The Urinary System
Functions of the Urinary
System
O Three Major Functions
O Excretion: The removal of organic waste
products from body fluid.
O Elimination: The discharge of fluid waste
products into the environment.(urination)
O Homeostasis: The regulation of the volume
and solute concentration of blood plasma.
Functions of the Urinary
System
O Other functions of the urinary system:
O Regulation Blood Volume & Blood Pressure.
O Regulating Plasma Concentrations of
Sodium, Potassium, Chloride, and other ions.
O Helping Stabilize Blood pH.
O Conserving Valuable Nutrients (glucose,
amino acids).
O These activities are carefully regulated to
keep the composition of blood within
acceptable limits.
Anatomical Structures of the
Urinary System
O Kidneys(2): Organ that produces urine.
O Urine: Fluid containing water, ions, and small
soluble compounds.
O Urinary Tract(two paired ureters): Transports
urine to the urinary bladder.
O Urinary Bladder: Temporarily stores urine
prior to elimination.
O Urethra: Conducts urine to the exterior (in
males also transports semen)
Urinary System
The Human Kidney
O In the human body there are two kidneys,
one located on either side of the vertebral
column.
O They are between the last thoracic and first
lumbar vertebrae.
O The right kidney is slightly lower than the
left.
O Each kidney is covered by a fibrous capsule
and is packed in cushion of adipose tissue.
Anatomy of the Human
Kidney
O Each kidney is typically reddish-brown in
color and about 4in. Long by 2.2in. Wide
with a thickness of about 1.2in.
O The kidney weighs in at about 5.5oz
O Each kidney has a ureter connected to it at a
indentation in the surface of the kidney
called the hilum.
O The hilum is also where the renal artery and
nerve connect to each kidney.
Anatomy of the Human
Kidney Continued
O Each kidney is divided based on its inner and
outer anatomy.
O The outer portion is called the renal cortex.
O The inner portion is called the renal medulla.
O Divided into 6-18 conical shaped structures called
renal pyramids.
O Urine production occurs within the renal pyramids
O The tip of each pyramid is called a renal papilla
O Ducts within each papilla discharge urine into a
drain called the minor calyx.
Anatomy of the Human
Kidney Continued
O 4-5 of the minor calyx will merge together to
form a major calyces, which combine
together form a funnel shaped chamber
called the renal pelvis.
O The renal pelvis is connected to the ureters
and allows for urine to be drained out of the
kidney.
The Kidney
Blood Supply to the Kidneys
O Because the kidneys main function is to
filter out waste from the blood it is highly
vascular.
O About 1200mL of blood flows through the
kidneys each minute.
O The main blood vessels of the kidney are the
renal artery and renal vein.
Blood Supply
The Nephron & Urine
Production
O In the renal cortex of the kidney are
specialized microscopic tubular structures
called nephrons.
O Each kidney contains about 1.25 million
nephrons.
O The nephron is the basic functioning unit of
the kidney.
O Each nephron consists of two main parts
the; renal corpuscle and the renal tubule.
The Nephron & Urine
Production
O The nephron is the location where the blood if
filtered to produce urine.
O The filtration process begins when the blood
reaches the renal corpuscle and dissolved
solutes are removed producing a fluid called
filtrate.
O The filtrate then enters the renal tubule where it
is gradually changed into tubular fluid.
O The fluid is then emptied into the collecting duct
and eventually into the papillary duct. The
papillary duct will empty the fluid now called
urine into the renal pelvis of the kidney.
The Nephron & Urine
Production
O The Nephron has three main functions that
O
O
O
O
it accomplishes via filtration and urine
production.
Reabsorb useful organic molecules
Reabsorb water (~90%)
Secret waste products
Remove additional water and salt remove
urine is released to the renal sinus.
The Nephron
Urine Production
O The purpose for urine production is to maintain
homeostasis(balance) in the body by regulating blood
volume and composition.
O The process also involves the excretion of three
dissolved solids
O Urea (most abundant, from breaking down amino acids.)
O Creatinine (generated in skeletal muscle from energy
production)
O Uric Acid (produced from breaking down and recycling
RNA)
O To accomplish this goal the kidney does three specific
functions:
O Filtration
O Reabsorption
O Secretion
Nervous System & Hormonal
Control
O Several hormones are involved in regulating
kidney function;
O Angiotensin II
O ADH (Antidiuretic Hormone)
O Aldosterone
O ANP (Atrial Natriuretic Peptide)
Ureters
O A pair of muscular tubes that conduct urine
from the kidneys to the urinary bladder.
O Each is about 12in long.
O About every 30 seconds a peristaltic
contraction begins at the renal pelvis and
sweeps along the ureters all the way to the
bladder forcing urine into the bladder.
Urinary Bladder
O A hollow muscular organ that stores urine prior
to urination.
O A full bladder can hold up to a liter of urine
O (Micturition reflex) Stretch receptors in the
bladder signal when the bladder is full and start
a chain reaction of neurological activity that
makes us consciously aware of our full bladder.
O Eventually muscle contraction and relaxation of
internal and external sphincters allow for the
bladder to empty and urination to occur.
Ureter & Bladder
Urethra
O Short tube that extends from the bladder to
the exterior body that allows the urine to exit
the bladder and the body.
O The urethra is shorter in females(1in) than
in males (7-8in).
O In males it is also involved in the
transportation of semen.
Balance & Homeostasis
O Many dynamics exits between the urinary
system and other systems in the body due to
balance and exchange of fluid between the
internal and external environment.
O Homeostasis involves the balance of fluid
volume, solute concentration, and pH.
O Fluid Balance
O Electrolyte Balance
O Acid-Base Balance
O Sodium Balance
O Potassium Balance
Diseases & Disorders
O Kidney Diseases
O Kidney Stones
O Incontinence
O Urinary Tract Infection
O Renal or Kidney Failure
O Bladder Infection
O ETC.