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Functions of the Urinary System

removes wastes, stabilizes blood volume, acidity, & electrolytes, regulates extracellular fluids of the body, secretes hormones (erythropoietin & renini), & regulates absorption of calcium ions by activating Vitamin D


controls the rate of red blood cell formation


regulates blood pressure


the functional unit of the kidney which is located within the cortex and the medulla

Function of the nephron

filters waste substances from the blood and simultaneously maintain the essential water and electrolyte balance

Renal corpuscle

part of the nephron that contains the glomerulus and glomerular capsule

Glomerulus & Glomerular (Bowman's) capsule

the two structures of the renal corpuscle


made up of tangled blood capillaries. Appropriate sized substances are pushed through pores in capillaries into glomerular capsule (Bowman's) by hydrostatic pressure

Glomerular (Bowman's) Capsule

thin walled cup-shaped structure that surrounds the glomerulus and collects the substances filtered through the glomerulus

Renal tubules

composed of proximal convoluted tubules, nephron loop (loop of Henle), & the distal convoluted tubules


slender, muscular tubes, 10-12 inches long, & carry urine formed in the kidney to urinary bladder

Urinary bladder

hollow muscular organ that holds the urine until it is expelled (micturation)


tube that carries urine outside the body. Male--8" & Female 1.5"


fluids and dissolved substances (based on size) are forced through the glomerulus into the glomerular capsule by hydrostatic pressure creating a liquid called "glomerular filtrate"


some of the substances that flow through the renal tubules that are needed by the body cross back into the blood by the peritubular capillaries surrounding the tubules. Ex..glucose, water & electrolytes


substances are transported from the peritubular blood capillaries into the renal tubules. Ex..metabolized drugs, K+, & hydrogen ions

Renal threshold level

when blood levels of a substance such as glucose reach a point at which no more can be reabsorbed & it is excreted in the urine. The blood glucose renal threshold level is 160-180 mg/dL

Flow of Urine

Bloodstream:renal afferent arterioles--Glomerulus--Glomerular (Bowman's) capsule--Renal tubules--Collecting ducts--Renal pelvis--Ureter--Urinary bladder--Urethra--Urinary meatus (where urine is expelled)


makes up 95% of the substances in urine

Nitrogen waste products

urea, uric acid, ammonia & creatinine


urea, uric acid & ammonia are derived from the breakdown of this

Other waste products found in urine

chloride, Na+, K+, Ca++, Mg+, phosphate & sulfate


elements or compounds that form positively or negatively charged ions that when dissolved can conduct electricity


approximately the amount of blood that passes into the renal arteries per minute


daily output of urine a day. But can vary depending on the amt of intake of fluids and the amt lost from perspiration, feces, and water vapor in the lungs


decreased urine volume


increase in the volume of urine output


no flow of urine


painful urination


excessive urination at night


passing abnormally large amounts of urine

First morning specimen

most concentrated and formed over an 8hr period, volume at least 25mL

Renal cortex

the outer area of the kidney

Renal medulla

inner region of the kidney

Renal pelvis

funnel-shaped hollow are of the kidney

Reducing substances

substances that easily loses electrons


intact red blood cells in the urine

Bence Jones protein

protein found in the urine of patients with multiple myeloma


red cells breaking open and releasing hemoglobin

Specific gravity

in urinalysis, the weight of urine compared with the weight of an equal volume of water; measures the amount of dissolved substances in urine


sugars (especially glucose) in the urine


intermediate substance in the formation of heme (part of hemoglobin)


waste product from the breakdown of hemoglobin. Enters the liver where it becomes water soluble and most of this bilirubin is excreted through the gallbladder/intestines


white blood cells in the urine which indicates the presence of an infection in the genitourinary system, usually neutrophils


elements excreted in the urine in the shape of the renal tubules and ducts


scale that measures the level of acidity or alkalinity of a solution

Bacteria, cells, casts, mucus & crystals

substances that can cause urine to be cloudy and turbid


when strip is left in urine too long


products of fat metabolism and are acid. Need to correlate with pH

Conditions of ketonuria

fevers, starvation, anorexia, prolonged vomiting & diets high in fat and low in carbs

Blood in urine

can be from bleeding in the urinary tract caused by renal disorders such as stones, tumors, lesions, cystitis & urethritis

Three substances that can cause pad to be positive for blood

intact red cells, Hgb from hemolyzed RBC's, & Myoglobin


a substance like hemoglobin that transports oxygen in muscle tissue

120 days

the lifespan of a red blood cell. Then they are lysed and release Hgb


bilirubin must attach to this protein for transportation through the blood because it cannot pass through the glomerulus

Excessive hemolysis & Liver damage

conditions that cause excessive blood levels of bilirubin. Can also be associated with hepatitis


results from the breakdown of bilirubin in the intestines by bacteria. Normally can have small amounts in the urine


large amounts of protein in the urine and is one of the first signs of renal disease. Small amounts are normal in the urine because protein molecules are too large to pass through the glomerulus


critical for DM, Htn, MI, stroke, & pregnancy. Levels of 3.4-33.9 indicate microalbuminuria


measures the amount of acid and alkaline in urine and the amount of hydrogen ions in the urine. Normal urine has a pH of 4.5-8 with most healthy patients being 6.0

pH of 7


pH of 0-6

is acid

pH of 8-14

is alkaline

Lungs & kidneys

responsible for maintaining the body's acid-base balance


blood pH less than 7.35


blood pH greater than 7.45

Conditions that cause acid urine

diets high in protein, certain meds, uncontrolled DM, Renal tuberculosis

Conditions that cause alkaline urine

diets high in vegetables, citrus fruits, milk, and other dairy products, infection, metabolic disorders, meds, respiratory disorders, stale urine


in the urine can be converted to nitrites by some UTI's. 1st morning specimen best because it takes 4 hrs for this conversion


present in a urine specimen that contains bacteria which could be an indication of a UTI. When leukocytes are lysed the release esterase

Microscopic urinalysis

examines the urine sediment, counts, and categorizes the substances present. Not categorized at CLIA waived


material at bottom after spinning down urine


liquid above sediment after spinning down urine

Squamous epithelial cells

most frequently seen and least significant. Come from the lining of the vagina and lower portions of the male and female urethra. Cells are large and have abundant, irregular cytoplasm and a central nucleus the size of RBC's

Transitional epithelial cells

come from the lining of the renal pelvis , bladder, and upper urethra. Smaller than squamous, spherical, polyhedral or caudate (with tail), with a central nucleus

Renal tubular epithelial cells

the most significant of renal damage. Round and slightly larger than WBC's and can be distinguished from leukocytes by the presence of single round nucleus that if "OFF" center


are formed primarily within the distal convoluted tubule and collecting duct. Shapes are usually parallel sides and rounded ends

Factors that lead to cast formation

decreased urine flow, increased acidity, increased solute concentration, and increased plasma protein

Hyaline casts

consist almost entirely of Tamm-Horsfall protein and appear colorless in urine

Granular casts

contain coarse and fine granule casts throughout the matrix


formed by the precipitation of urine salts when changes in pH, temperature, or concentration occur, which can affect stability. pH is the most important aid in the identification of urine crystals

Amorphous urates crystals

yellow-brown granules, often in shapeless clumps. Give the urine a macroscopic pink "brick dust" color

Calcium oxalate crystals

looks like envelopes with an X on them


very tiny and must be viewed on high power. Appear as either rod shaped (bacilli)or round (cocci)


small, oval organisms that may bud from branches. Difficult to differentiate from RBC's but budding is helpful. Candida albicans may be found in urine of women with a vaginal infection

Trichomonas vaginalis

a protozoan flagellate. Most frequently seen parasite in urine specimens. Pear shaped with rapid darting movement. Sexually transmitted

How casts are reported

as the average number seen per low power field (lpf)

How cells are reported

using numeric ranges based on teh average per high power field (hpf)

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