The urinary system consists of the kidneys, ureters, bladder, and urethra, with the kidneys filtering waste from the bloodstream to produce urine, which travels through the ureters to the bladder for storage and then exits the body through the urethra. The kidneys remove excess water, salts, and urea from the bloodstream, with the renal arteries carrying blood into the kidneys and the renal veins carrying blood away from the kidneys back to the heart. Damage to the kidneys can result in renal disease, which can be acute from trauma or chronic over a long period of time.

1. The Urinary System

2. The Urinary System
• The Urinary System consists of
– The kidneys (and blood vessels entering and
leaving them)
– The ureters
– The bladder
– The urethra

5. • Renal Arteries
– Carries blood into the kidneys. This blood
contains excess water and salts, along with urea
which was made in the liver
• Kidneys
– Removes excess water, salts and urea from the
blood. These compounds combine to form urine
• Renal Veins
– Takes blood away from the kidneys back to the
heart. This blood contains no waste material

6. • Ureters
– Tubes which carry urine from the kidney to the
bladder
• Bladder
– Stores the urine until it can be released from the
body
• Urethra
– The tube which takes urine from the bladder and
out of the body

7. OB20 understand the structure and function of the urinary system:
bladder, renal artery, renal vein, ureter, urethra and kidney
renal vein
renal
artery
ney
kid
ureter
bladder
urethra
urethra

8. OB20 understand the structure and function of the urinary system:
bladder, renal artery, renal vein, ureter, urethra and kidney
renal artery carries blood to kidney
renal vein carries blood from kidney
kidney filters blood to remove urea
ureter transports urine to bladder
bladder
bladder stores urine
urethra releases urine
urethra

9. Match the following parts of the Urinary system
with their function:
A. Renal 1. releases urine
vein
B. Ureter 2. carries blood to kidney
C. Bladder 3. filters blood to remove urea
D. Kidney 4. transports urine to bladder
E. Urethra 5. stores urine
F. Renal 6. carries blood from kidney
artery

10. The Kidney

11. 1. Blood containing water, salts and urea enters
the kidney
2. Urea, some salts and water are removed from
bloodstream by kidney and form urine
3. Urine leaves the kidney in the ureter

12. OB23 recall that waste products are removed from the bloodstream by
filtration in the kidneys in the form of urine, which contains urea,
water and salts
water
2
salt
urea, some salts and water
urea
are removed from
bloodstream by kidney and
1 form urine
blood containing
water, salts and urea
enters the kidney
3
the urine leaves the
kidney in the ureter

13. Rewrite the following stages of filtration in the kidneys
in the order that they occur in the body:
A. the urine leaves the kidney in the ureter
B. urea, some salts and water are removed from bloodstream by
kidney and form urine
C. blood containing water, salts and urea enters the kidney

14. OB23 urine is stored in the bladder before being released from the body
urethra

16.  A section through the kidney shows an outer darker region
(cortex) and a lighter inner zone (medulla).
Cortex
Pelvis
Medulla
Ureter

17. LEARNING CHECK
– Identify Cortex, Medulla, Pelvis, Ureter
D
A
B
C
A = Cortex B = Medulla C = Ureter D = Pelvis

18.  The kidneys work by filtering the blood and then absorbing
back what the body needs to keep. The wastes are allowed
pass to the bladder, for storage and release.
Filtration
Pelvis Cortex
Reabsorption
Medulla
Ureter
 As urine is produced, it flows into the renal pelvis, then into the
ureter, to the bladder.

19.  Filtration—In the outer cortex,
small molecules like glucose,
amino acids, water, urea and
salts filter out of the blood into
narrow tubules.
 Reabsorption—blood vessels
reabsorb back useful nutrients
from the tubules. Urea, excess
salts and water, are allowed to
continue down the tubule and
on to the bladder.

20.  Secretion is the production and release of chemicals
from cells.
 Some substances, especially potassium and hydrogen
ions, are secreted from the blood into the tubule in the
cortex region.
 When the blood becomes too acidic, hydrogen ions
are secreted into the urine.
 By controlling the hydrogen ion concentration in the
blood, the kidneys control blood pH.

21. Homeostasis – Water Levels in the
Body
 Land animals have a continuous need to conserve water.
 Water must be taken in daily and its loss must be carefully
regulated.
 Water is taken in as food and drink, and is also formed
inside the cells during some reactions, especially
respiration.
 Water is lost from the body through our lungs, skin,
intestines and kidneys.

22. Water is lost from the body through a number of ways:
 Lungs – some water gets evaporated as we exhale from our
warm, damp lungs.
 Skin – by evaporation from cells and through sweat.
 Intestines – in the faeces (undigested food).
 Kidneys – in dissolving the poisons and wastes we wish to
excrete from the body.

23.  We have no control
over the amount of
water lost each day
from the lungs, skin or
intestines.
 So the kidneys are
the water control
(osmoregulatory)
organs of the body –
conserving or
eliminating water as
the body requires.

24. Renal Disease
• Due to damage of the kidneys
• 2 kinds
– Acute
• Caused by trauma, severe dehydration or circulatory failure
• Signs include vomiting, Urea in blood, Lethargy and Diarrhoea
• Treatment involves fluid therapy and dialysis
– Chronic
• Caused abnormalities in the kidney or metabolic disorders
• Occurs over a long period of time. Signs are same as Acute
• Treatment in involves solving the original cause