Lymphatic and Immune System
Cells, tissues and organs responsible for defending the body against pathogens, toxins,
and cancer cells.
a fluid connective tissue – ground substance is lymph fluid, cells are
lymphocytes – respond to
presence of pathogens (viruses/bacteria)
abnormal body cells (infected or cancerous)
foreign proteins (bacterial toxins)
Cells and tissues involved with defense known as the immune system.
– the responses and actions taken by the body to defend against pathogens.
Primary function of the system is production, maintenance and distribution of
Lymphocytes primarily reside in lymphoid tissue – tonsils, spleen, thymus.
They circulate in blood, but can leave capillaries to enter tissues, and lymphatic vessels.
Lymphatic capillaries - Originate as blind pockets, and are larger than blood capillaries.
Act as a one way valve allowing fluid to drain from the tissues into the lymphatic
circulation, removing excess.
This also allows larger things, such as cells, bacteria,
viruses, proteins, etc. to enter the lymphatics so the lymphocytes can monitor the fluid
and respond to problems as necessary.
connective tissues with many lymphocytes.
Either a nodule (no
capsule, tonsil/appendix) or node.
large nodules in walls of pharynx.
Most people have 5 of them (2 palatine, one
pharyngeal <aka adenoids>, 2 lingual).
Can become infected, requiring removal (if
infection is more than can be handled).
Peyer’s patches – lymph nodules in ileum;
appendix – lymph nodule in large intestine.
have connective tissue capsule.
Lymph flows through a network of
sinuses bringing to lymphocytes inside; this way the lymph is exposed to immune cells
within the lymph node.
(cleaning, and checking for infection)
Node is also like a filter, to purify lymph before it goes back into the venous circulation.
About 99% of antigens in the lymph are removed before it leaves the node (macrophages
So, lymph node is the first warning area that detects the invasion of pathogens.
Swollen lymph glands often occur when activated - thisis due to increasing numbers of
However over-swelling can be symptomatic of things like cancers, chronic
viral infections, or endocrine disorders.
Draining lymph nodes – the first nodes occurring
relative to an area – usually checked in cancer patients for signs of metastasis.