Ammonotelic organisms: These organisms excrete nitrogenous wastes in the form of ammonia. Example: Fish.
Fish eliminate ammonia through their gills and kidneys.
Ammonia is highly toxic and requires a large amount of water for disposal.
Ureotelic organisms: These organisms excrete nitrogenous wastes in the form of urea. Example: Mammals.
Mammals, including humans, produce urea in the liver, and it is transported to the kidneys for excretion.
Urea is less toxic than ammonia and requires less water for disposal.
Uricotelic organisms: These organisms excrete nitrogenous wastes in the form of uric acid. Example: Birds and reptiles.
Birds and reptiles convert ammonia into uric acid, which is excreted in the form of solid uric acid crystals.
Uric acid requires very little water for disposal and helps conserve water in these organisms.
Excretory structure
The excretory system in animals is responsible for the elimination of metabolic wastes.
Example: The excretory system of a human being.
The human excretory system consists of kidneys, ureters, urinary bladder, and urethra.
The kidneys filter blood and remove waste products, excess water, and electrolytes.
The ureters transport filtered urine from the kidneys to the urinary bladder.
The urinary bladder stores urine temporarily until it is released through the urethra.
Structure and parts of the kidney and nephron with its function and location
The kidney is an essential organ of the excretory system that helps to maintain water and electrolyte balance in the body.
Location: The kidneys are located on either side of the vertebral column, behind the abdominal cavity.
Structure and parts
Cortex: The outer region of the kidney where ultrafiltration takes place.
Medulla: The inner region of the kidney responsible for concentrating the urine.
Renal pelvis: A funnel-shaped structure that collects urine from the nephrons and carries it to the ureter.
Nephron: The functional unit of the kidney responsible for filtration, reabsorption, and secretion.
Nephron function
Filtration: Blood is filtered in the glomerulus, and the filtrate moves into the renal tubules.
Reabsorption: Essential substances like water, glucose, amino acids, and ions are reabsorbed into the bloodstream.
Secretion: Unwanted substances like urea and excess ions are secreted into the renal tubules to be excreted as urine.
Counter current mechanism and urine formation
Counter current mechanism
The countercurrent mechanism refers to the exchange of substances between two fluids flowing in opposite directions.
It occurs in the Loop of Henle within the nephron and helps in the concentration of urine.
The ascending limb of the Loop of Henle is impermeable to water, while the descending limb is permeable.
This creates a concentration gradient in the interstitial fluid, which allows for concentrated urine formation.
Urine formation and regulation
Filtration: Blood is filtered in the glomerulus, forming a filtrate consisting of water, glucose, ions, and waste products.
Reabsorption: Essential substances like glucose, water, and ions are reabsorbed from the filtrate into the blood.
Secretion: Unwanted substances like drugs and excess ions are actively secreted into the nephron from the blood.
Regulation: The concentration and volume of urine are regulated by hormones such as antidiuretic hormone (ADH) and aldosterone.
Micturition and disorders
Micturition
Micturition is the process of emptying the urinary bladder through the urethra.
It is a voluntary and reflex action controlled by the nervous system.
The bladder muscle contracts, and the internal urethral sphincter relaxes, allowing urine to pass out of the body.
Kidney disorders
Kidney stone: The formation of hard deposits in the kidneys, causing pain and obstruction of the urinary tract.
Urinary tract infection (UTI): Infection in any part of the urinary system, commonly caused by bacteria.
Kidney failure: The inability of the kidneys to filter waste products and maintain electrolyte balance.
Glomerulonephritis: Inflammation of the glomeruli, leading to impaired kidney function.
Process of hemodialysis
Hemodialysis is a procedure used to filter and purify the blood in individuals with kidney failure.
It involves the use of a dialysis machine to remove waste products and excess fluid from the bloodstream.
Blood is drawn from the patient's body and passed through a dialyzer that contains a semipermeable membrane.
The membrane allows waste products and excess fluids to pass through while retaining essential substances.
The purified blood is then returned to the patient's body.
Hemodialysis is usually performed several times a week, as a substitute for normal kidney function.
excretory structures of animal kingdom
sponges , coelenterates,ctenophora :GBS
platyhelminthes; flame cells
ascheliminthes; renete cells
arthropoda; green gland / annetal gland , malphigian tubules, coxal gland
hemichordates; probiscs gland
chordates
cephalochordates; solenocytes
urochordates; neural gland
fishes and amphibian; mesonephric
reptiles aves and mammals; metanephric
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