Download Nephron

Matthew Menechella Srijan Mukherjee
Toriy Jones
AP Biology
Rachel Ivey
Daniel Schaffer
Excretion/Nephron
Excretion is the removal of metabolic waste, for example, nitrogenous wastes. Everything that
passes into the collecting tubule is excreted from the body. From the collecting tubule or duct,
urine passes through the ureter to the urinary bladder. Urine is temporarily stored in the urinary
bladder until it passes the body via the urethra. Nephrons depend upon the kidneys for support,
the ureters to collect the final filtrate, and depends upon the urethra to dispose of the urine
outside of the body.
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Filtration: The excretory tubule collects a filtrate from the blood
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Reabsorption: The transport epithelium reclaims valuable substances
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Secretion: Extracts toxins and extra ions from the body
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Excretion: The filtrate leaves the body system and the body
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Water and waste products move out of the circulatory system and into the excretory
system to be removed. These waste products diffuse into the blood cells to be carried
away. The blood circulates through organs such as the liver and kidney where eventually
it will be removed from the body. The nephron’s which make up the kidney carries its job
out in four steps. These four steps are filtration, secretion, reabsorption and finally
excretion. All these steps help remove the waste from the body. Filtration occurs as blood
pressure.
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Unicellular organisms can excrete waste through different ways like a specialized
excretory features like an anal pore, diffusion of waste across a membrane, or the use of
contractile vacuoles.
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Plants don't excrete their waste. Waste is stored in a large central vacuole until it can be
chemically converted in useful products
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Flat worms use Protonephridia, a system of tubules and flame bulb cells.
The excretory system depends on other body systems to secrete substance in order for the body
to remain in homeostasis.
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The respiratory system helps remove water vapor and carbon dioxide through the process
of exhalation.
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The circulatory system aids in passing blood through the kidneys in order for the blood to
be filtered and also circulates warm blood from deeper portions of the body to the
surface. Heat is then released, as well as water, mineral salts and urea through the process
of sweating.
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The digestive system aids in the process of excretion by passing indigestible waste out
through the anus
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Two solutes in the nephron contribute to the osmolarity of the interstitial fluid, NaCl and
urea. The loop of Henle maintains the interstitial gradient of NaCl, which increases in the
descending limb of the loop in decreases in the ascending limb, and urea diffuses out of
the collecting duct into the interstitial fluid. As filtrate flows through the collecting duct,
water flows out of the duct by osmosis, concentrating solutes left behind in the filtrate.
Matthew Menechella Srijan Mukherjee
Toriy Jones
AP Biology
Rachel Ivey
Daniel Schaffer
Excretion systems perform the process of disposing of metabolic waste and regulating
body fluid composition. The process is: filtration, reabsorption, secretion, and excretion.
Disruptions of the excretory system include:
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Ureterocele- Birth defect. swelling at the bottom of one of the ureters. Swollen area can
block urine flow. Symptoms include: abdominal pain, back pain, blood in urine.
Antibiotics are usually given to prevent further infections until surgery can be done.
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Cystitis- Inflammation of the bladder. May be due to reaction to some medicines,
bacterial infection, using catheter for long time in case of some diseases, undetected
underlying disease, or result of radiation therapy. Symptoms include pain or difficulty
urinating, foul smelling urine. Cystitis is normally treated with antibiotics.
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Proximal tubule- performs secretion and reabsorption. the most important function is
reabsorption of a lot of water and salt.
Descending the Loop of Henle- the membrane here is freely permeable to water and not
very permeable to salts. water is passively removed.
Ascending the Loop of Henle- the membrane here is permeable to salts and not to water.
Initially in the thin segment, salt passively diffuses out of the filtrate, the the salt starts being
actively transported out of fluid which causes it to become increasingly dilute.
Distal Tubule- helps refine filtrate and then empties into collecting duct.