first line of defence
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Expected Learning: To develop a comprehensive understanding of the first line of defence in the immune system. First Line of Defence. By Eden Aspinall and Theresa Hudson. Physical Barriers: Animals. Integumentary system (skin) is the main barrier, preventing pathogens from entering - PowerPoint PPT PresentationTRANSCRIPT
First Line of DefenceBy Eden Aspinall and Theresa Hudson
Expected Learning:• To develop a
comprehensive understanding of the first line of defence in the immune system.
Physical Barriers: Animals Integumentary system (skin) is the main
barrier, preventing pathogens from entering Like a blockade? Mucosal (mucus) membranes inhibits
bacteria Natural agents like sweat are secreted to
eradicate bacteria The body grows bacteria to provide a natural
competitor for other bacteria. http://
www.youtube.com/watch?v=Non4MkYQpYA&feature=related
Skin as a Barrier
Joharn‘s yucky ear!
BLEGH!
Natural Agents as a Barrier
Chemical Barriers: Animals Certain white blood cells destroy invading
microorganisms. Sweat and fatty acids have properties that
repel pathogens The immune system produces substances
and agents that are designed to attack the invading microorganisms.
Enzymes like lysozyme, found in tears and saliva ‘lyse’ or burst pathogenic substances
White Blood Cells asa Barrier
Immune System as a Barrier
What about plants? What!? They have no immune system!?
They actually don’t!!Many plants are resistant to pathogens and have several characteristics that protect them from infection from things such as insects and nematode worms.
Physical Barriers: Plants External covering of plants works like skin
while repelling bacteria. Plants have physical responses to prevent
infection spreading such as ‘galls’ Galls, like scabs, form a sort of ‘cork’ when a
plant is infected These stop the parasite or infection from
spreading throughout the plant. Often, the stomata is a common ‘entry point’. Thorns are another type of defence
Chemical Barriers: Plants Produce chemicals that act as
antibiotics. Some leaves have high silicon content to
prevent harmful pathogens. Some trees produce oils or gum to repel
or reduce infection Resins, Tannins and Phenolic substances
also help repel malevolent substances. ‘The tale of the Ouchie Mouth’
Chemicals as a Barrier
Internal Organs and Tissue in the Immune System Bone marrow – Stem cells differentiate
into a range of different cell types before leaving the bone marrow, mainly T cells and B cells
Thymus – T cells go through thymic selection and circulate in the bloodstream after maturing.
Spleen – B cells travel from the bone marrow into the spleen and mature.
More Organs and Tissues in the Immune System Lymph Vessels and Nodes Other Lymphoid Tissue ^Ears, eyes, gut etc.
Self and Non-Self Materials made by the body’s own cells is
called self. Foreign material is called non-self. When invaded by non-self material, the
immune system is activated. Self can be: blood cells, plasma,
reproductive cells, etc. Non-self can be: Toxins, dirt, bacteria,
pollen etc.
Major Histocompatibility Complex MHC: A cluster of genes that encode
information for the production of marker proteins on the surface of cells.
Two types of ‘markers’ in our bodies:Class 1 markers: Found on every cell except red blood cells. Class 2 markers: Found on Macrophages B and T cells.
How do they tell the difference? T and B cells recognise similar markers
on other cells and ignore them, as they are not a threat
They respond to the foreign MHC markers on ‘invaders’.
Like if you saw someone in the enemy’s uniform sneaking around your camp
When they come into contact with foreign, or non-self material, they
Antigens Any foreign substance that causes the
immune system to create antibodies against it
These activate the production of ‘antibodies’
‘Self-antigens’ can also be found in immune cells. These are like ‘markers’
Homework & Reflection Reflection
Answer the multiple choice questions on the following slide.
Homework Quick check pg.
250, questions 1 - 3
Reflection: Multiple Choice Question 13 First-line defences that mammals have
against invasion by disease-causing bacteria include
A. lysozymes. B. interferons. C. antibodies. D. killer T cells.
Reflection cont’d Question 19 First-line defence mechanisms in
humans include A. development of fever. B. action of phagocytes. C. use of antibiotics. D. presence of cilia.
Reflection cont’d Question 8 Evidence that a vascular plant has an
infectious disease includes the A. drying out of root hairs during drought. B. yellowing of leaves due to deficiency of
iron. C. presence of spores on fungal hyphae
growing out of stomata. D. presence of nitrogen fixing bacteria in the
root nodules of legume plants.