCYTES ("foot cells")- octopus-like cells that extend foot processes onto the capillary basement membranes- gaps/slits between these foot processes are called FILTRATION SLITS- it is here that the FILTRATE enters the capsular space. The FILTRATION MEMBRANE is a composite of the capillary basement membrane, the capillary fenestrated endothelium, and the foot processes of the podocytes (FILTRATION SLIT)
RENAL TUBULE consists of?
the proximal convoluted tubule (PCT), the nephron loop (of Henle), the distal convoluted tubule (DCT) and the collecting duct.
- 85%: located almost entirely in the cortex
15%: originate close to the cortexmedulla junction- play a critical role in the kidney's ability to produce concentrated urine (have long nephron loops that deeply invade the medulla).
Kidneys basically expels?
cell-free/protein free "blood" out of the body, then reclaims whatever the body needs at that moment;
Kidneys can also actively secrete specific things into the urine to?
finetune the body's chemical balance.
Your entire plasma volume is filtered more than?
60 times per day.
1st process of urine formation?
Filtration- glomerular, occurs in the renal corpuscle;
2nd process of urine formation?
Reabsorption- tubular, occurs in the renal tubules and collecting ducts; 99% of filtrate is reclaimed;
3rd process of urine formation?
Secretion- occurs in renal tubules and collecting ducts; active secretion of selective substances.
the volume of filtrate formed each minute by the kidneys.
GFR is Directly proportional to?
1.Net filtration pressure, controlled mainly by the HPgc, by changing the diameter of the afferent (and efferent) arteriole;
2.Total surface area available for filtration- mesangial cells can contract to adjust the surface area of the glomerular capillary bed;
3.Filtration membrane permeability
REGULATION OF FILTRATION involves 2 controls which are?
intrinsic and extrinsic
renal autoregulation- local control within the kidneys to maintain GFR
by nervous and endocrine systems- to maintain blood pressure.
Main variable in Urine Formation =
glomerular hydrostatic pressure (inc. blood pressure - inc. GFR - inc. urine output - dec. blood volume - dec. blood pressure)
Reabsorption can be an ACTIVE or PASSIVE process?
ACTIVE- requires ATP
PASSIVE- by diffusion or osmosis
most abundant cation in filtrate; 80% of energy goes towards reabsorbing Na+
Sodium reabsorption is an active process in which?
Via Na+-K+ ATPase pumps in the tubule cells
WATER Reabsorption is due to?
osmotic gradient created by the active pumping of Na+ (and other solutes)
Water moves by osmosis through channels called?
In PCT, many aquaporins - obligatory?
In Collecting Ducts, few if any aquaporins?
- water reabsorption dependent upon ADH = facultative water reabsorption.
Solute reabsorption happens?
solutes diffuse along their concentration gradient into the peritubular capillaries.
Requires the use of transport carrier proteins
Proximal Convoluted Tubule?
Most active part of the nephron for reabsorption.
(All) glucose and amino acids (AA's)
65% of Na+ and water reabsorption occurs in the PCT
Water reabsorption in the DESCENDING loop, but NOT?
the ASCENDING loop.
Solute reabsorption in the ASCENDING loop, but not?
the DESCENDING loop.
filtrate is MOST concentrated at the bottom of the loop; and Filtrate is LEAST concentrated at the?
end of the ascending loop.
Distal Convoluted Tubules and Collecting Ducts are where?
Fine-tuning of the filtrate occurs here either by enhanced reabsorption or secretion due to influence of hormones.
In the collecting ducts, ADH- increase permeability of collecting ducts to water, increasing?
In the collecting ducts, Aldosterone secretion is stimulated by?
dec. BP/blood volume; increase Na+ reabsorption (water follows) (active transport) in distal DCT and collecting ducts.
In the Distal Convoluted Tubules and Collecting Ducts, Atrial Natriuretic Peptide (ANP) secretion is stimulated by?
inc. BP or blood volume; inhibits Na+ reabsorption (and water) in the collecting ducts.
PTH- acts on DCT to increase reabsorption of?
Tubular secretion moves?
SELECTED substances from the peritubular capillaries, through the tubule cells, and into the filtrate (urine).
Secreted substances include?
- H+, K+, NH4+, creatinine, organic acids/bases, HCO3-.
Main site of secretion =?
PCT (also some occurs in the collecting ducts).
4 FUNCTIONS for SECRETION?
1.Disposing of substances bound to plasma proteins (since they cannot be filtered- too large)- e.g. certain drugs.
2.Elimination of undesirable substances/end products- e.g. urea and uric acid.
3.Ridding the body of excess K+ (via aldosterone Na/K exchange- occurs in the distal DCT and collecting ducts).
4.Controlling blood pH- increased blood acidity results in secretion of H+ and retention of HCO3-.
Kidneys regulate the solute load of body fluids by?
regulating urine concentration and volume.
COUNTERCURRENT MECHANISMS goals?
to establish and maintain an osmotic gradient extending from the cortex through the depths of the medulla- called the "medullary osmotic gradient".
Purpose of the COUNTERCURRENT systems is to?
create the MEDULLARY OSMOTIC GRADIENT;
ADH is main controller of?
a waste product for elimination, but ALSO used to form the medullary gradient;
Urea enters the filtrate in the?
ASCENDING loop by diffusion;
ADH release is inhibited by?
Inhibitors of Na+ reabsorption (and water)?
substances that are not reabsorbed and carry water out with it (e.g. artifical sweeteners).
Defined as the volume of plasma from which the kidneys clear (remove) a particular substance in one minute;
a plant polysaccharide, used as the basis for determining the GFR (glomerular filtration rate)?
Used to estimate the GFR?
Chronic renal disease=?)
(GFR < 60
(GFR < 15)
breakdown product of amino acids; uric acid (end product of nucleic acid metabolism), creatinine (metabolite of creatine).
Urine solute concentration includes?
Na+, K+, PO4-3, SO4-2 and Urea
Kidney stone predisposition?
frequent bacterial infections, urine retention, high blood levels of calcium, and alkaline urine.
Chemical examination of urine?
(specific gravity, pH, protein, glucose, ketones, hemoglobin, leukocyte esterase, nitrites, bilirubin, urobilinogen)
Microscopic examination of urine?
(epithelial cells, bacteria, yeast, WBC's, RBC's, casts, crystals)
Casts in urine are formed from?
Tamm-Horsfall proteins in the distal convoluted tubules and collecting ducts;
Hyaline casts can be seen in?
normal individuals (exercise/dehydration)
RBC/WBC/Epithelial cell casts can be seen with?
urinary tract injury/infection/tubular necrosis
seen in chronic kidney diseases- granules = breakdown of cellular components
suggests the very low urine flow associated with severe, longstanding kidney disease such as renal failure.
Crystals found in urine can be?
BUN is the end product of?
BUN is freely filtered by?
Decreased kidney function causes buildup of ?
BUN in the blood (increased levels)
Most important BUN Lab Test?
Berthelot reaction-urease reaction- NH3 undergoes an additional reaction that results in the production of NAD+
CREATINE is produced by the?
liver, and stored in muscle
Creatinine Functions as an energy source during?
intense activity- provides a phosphate group to convert ADP to ATP;
CREATININE is the waste/breakdown product of?
creatine- used to measure renal function as it is freely filtered and NOT reabsorbed in the kidney;
Since CREATININE production is constant (related to muscle mass)- its levels are not affected by?
diet, age, sex, exercise - an excellent indicator of renal function.
Important CREATININE- Lab Tests?
Jaffe reaction- uses alkaline picrate to form an orange-red complex; drawback- not specific for creatinine
Measures the rate of clearance of creatinine from blood = volume of serum that is cleared of creatinine per unit time?
Specimens required for creatinine clearance?
serum creatinine + 24 hour urine creatinine using formula (see next slide);
This is an End product of purine (adenosine and guanine) metabolism?
Uric acid levels are influenced by?
purine catabolism and dietary sources
Uric Acid Lab Testing?
Phosphotungstic acid colorimetric assay (blue)
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