The urinary system consists of the kidneys, ureters, bladder, and urethra. The kidneys filter the blood to remove wastes and produce urine. Each kidney contains over a million nephrons, the functional units of filtration. Within each nephron, blood is filtered by the glomerulus and waste products are removed through tubular reabsorption and secretion. The resulting urine is collected and stored in the bladder before exiting the body. The kidneys also regulate fluid balance and blood pressure through hormones like renin and erythropoietin.

2. Serves many crucial
functions relating to
homeostasis
And performs excretion of
wastes

3.  Blood is filtered to remove water and
small dissolved molecules
 Then nutrients are reabsorbed from the
filtrate
 Remaining water and dissolved wastes
are excreted

4.  Protonephridia= the first specialized excretory
structure that arose during evolution
 Still used by flatworms
› Regulates water balance
› Which consists of tubes that branch throughout the
body
 End in flame cells (single celled bulbs)
 Named for the cilia that extends into the bulb
 Water is filtered into the bulbs
› The continuously beating cilia conduct the fluid
through the tubes
› More waste is added and some nutrients are
reabsorbed
› Then it reaches a pore and leaves through diffusion

5. nucleus eyespot
flame tubule
cell
cilia
fluid
extended
pharynx
excretory
pores

6.  Earthworms, mollusks, and several others
have simple kidney like structures
(nephridia)
› Fluid fills the body cavity (coeluom) and
surrounds the organs collecting wastes
› Flows through the nephrostome that
reabsorbs salts and nurtients into the blood
› Leaves behind water and wastes that is
stored in a bladder area of the nephridium
 Then waste is excreted through the excretory
pores (an opening in the body wall)
› Each segment of an earthworm has its own
nephridia

7. coelom nephridia
(contains
coelomic fluid)
intestine
excretory pore
ventral nerve cord nephrostome

8.  Excretory systems must eliminate dissolved
wastes without losing too much water in the
process
› Water may also still contain nutrients
 Kidneys collect and absorb extra nutrients
from blood and other bodily fluids
› At the same time wastes and dangerous
chemicals, to be excreted, are also filtered out

9.  Regulating blood levels of ions such as
sodium, potassium, chloride, and calcium
 Regulates water content of blood
 Maintains pH of blood
 Retains nutrients like glucose and amino acids
 Secretes hormones such as erythropoietin
which stimulates red cell production
 Eliminates cellular waste such as urea

10.  Urea
is a product of amino acid
metabolism
› Digestive system breaks proteins into
amino acids
 Those are absorbed
 Some used for new proteins
 Others lose their amino groups (-NH2) and used for
energy or to synthesize new molecules
 The amino groups are released as ammonia
(NH3) which is toxic
 This travels in blood to the liver where it is
converted to urea (far less toxic)

11.  The Urea is then filtered from the blood by the
kidneys
› Excreted in urine (fluid containing water, dissolved
wastes, and excess nutrients)
 Mammals avoid ammonia’s dilapidating
effects by excreting it in water
› But then we lose water
› Reptiles excrete it in uric acid with little loss of
water

12. amino acid
R O
NH2 CH C
OH
1 In cells, amino acids are broken
into simpler molecules, releasing
ammonia.
ammonia
(NH3)
carried
in
blood
2 In the liver, ammonia is combined
with CO2 to produce urea.
urea
NH2 C NH2
O carried
in
blood
3 In the kidneys, urea and other
water soluble wastes are
converted into urine.
excreted
in
urine

14. The Urinary System Consists of the:
 Kidneys- paired organs located on either side of the spinal column
and extending slightly above the waist where blood carrying
cellular waste enters to be filtered.
 Renal Artery- The artery which blood enters each kidney.
 Renal Vein- The vein which blood exits each kidney.
 Ureter- Muscular tube through which urine leaves each kidney to
reach the bladder.
 Bladder- Hollow, muscular chamber which collects and stores urine.
› Muscles contained in the walls of the bladder are capable of considerable
expansion.
Urine is retained in the bladder by two sphincter muscles located at
its base.
 Urethra- Through this narrow tube, urine exits the body. 1.5 inches
long in females and 8 inches long in males.

15. Urinary System
Renal Artery/Vein

16. Structure of the Kidneys:
 Each kidney contains a sold
outer layer where urine is
formed, which consists of
the renal cortex overlying
the renal medulla, and a
subdivided inner chamber
called the renal pelvis, that
collects urine and funnels it
into the ureter.
 More the one million tiny,
Individual filters called
Nephrons are pack into the
Outer layer of each kidney.

17.  The three major parts of the nephron are the glomerulus, the
tubule, and the collecting ducts.
 With the help of these three structures. Each individual nephron is
able to filter the blood and produce urine to be excreted.

18. GLOMERULUS:
 Within a cup-shaped portion of the nephron- Bowman’s Capsule-
the arteriole, which supplies each nephron with blood and branches
from the renal artery, branches further into the microscopic
capillaries that intertwine in a mass called the glomerulus.
 Within its water permeable walls, pressure is created through
difference in diameter between the larger incoming arteriole and
the smaller outgoing arteriole. This process is termed filtration, and
the resulting fluid is called filtrate. This fluid
collects into the Bowman’s Capsule and
through the nephron.
 Blood after passing through the
glomerulus is more concentrated.

19. Tubule:
 Through the processes of tubular reabsorption, which occurs
primarily in the proximal tubule and tubular secretion, which occurs
primarily in the distal tubule, the tubule of the nephron will restore
needed nutrients and most of the water to the blood to the filtrate in
the Bowman’s Capsule. This will be done while retaining wastes for
elimination, maintaining a balance required for homeostasis.

20. Loop of Henle/Collecting Ducts:
 Urine can become concentrated because there is an osmotic
concentration gradient of salts and urea in the interstitial fluid that
surrounds the loop of Henle and the collecting ducts.
 As filtrate passes through this area, additional water may leave the
filtrate through walls of the collecting ducts, while wastes are left
behind. This filtrate, as is passes through the ducts, is now called
urine.
 It is important to produce concentrated urine when water is scarce,
and to produce dilute, watery urine when there is excess water in
the blood. All this depends on the permeability of the collecting
duct to water, which is, in turn, controlled by the amount of
antidiuretic hormone.

21. Loop of Henle

22.  Disorders of this system include:
› Gout, also known as gouty arthritis, is incredibly common and
painful. People with gout usually first experience pain in the joint
of the big toe.
› A kidney stone, also known as a renal calculus is a solid
concretion or crystal aggregation formed in the kidneys from
dietary minerals in the urine.
› Pyelonephritis is an ascending urinary tract infection that has
reached the pyelum or pelvis of the kidney. It can lead to kidney
failure and death.

23.  The kidneys regulate the water content
of the blood
 Human kidneys filter out about half a
cup of fluid from blood each minute
 Without reabsorption of water, your body
would produce 50 gallons of urine daily
 The amount of water reabsorbed is
controlled by an antidiuretic hormone
(ADH)

26.  Kidneys produce two hormones that are
essential to regulating blood
 When blood pressure fails, the kidneys
release renin into the bloodstream
› Renin is an enzyme that speeds up the
formation of the second hormone,
angiotensin
› Angiotensin is a protein that causes arteries
to constrict, raising blood pressure

27.  In response to low oxygen levels, the
kidneys release erythropoietin
 Erythropoietin travels to the bone
marrow, where the marrow is
stimulated to produce more red
blood cells
 Kidney failure leads to anemia
, because the kidneys do not produce
enough erythropoietin to make the
minimal number of red blood cells

28.  Different types of mammals have
different kidney structures depending on
the availability of water in their habitat
 The longer the Henle, the more
concentrated the urine is, which means
more water is conserved
 A loop of Henle is what recycles water,
the longer the loop, the less diluted the
urine is

29.  http://www.youtube.com/watch?v=guO
qyi5lUQQ