Urinary System

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Urinary System
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Functions of Urinary System

• Filter Blood
• Regulation of Blood Volume/Pressure renin
• Regulation of the solute concentration of the
  Blood Na, Cl-, K, Ca2, HPO4-2
• pH regulation of extracellular fluid
• Regulation of RBC synthesis erythropoietin
• Vitamin D activation

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Anatomy of the Urinary System
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Kidneys

• Primary organs of the urinary system
• Located between the 12th thoracic and 3rd lumbar
  vertebrae. Right is usually lower due to liver.
• Lie in shallow depressions against the posterior
  abdominal wall and behind the parietal peritoneum
  retroperitoneal
• Held in place by connective tissue renal fascia
  and surrounded by thick layer of adipose
  perirenal fat

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• Each kidney is approx. 3 cm thick, 6 cm wide and
  12 cm long
• Indentation on medial aspect hilus where
  renal vessels and ureter transverse
• Pyramids
• Papillae
• Calyces major/minor
• Columns

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Nephrons
Blood enters the nephron from a network that
begins with the renal artery. This artery
branches into smaller and smaller vessels and
enters each nephron as an afferent arteriole.
The afferent arteriole ends in a specialized
capillary called the Glomerulus. Each kidney has
a glomerulus contained in Bowmans Capsule. Any
cells that are too large to pass into the nephron
are returned to the venous blood supply via the
efferent arteriole. The efferent arteriole will
divides to become the peritubular
capillaries.

• Each kidney contains over a million nephrons
  functional structure

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Nephron
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,

• Proximal Convoluted Tubule PCT H2O, Na, Cl-,
  glucose, amino acids, Ca, Mg, K,
  micronutrients zn,cu,fe
• Descending Loop H2O, Cl-, Na
• Ascending Loop Cl-, Na not permeable to H2O
• Distal Convoluted Tubule DCT H20, Na, Cl-,
  HCO3-

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URINE FORMATION
At least 500 mL (17 oz) of urine must be
eliminated every day because this amount of fluid
is needed to remove potential toxic materials
from the body to maintain homeostasis. A normal
adult eliminates from 1.5 L (1.6 qt) to 2.3 L
(2.4 qt) of Urine a DAY, depending on the amount
of water taken in and the amount of water lost
through Respiration and Perspiration.
Urine flows from the nephron to the collecting
ducts, which extend to the tips of the pyramids,
and empty into the calyces. All the urine will
leave the kidney via the ureters.
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Juxtaglomerular Apparatus

• Monitors blood pressure and secretes renin, is
  formed from modified cells in the afferent
  arteriole and the ascending loop of the nephron
• The cells of the arteriole are called
  juxtaglomerular cells and the cells of the loop
  are called macula densa. The macular densa cells
  monitor NaCl in the urine, and the
  juxtaglomerular cells produce renin

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Renin-Angiotensin-Aldosterone

• Renin secreted by juxtaglomerular cells if
  blood pressure in afferent arteriole is low, or
  Na of urine decreases as it passes the macula
  densa cells.
• Renin enters the genl circulation via
  peritubular capillaries and activates
  angiotensinogen to angiotensin I. Angiotensin I
  ? angiotensin II via a converting enzyme found in
  the plasma.

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• Angiotensin II is a vasoconstrictor, acts on the
  hypothalamus causing the sensation of thirst,
  salt appetite and ADH secretion. It also causes
  the secretion of aldosterone from the adrenal
  cortex.
• Aldosterone a steroid hormone acts on the
  cells of the nephron esp. those of the
  ascending loop and DCT to reabsorb more Na.

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ureters
Each ureter is about 25 cm long and carries urine
from the renal pelvis to the urinary bladder via
peristaltic waves. .
The wall of the ureter consists of three layers.
The outermost is a fibrous coat, middle layer is
muscular circular longitudinal and the
innermost layer is called the mucosa, a
transitional epithelium that is continuous with
the lining of the renal pelvis and bladder, also
secretes a protective mucus.
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The Urinary Bladder is a temporary storage
reservoir for urine. When empty it resides in
the pelvis, when full will rise above the
symphysis pubis. A triangular region, called the
trigone, is formed by three openings in the floor
of the bladder. Two are from the ureters, and
third from the urethra. There are flaps of
mucosa covering the openings of the ureters and
act as valves.
A band of muscles encircles the opening to the
urethra forming the internal urethral sphincter.
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The innermost lining of the urinary bladder is a
mucous membrane layer, continuous with the
ureters. This layer covers the transitional
epithelium. When empty, the mucosa forms folds
called rugae. The second layer is called the
submucosa. It contains elastic connective tissue
fibers. The third layer is the muscularis this
collection of smooth muscle is known as the
detrusor muscle. Contraction of this muscle
expels urine from the bladder. The outermost
layer is dense connective tissue.
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Urethrathin walled tube conveys urine from
bladder to external environment. Similar
structure to ureterSphincters internal urethral
involuntary external urethral voluntary

• Male Urethra
• 20 cm long 7-8 in
• Transports both urine semen
• Eternal urethral orifice opens at tip of penis

• Female Urethra
• 3-4 cm long 1.5 in
• External urethral orifice opens just anterior to
  the vaginal opening

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Kidney Stones

• Kidney stones affect more than a million
  Americans each year. Twelve to 24 million
  Americans will develop stones in their lifetime
  and the incidence rate has increased dramatically
  over the last 20 years with approximately 350,000
  new stone cases reported each year.
• In the United States, 7 to 10 of every 1,000
  hospital admissions are due to kidney stones.

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Kidney stones are solid masses of mineral salt
deposits that are normally filtered through the
kidney and voided in urine. Urine naturally
contains substances that dissolve the waste
materials that form these solids or calculi.
However, when the amounts of these salts are
excessive, the urine may be unable to dissolve
them all, leaving crystals that accumulate in the
kidney and gradually increase in size.
The stones can be as small as a grain of sand or
as large as a golf ball. The size, shape, and
location of the stone can cause many different
symptoms.
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Most renal calculi are so small they are passed
through the urinary tract without any symptoms.
Larger calculi can obstruct the renal ducts, or
become lodged in the ureters. These larger
obstructions cause sharp, severe pain in the
sides and back as they move through the urinary
tract. In medical parlance, this condition is
called renal colic.
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Well, I guess you dont have kidney stones after
all.