CHAPTER TWENTY-FIVE The Urinary System
Introduction A. Urology=the branch of medicine that deals with urinary system and male reproductive tract. B. Functions of the excretory system 1. Adjusts blood volume and blood pressure. 2. Regulates plasma concentrations of sodium, potassium, chloride and other ions. 3. Stabilizes blood pH. 4. Excretes metabolic wastes and drugs or toxins. 5. Regulates RBC production, synthesizes calcitriol (a.k.a. vitamin D), and performs gluconeogenesis. C. Basic Gross Anatomy 1. Two bean shaped kidneys that are metabolically very active. At rest they receive about 25% of the cardiac output. The kidneys perform the excretory functions of the urinary system and produce urine, a fluid containing water, ions, and small soluble compounds. 2 Two ureters that receive urine from the kidneys and conduct it to the urinary bladder. Urine movement involves a combination of gravity and peristalsis. 3. The urinary bladder receives and stores urine prior to elimination from the body. The urinary bladder possesses rugae and is lined with transitional epithelium to allows the urinary bladder to stretch. 4. Urethra drains urine from urinary bladder and transports the urine to the outside. In females, it only drains urine. In males, it drains urine and semen. At the base of the bladder there is an internal and external urethral sphincter that regulates urination.
25.1 Physical Characteristics of Urine A. Characteristics of Normal Urine 1. Volume = a healthy adult typically produces 1200 mL of urine per day with an osmotic concentration of roughly 1000 mOsm/L. Urine volumes can vary however between 700 - 2000 ml per day. 2. Water content = 93% to 97% water. 3. Color = clear yellow because of an abundance of a yellow pigment called urochrome. If the urine is not clear, it is described as turbid and may be suggestive of a bacterial infection. Urine should contain no bacteria (sterile). 4. Odor = slightly aromatic when fresh but tends to develop an ammonia odor due to bacterial metabolism. Can vary according to composition and diet. 5. pH = urine is slightly acidic ranging normally between 4.5 -- 8.0 (but averaging about pH 6) 6. Specific gravity = textbook 1.003 - 1.030) 7. Normal Laboratory Values for Solutes in Urine: Sodium (Na*) = 40 - 220 mEq/L Proteins = 0.000 mg/dL Potassium (K*) = 25 - 100 mEq/L Urea = 1800 mg/dL Bicarbonate (HCO) = 1.9 mEq/L Creatinine = 150 mg/dL Glucose = 0.009 mg/dL Uric acid = 40 mg/dL Lipids = 0.002 mg/dL Ammonia = 60 mg/dL
8. Abnormal Constituents of Urine: Substance Name of Condition Glucose Glycosuria Proteins Proteinuria or albuminuria Ketone bodies Ketonuria Hemoglobin Hemoglobinuria Bile pigments Bilirubinuria Erythrocytes Hematuria Leukocytes Pyuria
Possible Cause Diabetes mellitus Pregnancy; heart failure, renal disease Starvation or untreated diabetes Severe burns; hemolytic anemia Liver disease; obstruction of bile ducts Trauma; kidney stones; infection Urinary tract infections
25.2 Gross Anatomy of Urine Transport A. Filtrate modification and urine production ends when the fluid enters the renal pelvis. The urinary tract (the ureters, urinary bladder, and urethr