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