By Alex Dupille & Emmanuel Rivera
What is the urinary system?
 The urinary system also known as renal system.
-Produces, stores, and eliminates urine
-Kidney filters blood to keep clean
-Metabolic waste
-Toxins
-Excess water
-Dispose of nitrogenous waste
-Urea, Uric Acid, and Creatinine
-Works with the lungs, skin, and intestines to maintain
balance of water and chemicals in the body
What does it consist of?
-Two pairs kidneys
-Two sets of ureters
-Bladder
-Sphincter
- Urethra
Functions & locations
 Kidney- removes urea and other toxics or wastes from
the blood through tiny filtering units called nephrons
 Ureter-25 centimeter long which begins at the renal
pelvis. Extends downward behind the parietal
peritoneum and runs parallel to the vertebral column
 Bladder –hollow, muscular organ that stores urine and
forces it into the urethra. Within the pelvic activity
and beneath parietal peritoneum.
 Urethra- tube that directs urine from bladder to the
outside. Within the pelvic cavity, goes medially,
joining the urinary bladder from underneath.
Kidney
 Kidney is a bean-shaped organ that is about the size of a
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fist
Kidneys are on both sides of the vertebral column,
depression high on the posterior wall of the abdominal
cavity
Adipose tissue (fat) and connective tissue surround the
kidneys and hold them in position
The left kidney is usually 1.5-2.0 centimeters higher than
the right one
Is to help maintain homeostasis by regulating the
composition, volume, and pH of extracellular fluid.
The Kidney
 Blood goes down the aorta valve to
the kidneys
 Both the renal artery, renal vein,
and ureter meet at the hilus.
 Blood, waste, and water leads into
the Renal artery where filtration
begins
Inside the Kidney
 Composed of two regions
~Renal medulla- has masses of tissue called renal pyramids
~Renal Cortex- Forms a shell around the medulla and between
the renal pyramid, forming renal columns.
~ Renal Columns- Carry blood vessels to renal cortex
~Renal pyramids-Urine runs through small tubules collecting
ducts which run down through here. Also it meets minor calyx
~Also runs through renal papilla before meeting the minor calyx
in the renal pyramid.
~Minor calyx leads to major calyx which in turn empties into the
renal pelvis.
~Urine in renal pelvis then into the ureter which leads into the
bladder.
Inside the Kidney
Nephron
 A kidney has 1 million nephrons which each nephron has a
renal corpuscle and renal tubule. Renal corpuscle is
composed of blood capillaries called glomerulus.
 Glomerulus are high pressure capillaries which filters
blood. They are incased in a thin-double wall capsule called
bowman's capsule.
 Space inside the capsule and surrounding the glomerulus is
Bowman’s space.
 Plasma like fluid is filtered from the capillary blood into
Bowman’s space through the glomerulus filtration
membrane. Which allows some particles to pass through.
Nephron (Cont.)
 Goes through a filtering process through the tubules system.
Some are added to the filtrate as part of urine formation and
some are reabsorbed into filtrate and passed into the blood.
 Filtrate passes through 4 segments before reaching the ureter
~Proximal Convoluted tubule-Drains bowman's capsule and
complete absorption of nutritional importance substances takes
place
~Loop of Henle-Reabsorbs water and ions from the urine and
plays a role in controlling concentration of urine
~Distal convoluted tubule-Regulates potassium, sodium, and pH
and where further dilution takes place.
~Collecting duct-Joins with other tubules, which collects filtrate
Also where final sodium regulation takes place.
Renal Bloodflow
 Lobular arteries further subdivide to form interlobular
arteries which branch off into afferent arterials. Blood
flows into the glomerulus through the afferent
arterials. Blood flows out of the glomerulus through
the efferent arterials
 Both afferent and efferent arterials regulate glomerulus
capillary pressure by dilating or constricting.
Renal Bloodflow (Cont.)
 Now filtered flows from the glomerulus via the efferent
arterials into the peritubulary capillary network.
Which is a low pressure, reabsorptive system surround
the tubule.
 Arrangement allows rapid movement of solutes in
water between the fluid in tubular lumen and blood in
capillaries.
 Peritubular capillaries rejoin to form venous channels
by which blood leaves the kidneys and empties into
inferior vena cava.
How Urine Is Formed
How Urine is Formed
 Urine formation involves filtration of blood by the glomerulus
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to form type of urine
Reabsorption of electrolytes of nutrients that’s needed to
maintain constistency of internal environment
Secretion of waste materials
Begins at glomerulus and plasma moves from bowman’s space.
Glomerular filtrate moves into tubular segments of the nephron.
Through tubular reabsorption , electrolytes and nutrients move
from the filtrate back into the blood stream.
Here also through tubular secretion, substances move from the
peritubular capillaries into the urine filtrate. The filtrate
concentrates then finds its way renal pelvis and leads to the
uretor.
Urine Composition
 Urine composition reflects the amount of water and
solutes that the kidneys must eliminate from the body
to maintain homeostasis
 Urine composition depends on dietary intake and
physical activity
 Urine is about 95% water, and contains other
chemicals
-Traces of amino acids
-Variety of electrolytes
-Varies with the diet
Urine Composition
Urea and Uric acid
 Urea is a product of amino acid catabolism. Its plasma
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concentration reflects the amount of protein in the
diet. Urea enters the renal tubule by filtration.
Only about half is reabsorbed, and the remaining urea
is excreted in urine.
Uric acid is a product of metabolism of certain organic
bases.
Active transport reabsorbs all the uric acid in
glomerular filtrate in the nephron.
Small amount is secreted into the renal tubule and is
excreted in urine.
Urine Elimination
 After urine forming, passes through the collecting ducts
through openings in the renal papillae and enters the
calyces of the kidney
 After which is passes through the renal pelvis, and moves it
through the ureter to the urinary bladder
 Ureter is 25 centimeters long that begins at the renal pelvis
 Ureter wall has three layers
-Mucous coat-(Inner layer)Lining with renal tubules and
urinary bladder
-Muscular coat-(Middle layer)Smooth muscle fibers also
-Fibrious coat-(Outer layer)Connective tissue
Urine Elimination & Ureters
 Muscular walls of the ureters propel the urine
 Muscular peristaltic waves force urine along the length
of the ureter.
 Once reached to the bladder, ureter ejects the urine
into the bladder. A fold of mucous membrane covers
the opening through which urine enters the bladder
which acts as a valve preventing backing up.
Bladder
 Pressure of surrounding organs alter the shape from
surrounding organs.
 The wall of the urinary bladder has four layers.
-Mucous coat
-Submucous coat
-Muscular coat
-Serous coat
Urination
 In micturition, the detrusor muscle contracts, as do
muscles in the thoracic as do the muscles in the
abdominal wall and pelvic floor.
 Muscle part of the urogenital diaphragm described,
surrounds the urethra about 3 centimeters from the
bladder and is composed of voluntary skeletal muscle
tissue
 Tension between the bladder walls fills with urine
which stimulates stretch receptors, triggering
micturition reflex(Spinal cord). Triggering a sensation
of urgency.
Urination and Urethra
 Urinary bladder holds as much as 600millimilters of urine
before stimulating pain receptors, but awareness of begins
at 150 milliliters. Within 300 millimilters or more, the
sensation of fullness intensifies, and contractions of
bladder wall due become more powerful.
 When triggered, the force is strong enough for internal
urethral sphincter to open, which another relax signals the
external urethral sphincter to relax, and the bladder can
empty.
 External urethral sphincter is skeletal muscle, it is under
conscious control.
 Nerve centers in the brainstem and cortex can inhibit the
micturition reflex and aid this control.
Urination and Urethra
 When deciding to urinate, the external sphincter
relaxes, and the micturition reflex is no longer
inhibited
 The detrusor muscle contracts, and urine is excreted
through the urethra. The detrusor muscle relaxes, and
the bladder begins to fill with urine again
 Urethra is lined with mucous membrane and contains
a thick layer of smooth muscle tissues. Urethral wall
contains urethral glands, which secrete mucus into the
urethral canal
Diseases or Disorders
 Hematuria-The presence of red blood cells in urine.
Hematuria can be caused by the result of a tumor
another serious issue.
 Urinary Tract Infection(UTI)-Caused when bacteria
from the digestive tract clings to the opening of the
urethra, the hollow tube that carries urine from the
bladder to the outside of the body and begins to
multiply.
 Bladder Cancer-Occurs when abnormal cancerous
cells grow in the bladder. Bladder cancer attacks men
four times more than women.
Work Cited
 http://www.livescience.com/27012-urinary-system.html
 http://nyp.org/health/urology-diseases.html
 http://medicalcenter.osu.edu/patientcare/healthcare_servi
ces/urinary_bladder_kidney/anatomy_urinary_system/Pag
es/index.aspx
 http://www.pc.maricopa.edu/Biology/pfinkenstadt/BIO20
2/202LessonBuilder/Urinary/index.html