15. Excretion and Osmoregulation part 04 - Role of other organs in excretion, Disorders and diseases

Role of other organs in excretion :
Skin :

Skin of many organisms is thin and permeable.
It helps in diffusion of waste products like ammonia.
Human skin is thick and impermeable. It shows presence of two types of glands namely,

Sweat glands

are distributed all over the skin.
They are abundant in palm and facial regions.
These simple, unbranched, coiled, tubular, glands open on the surface of skin through an opening called sweat pore.
Sweat is primarily produced for thermoregulation
It also excretes substances like water, NaCl, lactic acid and urea.

Sebaceous glands :

Lungs :

Lungs are the respiratory organs.
They help in excretion of volatile substances like CO2 and water vapour produced during cellular respiration.
They also excrete volatile substances present in spices and other food stuff.

Disorders and diseases :

Excessive albumin in urine (albuminuria) indicates injury to endothelial capsular membrane as a result of increased blood pressure, injury or irritation of kidney cells by substances such as toxins or heavy metals.
Presence of excessive quantities of ketone bodies in urine may be caused due to diabetes mellitus, starvation or too little carbohydrates in diet.
Presence of leucocytes in urine indicate possibility of infection of kidney or other urinary organs.

1. Kidney stones :

These are also called renal calculi -
They may be formed in any portion of urinary tract-from kidney tubules to external opening.
Depending on composition they are classified into :

Calcium stones : Usually are calcium oxalate stones or calcium phosphate ones.
Struvite stones : These are formed in response to bacterial infection caused by urea splitting bacteria. These grow quickly and become quite large.
Uric acid stones : In people who don't drink enough water or consume high protein diet can suffer from this type of stones.
Cystine stones : It is a genetic disorder that causes kidney to excrete too much of certain amino acid.

Symptoms :

Diagnosis :

Uric acid content of blood, colour of urine, kidney X-ray, sonography of kidney are different diagnostic tests prescribed depending on symptoms.

2. Uremia :

Blood normally contains 0.01 to 0.03% urea; but if it rises above 0.05%, it is called uremia.
It is harmful and may lead to kidney failure.

3. Nephritis :

It is inflammation of kidenys characterised by proteinuria caused due to increased permeability of glomerular capsular membrane, permitting large amounts of proteins to escape from blood to urine.
This lead to change in blood colloidal osmotic pressure, leading to movement of fluid from blood to interstitial spaces.
It is reflected as edema.

4. Renal Failure :

It is decrease or cessation of glomerular filtration, is classified into two types.

a. Acute Renal failure (ARF) :

ARF is sudden worsening of renal function that most commonly happens after severe bleeding.
There is decrease in urine output (oligouria-scanty urine) (less than 400 ml/day or less than 0.5 ml/kg/h in children).
Other causes of ARF may include acute obstruction of both ureters or nephrotoxic drugs.
ARF can be detected biochemically by elevated erum creatinine level.

b. Chronic kidney disease (CKD) :

It is progressive and generally irreversible decline in glomerular filtration rate (GFR).
It may be caused due to chronic glomerulonephritis.
It can be detected by reduced kidney size and possibility of anaemia.

Haemodialysis :

When renal function falls below 5 to 7%, accumulation of harmful substances in blood begins.
In such a condition, the person has to go for artificial means of filtration of blood.
In haemodialysis, dialysis machine is used to filter blood.
In haemodialysis, blood is filtered outside the body using dialysis unit.
In this procedure, patients’ blood is removed; generally from radial artery.
It is passed through a cellophane tube that acts as a semipermeable membrane.
The tube is immersed in a fluid called dialysate.
Dialysate is isosmotic to normal blood plasma.
Hence only excess salts if present in plasma pass through the cellophane tube into the dialysate.
Waste substances being absent in the dialysate, move from blood into the dialyzing fluid.
Filtered blood is returned to vein.
In this process it is essential that anticoagulant like heparin is added to the blood while it passing through the tube and before resending it into the circulation, adequate amount of anti-heparin is mixed.
The blood has to move slowly through the tube and hence the process is slow.
Dialysis is regarded as a 'holding measure' until a renal transplant can be performed or sometimes as the only supportive measure in those for whom a transplant would be inappropriate.

Peritoneal dialysis :

In this method, the dialyzing fluid is introduced in abdominal cavity or peritoneal cavity.
The peritoneal membrane acts as semipermeable dialyzing membrane.
Toxic wastes and extra solutes pass into the fluid. This fluid is drained out after prescribed period of time.
Peritoneal dialysis can be repeated as per the need of the patient.
It can be carried out at home at work or while travelling. But it is not as efficient as haemodialysis.
Kidneys are associated with secretion of erythropoietin, renin and calcitriol which is not possible using dialysis machine.

5. Kidney transplant :

It is organ transplant of a healthy kidney into a patient with end stage renal disease.
Kidney transplantation is classified as cadaveric (deceased donor) or living donor kidney transplant.
Living donor kidney transplant are further classified as genetically related (living-related) or non-related (living non-related) transplants.

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