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Renal function & Homeostasis

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What organs help maintain normal body functions and homeostasis via the elimination of the waste products of protein catabolism?
Kidneys
Waste products of protein catabolism:
1. Creatinine
2. Urea
3. Uric acid
4. Ammonia
Waste products of fat catabolism:
Ketones
What molecules do the kidneys reabsorb that are essential for normal body function and structure?
Glucose & Amino acids
What do the the kidneys regulate by selective reabsorption?
electrolyte concentrations, fluid balance, and acid-base balance.
What do renal tubules reabsorb and secrete?
Bicarbonate (HCO3-)
Water: 98-99% of filtrate is reabsorbed
Electrolytes: sodium, K+, Chloride
What is the functional unit of the kidney?
Nephron
The concentration of the urine varies in response to the amount of:
water & electrolytes that are reabsorbed under the influence of two hormones
What are the hormones involved in this modification?
antidiuretic hormone (ADH)
Aldosterone
What is the ADH produced by?
hypothalamus
Where is ADH stored?
posterior pituitary
What in the hypothalamus regulates the release of ADH?
Osmoreceptors
What is ADH released in response to?
elevated blood osmotic pressure or osmolality (dehydration & increased salt ingestion
ADH stimulates water reabsorption into what?
peritubular capillaries
What happens to the urine?
It becomes more concentrated or hypertonic
With aldosterone what is reabsorbed into blood & what is secreted in urine?
Na+ reabsorption into blood & K+ secretion in urine
What is aldosterone produced by?
adrenal cortex
What is aldosterone released in response to?
Decreased blood sodium
Decreased blood volume or pressure
Secondary to the adrenal cortex stimulation by Angiotensin II
In response to decreased blood sodium, blood volume, blood pressure and renal perfusion, the kidney releases the enzyme, ____________.
Renin
What does angiotensin II stimulate?
Vasoconstriction, increasing blood pressure
Aldosterone release by the adrenal cortex
How does the body respond to Aldosterone?
Sodium reabsorption from renal tubules
Chloride or bicarbonate follow sodium, depending on acid-base balance
K+ excretion from capillaries
reabsorption of water by osmosis into capillaries
What is the net effect of Aldosterone?
elevation of blood sodium levels and increased blood volume
What is crucial in maintaining normal body system functions and normal blood pressures?
water & electrolyte balance
What does low blood volume result in?
hypotension
What does high blood volume result in?
hypertension
___________ (high/low) sodium levels in the plasma cause hypertension as water follows sodium by osmosis.
high
What can cause severe cardiac effects, from severe bradycardia to cardiac arrest?
high K+ levels in the blood
What are the steps of a urinalysis?
Description as to color, transparency, and odor
Measurement of specific gravity (urine concentration)
Chemical analysis
Sedimentation analysis
What does specific gravity do?
compares the density of a solution to the density of water
What does specific gravity represent?
the amount of dissolved solids or total solute
What is the instrument for measuring the total solids of liquids like urine and antifreeze called?
refractometer
What is an ultrafiltrate of the plasma?
urine
What normally does not show up in normal urine?
protein b/c molecules are large
glucose
Proteinuria can occur secondary to diseases like:
DM, hyperthyroidism, hypertension, bladder inf, jaundice
What are some diseases that cause glycosuria?
primary renal glycosuria, DM, hyperadrenocorticism, renal tubular acidosis, and Fanconi syndrome.
What are ketones in urine consistent with?
starvation, malnourishment, high fat diets, excessive fat catabolism, diabetic ketoacidosis, anorexia nervosa, bulimia
Bilirubinuria occurs with what?
bile outflow obstruction, and liver disease
What could hematuria/hemoglobinuria be caused from?
kidney/bladder infections, stones, tumors, trauma
What is pyuria?
Leukocytes in urine
The presence of leukocytes in the urine indicates that there is an ___________ in the kidneys or some other part of the urinary tract.
infection
vaginitis, urethritis, prostatitis, balanoposthitis, cystitis, ureteritis, pyelonephritis
What is urobilinogenuria formed from?
breakdown of hemoglobin
What is a normal amount of urobilinogen considered to be?
trace amounts
An elevated amount of urobilinogen can occur with what conditions?
hemolytic anemias, infectious hepatitis, bile duct obstruction, jaundice, cirrhosis, CHF, infectious mononucleosis
What is normal pH for urine?
between 4.6 - 8.0
What can produce pH changes?
diet
What type of diet would cause a low pH?
high protein diet
What type of diet would cause a high pH (alkaline)?
Vegetarian diet
What are some other causes of high pH?
cystitis
drug therapy
acid-base status
How are nitrites formed?
from the bacterial breakdown of dietary nitrate
What would presence of nitrites indicate?
bacterial infection of bladder including:
Escherichia coli
klebsiella
Citrobacter
Proteus
How many RBC's would indicate hemmorhage?
4-5
How many WBC's would indicate inflammation/bacterial infections of urinary tract?
5-8
What are casts formed by?
precipitated protein molecules within the renal tubules
What would large numbers of casts indicate?
renal disease
A large number of cyrstals would indicate what?
tendency to form kidney stones
What would large numbers of uric acid crystals indicate?
gout
What are some crystals with a clinical significance?
Tyrosine: associated with liver disease
Cystine: congenital anomilies of metabolism
Sulfonamides from drug therapy
Calcium oxalate with some vegetables, plant toxicitics, & in some families with renal calculi
How much water does skin lose by evaporation?
600mL
How much water do the lungs lose?
400mL
How much water is excreted by the kidneys as urine?
1500mL
How much water is lost through the feces?
100mL
The loss of water must be balanced by intake of water. How much should we drink? How much obtained from solid foods we eat? Process of metabolizing food generates how much water?
1500mL; 1000mL; 100mL
When you are dehydrated your blood volume is _______ (low/high) and the body puts out more ____________.
low; ADH
If you lose water from exercise, etc the plasma compartment must replace it and it does so by:
osmotically pulling water from the interstitual compartment
If the water is not replaced what happens?
blood viscosity (thickness) and bp would increase leading to cardiovascular damage
Where is extra fluid always kept?
interstitual fluid compartment
If the interstitual fluid compartment becomes too low, water is pullsed from where?
intracellular compartment & you become seriously dehydrated
Water crosses cell membranes freely, from area of ________ (more/less) to areas of __________ (more/less) water.
more; less
What does the osmolarity of the extracellular fluid compartment (ECF) affect?
cell volume
If ECF osmolarity increases as a result of salt intake, water moves where? What happens to cells?
Water moves out of cells; cells shrink
If the ECF osmolarity decreases, water moves where?
water moves into cells and they swell
Blood pressure is proportional to what?
blood volume
If blood volume is low what happens to blood pressure?
bp low
What monitors blood pressure?
carotid & aortic baroreceptors
what can low blood volume be the result of?
hemorrhage, sepsis, diarrhea, vomiting, excessive sweating
What can cause high blood pressure?
excessive intake of salt, minimal kidney filtration, & atherosclerosis
What are electrolytes?
ions of salts, such as sodium (Na+), calcium (Ca+2), K+, magnesium (Mg+2), chloride (Cl-), and bicarbonate (HCO3-).
Electrolytes in correct concentrations are necessary for:
muscle contraction, heart beating, nervous impulse transmission, & delivery of O2 to tissues
What is responsible for the homeostatic maintenance of blood acid-base balance, water absorption and excretion, electrolyte balance, & the elimination of wastes from protein, lipid, and drug catabolism via urine production?
kidneys
What do kidneys produce that is associated with erythrocyte production, and rennin, which is involved in bp regulation?
erythropoieten
The renal arteries carry approximately 1200mL of blood to the kidneys each minute. The majority of that fluid is reabsorbed back into the blood stream, while the rest is excreted, producing about ___________ of urine per day.
1.2 to 1.5L
The normal components of urine include _____% water, breakdown products from _________ (urea, uric acid, ammonia, creatinine), ___________ (sodium, K+, chloride), and ____________ (calcium, phosphates, sulfates, hydrogen ions, & bicarbonate.
95%water; protein; electrolytes; chemicals
What would orange-yellow urine color denote?
urobilinogen or bilirubin from RBC destruction or reduced liver function
What would cloudy red urine color denote?
intact RBC's
What would green urine color denote?
sample exposed to light for over an hour
What are some things that change urine clarity (transparency of urine)?
bacteria, yeast, fungi, casts, WBC's, RBC's, epithelial cells, crystals, mucus thread, & sperm.
What would an ammonia odor indicate?
urea breakdown to ammonia due to bacteria
What would fruity or sweet odor indicate?
ketones from fat catabolism
What are normal values for specific gravity?
1.003 to 1.030
A high specific gravity may be due to:
dehydration, adrenal insufficiency, liver disease, or glycosuria
A low specific gravity may be due to:
chronic kidney disease, diabetes insipidus, or polydipsia
Diseases that cause glycosuria include:
acute emotional stress, excessive exercise, primary renal glycosuria, DM, hyperadrenocorticism, renal tubular acidosis, & Fanconi syndrome.
What is the renal threshold for glucose?
180mg/dL
Presence of ketones:
produced by fat catabolism & associated with high fat or low carb diets, starvation, bulimia, anorexia nervosa, unctrolled DM (diabetic ketoacidosis), fevers, prolonged vomiting
Presence of bilirubin:
bile outflow obstruction, liver disease like hepatitis, red cell hemolysis
Presence of blood:
intact RBC, hemoglobin, & myoglobin will give a pos reaction. May be due to UTI, hemorrhage, trauma, stones, tumors
Normal pH range:
4.6 to 8.0, 6.0 being average
Low pH:
high protein diet, meds, acid-base status
High pH:
vegetarian diet, cystitis, meds, acid-base status
Presence of protein:
large amounts could be kidney disease, DM, hyperthyroidism, HTN, UTI's, jaundice, glomerulonephritis, preeclampsia in pregnancy
Presence of urobilinogen:
cirrhosis, CHF, infectious mononucleosis, red cell hemolysis
Presence of nitrites:
signify UTI due to Gram neg bacteria such as e coli
Presence of leukocytes:
UTI's; urine w/ leukocytes should also be nitrite pos
Glomular filtration
the process by which the kidneys filter the blood, removing excess wastes and fluids. Glomerular filtration rate (GFR) is a calculation that determines how well the blood is filtered by the kidneys, which is one way to measure remaining kidney function.
Tubular reabsorption
about 1% of the glomerular fitrate actually leaves the body because the rest (the other 99%) is reabsorbed into the blood while it passes through the renal tubules and ducts. This is called tubular reabsorption and occurs via three mechanisms. They are:

Osmosis
Diffusion, and
Active Transport.
Reabsorption varies according to the body's needs, enabling the body to retain most of its nutrients.
Tubular secretion
Excess hydrogen ions (H+) and ammonia (NH3) are secreted into the fluid within the collecting ducts (the protons by active transport). Tubular secretion of H+ is important in maintaining control of the pH of the blood.
When the pH of the blood starts to drop, more hydrogen ions are secreted.If the blood should become too alkaline, secretion of H+ is reduced. In maintaining the pH of the blood within its normal limits of 7.3-7.4, the kidney can produce a urine with a pH as low as 4.5 or as high as 8.5.
Excess potassium ions (K+) are also disposed of by tubular secretion.
Chemicals that stay behind?
White bloods, red blood cells and large protein such as albumin.
Chemicals filtered out and excreted in urine?
Water-soluble waste products and toxins are filtered out of the blood by the kidneys. Urea, ammonia, potassium, bilirubin, creatinine and uric acid.
Chemicals reabsorbed from filtrate back into blood?
99% of water, and glucose are reabsorbed, (under normal physiological conditions) and most sodium ions are too.
Regulation of blood ion compostion? Blood volume? Blood pressure? Blood pH? Red blood cell production? Vitamin D sythesis? Excretion of waste and foreign substances?
The kidneys also regulate ion levels in the blood. Ions are substances such as sodium, potassium, calcium and chloride. The kidneys also regulate blood volume and blood pressure by balancing the water content in the blood. The kidneys also maintain pH by adjusting the hydrogen and bicarbonate concentration in the blood. The pH level determines if the blood is too acidic or too alkaline. Lastly, the kidneys produce hormones such as calcitrol, which is the active form of vitamin D that regulates calcium levels and red blood cell production.
Aldosterone
Low blood pressure causes the kidneys to release renin, which in turn causes the production of angiostensin II. Angiotensin II increases the secretion of the hormone aldosterone by the adrenal cortex. Aldosterone causes increased reabsorption of of sodium. Water is reabsorbed with sodium, increasing blood pressure. Increased reabsorption of water would also mean decreased excretion rate.
Renin
a renal proteolytic enzyme, produced by and stored in the juxtaglomerular apparatus that surrounds each arteriole as it enters a glomerulus. The enzyme affects the blood pressure by catalyzing the change of angiotensinogen to angiotensin I, which is then converted to angiotensin II, strong pressor.
Vasopressin
Antidiuretic hormone which is responsible for regulating plasma osmolality and volume. In high concentrations, raises blood pressure by inducing moderate vasoconstriction. It acts as a neurotransmitter.
What is the anatomical location of the kidneys
lie agaist the dorsal body wall in a retroperitonial position (beneath the parietal peritoneum) in the superior lumbar region. They extend from T12 to L3 vertebra....and the rigth kindey is slightly lower the left because of the liver.
Differences in urinary systems of men and women?
Male urethra is a lot longer than a womans. Bladder is situated in a slightly different position to the female and women do not have a prostate.
Normal urine composition and urinalysis information?
Urine is composed mostly of water containing organic wastes as well as some salts. The composition of urine can vary according to diet, time of day, and diseases. In one measure, the make-up of urine is 95 percent water and 5 percent solids. In terms of organic wastes (per 1,500 ml), urine contains 30 g of urea, 1-2 g each of creatinine and ammonia, and 1 g of uric acid. In terms of salts or ions, 25 g per 1,500 ml of urine contain the positive ions sodium, potassium, magnesium, and calcium, as well as the negative ions chlorides, sulfates, phosphates.
Information about kidney stones?
Small, hard deposits that form inside your kidneys. Made of mineral and acid salts. Have many causes and can affect any part of your urinary tract — from your kidneys to your bladder. Form when the urine becomes concentrated, allowing minerals to crystallize and stick together. Depending on your situation, you may need nothing more than to take pain medication and drink lots of water to pass a kidney stone. In other instances, surgery may be needed.
Renal failure and its risk factors?
Three types of conditions can cause acute kidney failure:
1. Pre-renal conditions which disrupt blood flow on its way to the kidney. Prevent adequate amount of blood or blood flow from reaching the kidneys: Extremely low blood pressure, Heart function problems, Low blood volume.

2. Renal conditions which directly damage the structures of the kidney. Any of the following conditions can cause renal failure:Bacterial infection, Kidney inflammation, Toxins (alcohol, cocaine, heavy metals, solvents, fuels or medications). Reduced blood flow to the renal tubules (atherosclerosis)

3. Post renal conditions which interfere with the urinary excretion of waste from the filtering process. Conditions that block the passage of urine out of the body an also lead to acute kidney failure. These include:Ureter obstruction (kidney stones, large kidney cyst, tumors), Bladder obstruction (prostate enlargement, bladder stone, blood clot, tumor or a nerve disorders).

Risk factors
Acute kidney failure usually occurs in connection with another medical condition or event. Most people who experience acute kidney failure are already in the hospital for other reasons. Conditions that increase your risk of acute kidney failure include: advanced age, bladder outlet obstruction, chronic infection, diabetes, heart failure, high blood pressure, immune disorders ( lupus, IgA nephropathy and scleroderma), kidney diseases, liver diseases, prostate gland enlargement, shock of any kind that causes decrease blood flow through the body, various blood disorders