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96 Cards in this Set
- Front
- Back
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Functions of the Urinary System
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production, storage, and elimination of urine
elimination of waste products (nitrogenous wastes, toxins, drugs) regulates aspects of homeostasis water and electrolyte balance acid-base balance in the blood blood pressure-renin red blood cell production-erythopoietin activation of vitamin D |
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Location of the Kidneys
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lie on the posterior abdominal wall behind the peritoneum and on either side of the vertebral column
at the level of T12 to L3 vertebrae bean shaped 11cm long, 5cm wide, and 3cm thick and weighing 130 grams superior pole protected by rib cage, right kidney slightly lower than left because of liver superior to it |
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Kidney Features
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renal hilum: medial indentation where several structures enter or exit the kidney (ureters, renal blood vessels, and nerves)
an adrenal gland sits atop each kidney |
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Coverings of the Kidneys
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1. Fibrous Capsule: surrounds each kidney
2. Perirenal Fat Capsule: Surrounds the kidney and cushions against blows 3. Renal Fascia: Outermost capsule that helps hold the kidney into place against the muscles of the trunk wall |
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Kidney Structures
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Renal Cortex: Outer Region
Renal Medulla: deep tissue below the cortex >Medullary Pyramids: triangular regions of tissue in the medulla. apex of the pyramids are called pyramidal papillae Renal Columns: extensions of cortical tissue deep into medulla that separate the pyramids Calyces: cup shaped structures that funnel urine toward the renal pelvis |
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Blood Supply
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one quarter of the total blood supply of the body passes through the kidneys each minute
renal artery provides each kidney with arterial blood supply it divides into segmental arteries as it approaches the hiul which further branches into interlobar arteries |
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Pathway of Renal Blood Vessels
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Aorta > Renal Artery > Segmental Artery > Interlobar Artery > Arcuate Artery > Cortical Radiate Artery > Afferent Arteriole >
Glomerulus (Capillaries) Efferent > Peritublar Capillaries > Cortical Radiate Vein > Arcuate Vein > Interlobar Vein > Renal Vein > Inferior Vena Cava |
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Nephron Anatomy and Physiology
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Nephron: structural and functional unit of the kidney that produces urine. 1 million nephrons/kidney
Main Parts 1. Glomerulus: a tuft of capillaries 2. Renal Tubule: begins as cup-shaped glomerular (bowmans) capsule surrounding the glomerulus and ends at collecting duct. |
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Glomerulus
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Knot of Capillaries
Capillaries are covered with podocytes from the renal tubule Sits within a glomerular/bowmans capsule, which is the first part of the renal tubule |
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Renal Tubule
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extends from glomerular capsule and ends at the collecting duct. it includes
1. Glomerular (bowman's) Capsule 2. Proximal Convoluted Tubule (PCT) 3. Loop of Henle 4. Distal Convoluted Tubule (DCT) |
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Cortical Nephrons
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located entirely in the cortex
includes mostly nephrons |
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Juxtamedullary Nephrons
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found at the boundary of the cortex and medulla
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Collecting Ducts
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receives urine from many nephrons
runs through the medullary pyramids delivers urine into the calyces and renal pelves |
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Nephron Capillary Beds
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Nephrons are associated with three capillary beds
1. Glomerulus 2. Peritublar Capillary Bed 3. Vasa Recta |
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Glomerulus
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red and drained by arterioles
afferent arteriole:arises from a cortical radiate artery and feeds the glomerulus efferent arteriole: receives blood that has passed through the glomerulus specialized for filtration: high pressure forces fluid and solutes out of blood and into the glomerular capsule blood pressure if high b/c efferent arterioles are smaller in diameter than afferent arterioles arterioles are high resistance vessels |
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Peritublar Capillaries
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arise from efferent arteriole of the glomerulus
low pressure, porous capillaries adapted for absorption instead of filtration cling close to the renal tubule to reabsorb (reclaim) some substances from collecting tubes empty into venules |
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Vasa Recta
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long vessels parallel to long loops of Henle
Arise from efferent arterioles of juxtamedullary nephrons Function in formation of concentrated urine |
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Juxtaglomerular Apparatus (JGA)
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one per nephron
important in regulation of filtrate formation and blood pressure involves modified portions of the distal portion of the ascending limb to the loop of Henle and afferent (sometimes efferent) arteriole three main types of specialized cells: granular cells, mascula densa and extraglomerular mesangial cells |
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Granular Cells (JG Cells)
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enlarged, smooth muscle cells of arteriole
secretory granules contain renin act as mechanoreceptors that sense blood pressure |
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Mascula Densa
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tall, closely packed cells of the ascending lim
act as chemoreceptors that sense NaCl content of filtrate |
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Extraglomerular Mesangial Cells
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interconnected with gap junctions
may pass signals between macula densa and granular cells |
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Filtration Membrane
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porous membrane between the blood and the capsular space
consist of 1. fenestrated endothelium of the glomerular capillaries 2. visceral membrane of the glomerular capsule (podocytes with food processes and filtration slits) 3. Gel-like basement membrane (fused basal laminae of the two other layers) allows for passage of water and solutes smaller than most plasm proteins. fenestrations prevent filtration of bloods cells. negatively charged basement membrane repels large anion such as plasm proteins |
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Mechanism of Urine Formation
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the kidneys filer the bodies entire plasma volume 60 times each day
filtrate- blood plasma minus proteins urine- less than 1% of total filtrate. contains metabolic wastes and unneeded substances |
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Urine Formation
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combination of three processes
1. glomerular filtration 2. tubular reabsorption 3. tubular secretion |
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Glomerular Filtration
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passive mechanical process driven by hydrostatic pressure
the glomerulus is a very efficient filter because its filtration membrane is very permeable and it has a large surface area. glomerular blood pressure is higher (55mg Hg) than other capillaries |
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Glomerular Filtration cont.
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molecules less than 5 nm are not filtered (e.g. plasma proteins) and function to maintain colloid osmotic pressure of the blood
nonselective. water and solutes smaller than proteins are forced through capillary walls Proteins and blood cells are normally too large to pass through the filtration membrane Filtrate is collected in the glomerular capsule and leaves via the renal tubule |
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Glomerular Filtration Rate (GFR)
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volume of filtrate formed per minute by the kidneys (120-125 ml/min)
governed by and directly proportional to the total surface area available for filtration, filtration membrane permeability, and net filtration pressure (NFP) |
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Tubular Reabsorption
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a selective transepithelial process
organic nutrients are reabsorbed water and ion reabsorption are hormonally regulated includes active (most) and passive processes useful substances reabsorb into peritubular capillaries glucose, amino acids, vitamins, water (by osmosis mostly), ions most reabsorption occurs in proximal convoluted tubule (PCT) |
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Rebabsorptive Capabilities of Renal Tubules and Collecting Ducts
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PCT- site of most reabsorption. 65% of Na+ and water. all nutrients, ions, small proteins
Loop of Henle- descending limb H20 ascending limb Na+, K+, Cl DCT and Collecting Duct- reabsorption is hormonally regulated. Ca2+ (PTH), Water (ADH), Na+ (aldosterone and ANP) |
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Tubular Reabsorption
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material not reabsorbed
nitrogenous waste products urea from protein breakdown uric acid from nucleic acid breakdown creatinine, associated with creatine metabolism in muscles |
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Tubular Secretion
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reabsorption in reverse, materials move from peritubular capillaries into the renal tubules
disposes of substances that are bound to plasma proteins eliminates undesirable substances that have been passively reabsorbed (urea and uric acid) |
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Tubular Secretion Cont.
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rids the body of excess K+
controls blood pH by altering amounts of H+ or HCO-3 in urine Secretion into the filtrate by diffusion>ammonia active transport> K+ reabsorbed in PCT, secreted in DCT and collecting duct H+ PCT, DCT, and collecting duct creatinine, histamine, penicillin |
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Characteristics of Urine
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in 24 hr 1-8 L of urine are produced
urine and filtrate are different filtrate contains everything that blood plasma does (except proteins) urine is what remains after the filtrate has lost most of its water, nutrients and ions urine contains nitrogenous wastes and substances that are not needed |
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Characteristics of Urine Cont.
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yellow color due to pigment urochrome (from the destruction of hemoglobin) and solutes
sterile, slightly aromatic, normal pH 6, specific gravity 1.001-1.035 solutes found in urine: sodium and potassium ions, urea, uric acid, creatinine, ammonia, bicarbonate ions solutes no found in urine: glucose, blood proteins, red blood cells, hemoglobin, white blood cells(pus), bile |
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Ureters
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convey urine from kidneys to bladder
retroperitoneal continuous with the renal pelvis enters the posterior aspect of the bladder peristalsis aids gravity in urine transport |
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Urinary Bladder
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smooth, collapsible, muscular sac for temporary storage of urine
males>prostate gland surround neck of bladder women>anterior to vagina and uterus |
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Urinary Bladder
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trigone-triangular region of the bladder base
3 openings> two from ureters, one of the urethre |
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Urinary Bladder Wall
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three layers of smooth muscle collectively called the detrusor muscle. mucosa is made of transitional epithelium
walls are thick and folded in an empty bladder (rugae) bladder can expand significantly without increasing internal pressure |
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Urinary Bladder Capacity
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a moderately full bladder is about 5 inches long and holds about 500mL of urine
capable of holding twice that amount of urine |
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Urethra
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thin walled tube that carries urine from the bladder to the outside of the body by peristalsis
release of urine is controlled by two sphincters 1. internal urethral sphincter (involuntary and made with of smooth muscle) 2. external urethral sphincter (voluntary and made of skeletal muscle. located at the bladder's distal inferior end in females and inferior to the prostate in males) |
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Urethra Gender Differences
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Length: females (1 inch) males (8 inches)
Location: females (along wall of vagina) males (through prostate and penis) Functions: females (only carries urine) males (carries urine and is a passageway for sperm cells |
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Micturition
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urination or voiding
three simultaneous events 1. contraction of detrusor muscle by ANS 2. opening of internal urethral sphincter by ANS 3. opening of external urethral sphincter by somatic nervous system |
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Micturition
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both sphincter muscles must open to allow voiding
stretching of the bladder wall activates stretch receptors in sacral region (pelvic splanchnic nerves) initiate bladder to go into reflex contractions urine is forced past the internal urethra sphincter and the person feels the urge to void the external urethral sphincter must be voluntarily relaxed to void |
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Blood Composition depends on 3 factors
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1. Diet
2. Cellular Metabolism 3. Urine Output |
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Kidneys have 4 roles in maintaining blood composition
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1. excretion of nitrogen-containing wastes
2. maintaining water balance of the blood 3. maintaining electrolyte balance of the blood 4. ensuring proper blood pH |
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Normal water balance in body
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Babies 75%
Young Adult Females 50% Young Adult Males 60% Elderly 45% |
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Distribution of Body Fluid (2 types)
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1. Intracellular Fluid (ICF): fluid inside cells 2/3 of body fluid
2. Extracellular Fluid (ECF): fluid outside of cells. >includes interstitial fluid and blood plasma |
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Composition of Body Fluids
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Water: universal solvent
Solutes: non-electrolytes> mostly organic and don't dissociate in water ex: glucose, lipids, creatinine, urea electrolytes> dissociate into ions in water ex: inorganic salts, all acids and bases, some protein. most abundant/numerous solutes. solutes in the body include electrolytes like sodium, potassium and calcium ions |
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Link between Water and Salt
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have greater osmotic power than nonelectrolytes, so may contribute to fluid shifts
determine the chemical and physical reactions of fluids changes in electrolyte balance causes water to move from one compartment to another >alters blood volume and pressure >can impair the activity of cells |
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Extracellular and Intracellular Fluids
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each fluid compartment has a distinctive pattern of electrolytes
ECF>all similar, except higher protein content of plasma. major cation: Na+ major anion: Cl- ICF> low Na+ and Cl-. major cation K+ major anion HPO42- |
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Sodium Ions
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90-95% of extracellular osmotic pressure
recommended intake 1.5 grams/day its reabsorption is regulated by aldosterone and it can affect extracellular fluid volume its concentration is regulated by the antidiuretic hormone mechanism, renin-angiotensin aldosterone mechanism, and atrial natriuretic mechanism |
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Potassium Ions
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important to maintain stable extracellular concentration
mainly regulated by aldosterone directly K is secreted while Na is reabsorbed by the tubular cells of the distal tubule under the effect of aldosterone |
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Maintaining Water Balance
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water intake=water output (2.5 liters/day)
water intake: ingested foods and fluids, water produced from metabolic processes water output: urine, insensitive water loss (skin and lungs), perspiration, feces |
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Regulation of Water Intake
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thirst mechanism is the driving force for water intake
the hypothalamic thirst center osmoreceptors are stimulated by 1. increase plasm osmolaity of 2-3% 2. angiotension II or baroreceptor input 3. dry mouth 4. substantial decrease in blood volume or pressure drinking water creates inhibition of the thirst center inhibitory feedback signals include relief of dry mouth and activation of stomach and intestinal stretch receptors |
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Maintaining Water Balance
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dilute urine is produced if water intake is excessive
less urine (concentrated) is produced if large amounts of water are lost proper concentrations of various electrolytes must be present body water and Na+ content are regulated in tandem by mechanisms that maintain cardiovascular function and blood pressure |
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Osmoreceptors
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cells in the hypothalamus that react to changes in blood composition by becoming more active
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Antidiuretic Hormone
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prevent excessive water loss in urine by increasing reabsorption of water in the collecting ducts
water reabsorption is proportional to ADH release lower ADH dilute urine and lower volume of body fluids higher ADH concentrated urine other factors may trigger ADH release via large changes in blood volume or pressure e.g. fever, sweating, vomiting, diarrhea, blood loss, traumatic burns |
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Diabetes Insipidus
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occurs when ADH is not released
leads to hugh outputs of dilute urine |
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Dehydration
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negative fluid balance. due to water loss from the ECF: hemorrhage, severe burns, prolonged vomiting or diarrhea, profuse sweating, water deprivation, diuretic abuse
insufficient intake of water or diabetes insipidus Signs: thirst, dry flushed skin, oliguria. if prolonged may lead to weight loss, fever, mental confusion, hypovolemic shock, and loss of electrolytes |
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Hypotonic Hydration
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cellular overhydration or water intoxication
occurs with renal insufficiency or rapid excess water ingestion ECF is diluted hyonatremia net osmosis into tissue cells, swelling of cells, sever metabolic disturbances (nausea, vomiting, muscular cramping, cerebral edema) possible death |
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Edema
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atypical accumulation of fluid only in the IF tissue swelling
due to anything that increases flow of fluid out of the blood or hinders its return blood pressure, capillary permeability (usually due to inflammatory chemicals), incompetent venous valves, localized blood vessel blockage congestive heart failure, hypertension, blood volume |
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Edema
Imbalance in Colloid Osmotic Pressures |
hindered fluid return occurs with an imbalance in colloid osmotic pressures ex: hypoproteinemia (plasma proteins)
fluid fails to return at the venous ends of capillary beds results from protein malnutrition, liver disease, or glomerulonephritis |
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Edema
Blacked or Surgically removed Lymph Vessels |
cause leaked proteins to accumulate in IF
Colloid osmotic pressure and severely impaired circulation |
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Renin-Angiotension Mechanism
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mediated by the juxtaglomerular apparatus (JGA)
granular cells of the JGA are stimulated to produce renin in response to SNS stimulation by low blood pressure (stretch) filtrate osmolarity |
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Renin-Angiotension Mechanism Cont.
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renin produces angiotension I from angiotensinogen, ACE produces angiotensin II
angiotensin causes vasoconstriction and aldosterone release from adrenal cortex result is increase in blood volume and blood pressure |
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Aldosterone
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regulates sodium ion content of ECF
Sodium is the electrolyte most responsible for osmotic water flows aldosterone promotes reabsorption of sodium ions 65% is reabsorbed in proximal tubules 25% is reclaimed in the loops of Henle aldosterone active reabsorption of remaining Na+ water follows salt aldosterone release also triggered by elevated K+ in ECF |
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Regulation of Sodium Balance: ANP
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released by atrial cells in response to stretch (blood pressure)
results in a decrease in blood pressure and blood volume ADH renin and aldosterone production excretion of Na+ and water promotes vasodilation directly and also by decreasing production of angiotension II |
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Influences of other Hormones
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estrogens: NaCl reabsorption (like alsosterone)
H2) retention during menstrual cycles and pregnancy progesterone: Na+ reabsorption (blocks aldosterone) and promotes Na+ and H2O loss glucocorticoids: Na+ reabsorption and promotes edema |
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Cardiovascular System Baroreceptors
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baroreceptors alter the brain of increase in blood volume and pressure
sympathetic nervous system impulses to the kidneys decline afferent arterioles dilute GFR increases Na+ and water output increase |
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Calcium Ions
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Important to maintain extracellular concentration within narrow range
decrease extracellular Ca2+ increase in Na+ permiability and increase excitability increase in extracellular Ca2+ decrease in Na+ permeability decrease excitability and muscle weakness or paralysis regulated by PTH and calcitonin |
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Acid-Base Balance
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pH affects all functional proteins and biochemical reactions
Normal pH of body fluids Arterial Blood: pH 7.4 Venous Blood and IF fluid pH 7.35 ICF pH 7.0 |
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Maintaining Acid-Base Balance in Blood
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blood pH must remain between 7.35 and 7.45 to maintain homeostasis
Alkalosis: pH above 7.45 Acidosis: pH below 7.35 physiological acidosis: pH between 7.35 and 7.0 most ions originate as by-products of cellular metabolism |
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Acid-Base cont.
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acids produced by the body
-phosphoric acid, lactic acid, fatty acids, ketone bodies carbon dioxide (forms carbonic acid), ammonia most acid-base balance is maintained by the kidneys other acid-base controlling systems>blood buffers and respiration |
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Blood Buffers
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Acids are Proton H+ Donors: strong acids (HCl) dissociate completely and liberate all of their H+ in water. weak acids (carbonic acid) dissociate only partially
Bases are proton H+ Acceptors: strong bases (NaOH) dissociate easily in water and tie up H+. weak bases (bicarbonate ion and ammonia) are slower to accept H+ |
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Buffer
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a substance that minimizes change in the acidity of a solution when an acid or base is added to the solution
molecules react to prevent dramatic changs in hydrogen ion (H+) concentrations. bind to H+ when pH drops, releases H+ when pH rises |
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3 Major Chemical Buffer Systems
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1. Bicarbonate Buffer System
2. Phosphate Buffer System 3. Protein Buffer System |
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Bicarbonate Buffer System
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mixture of carbonic acid (H2CO3 weak acid) and salts of HCO3- (sodium bicarbonate, NAHCO3, a weak base)
buffers ICF and ECF |
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Extracellular Buffer System: If strong acids is added
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HCO3 ties up H+ and forms H2CO3
HCl + NaHCO3 H2CO3+ NaCl pH decreases only slightly, unless all available HCO3 (alkaline reserve) is used up HCO3- concentration closely regulated by the kidneys |
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Extracellular Buffer System: If strong base is added
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it causes H2CO3 to dissociate and donate H+
H+ ties up the base (ex: OH) NaOH + H2CO3 NaHCO3 + H20 pH rises only slightly H2CO3 supply is almost limitless (from CO2 released by respiration) and is subject to respiratory controls |
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The Phosphate Buffer System
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H3PO4 <> H2PO4 + H+ <> HPO 42 + H+ <> PO43 + H+
phosphoric acid (H3PO4) changes rapidly into dihydrogen phosphate (H2PO4) an excellent buffer since it can either grab up a hydrogen ion and reform phosphoric acid or it can give off another hydrogen ion and become monohydrogen phosphate (HPO42-). in extremely basic conditions it can even give up its remaining H+ if the H2PO4 is in an acidic solution, the reactions above go to the left, and if the H2PO4 is in a basic solution, the reactions above proceed to the right |
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The Phosphate Buffer System Cont.
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the phosphate buffer system can accept or donate hydrogen ions depending on the solution it is in
the phosphate buffer system is the main intracellular buffering system action is nearly identical to the bicarbonate buffer components are sodium salts of: dihydrogen phosphate H2PO4 a weak acid monohydrogen phosphate HPO42 a weak base effective buffer in urine and ICF where phosphate concentration is high |
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Protein Buffer System
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intracellular proteins are the most plentiful and powerful buffers, plasma proteins are also important
protein molecules are amphoteric (can function as both weak acid and weak bases) when pH rises, organic acid or carboxyl (COOH) groups release H+ when pH falls NH2 groups bind h+ |
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Respiratory System Controls of Acid-Base Balance
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carbon dioxide in the blood in converted to bicarbonate ion and transported in the plasma
increases in hydrogen ion concentration produces more carbonic acid excess hydrogen ion can be blown off with the release of carbon dioxide from the lungs respiratory rate can rise and fall depending on changing blood pH Carbon dioxide + Water <> Carbonic Acid (H2CO3) <> Hydrogen Ion + Bicarbonate Ion (HCO3-_ |
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Respiratory Regulation of H+
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respiratory system eliminates CO2
a reversible equilibrium exists in the blood during CO2 unloading the reaction shifts to the left (and H+ is incorporated into H2O) during CO2 loading the reaction shifts to the right (H+ is buffered by proteins) |
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Respiratory Regulation of H+ cont.
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Hypercapnia activated medullary chemoreceptors
more CO2 is removed from the blood H+ concentration is reduced Alkalosis depresses the respiratory center respiratory rate and depth decrease H+ concentration increases |
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Renal Mechanisms of Acid-Base Balance
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excrete bicarbonate ions if needed
conserve (reabsorb) or generate new bicarbonate ions if needed when blood pH rises, bicarbonate ions are excreted and hydrogen ions are retaining by kidney tubules cells when blood pH falls, bicarbonate ions are reabsorbed, hydrogen ions are secreted urine pH varies from 4.5-8.0 |
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Respiratory Acidosis and Alkalosis
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most important indicator of adequacy of respiratory functions is P CO2 level (normally 35-45 mm Hg)
P CO2 above 45 MM Hg = respiratory acidosis most common cause of acid-base imbalances due to decrease in ventilation or gas exhange characterized by falling blood pH and rising PCO2 P CO2 below 35mm Hg = respiratory alkalosis a common result of hyperventilation due to stress or pain |
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Metabolic Acidosis
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and pH imbalance not caused by abnormal blood CO2 levels
indicated by abnormal HCO3 levels Causes of Metabolic Acidoses -ingestion of too much alcohol (acetic acid), excessive loss of HCO3- (persistent diarrhea) accumulation of lactic acid shock, ketosis in diabetic crisis, starvation, kidney failure |
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Metabolic Alkalosis
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much less common that metabolic acidosis
indicated by rising blood pH and HCO3- caused by vomiting of the acid contents of the stomach or by intake of excess base (antacids) |
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Effects of Acidoses and Alkalosis
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blood pH below 7 depression of CNS, coma, death
blood pH above 7.8 excitation of nervous system, muscle tetany, extreme nervousness, convulsions, respiratory arrest |
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respiratory and renal compensations
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if acid-base imbalance is due to malfunction of a physiological buffer system, the other one compensates
respiratory system attempts to correct metabolic acid-base imbalances kidneys attempt to correct respiratory acid-base imbalances |
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Respiratory Compensation
Metabolic Acidosis |
in metabolic acidosis> high H+ levels stimulate the respiratory center. rate and depth of breathing are elevated, blood pH is below 7.35 and HCO3 level is low, as CO2 is eliminated by the respiratory system, P CO2 falls below normal
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Respiratory Compensation
Respiratory Acidosis |
the respiratory rate is often depressed and is the immediate cause of the acidosis, respiratory compensation for metabolic alkalosis is revealed by slow, shallow breathing, allowing CO2 accumulation in the blood, high pH (over 7.45) and elevated HCO3 levels
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Renal Compensation
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hypoventilation causes elevate P CO2 (resp. acidosis)
renal compensation is indicated by high HCO3- levels respiratory alkalosis exhibits low P CO2 and high pH, renal compensation is indicated by decreasing HCO3- levels |
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Developmental aspects of Urinary System
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functional kidneys are developed by the third month
urinary system of a newborn: bladder is small, urine cannot be concentrated for first 2 months, void 5-40 times per day control of the voluntary urethral sphincter does not start until 18 months complete nighttime control may not occur until 4 urinary infections are the only common problems before old age escherichia coli (e.coli) accounts for 80% of UTI |
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Aging and the Urinary System
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progressive decline in urinary function
bladder shrinks and loses bladder tone urgency>feeling that it is necessary to void frequency> frequent voiding of small amounts of urine nocturia> need to get up during the night to urinate incontinence> loss of control urinary retention> common in males, often the result of hypertrophy of the prostate gland |
