lines of defence Flashcards
first line of defence (non-specific)
- structures, chemicals, processes that work to prevent pathogens entering the body
- includes the skin and mucous membranes of the respiratory, digestive, urinary and reproductive systems
normal flora or gut microbiota
protect the body by competing with potential pathogens:
- this is called microbial antagonism
protects by :
- consuming nutrients that would otherwise be available to pathogens
- change pH to hinder competing microbes
- stimulates 2nd line of defence
- improve overall health by producing several types of vitamins
skin (physical defence)
- epidermis
- multiple layers of tightly packed cells
- sheds dead skin cells
- few pathogens can penetrate - dermis
- collagen
strength and plilability to resist abrasions that could introduce microorganisms
second line of defence (non-specific)
- activated when pathogens penetrate skin or mucous membrane
- cells, antimicrobial chemicals, and processes (but no physical barriers)
- many of these components are contained or originate in the blood
leukocytes extracellular killing (2nd line of defence )
- natural killer lymphocytes
- eosinphils
- neutrophils
eosinophils
main effector cells in allergic responses and asthma
also fight helminth (worm) colonization
neutrophils
most abundant WBC
predominant cells in pus (white apperance)
responds quickly after tissue injury
acute inflammation
basophils
least common granulocyte
when activated, release histamine and other inflammatory chemicals
leukocytes agranulocytes
- lymphocytes
most involved in specific immunity (3rd line) - monocytes
leave the blood and mature into macrophages
(phagocytic cells of the second line of defense)
T lymphocytes - T cells
- helper T cells
- killer T cells (cytotoxic)
- circulate in the lymph and blood, migrate to the lymph nodes
part of the cellular immune response against:
- endogenous invaders
- abnormal invaders
B lymphocytes - B cells
produce:
plasma - cells make antibodies to a pathogen
- memory cells - remember the same pathogen for a faster antibody production in future infection
second line of defense (how does it work)
- leukocytes phagocytosis - how phagocytes ingest and destroy foreign matter such as microorganisms
- extracellualr killing by leukocytes - non specific chemical defence
- inflammation
- fever
lymphocytes
- WBC of specific immunity
- produced from blood stem cells in the red blood marrow
- B and T cells
B and T cells mature and circulate in the blood and lymph
- circulation ensures they come into contact with pathogens and each other
leukocytes granulocytes
white blood cells with granules in the cytoplasm
- neutrophils
- basophils
- eosinophils
blood formed elements
three types of formed elements
- erytinrocytes - red blood cell, carry oxygen and carbon dioxide in the blood
- platelets - involved in blood clotting ( also called thrombocytes)
- leukocytes - white blood cells -involved in defending the body against invaders
- granulocytes
- agranulocytes
lymphatic system (3rd line)
- screens tissue of the body for foreign antigens
- composed of lymphatic vessels and lymphatic cells
- a one-way system that conducts lymph from local tissues and returns it to the circulatory system
- lymph nodes housed with blood cells called lymphocytes that recognize and attack foreign antigens present in the lymph
third line of defenence (acquired)
the body’s ability to recognize and defend itself against distinct invaders
- specific and adaptive immunity
- “memory” allows it to respond rapidly to additional encounters with a pathogen
Two types:
1. naturally acquired
2. artificially acquired
artificially acquired
response to antigen introduced via vaccine
naturally acquired
immune response against antigens encountered in daily life
skin (chemical defence)
perspiration
-salt and water
- antimicrobial peptides
- lysozyme - destroys cell wall of bacteria
-
sebum
- keeps skin pliable and less likely to tear
- lowers pH of skin - inhibitory to many bacteria
