Biology 20
Excretory System
Excretion
Introduction
• Humans are 70% water
– 1/3 of this is in plasma
• Blood – carries nutrients, picks up waste
• Wastes need to be removed
• Composition of fluids need to be kept in balance
• Excretion: monitor, analyze, select, reject
EXCRETION
• Excretion is the process of __________________________________.
• During the metabolic processes of the body waste products are
removed from the site of production by the ____________.
• As these wastes accumulate, the kidney removes them from the blood
and ____________ them to the environment
• The excretory product becomes ________________.
EXCRETION
• Process of removing cellular waste
• Balance pH of blood
• Maintain water balance
• Happens in Kidney
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Biology 20
Excretory System
FUNCTIONS OF THE EXCRETORY SYSTEM
• Functions:
• ___________________________________________________
• Regulates and stabilise the internal environment by controlling 4
groups of chemicals
1. ______________________
2. ________________________________: Elimination of
poisonous by-products of chemical reactions:
3. _________________________________: regulation of
hydrogen, sodium, potassium, calcium, chloride ions:
4. _________________________________: Removal of essential
nutrients that dangerous in excess:
WASTE PRODUCTS
• The principle metabolic wastes in most animals are:
o ____________________– is excreted through the respiratory
surfaces
o ______________ – excreted through respiratory surfaces, skin
as sweat as well as kidneys
o _________________________ – products of protein and
nucleic acid digestion
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Excretory System
NITROGENOUS WASTES
• Ammonia –The first metabolic product of amino acid
_________________ – hydrolysis (protein digestion)
o highly toxic
o cannot accumulate in body
o must be converted into ________________________________
• Uric Acid – produced from ammonia
o not very soluble – can be excreted as a paste with little water
loss
o non - toxic
Deamination & Urea
• Proteins – contain a nitrogen molecule
– Amino acid – building blocks of protein
• Nitrogenous base
• Removal of N and H
• Occurs in the ________________
• Byproduct – ammonia
– Toxic substance
• Ammonia combines _______________________________
• Urea –less toxic
• Uric acid – waste product from the breakdown of nucleic acids
(DNA)
• Urea – converted from ammonia
– less toxic than ammonia
– produced in the liver
– can be excreted in concentrated form
– requires more water to excrete than uric acid
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Biology 20
Excretory System
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Biology 20
Excretory System
ORGAN: Function
• ________________ : site of blood filtration
• ________________: brings blood to kidney
• ______________: brings blood back to heart
• ____________: Brings waste TO bladder
• _____________: Temporary urine storage site
• _____________: Brings waste FROM bladder, out of system
The Kidney
Structure
Function
Cortex
Medulla
Renal Pelvis
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Biology 20
Excretory System
STRUCTURE AND FUNCTION OF KIDNEY
Three distinct regions of the kidney
o Cortex – outer region
o Medulla – just below cortex
o Pelvis – a hollow chamber within the medulla
• The cortex and medulla of each kidney are made up of a approximately
___________________________
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Excretory System
• NEPHRON
– __________________________________________
STRUCTURE
FUNCTION
Brings blood to glomerulus
Leaves glomerulus, goes to vein
Ball of capillaries – site of filtration
Filter
First tube in nephron. From BC…
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Biology 20
Excretory System
Leads to collecting duct
Empties waste into renal pelvis
Collecting site for all nephrons –
waste out to ureter
• BOWMAN’S CAPSULE
o a double walled chamber – start of the tubule.
• GLOMERULUS
o network of capillaries within the Bowman’s capsule
o __________________ (4x higher than in capillaries)
• PROXIMAL TUBULE
o active transport of many valuable substances back into blood
network
________________, ________________, ________________
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Excretory System
• LOOP OF HENLE
o the long hair-pin turn!!
o some of the remaining water and salt will be _____________to
the blood
o lies in the medulla which is relatively salty (hypertonic)
• DISTAL TUBULE and COLLECTING DUCTS
o _____________________________________________
• This depends on the presence of certain hormones
• (ADH) Anti diuretic Hormone
o Exact amounts of substances are reclaimed to the blood
• very precise
•
Urine Formation
• Depends on three functions:
– __________________
• Movement from blood – Bowman’s capsule
– _____________________
• Transfer of needed nutrient back INTO blood
• Tubules
– ______________________
• Movement of material from blood back into nephron
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Excretory System
Four Steps to Urine Formation
1)
FILTRATION
– Occurs at the junction of the ______________ and the wall of the
___________________
– Each glomerulus receives blood from an _____________ and
discharges its blood into an __________________ (hypertonic).
– Fluid and dissolved materials (nutrients, wastes, ions) in the blood
plasma pass from the _______________ into Bowman’s capsule
• due to a local increase in blood pressure within the
glomerulus
– this material is then called ________________.
– blood cells, plasma proteins and platelets are too large to pass
through the wall of the capillary and therefore remain within the
capillary.
2)
REABSORPTION
– _________________________________
– returns about ________ of filtrate to the blood
– efferent arteriole feeds second capillary network that surrounds
the tubule
– this network receives __________________________
• eventually leads to ______________________
• Water rushes into the blood because of _______________
Problem
• Not enough water is returned this way.
Solution
• Just actively transport water into the blood right?
Wrong!!! There is no way of ACTIVELY transporting water
So how can we transport more water into the blood?
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Excretory System
o active transport of solutes into the capillary bed
• _______________
• _______________
• _______________
• _________________ (Na+)
o water is ________________ reabsorbed from the proximal tubule
as these solutes are actively removed from the filtrate
o Reabsorption and the distal tubule.
o A more selective, precisely regulated reabsorption occurs in the
_____________________
o Additional quantities of ________ and ______ may be reabsorbed
o The exact amount of each substance reclaimed occurs in the
________________.
o excess is excreted in urine e.g. glucose and diabetes
3) SECRETION
– This is the last chance for anything to leave the blood and enter
the urine
– _______________________
– Occurs in the ________________ and _________________
– Hydrogen ion secretion – helps regulate blood ____________
• Distal tubule
• Na+ moves into the blood and H+ moves into the tubule
filtrate
– ____________________ (ranges 7.3 - 7.4)
– _____________________ (ranges 4.5 - 8.5)
– potassium secretion
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Excretory System
• prevents accumulation of potassium that can create neural
and muscular problems
– some drugs are removed from the body by secretion
– substances eliminated in this manner are
• ___________________ – by product of protein metabolism
• ___________________
• ___________________
4)
Elimination
• Pathway
o _________________
o _________________
o _________________
o _________________
o _________________
o _________________
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Excretory System
What is in urine?
• ___________________
• ___________________
• ___________________
• ___________________
• ___________________
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Excretory System
Control of Excretion
Disorders and Treatments
HORMONES
• _____________
• The ___________________________
– influences the RATE of water reabsorption into blood from
collecting ducts
– released by the pituitary gland in the brain
• Osmoreceptors in brain stimulated by low __________________ and
increased _________________________
– both of those means that there is not enough water in the blood.
– rate of ADH secretion is increased. ADH saves water.
– More ADH = ___________________ = increased urine
concentration
– Very yellow concentrated urine
• Most water reabsorbed in _______________________
– permeable
• Rest of tubule permeable ONLY IF ADH is present
– Ascending loop
– Distal tubule
Aldosterone and Sodium
• Aldosterone – _____________________
– Produced in __________________
– Increased ____________________
– More water may also move out
• Osmosis (high to low)
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Biology 20
Excretory System
• Blood pressure
– Less fluid – _____________________________
– Angiotensin produced
• Constricts blood vessels, increase blood pressure
• Causes release of __________________
– Aldosterone acts on _______________ and ________________
• More sodium reabsorbed
• Fluid level increase
• BP increases
Kidney Disease
• Diabetes Insipidus
– Problems with ADH production
– No ADH, no H2O reabsorption
– Huge urine output
• Up to 20 L/day
• Kidney Stones
– Minerals forming solid crystals (Ca+, Na+)
– Get lodged in pelvis or ureter
– Can tear tissues as it moves out
– OHMYGOODNESSMAKEITSTOPICANNOTSTANDTHE
PAIN!!!!!!!!!!!!!!!!
• Stone removal
– Surgery
– Ultrasound
– catheter
• Kidney Dialysis
– Cleaning of blood
– Treatment of kidney failure
– Blood goes through a filter
– Concentration gradients remove waste
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Biology 20
Excretory System
• Kidney Donation
– Human system built in twos
– Extra kidney for backup
– One kidney – can do all the work
– With less than 20% kidney function, problems occur
• Requires kidney dialysis
– If problem gets really bad, might need a new one 
TRANSPLANT
Week 17-18 formative
Complete the assignment linked in PowerSchool and send it to me.
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