San Francisco de Paula, Science Department.
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        • 2.6 Structure of DNA and RNA
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        • 4.1 Chromosomes, genes, alleles and mutations
        • 4.2 Meiosis
        • 4.3 Theoretical genetics
        • 4.4 Genetic engineering and biotechnology
      • Topic 6: Human health and physiology >
        • 6.1 Digestion
        • 6.2 The transport system
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        • 6.6 Reproduction
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    • The International Baccalaureate
    • Conceptual learning
    • How will I be assessed?
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  • MYP Year 6
    • Yr 6 Syllabus & Assessment
    • Contents >
      • Unit 1: Introduction to investigation >
        • How to write Lab Reports
      • Unit 2: Living things
      • Unit 3: Classification of living things
      • Unit 4: Fungi, Protists and Bacteria
      • Unit 5: Nutrition I
    • Laboratory and Tasks
  • MYP Year 7
    • Yr 7 Syllabus & Assessment
    • Contents >
      • 7º PAI en español
      • Unit 1 - What do scientists do? >
        • How to write a lab report
        • SI Units
      • Unit 2 - The Earth in the Universe
      • Unit 3: How can we study living things >
        • Unit 3a - Living things
        • Unit 3b - The Diversity of Life >
          • Monera
          • Protists
          • Fungi
          • The Plant Kingdom
          • The Animal Kingdom
      • Unit 4 - Ecosystems & Biodiversity
      • Unit 5: The systems of the Earth >
        • Unit 5a - The Geosphere and the Atmosphere
        • Unit 5b - The hydrosphere and the Biosphere
      • Unit 6: Our changing home >
        • Unit 6a: Internal Geodynamics
        • Unit 6b: External Geodynamics
    • Laboratory & Tasks
  • MYP Year 8
    • Yr8 Syllabus & Assessment
    • Contents >
      • Units 1, 2 and 3 - Measuring Matters >
        • Unit 1 Physical quantities and Scientific Activity >
          • Converting Units
        • Unit 2 Matter and its Properties
        • Unit 3 Pure Substances and Mixtures >
          • Concentration and units (g/L, % mass)
      • Units 4 and 5 - Chemical Cooking >
        • Models of the Atom
        • Electronic structure of matter.
        • Periodic table (distribution of elements).
        • Chemical formulation
        • Molecular mass
        • Moles
        • Types of reactions
        • Lavoisier's law: Balancing of equations
        • Reaction rates: Factors that affect the speed of a reaction
      • Units 6, 7 and 8 - Move It! >
        • Unit 6 - Motion (URM)
        • Unit 6 - Motion (UARM)
        • Unit 7 - Forces and Mass
        • Unit 8 - Energy and Transformations
    • Laboratory & Tasks >
      • How to write a lab report
  • MYP Year 9
    • Yr9 Syllabus & Assessment
    • Contents >
      • Unit 1 - General organization of the human body, health and illness >
        • Human cells: levels of organisation
        • Health and types of diseases
        • Preventing diseases
        • The Immune System
        • Transplants
        • Addictive substances and associated substances
        • Complete Unit 1
      • Unit 2 - Nutrition >
        • Nutrition and nutrients
        • The Mediterranean diet
        • The anatomy and physiology of the digestive system
        • The anatomy and physiology of the circulatory system >
          • Revision quizzes
        • The anatomy and physiology of the respiratory system
        • The anatomy and physiology of the excretory system
        • Nutrition Documentaries
      • Unit 3 - Interaction and Coordination >
        • The function and anatomy of the nervous system
        • The endocrine system
      • Unit 4 - The reproductive system >
        • Anatomy and physiology of the human reproductive system.
        • Gametogenesis
        • Menstrual cycle
        • Fertilization
        • Infertility, contraception and STDs
      • Unit 5 - Genetics >
        • DNA and genetic modification
        • Cells and Inheritance
        • MORE ON MITOSIS VS MEIOSIS
        • Mendelian genetics
      • Unit 6 - Evolution >
        • Evolutionary theories
        • Evolution Simulators
      • EXTRA Unit 7 - Ecology and the environment >
        • Ecology
    • Laboratory & Tasks
  • MYP Year 10
    • Yr10 Syllabus
    • Contents >
      • Unit 0 - Formulation
      • Unit 1 - Scientific Activity
      • Unit 2 - Kinetic theory
      • The Atmosphere
      • Unit 3 - Mixtures and pures substances: Colligative properties
      • Unit 4 - The structure of matter
      • Unit 5 - Stoichiometry
      • Unit 6 - Redox Reactions
      • Unit 7 - Movement
      • Unit 8 - Forces
      • Unit 9 - Electricity
      • Unit 10 - Energy
    • Revision
    • Assessments and Lab Sessionss >
      • Assessments >
        • Criterion D - Water crisis
      • Session 1 - Paper balls
      • Sessions 2 - Properties of substances
      • Session 3 - Preparing a Schlenk tube
      • Session 4 - Gas constant
      • Session 5 - Colligative properties
      • Session 6 - Job´s method
      • Session 7 - Redox titration
      • Session 8 - UARM
      • Session 9 - Hooke´s Law
    • PISA questions
  • DP Biology SL
    • Contents >
      • Topic 1: Cell biology >
        • 1.1 Introduction to cells
        • 1.2 Ultrastructure of cells
        • 1.3 Membrane structure
        • 1.4 Membrane transport
        • 1.5 The origin of cells
        • 1.6 Cell division
      • Topic 2: Molecular biology >
        • 2.1 Molecules to metabolism
        • 2.2 Water
        • 2.3 Carbohydrates and lipids
        • 2.4 Proteins
        • 2.5 Enzymes
        • 2.6 Structure of DNA and RNA
        • 2.7 DNA replication, transcription and translation
        • 2.8 Cell respiration
        • 2.9 Photosynthesis
      • Topic 3: Genetics >
        • 3.1 Genes
        • 3.2 Chromosomes
        • 3.3 Meiosis
        • 3.4 Inheritance
        • 3.5 Genetic modification and biotechnology
      • Topic 4: Ecology >
        • 4.1 Species, communities and ecosystems
        • 4.2 Energy flow
        • 4.3 Carbon cycling
        • 4.4 Climate change
      • C: Ecology and conservation >
        • C.1 Species and communities
        • C.2 Communities and ecosystems
        • C.3 Impacts of humans on ecosystems
        • C.4 Conservation of biodiversity
      • Topic 5: Evolution and biodiversity >
        • 5.1 Evidence for evolution
        • 5.2 Natural selection
        • 5.3 Classification of biodiversity
        • 5.4 Cladistics
      • Topic 6: Human physiology >
        • 6.1 Digestion and absorption
        • 6.2 The blood system
        • 6.3 Defence against infectious disease
        • 6.4 Gas exchange
        • 6.5 Neurons and synapses
        • 6.6 Hormones, homeostasis and reproduction
    • Labs >
      • Statistical analysis
    • Previous to 2015 >
      • Topic 1: Statistical analysis
      • Topic 2: Cells >
        • 2.1 Cell theory
        • 2.2 Prokaryotic cells
        • 2.3 Eukaryotic cells
        • 2.4 Membranes
        • 2.5 Cell division
      • Option F: Microbes and biotechnology >
        • F1 Diversity of microbes
        • F2 Microbes and the environment
        • F3 Microbes and biotechnology
        • F4 Microbes and food production
      • Topic 5: Ecology and evolution >
        • 5.1 Communities and ecosystems
        • 5.2 The greenhouse effect
        • 5.3 Populations
        • 5.4 Evolution
        • 5.5 Classification
      • Option D: Evolution >
        • D1 Origin of life on Earth
        • D2 Species and speciation
        • D3 Human evolution
      • Topic 3: The chemistry of life >
        • 3.1 Chemical elements and water
        • 3.2 Carbohydrates, lipids and proteins
        • 3.3 DNA structure
        • 3.4 DNA replication
        • 3.5 Transcription and translation
        • 3.6 Enzymes
        • 3.7 Cell respiration
        • 3.8 Photosynthesis
        • TO DELETE
      • Topic 4: Genetics >
        • 4.1 Chromosomes, genes, alleles and mutations
        • 4.2 Meiosis
        • 4.3 Theoretical genetics
        • 4.4 Genetic engineering and biotechnology
      • Topic 6: Human health and physiology >
        • 6.1 Digestion
        • 6.2 The transport system
        • 6.3 Defence against infectious disease
        • 6.4 Gas exchange
        • 6.5 Nerves, hormones and homeostasis
        • 6.6 Reproduction
    • Tasks >
      • Databases
    • Documents
    • DP Biology Resources
    • Interesting links
  • Biología 12º
    • Bloque 1. Bioquímica
    • Bloque 2. Biología celular
    • Bloque 3. Genética y evolución
    • Bloque 4. Microbiología y biotecnología
    • Bloque 5. Inmunología
  • IB Biología NS
  • IB Chemistry HL
    • Contents >
      • Year 1 >
        • Topic 0 - Formulation
        • Topic 1 - Stoichiometric relationships
        • Topic 2 and 12 - Atomic structure
        • Topic 3 and 13 - Periodicity
        • Topic 4 and 14 - Chemical structure and bonding
        • Topic 5 and 15 - Energetics
        • Topic 10 and 20 - Organic chemistry
      • Year 2 >
        • Topic 6 and 16 - Chemical kinetics
        • Topic 7 and 17 - Equilibrium
        • Topic 8 and 18 - Acids and bases
        • Topic 9 and 19 - Redox processes
        • Topic 11 and 21 - Measurement and data processing
        • Option D - Medicinal chemistry
    • Lab work >
      • SFP Campus lab reports
      • Internal assessment structure
      • Internal Assessment examples
    • Nature of science
    • General revision
    • Selectividad
    • General information
    • Extended Essay
  • Other resources for students
    • Science Fair
    • Science essays >
      • How to Reference
    • Chemical formulation
    • Laboratory >
      • How to write a lab report
      • Microscopy
      • Excel for graphs and calculations >
        • Calculate the mean and SD
        • Drawing graphs
        • Add error bars to excel graphs
      • Lab videos!
    • Further Reading >
      • Women In Science
      • Infographics
    • Proyecto integrado
San Francisco de Paula, Science Department.

The excretory system
Download the class presentation here

Key Words

haemoglobin               Convoluted tubule       Loop of Henle             nephron           ureter/-s
sweat glands               Bowman’s capsule      Glomerulus                 cholesterol       Bladder
Excretion is the removal of waste products of metabolism from the blood. 

The excretory system is made up of the urinary system and a number of other organs and systems that contribute to the excretion of waste products.
 
- The respiratory system (removing CO2 from the blood)
- Sweat glands (remove various waste products together with the sweat)
- Liver (Removes products left after the breakdown of haemoglobin from old red blood cells. It also eliminates a small amount of cholesterol and some toxic substances)
 
 
But the most important part of the excretory system is the Urinary system.
 
The urinary system eliminates excretory products in the form of urine. The excretory products released include, CO2, urea, uric acid and other substances. It is necessary to keep the body’s vital functions in balance. It regulates the amount of water in tissues (water homeostasis), the concentration and type of mineral salts in the blood and the blood’s pH levels. 


Anatomy and physiology of the kidney

The kidneys and their blood vessels are located in the abdomen. They constantly produce urine which then passes to the bladder.
The kidneys are specilised organs that:
  • Remove the toxic waste product urea from the blood
  • Regulate the water content of the blood (osmoregulation)
They are well adapted to enable them to carry out these processes.
  • Each kidney receives a good supply of blood at high pressure through the renal artery.
  • Each kidney contains hundreds of thousands of tubes called nephrons which filter substances from the blood.
  • Each kidney has an exit tube, the ureter, to carry away the urine (solution of wastes dissolved in water)
  • The kidney is under close control by a feedback system so that water saving is always exactly balanced to the body’s needs
Picture

The nephron

The functional unit of the kidney is the nephron. The nephrons are small tubes surrounded by blood capillaries which filter the blood and produce urine.
Each nephron is made up out of several parts:
  • Bowman’s capsule. This is the first part of the nephron. It is a round sac which contains a curled-up capillary called the Glomerulus.
  • Convoluted tubule. This is a long, twisted tube with two distinct sections: proximal and distal tubule.
  • Loop of Henle. This u-shaped portion of the nephron is located between the proximal and distal convoluted tubes.
           CLICK HERE FOR A GREAT ANIMATION ON THE ULTRAFILTRATION AND REABSORPTION 
Picture
Activities:
  1. What is the function of the kidney?
  2. Where in the kidney is blood filtered? Can you explain the process?


The urinary tracts
​

Ureters: these two narrow tubes, around 28 cm long, connect the renal pelvis of the kidney to the urinary bladder; an elastic sac where urine is stored before it is expelled from the body.
 
Urethra: this duct leads to the outside of the body. At the beginning of the urethra there is a sphincter which stays closed as long as the brain does not send a nervous stimulus to open it (the micturition reflex).
Picture
Activities
  1. Draw and label the urinary system.
  2. Define the concept of excretion.
  3. Define the function of the ureters, bladder and urethra.
  4. Does the urethra have any other functions?

Production of urine
 
Urine is a liquid obtained from the blood and made up of water, various amounts of mineral salts, urea and uric acid and other substances. Urine is produced in two phases:
 
Glomerular filtration (ultrafiltration): In this phase certain substances in the blood in the renal corpuscle pass through into the Bowman´s capsule. This process filters the water and most other soluble substances circulating in the blood plasma.
 
Tubular reabsorption: As they travel through the nephron’s tubule, a lot of the filtered substances are reabsorbed, meaning that they go back into the blood in the surrounding capillaries. These substances include nutrients (glucose, vitamins, amino acids, etc). Some water and mineral salts are also reabsorbed to keep their levels in the blood constant. Water molecules are reabsorbed in the loop of Henle while other substances are reabsorbed in the proximal tubule.
Waste products are not reabsorbed.

Test your knowledge with this quiz


​References

Academic.kellogg.edu (2009). academic.kellogg.edu. Retrieved 28 Nov 2012, from: http://academic.kellogg.edu/herbrandsonc/bio201_mckinley/f27-1al_urinary_system__c.jpg
 
Beltina.org (2011). Beltrina.org Retrieved 28 Nov 2012, from: http://www.beltina.org/pics/nephron.jpg 

Cabrera, C. A. M. (2011). Biology and geology, ESO 3: Oxford Clil. San Fernando de Henares: Oxford Educación.

Pickering, W. (2006). Complete biology for IGCSE. Oxford (England): Oxford University Press.
 
Umm.edu (2010). University of Maryland. Retrieved 28 Nov 2012, from: http://www.umm.edu/graphics/images/en/1101.jpg 

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