Defect/Diseases of Excretory System

Defect/Diseases of Excretory System

Phenylketonuria : It is a genetic or metabolic error disease in which no metabolism of phenylalanine takes place in the body and that comes out with urine.

Alkaptonuria : Due to deficiency of enzyme homogentisic acid oxidase, the homogentisic acid is not metabolised and comes out with urine.  In contact with air this turns black hence the color of urine becomes black.  It is a kind of genetic disease.

Bright’s disease (Nephritis) Inflammation of kidney (Glomerulo-nephritis)

Cystitis : Inflammation of urinary bladder.

Casts : Nephrons are lined with calcareous substances called as casts. These are also excreted along with urine.

Diuresis : Passing of excess urine

Enuresis : Bed-wetting

Anuria : The failure of kidney to form urine

Dysuria :  Painful urination

Glycosuria : Presence of sugar in urine.  A pathological glycosuria results from diabetes mellitus.

Haematuria : Presence of RBCs or blood in urine.

Urethritis : Lining of urethra undergoes inflammation by the infection of bacteria like gonococeus. It causes severe painful urination.

Polyuria : Excessive frequency of urination

Pyuria : WBCs or pus in the urine.

Oliguria : Scanty urination

Uremia : High blood urea level due to kidney failure

Ketosis : Presence of ketone or acetone bodies (aceto-acetic acid, b-hydroxybutyric acid and acetone) in urine (Acetonuria)

Kidney stone :  (Renal calculi) Crystallized chemicals like uric acid, calcium oxalate and calcium phosphate form stones in kidney, it causes pain called renal colic.

Micturition : Act of passing urine.

Polydipsia : Excessive thirst.

Nocturia : is a disease in which volume of urine rises so much at night that the person is compelled to wake upto ease out.

Dialysis or Artificial Kidney :

Dialysis is the process of separation of molecules like urea, uric acid, creatinine, phosphate and sulphate from the blood.  Blood is flown through a machine (dialyser) in which cellophane

membrane bag is placed in a dialyser fluid which contains small molecules as solute.  Blood passes through this and the above said waste molecule diffuse out into the dialyser fluid from the blood. The useful substances do not move out of blood since these remain in the dialyser fluid in equal concentration.

Blood is mixed with heparin, to prevent clotting, temperature is maintained through thermostat and flow pressure is maintained by pump.

POINTS TO REMEMBER

Renal threshold of a substance is its highest concentration in the blood upto which it is totally reabsorbed from glomerular filterate.

Nephrectomy – Surgical removal of nephrons.

Main aim of excretion is to keep a constant internal composition called homeostasis.

Organisms without any excretory system are mostly ammonotelic.

Kidney is mesodermal in origin.

The inward directed concavity of kidney is called hilus or hilum.

Ultra filteration is entirely a passive process.

Urate cells are present in fat bodies of insects and accumulate nitrogenous wastes which stay there for the whole life of organism.

Water is a waste product of metabolism. It must be excreted out to avoid a serious condition of oedema.

In humans if blood urea content rises above 0.05%, then uremia develops. Elasmobranch fishes can retain 2.0-2.5% of urea in their blood for osmotic regulation.

Wall of pelvis contains smooth muscles and is lined with transitional epithelium. Peristalsis of smooth muscles originating in pacemaker cells in the wall of calyces propel the urine through pelvis and ureters to the urinary bladder.

Collecting tubules open into collecting ducts and the same joins to form larger ducts of Bellini. It opens at papillae of renal pyramids which pass urine to calyses  and calyses into pelvis.

Urology is the science which deals with study of urinary tract. Nephrology is the study of kidneys & diseases which affect than.

Cockroach doesn’t drink water. Malpighian tubules pour water into alimentary canal.

Urine formed has both filtered substances as well as secreted substances.

Moderately active man consuming about 300 gm of carbobohydrates, 100 gm of fats and 100 gm of proteins must excrete 16.5 gm of nitrogen daily. 95% of it is eliminated by kidneys in

the form of urea and remaining 5% is eliminated through faeces.

Humans have maximum urate concentration (very near to gout formation) amongst primates. Its selective advantage is that urate is a strong antioxidant which is a very good scavenger of

reactive oxygen, just similar to vitamin C.

pH of urine is 4.5-8.2, average is 6.0. Urine is acidic but becomes alkaline on standing. Urea is changed to ammonia by environmental bacteria and gives characteristic smell.

Visceral layer of Bowman’s capsule is made up of podocytes and parietal layer is made up of squamous epithelial cells. PCT has cuboidal epithelium bearing brush border of microvilli

LOH has cuboidal epithelium with less microvilli and few mitochondria. Presence of very few cell organelles indicate a passive rather than active role in ionic movements. DCT is lined by cuboidal cells that have few small & irregularly spaced microvilli (no brush border) Crocodiles excrete uric acid on land and ammonia in water. Lung fishes excrete urea on land and ammonia in water. Tadpole of frog excretes ammonia whereas adult frog excretes urea.

Xenopus continues to excrete ammonia. Earthworm excrete urea during starvation and ammonia when plenty of water is available.

Human urine has highest concentration of salt 6 g/L. Sea water has 12g/L.

Glomerular filteration is called ultrafilteration because it filters out molecules which are much smaller than particles that are separated by filters such as filter paper. The actual filter is

basement membrane of endothelium of glomerular capillaries.

In PCT filterate is ISOTONIC to plasma. In D-LOH it becomes HYPERTONIC and in A-LOH it becomes HYPOTONIC to blood plasma. In DCT it again becomes ISOTONIC to plasma.

In collecting tubules & duct it becomes HYPERTONIC. Finally the urine which is passed out is HYPERTONIC to plasma.

Chloragogen cells (yellow cells) are additional excretory structures in earthworm, these are analogous to liver of higher vertebrates. Contractile vacoule of protozoansis analogous to kidney of higher animals.

Urinary bladder is absent in snakes, crocodiles and birds (except ostrich and Rhea).

Largest number of sweat glands in man are found on palms.

Sonoram desert toad is Bufo-alvarius. Water holding frog from South Australia is cyclorana platycephala.

Hormone erythropoietin is normally produced by peritubular capillary epithelion of kidneys in adults, and by liver in new borns in response to low oxygen tension in blood.

Erythropoietin (EPO) is a glycoprotein hormone and is responsible for RBC production. It is also Erythrogenin or Renal Erythropoietic factor (REF).

Kidneys not only remove waste products from blood but also play a very important role in maintaining constant composition of blood irrespective of nature of food or fluids intake.

Haematuria is presence of blood in urine. Uraemia is high concentration of urea in blood. In jaundice bile pigments appear in urine.

Insoluble calcium phosphate is eliminated by large intestine.

Excretion is required for maintaining homeostasis of body fluids through regulation of their volume, composition, pH and osmotic potential.

Term urine can be first used in collecting tubules.

Blood entering the kidney has more sugar than blood leaving the kidney because sugar is used by kidney cells during metabolism.

Excretory products of mammalian embryo are eliminated through placenta.

Workers in deep mines usually suffer from dehydration because water is lost along with salts in the form of sweat.

Hepatic vein has maximum amount of urea and renal vein has minimum amount.

Trimethylamine is the excretory product in marine teleosts. Elasmobranch fishes can retain large amount of urea in their blood.

Kidney stones are produced due to crytallization of oxalates.

Urine of a person suffering from diabetes insipidus is watery and tasteless.

Glomerular filterate contains less glucose than plasma because some amount of glucose is utilized by cells of Bowman’s capsule.

Sea Gulls excrete salt through nasal glands. Aquatic reptiles are ureotelic.

Concentration of urine in organisms depends on length of LOH. If LOH is absent then urine will be Hypotonic. Birds and mammals have longer LOH for producing hypertonic urine.

Normal range of urea in 100 ml of human blood is 17-30 mg.

Gravidex test – Presence of human chorionic gonadotroopic hormone in the urine which shows the pregnancy.

Hepatic vein has highest concentration of urea, whereas renal vein has least concentration urea.

Euryhaline – Organism that can tolerate a wide range of salinity.

Stenohaline – Organism that can tolerate a narrow range of salinity.

Echinodermata : Excretory Organs absent (But contains nephrocytes, rectale caeca, amebocytes etc.)

Hemichordata : Contains single glomarulus found in proboscis gland e.g. Balanoglossus

Protochordata : Excretion by neural gland e.g. Herdmania

Cephalochordata : Solenocytes / flame cells amphioxus

In male frog bidders canal present concern with passage of sperms from testis

In marine reptiles birds possess salt glands and they are generally nasal gland

Sea turtles have lacrimal or tear glands for salt excretion

Brackish water crocodiles have salt glands in the tongue region

In marine bony fish must continuously acquire water and get rid off salt

Nephridium of earthworm drains material directly from the celom

Malpighian tubules of insects remove nitrogenous waste from the haemocoel and function in osmoregulation

In rotifers excretion occur by protonephridia

Gill epithelia of marine teleosts possess ionocytes or chloride cells that actively excrete Na+, Cl–, K+.