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DP IB Biology: SL

Revision Notes

Home / IB / Biology: SL / DP / Revision Notes / 6. Human Physiology / 6.3 Defence Against Infectious Disease / 6.3.1 Skin


6.3.1 Skin


Skin

  • The skin and mucous membranes form a primary defence against pathogens that cause infectious disease
  • Skin is the largest organ of the body and is covered in microorganisms that usually cause no issues, as they can't enter the body. Skin provides:
    • A tough physical barrier that prevents entry of pathogens into our bodies
    • Cuts in the skin are sealed by formation of blood clots to prevent entry of pathogens
    • Chemical protection through the production of sebum from the sebaceous glands of the hair follicles
      • Sebum is a chemical responsible for maintaining a low skin pH which inhibits the growth of microorganisms
  • Mucous membranes are found lining vulnerable areas which may be a route for pathogens into the body
    • This includes the airways, areas around the reproductive organs (foreskin and vagina) and the digestive system

  • The membranes contain goblet cells which produce mucus containing glycoproteins
    • Microorganisms and particles become trapped by the mucus and are then either swallowed (into the stomach) or expelled, therefore preventing infection
    • Mucus also contains lysozyme enzymes which have antibacterial properties, providing more protection from invading microorganisms



    • 1. Cell Biology
      • 1.1 Cells: Theory
        • 1.1.1 Cell Theory
          • 1.1.2 Functions of Life
            • 1.1.3 Surface Area to Volume Ratio
              • 1.1.4 Cell Specialisation
                • 1.1.5 Stem Cells
                  • 1.1.6 Skills: Cell Theory
                  • 1.2 Cells: Origin & Ultrastructure
                    • 1.2.1 Origin of Cells
                      • 1.2.2 Endosymbiotic Theory
                        • 1.2.3 Prokaryotic Cell Structure
                          • 1.2.4 Eukaryotic Cell Structure
                            • 1.2.5 Exocrine Pancreatic & Palisade Mesophyll Cells
                              • 1.2.6 Comparison of Prokaryotic & Eukaryotic Cells
                                • 1.2.7 Microscopes
                                  • 1.2.8 Skills: Drawing Cells
                                    • 1.2.9 Skills: Cell Origin & Ultrastructure
                                    • 1.3 Cells: Membrane Structure & Transport
                                      • 1.3.1 Phospholipid Bilayer Properties
                                        • 1.3.2 Membrane Proteins
                                          • 1.3.3 History of Fluid Mosaic Model
                                            • 1.3.4 Membrane Transport
                                              • 1.3.5 Active Transport & Bulk Transport
                                                • 1.3.6 Skills: Membrane Structure & Transport
                                                  • 1.3.7 Skills: Estimation of Osmolarity
                                                  • 1.4 Cells: Division
                                                    • 1.4.1 Cell Cycle
                                                      • 1.4.2 Phases of Mitosis
                                                        • 1.4.3 Cancer
                                                          • 1.4.4 Skills: Cell Division
                                                        • 2. Molecular Biology
                                                          • 2.1 Metabolism & Water
                                                            • 2.1.1 Molecules
                                                              • 2.1.2 Metabolism
                                                                • 2.1.3 Hydrogen Bonds
                                                                  • 2.1.4 Water
                                                                  • 2.2 Carbohydrates & Lipids
                                                                    • 2.2.1 Carbohydrates
                                                                      • 2.2.2 Fatty Acids
                                                                        • 2.2.3 Lipids
                                                                          • 2.2.4 Skills: Visualising Carbohydrates
                                                                            • 2.2.5 Skills: Calculating BMI
                                                                            • 2.3 Proteins
                                                                              • 2.3.1 Proteins
                                                                                • 2.3.2 Protein Structure & Function
                                                                                  • 2.3.3 The Variety of Proteins
                                                                                    • 2.3.4 Skills: Molecules
                                                                                    • 2.4 Enzymes
                                                                                      • 2.4.1 Enzymes
                                                                                        • 2.4.2 Immobilised Enzymes
                                                                                          • 2.4.3 Skills: Enzyme Experiments
                                                                                          • 2.5 Nucleic Acids: Structure & DNA Replication
                                                                                            • 2.5.1 DNA & RNA Structure
                                                                                              • 2.5.2 DNA Replication
                                                                                                • 2.5.3 Skills: DNA Replication
                                                                                                • 2.6 Transcription & Translation
                                                                                                  • 2.6.1 Transcription
                                                                                                    • 2.6.2 Translation
                                                                                                      • 2.6.3 Biotechnology
                                                                                                        • 2.6.4 Skills: DNA, RNA & Protein Synthesis
                                                                                                          • 2.6.5 Skills: Interpreting Sequences
                                                                                                          • 2.7 Cellular Respiration
                                                                                                            • 2.7.1 Cellular Respiration
                                                                                                              • 2.7.2 Anaerobic Respiration
                                                                                                                • 2.7.3 Aerobic Respiration
                                                                                                                  • 2.7.4 Skills: Respiration
                                                                                                                  • 2.8 Photosynthesis
                                                                                                                    • 2.8.1 Photosynthesis
                                                                                                                      • 2.8.2 Photosynthesis Continued
                                                                                                                        • 2.8.3 Skills: Photosynthesis
                                                                                                                          • 2.8.4 Skills: Separating Photosynthetic Pigments
                                                                                                                        • 3. Genetics
                                                                                                                          • 3.1 Genes & Chromosomes
                                                                                                                            • 3.1.1 Genes
                                                                                                                              • 3.1.2 Alleles
                                                                                                                                • 3.1.3 Mutation
                                                                                                                                  • 3.1.4 Genome
                                                                                                                                    • 3.1.5 Prokaryotic Chromosomes
                                                                                                                                      • 3.1.6 Eukaryotic Chromosomes
                                                                                                                                        • 3.1.7 Chromosome Number
                                                                                                                                          • 3.1.8 Sex Determination
                                                                                                                                            • 3.1.9 Karyograms
                                                                                                                                              • 3.1.10 Skills: Using Databases
                                                                                                                                              • 3.2 Meiosis
                                                                                                                                                • 3.2.1 Meiosis
                                                                                                                                                  • 3.2.2 Stages of Meiosis
                                                                                                                                                    • 3.2.3 Genetic Variation
                                                                                                                                                      • 3.2.4 Non-disjunction
                                                                                                                                                        • 3.2.5 Skills: Meiosis
                                                                                                                                                        • 3.3 Inheritance
                                                                                                                                                          • 3.3.1 Inheritance
                                                                                                                                                            • 3.3.2 Inheriting Alleles
                                                                                                                                                              • 3.3.3 Skills: Inheritance
                                                                                                                                                                • 3.3.4 Inheritance of Genetic Diseases
                                                                                                                                                                  • 3.3.5 Mutations & Disease
                                                                                                                                                                  • 3.4 Genetic Modification & Biotechnology
                                                                                                                                                                    • 3.4.1 Electrophoresis & PCR
                                                                                                                                                                      • 3.4.2 DNA Profiling
                                                                                                                                                                        • 3.4.3 Genetic Modification
                                                                                                                                                                          • 3.4.4 Cloning
                                                                                                                                                                            • 3.4.5 Skills: Genetic Modification & Biotechnology
                                                                                                                                                                          • 4. Ecology
                                                                                                                                                                            • 4.1 Species, Communities, Ecosystems & Energy Flow
                                                                                                                                                                              • 4.1.1 Species & Population
                                                                                                                                                                                • 4.1.2 Methods of Nutrition
                                                                                                                                                                                  • 4.1.3 Community
                                                                                                                                                                                    • 4.1.4 Nutrient Cycling
                                                                                                                                                                                      • 4.1.5 Energy Flow
                                                                                                                                                                                        • 4.1.6 Energy Losses
                                                                                                                                                                                          • 4.1.7 Skills: Species, Communities, Ecosystems & Energy Flow
                                                                                                                                                                                            • 4.1.8 Skills: Chi-squared test & Statistical Significance
                                                                                                                                                                                              • 4.1.9 Skills: Pyramids of Energy
                                                                                                                                                                                              • 4.2 Carbon Cycling & Climate Change
                                                                                                                                                                                                • 4.2.1 Carbon Cycle: Carbon Dioxide
                                                                                                                                                                                                  • 4.2.2 Carbon Cycle: Carbon Dioxide in the Atmosphere
                                                                                                                                                                                                    • 4.2.3 Carbon Cycle: Methane
                                                                                                                                                                                                      • 4.2.4 Carbon Cycle: Organic Matter
                                                                                                                                                                                                        • 4.2.5 Climate Change: Greenhouse Effect
                                                                                                                                                                                                          • 4.2.6 Climate Change: Impact
                                                                                                                                                                                                            • 4.2.7 Climate Change: Causes
                                                                                                                                                                                                              • 4.2.8 Skills: Carbon Cycling & Climate Change
                                                                                                                                                                                                            • 5. Evolution and biodiversity
                                                                                                                                                                                                              • 5.1 Evolution & Natural Selection
                                                                                                                                                                                                                • 5.1.1 Evolution
                                                                                                                                                                                                                  • 5.1.2 Evolution: Evidence
                                                                                                                                                                                                                    • 5.1.3 Variation
                                                                                                                                                                                                                      • 5.1.4 Natural Selection
                                                                                                                                                                                                                        • 5.1.5 Natural Selection Examples
                                                                                                                                                                                                                        • 5.2 Classification & Cladistics
                                                                                                                                                                                                                          • 5.2.1 Classification System
                                                                                                                                                                                                                            • 5.2.2 Classifying Organisms
                                                                                                                                                                                                                              • 5.2.3 Plant Phyla Features
                                                                                                                                                                                                                                • 5.2.4 Animal Phyla Features
                                                                                                                                                                                                                                  • 5.2.5 Cladistics
                                                                                                                                                                                                                                    • 5.2.6 Reclassification
                                                                                                                                                                                                                                      • 5.2.7 Skills: Classification & Cladistics
                                                                                                                                                                                                                                    • 6. Human Physiology
                                                                                                                                                                                                                                      • 6.1 Digestion & Absorption
                                                                                                                                                                                                                                        • 6.1.1 Digestion
                                                                                                                                                                                                                                          • 6.1.2 Villi & Absorption
                                                                                                                                                                                                                                            • 6.1.3 Absorption
                                                                                                                                                                                                                                              • 6.1.4 Skills: Digestion & Absorption
                                                                                                                                                                                                                                              • 6.2 The Blood System
                                                                                                                                                                                                                                                • 6.2.1 The Blood System: History
                                                                                                                                                                                                                                                  • 6.2.2 The Blood System: Vessels
                                                                                                                                                                                                                                                    • 6.2.3 The Blood System: Double Circulation
                                                                                                                                                                                                                                                      • 6.2.4 The Blood System: Cardiac Cycle
                                                                                                                                                                                                                                                        • 6.2.5 The Heart Rate
                                                                                                                                                                                                                                                          • 6.2.6 Skills: The Blood System
                                                                                                                                                                                                                                                          • 6.3 Defence Against Infectious Disease
                                                                                                                                                                                                                                                            • 6.3.1 Skin
                                                                                                                                                                                                                                                              • 6.3.2 Blood Clotting
                                                                                                                                                                                                                                                                • 6.3.3 White Blood Cells
                                                                                                                                                                                                                                                                  • 6.3.4 Antibiotics
                                                                                                                                                                                                                                                                    • 6.3.5 Antibiotic Resistance
                                                                                                                                                                                                                                                                    • 6.4 Gas Exchange
                                                                                                                                                                                                                                                                      • 6.4.1 Ventilation: Function & Structures
                                                                                                                                                                                                                                                                        • 6.4.2 Ventilation: Mechanism
                                                                                                                                                                                                                                                                          • 6.4.3 Lung Diseases
                                                                                                                                                                                                                                                                            • 6.4.4 Skills: Monitoring Ventilation
                                                                                                                                                                                                                                                                            • 6.5 Neurones & Synapses
                                                                                                                                                                                                                                                                              • 6.5.1 Neurones: Function & Structure
                                                                                                                                                                                                                                                                                • 6.5.2 Nerve Impulses
                                                                                                                                                                                                                                                                                  • 6.5.3 Synapses
                                                                                                                                                                                                                                                                                    • 6.5.4 Skill: Neurones & Synapses
                                                                                                                                                                                                                                                                                    • 6.6 Hormones, Homeostasis & Reproduction
                                                                                                                                                                                                                                                                                      • 6.6.1 Hormones
                                                                                                                                                                                                                                                                                        • 6.6.2 Hormones Continued
                                                                                                                                                                                                                                                                                          • 6.6.3 Reproduction: Background
                                                                                                                                                                                                                                                                                            • 6.6.4 Reproduction: Sex Determination in Males
                                                                                                                                                                                                                                                                                              • 6.6.5 Reproduction: Sex Determination in Females
                                                                                                                                                                                                                                                                                                • 6.6.6 Skills: Reproduction Diagrams
                                                                                                                                                                                                                                                                                              Ruth Brindle

                                                                                                                                                                                                                                                                                              Author: Ruth

                                                                                                                                                                                                                                                                                              Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. With 10 years of teaching experience across the 3 key science disciplines, Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.


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