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EXCRETION & EXCRETORY PRODUCTS - Coggle Diagram
EXCRETION & EXCRETORY PRODUCTS
Excretion Processes
Ammonotelism
Many bony fishes, aquatic amphibians and aquatic insects
Ureotelism
Mammals, terrestrial amphibians and marine fishes
Uricotelism
Reptiles, birds, land snails and insects
Excretory Organs
Protonephridia or flame cells: Platyhelminthes
Nephridia: Earthworms and other annelids
Malpighian tubules: Most insects
Antennal or green glands: Crustaceans
Human Excretory System
It consists of a pair of kidneys, a pair of ureters, urinary bladder, urethra
Kidneys are reddish brown, bean shaped structures situated between the levels of last thoracic and third lumbar vertebra close to the dorsal inner wall of abdominal cavity
Nephrons are the structural and functional unit of kidneys
Structure of Nephrons
Glomerulus: Tuft of capillaries formed by afferent arteriole
Bowman's Capsule: Renal tubule begins this double walled cup-like structure which encloses the glomerulus
Malpighian body = Glomerulus + Bowman's Capsule
PCT, DCT and Loop of Henle, collecting duct, vasa recta and peritubular capillaries
Cortical and juxta medullary nephrons
Urine Formation
1. Glomerular filtration
Filtration of blood (1100-1200ml)
2. Ultrafiltration
Podocytes are arranged leaving minute pores for filtering blood
GFR: 180L per day
Regulated by JGA which when stimulated releases renin
3. Reabsorption
Performed by either active or passive mechanisms
Water, glucose, amino acids, Na+ are reabsorbed
4. Tubular Secretion
Tubular cells secrete H+, K+ and ammonia into the filtrate
Concentration of urine
Loop of Henle and vasa recta play a very important role
The direction of filtrate and blood are in opposite directions in the two limbs of Henle's loop and vasa recta respectively
NaCl is transported from AL of Henle's loop to DL of vasa recta
AL of vasa recta transports Na Cl to interstitial fluid. Thus, a concentration gradient of 300 mOsm to 1200 mOsm is created between the cortical and medullary regions
Urea is then transported to interstitium by DL of Henle's loop
A urine flows down in collecting tubule, it encounters higher concentrations of solutes, thus, losing water by osmosis. Hence, urine gets concentrated.
Regulation of Kidney Function
By Antidiuretic hormone (vasopressin)
By JGA (Renin-Angiotensin mechanism)
By heart (Atrial Natriuretic factor)
Micturition
Voluntary neural signals from CNS to remove urine from urinary bladder which is initiated by stretching of walls of urinary bladder
Role of Other Organs in Excretion
Lungs: CO2
Skin: Sweat (NaCl, urea, lactic acid)
Liver: Bile-containing substances (biliverdin, bilirubin, cholesterol)
Disorders
Uremia
Renal failure
Renal calculi
Glomerulonephritis