LU 3 : EXCRETION Def : Remove metabolic waste from body to a constant…
LU 3 : EXCRETION
Def : Remove metabolic waste from body to a constant internal environment
3 STEPS URINE FORMATION :
Step 2 : TUBULAR REABSORPTION
Reabsorption, during which molecules and ions will be
into the circulatory system.
The fluid passes through the components of the
(the proximal/distal convoluted tubules, loop of Henle, the collecting duct) as water and ions are removed as the fluid osmolarity (ion concentration) changes.
, secretion will occur before the fluid leaves the ureter in the form of urine.
Step 1 : GLOMERULUS ULTRAFILTRATION
During filtration, blood enters the afferent arteriole and flows into the glomerulus where
blood components, such as water and nitrogenous waste, will move towards the inside of the glomerulus, and
components, such as cells and serum albumins, will exit via the efferent arteriole.
These filterable components accumulate in the glomerulus to form the glomerular filtrate.
Step 3: TUBULAR SECRETION
During secretion, some substance, such as hydrogen ions, creatinine, and drugs—will be removed from the blood through the peritubular capillary network into the collecting duct.
The end product of all these processes is
, which is essentially a collection of substances that has not been reabsorbed during glomerular filtration or tubular reabsorbtion.
ROLE OF KIDNEY
The kidneys filter unwanted substances from the blood and produce urine to excrete them.
Formation of urine is a process important for the whole organism. Not only acid-base balance is modulated by it, but also blood osmolarity, plasma composition and fluid volume, and thus it influences all cells in our body.
The other main component of urine is urea, a highly soluble molecule composed of ammonia and carbon dioxide, and provides a way for nitrogen (found in ammonia) to be removed from the body.
DIFFERENT AMONG DIFFERENT ANIMAL
Nephridium (excretory organ)
End of each blind tubule of nephridium ciliated flame cell.
fluid pass down tubules, solutes reabsorbed, returned to body fluid
Has metanephridia, due to closed circulatory system, dilute urine is secreted.
Metanephridia obtain fluid through filtration NaCl reabsorbed by Active transport processes
Body fluid is drawn into malphigian tubules by osmosis pass back into body
Water reabsorbed and waste excrete
All have paired kidney
similar in that they function on filtration
Reabsorption principle with tubular
Epithelial Excretory Surfaces
Tubular Excretory Organs
, most amphibians, sharks, some bony fishes
, including birds, insects, land snails
animals, including most bony fishes