Urinary or Excretory System
Functions:
Removes certain wastes and
excess water from the body
Maintains the acid-base balance
of the body
Parts
include two
kidneys, 2
ureters, the
bladder,
and the
urethra
Kidneys
 Two bean-shaped organs
 Located on either side of the vertebral column behind the
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upper part of the abdominal cavity and separated from this
cavity by the peritoneum
Protected by the ribs and a heavy cushion of fat
Connective tissue helps hold the kidneys in position
Each kidney is enclosed in a mass of fatty tissue called the
adipose capsule
Cover externally by a tough, fibrous tissue called the renal
fascia or fibrous capsule
Kidney Sections:
Cortex
 (1) Outer section of the kidney
 (2) Contains most of the nephrons that aid
in the production of urine
 Medulla
 (1) Inner section of the kidney
 (2) Contains most of the collecting tubules
that carry the urine from the nephrons on
through the kidney
Hilum of Kidney:
 Notched or indented
area on each kidney
 Area where ureter,
nerves, blood vessels,
and lymph vessels enter
and leave the kidney
Nephrons
 Microscopic filtering units
located in the kidney
 Over one million per
kidney
 Each nephron consists of a
glomerulus, Bowman’s
capsule, a proximal and
distal convoluted tubule,
and a collecting duct
(tubule)
 Renal arteries carry blood to the kidney
 Branches of the renal artery pass through the
medulla to the cortex where the blood enters
the first part of the nephron, the glomerulus
Glomerulus of the Nephron:
 (1) Cluster of
capillaries
 (2) As blood passes
through water,
mineral salts, sugar,
metabolic products
and other
substances are
filtered out of the
blood
 (3) Red blood cells
and proteins are
not filtered out
Glomerulus continued:
 Filtered blood leaves the glomerulus
and eventually is carried to the renal
vein, which carries it away from the
kidney
 Substances filtered out in the
glomerulus enter the next section of
the nephron, Bowman’s capsule
Bowman’s Capsule:
 (1) C-shaped structure
that surrounds the
glomerulus
 (2) It is the start of the
convoluted tubule
 (3) Picks up the
materials filtered from
the blood in the
glomerulus
 (4)Passes the materials
into the convoluted
tubule
Convoluted Tubules:
 As these materials pass through
the various sections of the
tubule, substances needed by the
body are reabsorbed and
returned to blood capillaries
 At the end, most of the water,
sugar, vitamins, and mineral salts
have been reabsorbed
 Excess sugar and salts, some
water, and wastes, including
urea, uric acid, and creatinine,
remain in the tubules and
become known as the
concentrated liquid called urine
Collecting Ducts:
 Urine now enters
collecting ducts or tubules
located in the medulla
 Collecting tubules empty
into a funnel-shaped
structure, the renal basin
or pelvis, which is the first
section of the ureter
Ureters
 Two muscular tubes about 10 to 12
inches long
 One extends from the renal pelvis
of each kidney to bladder
 Peristalsis, a rhythmic wavelike
motion of the involuntary muscle,
moves the urine through the ureter
from the kidney to the bladder
Bladder
 Hollow muscular sac
 Lies behind the symphysis
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pubis at the midline of the
pelvic cavity
Has lining of mucous
membrane
Arranged in a series of folds
called rugae
Rugae disappear as muscles of
the bladder allow it to expand
and fill with urine
Three layers of visceral
(smooth) muscle form the
walls
Bladder Functions:
 Receives the urine from the ureters
 Stores the urine until it is eliminated
from the body
 Urge to void (urinate or micturate)
occurs when the bladder contains about
250 cc (1 cup) of urine, but bladder can
hold much more urine
Circular Sphincter Muscles:
 Control the bladder opening to prevent
emptying
 When bladder is full, receptors in the
bladder will send out a signal for a
reflex that will open the muscle
 Reflex action cannot be controlled by
infants, but as children get older, they
learn to control this reflex
Urethra:
Tube that carries the
urine from bladder to the
outside
External opening is called
the urinary meatus
Different in females than
males
Urethra cont.
Females
 Tube about 1 ½ inches
(3.75cm) long
 Opens in front of the
vagina
 Carries only urine to the
outside
Urethra cont:
Males
 S-shaped tube about 8
inches (20 cm) long
 Passes through the prostate
gland and out through the
penis
 Carries both urine from the
urinary system and semen
from the reproductive
system
Urine
 1. Liquid waste product produced by the urinary system
 2. About 95 percent water
 3. Waste products dissolved in this water are urea, uric
acid, creatinine, mineral salts, and various pigments
 4. Excess useful products, such as sugar, can also be
found in urine but their presence usually indicates
disease
 5. About 1,500 to 2,000 cc (1½ to 2 quarts) of urine are
produced daily from the approximately 150 quarts of
liquid that is filtered through the kidneys
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Conditions affecting urination
 1. Polyuria: excessive urination
 2. Oliguria: below normal amounts of urination
 3. Anuria: absence of urination
 4. Hematuria: blood in the urine
 5. Pyuria: pus in the urine
 6. Nocturia: urination at night
 7. Dysuria: painful urination
 8. Retention: inability to empty the bladder
 9. Incontinence: involuntary urination
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