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Topic 11 Excretion
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Observe the solutions A & B!Compare the colour!Compare the volume!Compare the smell!Compare the temperature!(optional) Compare the texture!
(optional) Compare the taste!
2 samples of solution
Subject XUrine collect from this boy an hour after he drank 1 litre of water.
2 samples of solution
Subject YUrine collected from this energetic boy who did not drink any water for the past 5 hours.
2 samples of solution
2 samples of solutionWhich sample belongs to subject X?
Which sample belongs to subject Y?
Why???
Chapter 11Part 1
Structure of the
Kidneys
Excretion in Humans
define excretion and explain the importance of removing wastes from the body.
to identify and state the functions of different parts of the urinary system.
Lesson Objectives
(1)What is Excretion?• Removal of metabolic wastes &
toxic materials
• Metabolism = all the chemical activities in living cells
Metabolism = Catabolism +
Anabolism
Chemical processes that cause the breakdown of complex substances into simpler onesExamples:
1) Aerobic or anaerobic respiration
2) Deamination of proteins and excess amino acids in the liver to form urea.
3) Digestion of food substances
1) Catabolism
Chemical processes that form complex substances from simpler onesExamples:
1) Photosynthesis2) Conversion of glucose into
glycogen or starch3) Synthesis of new cells
2) Anabolism
Excreted substances are:Carbon dioxide?
Can change the pH level of blood plasmaWater?
Can change the water potential in the blood plasma
Urea?Can be toxic if accumulated to high
amountsNot useful to the body, excrete!
Why have excretion?
Excretory product
Excretory organ
Carbon dioxideLungs excreted during exhalation
Urea Kidneys excreted in the form of urineExcess water
Excretory products &Organs
Human Urinary System
CENSORED
KidneysA pair of dark red, bean-
shaped organsThey are attached to the
dorsal body wall, one on each side of the spinal cord
The left kidney is slightly higher than the right one (Why ley?)
a) Ureter: – A narrow tube
carrying urine from the kidneys to the bladder
– By peristalsis
b) Renal Pelvis:– The enlarged
portion of the ureter inside the kidney
Parts of the Urinary System
c) Urinary Bladder: A hollow muscular bag used to store urine temporarily
d) Sphincter muscles:
Relaxes to allow urine to flow from the bladder to the urethra
e) Urethra: A tube which carries urine out of body
Parts of the Urinary System
Inside the KidneyEach kidney is covered
by an outer layer of protective cells called the capsule
It has 2 main regions:MedullaCortex
Inside the KidneyMedulla
the inner regionIn man, it is split into
12 -16 conical structures, called the pyramids
Cortexthe outer region
Kidney Tubule - Nephron
The functional unit of the kidney
Part of it is located in the medulla, part of it is located in the cortex
Urine is formed in the nephron
About 1 million in each kidney
Each is about 3 cm in lengthTotal length: about 60 km
Kidney Tubule - Nephron
(i) Entry of blood into the kidney• The renal artery brings
blood from the body into the kidneys.
• It branches into numerous afferent arterioles.
• Each arteriole branches into a mass of blood capillaries in the renal capsule
Blood from the body
(ii) Formation of the glomerulus• This mass of
blood capillaries is called the glomerulus.
Glomerulus+
Renal Capsule
Malpighian (Renal)
Corpuscle
(iii) Blood leaving the kidney• Blood leaves the
glomerulus through the efferent arteriole and enters blood capillaries surrounding the tubule.
• These blood capillaries then unite to form the renal vein
Blood leaves the kidneys
(iv) Renal / Bowman’s Capsule
Small substances are forced under high pressure from the glomerulus into the renal capsule
Ultrafiltration occurs here
(v) Proximal Convoluted TubuleThe renal
capsule leads into the Proximal Convoluted Tubule
Selective reabsorption occurs here
(vi) The loop of Henle
The proximal convoluted tubule straightens out as it passes into the medulla, makes a U-turn & passes back into the cortex Selective
reabsorption continues here
(vii) Distal convoluted tubule
Distal Convoluted Tubule: The tubule then becomes coiled again
Selective reabsorption
continues here
(viii) Collecting Duct
It then leads into a Collecting Duct and eventually leads into the renal pelvis
Selective reabsorption
continues here
Time for activity!
And Now…
Different in diameterAfferent has a bigger diameter than efferent
So what???
What is the difference between afferent and efferent arteriole?
Topic 8: Chapter 11Part 2
Formatio
n of
Urine
Excretion
Excretion
Waste Products removed by the Kidneys
Excess
Mineral Salts
Nitrogenous waste
• Mainly urea
• Creatinine
• Uric acid
Excess H2O
Right Kidney Left Kidney
Sphincter Muscle
Inferior Vena Cava
Dorsal Aorta
Renal ArteryRenal Vein
UreterUreter
Urinary Bladder
Urethra
Role of the Kidney
Carry out High Pressure Filtration of the blood to achieve 2 functions
Removal of Urea and toxins from
the blood
Osmoregulation
Maintain a constant blood
plasma concentration
Renal Cortex
Medulla
The Right Kidney
The Nephron
Proximal Convoluted Tubule
Descending Limb of Loop of Henle
Ascending Limb of Loop of Henle
Distal Convoluted Tubule
Bowman’s Capsule
Glomerulus
Collecting Duct
Blood Capillaries
Ultrafiltration
Forced out of blood into kidney tubules Remains in the blood
Water RBCPlateletsBlood Proteins (e.g Fibrinogen)
Small Solute Molecules• Glucose • Amino Acids• Nitrogenous waste products
(especially Urea)• Mineral Salts
2 conditions required:
1) High Blood Pressure – Afferent arteriole has a larger diameter than the efferent arteriole
2) Partially permeable membrane – Basement membrane of glomerulus has small pores that allows only water and small molecules to pass through
Diffusion and Active transport of• Ions (Na+, Cl-)• Amino Acids• GlucoseBack into the bloodstream
1
Water potential gradient created
H2O flows out of tubule into the blood capillaries by Osmosis
2
* Descending Limb is impermeable to Na+ and Cl- ions
As the filtrate moves through the Distal tubule and down the Collecting Duct, more H2O is reabsorbed from the filtrate by Osmosis
* Ascending Limb is impermeable H2O
4
Na+ and Cl- ions leaves the Ascending Limb into the interstitial fluid and is reabsorbed into the bloodstream by Diffusion & Active Transport
Proximal Convoluted Tubule
Proximal Convoluted Tubule + Descending Loop of Henle
Distal convoluted Tubule + Collecting Duct
Ascending Limb + Distal Convoluted Tubule
Selective Reabsorption
3
Interstitial Fluid
2
1
H2O
H2O
H2O
H2O
Na+
Cl-
3
H2O
H2O
H2O
H2O
H2O
H2O
4
Urine to Ureter
H2O
Na+
Cl-
Flows through
Ureter
Urinary Bladder
Bladder wall is stretched
Bladder muscle will contract
Urine from the urinary bladder flows into the urethra
To the
Urine flows out of the body
UrineUrea + Other nitrogenous waste (Creatinine, uric acid) +
Excess Salts and ions + Excess water
Topic 8: Chapter 11Part 3
Osmoregulation
Excretion
What is Osmoregulation?
• Maintenance of a constant water potential in the body
• by regulating the water and solute levels in the blood
• This is an example of homeostasis (the maintenance of a constant internal environment)
Absence of osmoregulation - Effects
• Blood plasma water potential will be higher than the surrounding cells and tissues
• Water will enter the blood cells and surrounding tissue cells by osmosis
• Cells will swell and burst
Blood plasma too dilute
Blood plasma too concentrated
• Blood plasma water potential will be lower than the surrounding cells and tissues
• Water will leave the blood cells and surrounding tissue cells by osmosis
• Cells will shrink and crenate and be unable to perform its metabolic functions
Kidneys as osmoregulators
1) Hypothalamus • Control centre in the brain which controls body activities (e.g
temperature regulation, blood plasma regulation and other involuntary responses in the body)
2) Pituitary gland• Releases hormones (e.g Antidiuretic Hormone) which are
transported in the bloodstream to target organs to carry out its effect
3) Antidiuretic Hormones (ADH) • Increases water reabsorption by the kidney tubules back to the
bloodstream• Causes vasoconstriction of arterioles
Organs/Glands/Hormones involved in osmoregulation
The pituitary gland
Negative feedback mechani
sm1) Blood Plasma •volume drops
• water potential decreases
• volume increases• water potential increases
Stimulus
2) Receptors in the Hypothalamus
Are triggered Are triggered Receptor
3) Pituitary Gland Releases more ADH Releases less ADH Corrective mechanismswhich brings about a response
4) Distal Convoluted Tubule and
Collecting Duct
More permeable to water
Less permeable to water
5) Effect: More water reabsorbed back to the bloodstream
Less water reabsorbed back to the bloodstream
6) Urine • Becomes more concentrated
• Volume decreases
• Becomes more dilute• Volume increases
Effect
7) Blood Plasma • Volume increases• Water potential increases
• Volume decreases• Water potential decreases
Water potential returns to normal• Hypothalamus
detects the normal blood plasma water potential and decreases the release of ADH by the pituitary gland.
• Hypothalamus detects the normal blood plasma water potential and increases the release of ADH by the pituitary gland back to the normal level.
Negative feedback to resume normal activity of pituitary gland
Water lost through sweat
Water gained
through drinking
Water
content
regulation
Salt content
regulation
• Sodium chloride concentration in the blood plasma also has an effect on the water potential of the blood plasma.
• If sodium chloride content in the blood plasma is high,
• Sodium and chloride ion re-absorption from the glomerular filtrate back to the bloodstream will be reduced.
Kidneys controlling blood pressure
Blood Volume Diameter of blood vessels
High blood pressure High Narrow
Low blood pressure Low Wide
How are the kidneys involved in the treatment of
high blood pressure?
• By the prescription of “Diuretics” • Reduces the reabsorption of water from the distal
convoluted tubule and collecting duct back to the blood capillaries
• Blood volume decreases, Urine volume increases• Blood pressure decreases
Topic 8: Chapter 11
Part 4
Dialysis
Excretion
- Partially -Permeable- Allows small molecules
to pass:• Water• Sugars• Salts• Amino acids• Urea - Long and coiled to
increase SA to VR for exchange of substances
Consists of: Purpose:
• H2O at a preset temperature
To maintain an environment as close to the body as possible
•Normal concentrations of essential substances as blood: (1)Glucose, (2)Mineral Ions, (3)Amino Acids
- To ensure similar osmotic concentrations on both sides of tubing. (Minimize loss of water and essential substances from blood)
•Blood and Dialysis Fluid flow in opposite directions
- To create and maintain a diffusion gradient
•Anti Coagulant Prevent blood from clotting
The Dialysis Machine
Pump
Dialysis Tube
Dialysis Fluid
Pump
• Smoothen the blood flow• Maintain blood pressure • Maintain speed of blood
flow
Difference in the concentration between the blood and dialysis fluidResults in
Blood is purified
Therefore
Blood is drawn from an artery in the patient’s arm
• Diffusion of urea and waste products down a concentration gradient
• Diffusion of excess mineral down a concentration gradient
• Movement of excess water out of blood by osmosis
• Diffusion of essential mineral salts if lacking in blood
Blood to Dialysate
Dialysate to Blood
Blood is returned to a vein in the patient’s arm
Difference between the Dialysis Machine and the Nephron
Dialysis Machine Nephron
Filtration does not take place Ultrafiltration occurs at the Bowman’s Capsule
The pump keeps the blood pressure constant throughout the tubing
Blood is under great pressure
No active transport of solutes Active transport of solutes at the proximal and distal convoluted tubule, and loop of Henle.
Depends largely on diffusion Depends largely on active transport and osmosis. Minimal diffusion
Name: …………………………… ( ) Class: ……… Date: ……….………
Diagram of a Kidney
Diagram of a Kidney Tubule (Nephron)
Renal Cortex
Medulla
The Right Kidney