Excretion system of urea in human revise by Ahmed Ghdhban Alziaydi

2. Excretory System
The kidneys regulate the amount of water, salts
and other substances in the blood.
The kidneys are fist-sized, bean shaped
structures that remove nitrogenous wastes
(urine) and excess salts from the blood.
The ureters are tubes that carry urine from the
pelvis of the kidneys to the urinary bladder.
The urinary bladder temporarily stores urine
until it is released from the body.
The urethra is the tube that carries urine from
the urinary bladder to the outside of the body.
The outer end of the urethra is controlled by a
circular muscle called a sphincter.

3. How blood is Filtered
The filtering units of the kidneys are the nephrons.
There are approximately one million nephrons in
each kidney.
The nephrons are located within the cortex and
medulla of each kidney.
The tubes of the nephron are surrounded by cells
and a network of blood vessels spreads throughout
the tissue. Therefore, material that leaves the
nephron enters the surrounding cells and returns to
the bloodstream by a network of vessels.

4. Function of the Kidney
The principal function of the kidney is
to filter blood in order to remove
cellular waste products from the body.
2. They regulate the concentrations of
substances found in body fluids

5. The kidney has other functions but it
is usually associated with the
excretion of cellular waste such as :
1) urea (a nitrogenous waste
produced in the liver from the
breakdown of protein. It is the main
component of urine) ;
Function of Excretory System
1. Filtration and excretion of metabolic wastes
2. The regulation of blood content.
3. The regulation of blood pH.
4. Homeostasis.

6. Function of urinary system
• Excretion
• Keeping homeostasis
• Keeping acid-base balance
• Secretion (rennin,, erytropoetin)
Excreted products:
• Product of the metabolism
• Water
• Hormones
• Vitamins
• Toxic substances

7. Kidney function
• Step 1: Filtration
• Step 2: Reabsorption
• Step 3: Secretion
• Step 4: Excretion.

8. Filtration
• During filtration, substances pass
from the blood into the Bowman’s
capsule.
• Under pressure, water and many
small molecules such as salts, urea,
glucose and aminoacids pass from
glomerulus into Bowman’s capsule.

9. Reabsorbtion
• The absorbtion of needed materials
such as glucose, amino acids and water
from nephrons to blood capillaries is
called reabsorbtion.
• Water is reabsorbed passively by
osmosis. But reabsorbtion of glucose,
aminoacids and salt ions occurs by
active transport.

10. • The cells of distal tubule excrete molecules such as
penicilin, ammonia, potassium and excess acids. This
process is called secretion.
• After secretion, the fluid remaining in the nephrons is
called urine.
• Urine contains urea, uric acid, sodium, potassium,
calcium, chlorine, phosphorus, water and small amount
of cells.

11. Excretion
Excretion is the removal of metabolic waste from
the cells. Metabolic waste is the unwanted material
that is formed as a result of the bodies metabolism.
That is the large number of chemical reactions that
occur in the cells, tissues and organs. The waste
products of metabolism are frequently toxic and so
must be removed from the body.
Excretory Substances
The metabolic wastes of cells are;
WATER, CO2, NITROGENOUS COMPOUNDS

12. NITROGENOUS WASTES
•At the end of the catobolisation of aminoacids,
AMMONIA(NH3) is formed.
•In some organisms, ammonia is removed from
body directly.
•But in some organisms ammonia is converted to
other substances such as UREA and URIC ACID.

13. Deamination and Urea Synthesis
In the liver deamination is the process which
breaks down excess amino acids in to ammonia
and keto acids. Ammonia is still very toxic so it
is converted to urea by the process called urea
synthesis. Urea is less toxic than ammonia and so
can travel in the blood, but it must be got rid of
quickly because it can still have ill effects. Urea
is then transported by the blood from the liver to
the Kidneys where it forms part of urine.

14. Ammonia reacts with CO2 in the liver to produce
UREA:
2 NH3 + CO2
+ H2O

16. Catabolism of proteins and nucleic acids results in formation of
so called nonprotein nitrogenous compounds.
Protein
 Proteolysis, principally enzymatic
Amino acids
 Transamination and oxidative deamination
Ammonia
 Enzymatic synthesis in the “urea cycle”
Urea

17. PARTS OF HUMAN EXCRETORY SYSTEM
1. Kidneys
2. Ureter
3. Urinary bladder
4. Urethra

18. The urinary
system
Kidney
Ureter
Aorta
Renal vein
Bladder
Renal artery
Vena cava
Urethra
© 2008 Paul Billiet ODWS

19. The Kidney
Cortex
Medulla
Calyx
Pelvis
Ureter
PapillaPyramid
Column

20. The nephron
Bowman’s capsule
Glomerulus
Proximal
convoluted tubule
Capillary
Loop of Henlé
Collecting duct
Distil convoluted
tubule
Branch of renal
vein
Branch of renal
artery
© 2008 Paul Billiet ODWS

21. Key functions of the nephron

22. Functions of the Nephron
Filtration
Reabsorption Secretion
Excretion

23. URINARY BLADDER
 Stores urine

24. URETHRA
 Tube that carries urine
from the bladder to the
outside of the body

26.  Reabsorption stage:
 water, minerals,
amino acids and
glucose are
reabsorbed by active
transport from the
renal tubule into the
capillaries

27. Filtration in the glomerulus
 Blood enters the glomerulus
from a branch of the renal
artery
 This blood is under high
pressure
 The capillary walls are one
cell thick
 The plasma filters though
the membrane under
pressure
 Proteins do not pass Southern Illinois School of Medicine
© 2008 Paul Billiet ODWS

28. Filtration in the glomerulus
 A membrane surrounds
each capillary of the
glomerulus
 The blood plasma is
filtered at about 150 litres
per day
Southern Illinois School of Medicine
© 2008 Paul Billiet ODWS

31.  The remaining material is
urine which contains water,
salt and urea

32. Excretory System Problems
• Kidney stones – crystalized mineral salts and uric
acid salts in the urine. Stones block flow of urine and
cause excruciating pain.
• Kidney failure - can be caused by long-term diabetes,
infections, physical injuries, chemical poisoning.
Causes toxic materials to build up to lethal levels.
Dialysis or kidney transplant is the treatment.

33. Effects of Aging upon Urinary System
• Reduced blood supply to kidneys – less filtering of
blood.
• On top of that, the kidney become less efficient
with respect to the filtering process.
• Poorer salt-water/pH balance – dehydration more
evident in the elderly.
• Bladder control adversely affected.
• In men, the prostate may enlarge and apply
pressure to the urethra making urination difficult
(surgery required).

34. Excretory System
UTI (Urinary Tract Infection)
• Is a very common disorder. If the bladder has
become infected, it is known as cystitis. If the
urethra is infected., it is called urethritis.
• Symptoms include painful urination burning
sensation), frequent urination (even if no urine
present) and bloody or brown urine.
• This can lead to chills, fever, nausea, vomiting and
upper abdomen tenderness.
Disorders of the Excretory System

35. Renal function tests
 Detect renal damage
 Monitor functional damage
 Help determine etiology

36.  glomerular filtration
rate (GFR)
 plasma creatinine
 plasma urea
 urine volume
 urine urea
 minerals in urine
 urine protein
 urine glucose
 hematuria
 osmolality
Laboratory tests of renal function

37. Biochemical Tests of Renal Function
 Measurement of GFR
 Clearance tests
 Plasma creatinine
 Urea, uric acid and β2-microglobulin
 Renal tubular function tests
 Osmolality measurements
 Specific proteinurea
 Glycouria
 Aminoaciduria
 Urinalysis
 Appearance
 Specific gravity and osmolality
 pH
 osmolality
 Glucose
 Protein
 Urinary sediments

38. Why Test Renal Function?
 To identify renal dysfunction.
 To diagnose renal disease.
 To monitor disease progress.
 To monitor response to treatment.
 To assess changes in function that may impact on
therapy (e.g. Digoxin, chemotherapy).

39. When should you assess renal
function?
 Older age
 Family history of Chronic Kidney disease (CKD)
 Decreased renal mass
 Low birth weight
 Diabetes Mellitus (DM)
 Hypertension (HTN)
 Autoimmune disease
 Systemic infections
 Urinary tract infections (UTI)
 Nephrolithiasis
 Obstruction to the lower urinary tract
 Drug toxicity

40.  Studies about Urea Excretion in human

47. References:
1- Cotran, RS S.; Kumar, Vinay; Fausto, Nelson; Robbins, Stanley L.; Abbas,
Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis,
MO: Elsevier Saunders. ISBN 0-7216-0187-1.
2- Glodny B, Unterholzner V, Taferner B, et al. (2009). "Normal kidney size
and its influencing factors - a 64-slice MDCT study of 1.040 asymptomatic
patients". BMC Urology 9: 19. doi:10.1186/1471-2490-9-19. PMC 2813848.
PMID 20030823.
3- Bålens ytanatomy (Superficial anatomy of the trunk). Anca Dragomir, Mats
Hjortberg and Godfried M. Romans. Section for human anatomy at the
Department of medical biology, Uppsala university, Sweden.
4- Walter F. Boron (2004). Medical Physiology: A Cellular And Molecular
Approach. Elsevier/Saunders. ISBN 1-4160-2328-3.
5- Clapp, WL. "Renal Anatomy". In: Zhou XJ, Laszik Z, Nadasdy T, D'Agati
VD, Silva FG, eds. Silva's Diagnostic Renal Pathology. New York: Cambridge
University Press; 2009.

48. धन्यवाद