Unit 7 (Chapter 17) The Urinary System Presented by Dawn Duran, PT, MHS, CSCS Adjunct Professor, Kaplan University

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Kidneys For the formation of urine, it is essential that the kidney has a high rate of blood flow

Functions of the kidneys include: Stimulating the production of red blood cells Maintaining blood pressure Regulating water balance Regulating electrolytes Excretes toxins and nitrogenous wastes

Kidneys Internal structure Renal cortex - outer part of the kidney Renal medulla - inner portion of kidney Renal pyramids - triangular divisions of medulla Renal papilla - narrow, innermost end of pyramid Renal pelvis - the basin-like structure that the urine flows into as it leaves the kidney Renal calyces—divisions of renal pelvis

Kidneys Renal Microscopic structure Nephrons are the structural and functional units of the kidney. The major components of the nephron are the renal corpuscle and renal tubule. There are approximately 1-2 million nephrons in each kidney. Cortical nephrons make up 85% of total Juxtamedullary nephrons play a specialized role in concentrating urine

Kidney Renal corpuscle Bowman’s capsule is the cup-shaped top Glomerulus is a tuft or network of blood capillaries surrounded by Bowman’s capsule An efferent tubule drains blood from the glomerulus while an afferent tubule carries blood to the glomerulus The primary function of the glomerulus is filtration. Filtration occurs in the glomerulus.

Kidneys Renal tubule Proximal convoluted tubule—first segment Primary function is reabsorption Loop of Henle—extension of proximal tubule; consists of descending limb, loop, and ascending limb Distal convoluted tubule—extension of ascending limb of loop of Henle Collecting tubule—straight extension of distal tubule

Fun Facts Approximately 99% of water that leaves the blood each day is returned to the blood. A person can live with only one kidney

Formation of Urine Occurs by a series of three processes that take place in successive parts of nephron: filtration, absorption and secretion The formation of urine begins with filtration Filtration is a continuous process in renal corpuscles glomerular blood pressure causes water and dissolved substances to filter out of glomeruli into Bowman’s capsule normal glomerular filtration rate 125 ml per minute In other words, filtration occurs in the glomerulus An increase in systemic blood pressure causes filtration through the glomerular-capsular membrane to increase.

Formation of Urine Reabsorption is the movement of substances out of renal tubules into blood in peritubular capillaries water, nutrients, and ions are reabsorbed; water is reabsorbed by osmosis from proximal tubules Secretion is the movement of substances into urine in the distal and collecting tubules from blood in peritubular capillaries hydrogen ions, potassium ions, and certain drugs are secreted by active transport; ammonia is secreted by diffusion

Formation of Urine Urine volume excretion is regulated by hormones: aldosterone, ADH, atrial natriuretic hormone Urinalysis is an examination of the physical, chemical, and microscopic characteristics of urine; may help determine the presence and nature of a pathological condition Normal adult urine output is approximately 1500-1600 mL/day The color of “normal” urine is transparent yellow, amber or straw colored Nitrogenous wastes, creatinine and urea are normally found in urine Ketones, including acetone, are not An acetone odor to the urine is indicative of diabetes mellitus

Hormones Aldosterone causes the retention of salt and water. This is a salt and water retaining hormone secreted by the adrenal cortex. Secretion of aldosterone causes sodium to be reabsorbed. This increases blood volume. Secretion of aldosterone causes water to be retained ADH (Antidiuretic hormone) causes the retention of water and decreased urine production. ANH (atrial natriuretic hormone) causes salt and water loss.

Ureters Ureters are narrow long tubes with an expanded upper end (renal pelvis) located inside kidney and lined with mucous membrane and muscular layer Function—drain urine from renal pelvis to urinary bladder

Urinary Bladder Structure Functions Elastic muscular organ, capable of great expansion When the bladder is empty, the inner lining is wrinkled and lies in folds called rugae Functions Storage of urine before voiding Assist with micturition Voiding

Urinary Bladder The openings of the ureters and the urethra in the urinar bladder is a triangular region called the trigone The uterus is locaed posterior and superior to the urinary bladder

Urethra Structure Functions Narrow tube from urinary bladder to exterior Lined with mucous membrane Opening of urethra to the exterior called urinary meatus In males, the urethra passes through the prostate gland The urethra is longer in men than it is in women Functions Passage of urine from bladder to exterior of the body in both men and women Passage of male reproductive fluid (semen) from the body Therefore, in women the urethra is only a component of the urinary tract whereas in men it is part of both the urinary and reproductive tracts

Micturition Passage of urine from body (also called urination or voiding) Regulatory sphincters Internal urethral sphincter (involuntary) External urethral sphincter (voluntary) Bladder wall permits storage of urine with little increase in pressure

Micturition The sacral spinal cord is involved with the regulation of micturition Emptying reflex Initiated by stretch reflex in bladder wall Bladder wall contracts Internal sphincter relaxes External sphincter relaxes, and urination Enuresis—involuntary urination in young child

Micturition Urinary retention—urine produced but not voided Incontinence is when urine is voided involuntarily May be caused by spinal injury or stroke Neurogenic bladder—paralysis or abnormal function of the bladder, preventing normal flow of urine out of the body Types include urge, stress, and reflex

Micturition Anuria is the absence of urine Oliguria is a scanty amount of urine Proteinuria means protein in the urine A common temporary condition that occurs after exercise in many individuals Glycosuria means glucose in the urine Glucose is not normally found in urine If urinalysis detects glycosuria then diabetes mellitus might be present

Diuretics Diuretics are drugs that stimulate the production of urine

Renal & Urinary Disorders Obstructive disorders interfere with normal urine flow, possibly causing urine to back up and cause kidney damage Renal calculi (kidney stones) may block ureters, causing intense pain called renal colic Lithotripsy is a process where kidney stones are broken up by ultrasound waves Kidney stones are NOT a type of cancer. Tumors—renal cell carcinoma (kidney cancer) and bladder cancer are often characterized by hematuria (blood in the urine)

Renal & Urinary Disorders Urinary tract infections (UTIs) are often caused by gram-negative bacteria Urethritis—inflammation of the urethra Cystitis—inflammation or infection of the urinary bladder Pyelonephritis—inflammation of the renal pelvis and connective tissues of the kidney; may be acute (infectious) or chronic (autoimmune)

Renal & Urinary Disorders Glomerular disorders result from damage to the glomerular–capsular membrane of the renal corpuscles Nephrotic syndrome accompanies many glomerular disorders Proteinuria—protein in the urine Hypoalbuminemia—low plasma protein (albumin) level; caused by loss of proteins to urine Uremia - a condition where dangerous levels of toxins build up in the blood

Renal & Urinary Disorders Kidney failure or renal failure occurs when the kidney fails to function Acute renal failure—abrupt reduction in kidney function that is usually reversible

Renal & Urinary Disorders Chronic renal failure—slow, progressive loss of nephrons caused by a variety of underlying diseases Early in this disorder, healthy nephrons often compensate for the loss of damaged nephrons Loss of kidney function ultimately results in uremia (reflected by high BUN levels) and its life-threatening consequences Complete kidney failure results in death unless a new kidney is transplanted or an artificial kidney substitute is used

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