THE URINARY SYSTEM

1
THE URINARY SYSTEM

• The anatomy
• The functions

2
The functions of the system

• To filter the blood and form urine .
• To remove waste products .
• To reabsorb nutrients , acids, trace elements and
  water as required .
• To work together with the Endocrine and cardio
  vascular and digestive systems in the regulation
  of fluids , blood cells , electrolytes , minerals
  and hormones in the body .

3
The anatomy consists of

• Two kidneys.
• Two ureters
• 1 bladder
• 1 urethra

4
The kidneys

• 1.The kidneys are surrounded by an outer fibrous
  renal capsule .
• 2. Underneath this is found the cortex in which
  is found visceral connective tissue , blood
  vessels and capillaries.
• 3. Underneath this is found the medulla ,
  containing the renal pyramids with arcuate
  arteries and veins and interlobular vessels .
• 4. Within the pyramids are located the nephrons
  or filtering units .
• 5. At the base of the pyramids are located the
  minor and major calyxes. These are part of the
• renal pelvis , which eventually gives way
  to the ureter.
• 6. The pelvis is found in an area of the kidney
  known as the hilus where the ureters , renal vein
  and arteries enter and exit .

5
The Nephron
Within each pyramid are found thousands of
nephrons. Each one with its own set of convoluted
tubules. 1 Proximal tubule 2.Loop of Henle
3. Distal tubule 4. Collecting duct. These
structures are surrounded by capillaries. At the
top end, the distal tubule divides to form the
Bowmans Capsule. Which houses The Glomerulus , a
collection of specialised capillaries which
filter the blood.
6
The Glomerulus

• The Glomerulus is fed by an arteriole, bringing
  blood to be filtered under pressure into the
  Bowmans capsule from where it passes into the
  proximal tubule .
• The capillaries have special cells which are
  called podocytes, they look as if they have legs
  which pass around the vessel , assisting in the
  filtration process.
• Large molecules and blood cells will remain in
  the blood stream .
• The glomerulus is unusual as it is both fed and
  drained by an arteriole

7
Formation of Urine

• This takes place in three phases
• 1.Simple Filtration
• Blood is filtered under pressure through the
  glomerulus into the
• bowmans capsule and proximal renal tubule .
• This will be a mixture of water, sodium ,
  potassium ,acids
• bicarbonate and urea. Components staying in
  the glomerulus include
• plasma proteins , corpuscles and other large
  molecules
• 2. Selective re absorption
• As the filtrate passes on and into the loop
  of Henle and distal renal tubule , the filtrate
  will be altered by hormonal messages , osmotic
  pressure and feed back systems connected to the
  endocrine , cardio vascular and respiratory
  systems .
• 3. Secretion
• At the collecting tubule end , the resultant
  urine will pass down and into the renal pelvis
  before eventually descending with the assistance
  of peristaltic action into the bladder

8
Urine
WATER 96
UREA 2
URIC ACID
CREATINE
AMMONIA
SODIUM
POTASSIUM 2
CHLORIDES
PHOSPHATES
SULPHATES
OXALATES
9
URETERS , BLADDER , URETHRA

• The ureters are long three layer muscular tubes
  which convey the urine from the kidney and to the
  bladder.
• The bladder is described as a pear shaped organ .
  The peritoneum covers the superior surface and
  posteriorly it is surrounded by the uterus in the
  female and the rectum in the male . It has three
  layers , the outer is loose connective tissue and
  the middle is smooth muscle and elastic fibres.
• The innermost layer is transitional
  epithelium .It can contain from 300mls to 800mls
  of urine .
• When the bladder is empty it forms into
  folds called ruggae and when full takes on a
  smooth appearance .
• The three orifices form a triangle called
  the trigone .
• The lower orifice leads into the urethra
  and the internal sphincter which is not under
  conscious control.

10
THE MALE AND FEMALE PELVIC CAVITIES

• The Urethra is a canal which extends from the
  bladder to the outside . In women it is around 4
  inches long and in men it extends through the
  penis, surrounded by the prostate gland and the
  erectile tissues . The external orifice is
  guarded by another sphincter muscle which is
  under conscious control .

11
SOME DISEASES AND DISORDERS
Cystitis This is inflammation of the bladder,
which causes pain when urinating . This is
usually as a result of an infection . It is more
common in women than men where the urethra is
far shorter and closer to the other orifices . It
can be very debilitating and reoccur. Nephritis
or Brights disease This is inflammation of the
filtration units of the kidneys, where it
includes the glomerulus it is known as Glomerula
nephritis. This can become a very troublesome
disorder and again very painful with pain
radiating out and around to the groin and lower
abdominal areas. Both the above are aided by
hydration . Kidney stones This is caused by
oxalates and calcium deposits which form over a
period of time within the kidney , renal pelvis
and bladder . These can be extremely painful if
passed and attempts to dissolve them en situ are
far more preferable. Diabetes Insipidus This
is caused by lack of ADH and leads to very
frequent urination , leading to a build up of
toxins in the body . Cancer It is worth noting
that cancers of the bladder and kidneys can often
be secondary to prostate cancer .