1 Excretory System Ashley Donato Excretory System Excretion is a the process in which the organism rids itself of metabolic wastes. Elimination of fecal material is not part of the excretory system because fecal material stays in the intestine which is not in the body proper. In humans the metabolic waste comes from urine, sweat and tears. Excretory System Only waste material from metabolic activities are excretory products CO 2 is a major excretory product as well as nitrogen CO 2 arises from the breakdown of organic fuel molecules. Some CO 2 is used for synthetic reactions, but most is excreted from the body.
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
Excretory System
Ashley Donato
Excretory System
Excretion is a the process in which the organism ridsitself of metabolic wastes.
Elimination of fecal material is not part of theexcretory system because fecal material stays in theintestine which is not in the body proper.
In humans the metabolic waste comes from urine,sweat and tears.
Excretory System
Only waste material from metabolic activities areexcretory products
CO2 is a major excretory product as well as nitrogen
CO2 arises from the breakdown of organic fuelmolecules. Some CO2 is used for syntheticreactions, but most is excreted from the body.
2
Excretory System
When protein is used as a fuel the amino acids arebroken down and the nitrogen is removed.
Nitrogen can be excreted out of the body in 3 formsas ammonia, urea, or uric acid.
The availability of water determines how thenitrogen will be excreted.
Excretory System
Commonly aquatic organisms can excrete ammoniabecause water is more freely available to them.
For nonaquatic organisms ammonia is toxic andusually needs to be neutralized into urea.
Humans are ureotelic which mean they excretenitrogen as urea.
Excretory System
Ureotelic organisms produce uric acid which is nontoxic. It’s relatively insoluble in water and less fluid isneeded to get rid of it, but there is a higher energycost to form it.
This process takes place in the liver and the filtrate isbrought to the kidneys and excreted as urine.
3
Excretory system of Invertebrates
Protista and sponges excrete wastes by a contractilevacuole.
Contractile vacuole is full of fluid and it contracts toforce fluid, salts and waste material out of the cell.
Some protists lack the vacuole and excrete theirwaste across the permeable cell membrane.
Excretory system of Invertebrates
Flatworms use the flame cell system. Which is two highly branched tubules with hollow
bulbs on the ends with cilia. The beating cilia make itlook like a flame.
The cilia create a current that carries the fluid andwaste material out of the body through the excretorypores.
Flame cell system
4
Excretory system of earthworms
Earthworms have a pair of nephridia on eachsegmented part of their body.
Fluid enters a nephridium through the nephrostome The nephridium moves the waste into a bladder and
then it exits through the nephridiopore.
Excretory system of earthworms
Excretory system of insects
Insects haveMalpighian tubuleswhich areoutpocketings locatedat the joint of themidgut and hindgut.
These are tubular sacsthat collect the wastematerial at the closedends.
5
Excretory system of insects
Insects form uric acid inthe tubules and waterand salts arereabsorbed.
The urine formed ismoved to the hindgutand excreted out of thebody.
Vertebrate Kidney Structure
Kidneys are unique organs to vertebrates. They function as the excretory organ in most
vertebrates and in fish the main function isosmoregulation.
Kidney ducts and the reproductive system areinterrelated because they often share the sameexternal opening.
Vertebrate Kidney Structure
Kidney development starts off as series of tubulesthat are associated with segments of the body.
The tubules lengthen and become nonsegmented. The nonsegmented tubules form a duct called the
ureter. The ureter moves the urine formed in the kidneys to
the urinary bladder. The urethra moves the urine from the bladder to
outside the body.
6
Vertebrate Kidney Structure
The kidney has 3sections
Outer cortex Middle medulla Center pelvis. Urine collects in the
renal pelvis and ismoved to the bladderby the ureter.
Vertebrate Kidney Structure
Vertebrate Kidney Structure
The nephron producesthe urine.
The nephron has 3parts
Glomerulus Convoluted tubule Collecting tubule
7
Vertebrate Kidney Structure
The glomerulusconsists of tightlypacked capillaries thatfilter the blood
Small particles andsalts are filtered out,but larger particles suchas proteins are left inthe blood
Vertebrate Kidney Structure
The filtrate is thenpassed to theconvoluted tubule,
The convoluted tubuleconsists of theBowman’s capsule, theproximal section, loopof Henle and the distalsection
Vertebrate Kidney Structure
In the convoluted tubule water and ions arereabsorbed and put back into the bloodstream
Urine is passed on to the collecting tubule.
8
Vertebrate Kidney Structure
In the collecting tubule more water is reabsorbed ifpossible
The urine is moved from the collecting tubule to thepelvis of the kidney.
Vertebrate Kidney Structure
The glomerulus, Bowman’scapsule, proximal and distalsections are located in thecortex of the kidney.
The loop of Henle andcollecting tubules are in themedulla.
Human Kidney Function
Human kidneys are able to produce veryconcentrated urine due to a steep concentrationgradient in the renal medulla.
Hypoosmotic urine passes from the descending armof the loop of Henle into the collecting tubule.
9
Countercurrent multiplier theory
Na+ and Cl- circulate from the ascending arm to thedescending arm of the loop of Henle.
This occurs by filtrate descending the loop of Henleand water passing by osmosis into the tissue fluidand around the tubule.
Na+ and Cl- diffuse into the tubule at the same timethat the water is passing into the tissues.
Countercurrent multiplier system
The ascending arm of the loop actively expels Na+and Cl- expels passively.
This repeating filtration process produces highlyconcentrated urine
This theory had been doubted and the newhypothesis is the two-solute model
Two-solute model
The filtrate fluid is initially isotonic with blood plasma The filtrate moves down the descending arm and
loses water and becomes concentrated. At the bottom of the loop the tubule is permeable to
NaCl . As the filtrate moves up the ascending arm salt is
actively pumped out as well as additional water loss.
10
Two-solute model
The filtrate is brought to the collecting ducts whichare permeable to urea.
The urea passes out of the ducts and into thesurrounding tissues.
The salt and urea pull more water from the filtrate asit moves from the capsule to the ureter.
Fresh water fish
Kidney function in fresh water fish is very importantbecause they have to conserve salts and excrete outlots of fluid, they produce large amounts of urine andfairly quickly
Fluids are pushed across the vessel membrane inthe glomerulus, then the neck of the Bowman’scapsule is highly ciliated so that large amounts ofwater can move through the nephron.
Fresh water fish
Ions such as Na+, K+and Cl- are reabsorbedusing active transport.
Urine is formed andmoved to the urinarybladder and thenreleased into the water.
Fish excrete outammonia through theirurine and it passesthrough their gills
11
Marine fish
Produce urine moreslowly because theyhave to reabsorb freshwater from the filtrate.
Marine fish drink thesalt water to counterbalance their loss ofwater to theirhypertonicenvironment.
Homeostasis
The kidneys also help maintain homeostasis byregulating the salt and water balance.
The kidneys control the solutes that get reabsorbedback into the bloodstream after they get filtered inthe tubules
Homeostasis
Glucose is a solute that is usually entirelyreabsorbed.
In diabetics the glucose does not get reabsorbedand they have high levels of glucose that theyexcrete out in their urine.
When the body is losing glucose through urine morewater is drawn into the nephron and large amountsof urine is produced.
Frequent urination can be one of the first signs ofdiabetes.
12
Homeostasis
Antidiuretic hormone (ADH) is produced in thehypothalamus and it functions to maintain waterbalance.
ADH helps the body to retain water and produceconcentrated urine.
Low levels of ADH produces large amounts of diluteurine taking water out of the body.
Homeostasis
Aldosterone is a steroid produced in the adrenalcortex that regulates active transport of Na+.
It helps to retain salts in the body. With low levels of this steroid salts are lost from the
body.
Sweating
Sweating can also be aexcretion process.
Sweat glands in theskin are also ways thatthe body can lose waterand salts such as NaCl,K+ and Mg²+.
13
Tears
Tears which function tomoisten the eye arealso part of theexcretory process.
Tears are dilute NaClsolutions.
Sources
Fried, George and Hademenos, George.Schaum’s Outline to Biology. New York:McGraw Hill. 2009.
www.google.com/images
Related Documents
