Excretory Products and their Elimination Flashcards
Main function of the excretory system
Elimination of nitrogenous waste products
Types of nitrogen excretion
- Ammonotelism
- Ureotilism
- Uricotelism
Ammonotelism
- Ammonia is formed as the result of deamination of amino acids
- Simplest form of nitrogenous waste and excreted from body surfaces or gill surfaces
- Ammoniotelic organisms- aquatic invertebrates, freshwater fish, aquatic amphibians
Ureotelism
- Excretion of urea and uric acid as nitrogenous waste
- Ammonia metabolized is converted to urea, which is then sent to the liver. From the liver it is filtered out into the blood and excreted out by the kidneys.
- Ureotelic organisms- Mammals, aquatic reptiles, semi-aquatic amphibians
Uricotelism
- The main nitrogenous waste product is uric acid
- The white part of the faeces excreted by birds contains uric acid and urates
- Uricotelic organisms- Birds, terrestrial reptiles, snails and insects
Steps of urine formation
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
Ultrafiltration
- Takes place in Glomerular Filtration step of urine formation
- Blood with waste products reaches the kidneys at the Bowman’s capsule.
- The network of capillaries in the glomerulus acts as a mesh and filters blood constituents except proteins.
- This is known as ultrafiltration.
- The filtered plasma is known as Glomerular filtrate
How much blood is filtered
5 litres of blood in the body
How much blood circulates in the kidneys per minute?
1250 ml
Quantity of plasma in 1250 ml of blood
650 ml plasma
How much glomerular filtrate is produced from 650 ml of plasma?
125 ml
What is the composition of the glomerular filtrate?
H2O, Na+, H+, K+, Cl-, HCO3-, Glucose, Creatine, Amino acids, Urea and Uric acid
Amount of
1. Glomerular filtrate produced per day
2. Urine formed per day
- 180 litres of glomerular filtrate/day
- 1.5 litres of urine/day
Why is there such a drastic difference in the amount of urine formed per day and GFR formed per day?
- There are many useful substances that need to be sent back to the blood
- A concentrated hypertonic urine needs to be eliminated
Tubular reabsorption
Filtrate that moves out of the glomerulus contains essential substances that need to be sent back to the body through the blood.
This is done by selective reabsorption by the renal tubules.
what is reabsorbed
PCT
- Proximal convoluting tubule (70-80% of electrolytes and water)
- Reabsorption into the blood- H2O, Na+, K+, Glucose, amino acids, Cl-, HCO3-, Urea
what is reabsorbed
DCT
- Distal convoluting tubule
- Reabsorption into the blood H2O, Na+, Cl-
what is reabsorbed
Collecting duct
Reabsorption into the blood- H2O, Na+, HCO3-, Urea
Tubular secretion
Tubular secretion is the transfer of materials from the peritubular capillaries to the renal tubular lumen and occurs mainly by active transport and passive diffusion
what is secreted
PCT secretion
Secretion into the urine: H+, NH4, Urea, and Creatine
Loop of Henle secretion
Secretion into the urine: Urea
DCT secretion
Secretion into the urine: K+, H+, Drugs, antibiotics, anabolic steroids
Composition of urine
- Creatinine, ammonia, and uric acid: 0.2%
- Dissolved salts and other ions: 2.8%
- Urea: 2%
- Water: 95%
Countercurrent mechanism
Countercurrent mechanism in the kidneys is the process of using energy to generate an osmotic gradient that enables you to reabsorb water from the tubular fluid and produce concentrated urine
Renal calculi
The crystals of salts (calcium, uric acid) present in the urine solidify into insoluble stones
Excruciating pain when the stone gets stuck in the ureter
Treatment:
* Surgery
* Shock wave lithotropy which pulverizes the stone so that the fragments are small enough to be passed out in the urine
Glomerulonephritis
- Bright’s Disease
- Inflammation of the glomeruli in the nephrons of the kidney
- Glomerular membrane- highly permeable and it allows infiltration of blood and proteins
Symptoms
* Intense pain
* redness swelling and heat in the glomeruli of the nephrons
Uraemia
- Accumulation of urea in the blood
- Reduced glomerluar filtration
- develops after seven days of anuria- absence of urine
Renal failure
- Decrease or cessation of glomerular filtration
-
Acute renal failure- kidneys stop functioning abruptly
* Suppression of urine flow -
Chronic renal failure- progressive, irreversible decline of rate of glomerular filtration
* Persons suffering from CRF need dialysis and possibly a kidney transplant operation.
Effects of renal failure
Effects of renal failure
* Oedema- fluid retention
* Anaemia and osteomalacia- two main problems associated wwith renal failure
* Elevated blood potassium levels that can lead to cardiac arrest
Where is the fistula created furing haemo-dialysis?
A fistula is created between the radial artery/branchial artery and the cephalic vein for haemo-dialysis to be carried out
UTI
- Urinary tract infection
- Caused due to increased acidity of the urine and that region
- Acidity causes E. coli ( * underline) to multiply
- Intensity of UTI depends on the number of microorganisms and the region where is takes place
Symptoms
* Burning sensation while urinating
* Pain in the lower back
* Radiating pain
