Unit 7 (Chapter 17)
The Urinary System
Presented by Dawn Duran, PT, MHS, CSCS
Adjunct Professor, Kaplan University
Welcome to the Seminar!
Kidneys
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For the formation of urine, it is essential
that the kidney has a high rate of blood flow
Functions of the kidneys include:
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Stimulating the production of red blood
cells
Maintaining blood pressure
Regulating water balance
Regulating electrolytes
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Excretes toxins and nitrogenous wastes
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Kidneys
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Internal structure
Renal cortex - outer part of the kidney
 Renal medulla - inner portion of kidney
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Renal pyramids - triangular divisions of medulla
 Renal papilla - narrow, innermost end of pyramid
 Renal pelvis - the basin-like structure that the
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urine flows into as it leaves the kidney
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Renal calyces—divisions of renal pelvis
Kidneys
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Renal Microscopic structure
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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.
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Cortical nephrons make up 85% of total
Juxtamedullary nephrons play a specialized role in concentrating urine
Kidney
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Renal corpuscle
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Bowman’s capsule is the cup-shaped top
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Glomerulus is a tuft or network of blood capillaries
surrounded by Bowman’s capsule
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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
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Approximately 99% of water that leaves the
blood each day is returned to the blood.
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A person can live with only one kidney
Formation of Urine
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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
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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
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In other words, filtration occurs in the glomerulus
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An increase in systemic blood pressure causes filtration through the
glomerular-capsular membrane to increase.
Formation of Urine
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Reabsorption is the movement of substances out of renal
tubules into blood in peritubular capillaries
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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
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hydrogen ions, potassium ions, and certain drugs are secreted by
active transport;
ammonia is secreted by diffusion
Formation of Urine
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Urine volume excretion is regulated by hormones:
aldosterone, ADH, atrial natriuretic hormone
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Urinalysis is an examination of the physical, chemical, and
microscopic characteristics of urine; may help determine the
presence and nature of a pathological condition
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Normal adult urine output is approximately 1500-1600
mL/day
The color of “normal” urine is transparent yellow, amber or
straw colored
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Nitrogenous wastes, creatinine and urea are normally found
in urine
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Ketones, including acetone, are not
An acetone odor to the urine is indicative of diabetes
mellitus
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Hormones
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Aldosterone causes the retention of salt and water.
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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
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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
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Structure
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Elastic muscular organ, capable of great expansion
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When the bladder is empty, the inner lining is wrinkled
and lies in folds called rugae
Functions
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Storage of urine before voiding
Assist with micturition
Voiding
Urinary Bladder
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The openings of the ureters and the urethra
in the urinar bladder is a triangular region
called the trigone
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The uterus is locaed posterior and superior
to the urinary bladder
Urethra
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Structure
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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
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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
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Passage of urine from body (also called
urination or voiding)
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Regulatory sphincters
Internal urethral sphincter (involuntary)
 External urethral sphincter (voluntary)
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Bladder wall permits storage of urine with little
increase in pressure
Micturition
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The sacral spinal cord is involved with the
regulation of micturition
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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
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Micturition
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Urinary retention—urine produced but not
voided
Incontinence is when urine is voided
involuntarily
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May be caused by spinal injury or stroke
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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
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Anuria is the absence of urine
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Oliguria is a scanty amount of urine
Proteinuria means protein in the urine
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A common temporary condition that occurs after
exercise in many individuals
Glycosuria means glucose in the urine
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Glucose is not normally found in urine
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If urinalysis detects glycosuria then diabetes mellitus
might be present
Diuretics
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Diuretics are drugs that stimulate the
production of urine
Renal & Urinary Disorders
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Obstructive disorders interfere with normal urine flow,
possibly causing urine to back up and cause kidney
damage
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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
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Urinary tract infections (UTIs) are often caused
by gram-negative bacteria
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Urethritis—inflammation of the urethra
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Cystitis—inflammation or infection of the
urinary bladder
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Pyelonephritis—inflammation of the renal pelvis
and connective tissues of the kidney; may be acute
(infectious) or chronic (autoimmune)
Renal & Urinary Disorders
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Glomerular disorders result from damage to the
glomerular–capsular membrane of the renal corpuscles
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Nephrotic syndrome accompanies many glomerular disorders
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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
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Kidney failure or renal failure occurs when the
kidney fails to function
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Acute renal failure—abrupt reduction in kidney
function that is usually reversible
Renal & Urinary Disorders
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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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Questions? Ask Me OR your
classmates!
Thanks for attending! See you in
Discussion!