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toxic metabolic wastes

nitrogenous wastes


most toxic nitrogenous waste

ammonia, excreated out in forms of urea and uric acid


process of removal of nitrogenous wastes




Osmoconformers are animals that do not actively control The osmotic concentration of the body fluids. They change body Fluids according to the osmolarity of the surrounding medium.

Marine and freshwater invertebrates and vertebrate hagfish(myxine)



maintain an internal osmolarity, different from the surrounding medium that they inhabit by taking in or releasing fluids from their bodies with the expenditure of energy.

most aquatic vertebrates are strict osmoregulators except sharks and rays and hagfish


what is the osmolarity of fresh water and of freshwater organisms

50 mOsm per litre and 200-300 mOsm per litre


how do freshwater organisms combat loss of salts and entry of water from the environment

protozoa like amoeba and paramoecium have special contractile vacuoles that pump out excess water

other organisms have
scales of adipose
do not drink water
dilute urine
presence of ionocytes like chloride that can readily uptake salts


osmolarity of seawater

1000mOsm per litre


how do marine and bony fishes prevent water loss in a hypertonic environment

the fish
drink seawater
the cl cells of gill membranes help eliminate excess monovalent ions from body fluid to seawater and divalent cations are eliminated through faecal matter


name two osmolyte

urea and trimethylamine oxide.. they raise osmolarity of the body like in hagfish to make them isotonic to the environment, or slightly hyperosmotic like in sharks


percentage of water required to keep a human alive

at least 88% if they lose 12% of water, they die.


how do desert animals compensate for water loss

they can recover 90% water from metabolic water. once water is available,they rehydrate. example, a can drink 80L of water in 10 mins.


different classifications of animals based on their excretory products

ammonotelism: ammonia, requires large amounts of water to be excreted
found in many bony fishes, aquatic amphibians and aquatic insects such as amoeba,sponge,hydra,cray fish,bony fish and frog tadpole
excreted through diffusion from body surfaces or gills as ammonium ions

ureotelism:terrestrial adaptation, less toxic nitrogenous waste, as urea and uric acid for the conservation of water.urea can be tolerated more as it is 100000 times less toxic than ammonia
in mammals,land amphibians like adult frog and some marine fish

uricotelism:reptiles,birds,land snails,insects. uric acid excreted in form of pellets or gel paste. insolube in water.its important for organisms producing shelled eggs, as uric acid being insoluble precipitates with the egg shell only and doesn't enter the embryo and harm it.


the ornithine cycle step by step

aka kreb henseleit cycle, occurs in the liver
1. co2+ATP+NH3-> carbonyl phosphate
2.carbonyl phosphate+orthinine-> citrulline
3.citruline+aspartic acid->arginosuccinic acid
4.arginosuccinic acid->fumaric acid+arginine
5. Arginine+water->urea +orthinine
6. the orthinine generated is used in step 2


different excretory structures in different animals

vertebrates: tubular organs called kidneys

Platyhelminthes(like flatworms), rotifers, some annelids and cephalochordate amphioxus: protonephridia/flame cells mainly concerned with osmoregulation

annelids like earthworms: tubular nephridia which remove nitrogenous wastes and help keep an ionic and fluid balance.

insects like a cockroach: Malpighian tubules. help in the removal of wastes and osmoregulation

crustaceans like prawns: green glands/antennal glands


types of nitrogenous wastes

1. ammonia: most toxic protein metabolic waste requires a lot of water for its removal. produced in the lives by deamination
2.urea: white crystal solid produced by the liver, less toxic, made with CO2+ NH3
3.uric acid: produced in the liver, semisolid saves water. found in phosphate-rich bird droppings
4.:xanthines and guanines: nucleotide metabolism found in spiders and penguins
5. Trimethylamine oxide: specialised product in marine bony fishes
6.ornithuric acid: in birds
7.Hippuric acid: produced from benzoic acid in mammals
8.creatinine: from creatine phosphate present in muscles. increased levels indicate kidney damage.


urea level in blood

18-38mg/100 ml of blood


kidneys location

reddish-brown, bean-shaped at the last thoracic and 3 lumbar vertebrae,close to the inner wall of the abdominal cavity.
left kidney is a little higher than the right one due to the space being occupied by the liver on the right side. it is the opposite in other mammals.


weight of a kidney

120-170 gms


place on the kidney from where vessels, ureters and nerves emerge

hilum, at the inner concave notch


3 protective coverings of the kidney

1.renal fascia: outermost fibrous covering linking it with the abdominal wall. the kidneys are fused with the body wall on the dorsal side. the peritoneal cover is present on the ventral side, making it retroperitoneal arrangement

2. adipose capsule: middle covering involving adipose tissue and acts as a shock absorber

3.renal capsule: it is the innermost tough protective cover made up of white connective tissues, with a few elastic fibres and few muscles.


internal structure of the kidney

inner to the hilum is the broad funnel-shaped base called renal pelvis lined by transitional epithelium with projections called calyces
the outer layer is a tough capsule
there are two zones, the outer cortex and inner darker medulla. the medulla is divided into few conical masses called the medullary pyramids which project into the calyces.
the cortex that extends to the calyces and is in between the pyramids is called columns of Bertini


the renal pyramids

larger base towards the cortical side and apex called renal papilla towards the cavity. the papillae project into the cavity forming minor calyces which join to form major calyces.
medulla region has a higher osmotic concentration equal to 1200mOsm/L due to conc of NaCl and urea


cortex close to the medulla region

juxtamedullary area



pair of whitish distensible muscular tubes of 25-30 cm in length and 3mm in diameter


walls of ureter

adventitia, middle muscular and inner mucosa. the muscles are always undergoing peristalsis.
outer longitudinal, middle circular and inner longitudinal muscles of the muscular coat.


urinary bladder

median pyriform sac
the fully distended bladder becomes ovoid in shape
has three parts, apex fundus and neck
fundus has a triangular area called trigone. it has openings of ureters and internal urethral orifice
neck region has two sphincters, involuntary internal sphincter and external voluntary sphincter


walls of the urinary bladder

outer adventitia made of soft connective tissue
middle muscular layer aka the detrusor muscle.has involuntary circular muscles in the middle and longitudinal on the sides.
inner mucosa has loose connective tissue towards the side and transitional epithelium/ureothelium towards the luemn.



only in mammals
straight in females,2-4 cm long, the urinary aperture in the vulva in front of the vaginal aperture.
in males, it is 20cm long, passes through prostate ad the cowpers glands and also releases sperms


structural and functional unit of the kidney

nephron/uniferous tubule