Urinary System Anatomy and Physiology

Urinary System Anatomy and Physiology Part I Urinary System  Kidneys (2)   Most important excretory organ Eliminate waste     Ureters (2) Bladder (1) Urethra (1) Nephron Unit    Functional unit of the kidney Formation of urine Tubular and vascular structures Kidney Location and Protection      Kidneys are located in the posterior wall of the abdominal cavity In the retroperitoneal space Connective tissue (renal fascia) hold the kidneys in place Adipose tissue cushion the kidneys The lower rib cage partially enclose the kidney and protect them Urinary System – Anterior/Posterior Views Kidney Structures      Kidney is reddish-brown Looks like a bean Approximately 4 inches x 2 inches Hilus – indentation where blood vessels and structures enter or exit the kidney Three Regions in the kidney if sliced in half – renal cortex, renal medulla, renal pelvis Renal Cortex   Light, outside region Cortex means “bark” Renal Medulla     Dark, triangular structure Form small cone shaped regions called renal pyramids Each pyramid is separated by renal columns The lower ends of the pyramids point to the renal pelvis Renal pelvis    A basin that collects the urine made by the kidney and helps form the upper end of the ureter The edges of the renal pelvis closest to the renal pyramids are called calyces Calyces collect the urine formed in the kidney How do they work?        Need a blood supply Brought to the kidney via the renal artery Renal artery stems from the abdominal aorta 20-25% of cardiac output goes to the kidneys Smaller arteries supply blood to the nephron unit Blood leaves the kidney via the renal veins The renal veins empty into the inferior vena cava Functions of the Kidneys  Excrete nitrogenous waste from the body Urea  Ammonia  Creatinine       Regulate blood volume Help regulate electrolyte content of the blood Regulate acid-base balance (pH) Regulate blood pressure Regulates red blood cell production The Formation of Urine      The Nephron Unit Each kidney contains about 1 million nephron units The number does not increase after birth They cannot be replaced if damaged 2 parts Tubular component (renal tubule)  Vascular component  Renal Tubules   Glomerular capsule (Bowman’s Capsule) – “C” shaped capsule surrounding the glomerulus Glomerulus – cluster of capillaries Proximal convoluted tubule  Loop of Henle – ascending and descending limb  Distal Convoluted tubule  Collecting duct  Nephron Renal Vasculature        Receives blood from the renal artery Renal artery branches into the afferent arterioles Afferent arterioles feed into Bowman’s capsule The efferent arterioles exit Bowman’s capsule The efferent arterioles form the peritubular capillaries The peritubular capillaries empty into the venules, large veins, and then into the renal veins It is imperative you know the relationship between the tubular and vascular structures. Urine Formation    Formed in the nephron unit Water and dissolved substances move through the renal tubules and vessels Three processes are involved in urine formation Glomerular filtration  Tubular reabsorption  Tubular secretion  Composition of Urine       Sterile 95 % water Nitrogen containing waste – urea, uric acid, ammonia, creatinine Electrolytes Light yellow color of urine is due to a pigment called urochrome Urochrome is formed from the breakdown of hemoglobin in the liver Urine Specific Gravity     Ratio of the amount of solute to the total volume Solute = substance dissolved in the urine The greater the solute = greater the specific gravity Concentrated Urine = high specific gravity  Ex. dehydration Ex. Overhydration, diabetes insipidus  Dilute Urine = low specific gravity  Urine Characteristics       Amount – 1500 ml in 24 hours pH – average 6.0 Specific Gravity – heavier than water (1.0011.035) Color – yellow (amber, straw colored, concentrated, orange, brown, red, sediment, clear or cloudy) Dehydrated = deep yellow, dark Overhydrated = pale yellow, colorless Abnormal Constituents of Urine        Albumin (protein) Glucose Red blood cells Hemoglobin White blood cells Ketone bodies Bilirubin Urine Testing       Urinalysis Microscopic exam Culture and sensitivity Urine dipstick Urine Drug and alcohol screening 24 hour urine testing Your Plumbing – The Urinary Tract (Ureters, Urinary bladder, Urethra)    Ureters Transport urine, they do not alter it in any way Urine moves in response to gravity and muscular movements called peristalsis through ureters. Your “Plumbing” The Bladder     Stores urine temporarily until elimination Located behind the symphasis pubis A distended bladder or full bladder can be palpated above the syphasis in the abdominal cavity. Bladder has 4 layers     Mucous membrane Submucosa Detrusor muscle – involuntary smooth muscle Serosa   Contain rugae to allow for stretching Trigone – triangular area in the floor of the bladder Urination – “Micturition”        Expelling urine from the bladder The urge to urinate (void) happened at about 200 ml of urine in the bladder At about 300 ml urine in the bladder, the urge becomes more uncomfortable Moderately full = 500 ml urine Overdistended bladder may have over 1000 ml urine Bacteria in your bladder doubles every 4 hours. Stimulated by stretch receptors Urethra      Carries urine from the bladder to the outside of the body Internal sphincter prevents urine from emptying; composed of smooth muscle; involuntary External sphincter at the upper portion of the urethra allows you to resist the urge to urinate; composed of skeletal muscle; voluntary Female – short, opens to the outside at the urethral meatus Male – longer, passes through the prostate gland; carries urine and sperm Urinary Retention and Suppression  Retention - Inability to void Post operative; anesthesia  Bladder dysfunction   Suppression – no urine formation  Kidney dysfunction Data Collection & Documentation  Characteristics of urine     Color Sediment Clear or cloudy Odor    How does the patient/resident void? Urinary diversions? Signs and symptoms     Urgency Frequency Burning sensation Hesitancy What is the Costovertebral Angle? T11 R. Kidney T12 L1 L. Kidney 12th Rib Costovertebral Angle Region to assess for kidney tenderness Disorders of the Urinary System       Glomerulonephritis Polycystic Kidney Pyelonephritis Renal Calculi – kidney stones Renal Failure UTI – urinary tract infection As We Age     By age 80 there is a 50% reduction in nephron units; therefore a decreased ability to concentrate urine Urinary bladder shrinks and becomes less able to contract and relax; therefore the elderly must void frequently Bladder infection incidence increases Increase in bladder incontinence due to weakened muscles