The lymphatic system Flashcards
what is the main function of the lymphatic system?
to collect some of the fluid that escapes the blood capillaries and return it to the circulatory system.
also bodies internal defence against disease causing organisms.
what does the lymphatic system consist of?
a network of lymph capillaries joined to larger lymph vessels.
lymph nodes which are located along the length of some lymph vessels.
why does fluid tend to leak out of the arterial end of a lymph vessel?
due to high pressure in the vessel.
some of the fluid returns to the capillary at the venous end.
lymph vessels
lymph vessels originate as blind-ended tubules in spaces between the cells of most tissues.
lymph capillaries are larger and more permeable than blood capillaries.
proteins and disease causing organisms in intracellular fluid easily pass through the walls of the lymph capillaries into the lymph.
network of lymph capillaries join to form two lymphatic ducts that empty lymph into large veins in the upper chest.
how is lymph moved through lymph vessels?
from smooth muscle, skeletal muscle and valves.
the skeletal muscles surrounding the vessels contract, providing additional force.
as there is no central pump, there is no force driving the direction of the flow of lymph, therefore, the larger lymph vessels have valves that close when the pressure drops, preventing the back flow of lymph.
where are lymph nodes located?
in intervals along the lymphatic vessels.
numerous in the neck, armpits, groin and alimentary canal.
structure and function of lymph nodes
bean shaped structure surrounded by a capsule of connective tissue that extends into the node. within this are masses of lymph tissue, containing cells know as lymphocytes, macrophages and plasma cells.
lymph enters on convex side.
role of the lymphatic system in defence against disease
lymph entering lymph nodes contain foreign particles, debris and micro-organisms may be able to cause disease and therefore need to be destroyed.
large particles such as bacteria are trapped in meshwork of fibres as lymph flows through the spaces in the nodes. macrophages ingest these particles by phagocytosis. it is the destroyed by enzymes in the cell.
what happens when infections occur in lymph nodes?
the formation of lymphocytes increases, causing lymph nodes to become swollen and sore.
eg and infected finger may cause swelling and tenderness in the armpit, where there are a large number of lymph nodes.
define lymph
the excess fluid in the tissues returned to the blood by the lymphatic system.
where can lymphoid tissue be found?
mostly in lymph nodes but also in bone marrow, tonsils, spleen and thymus.
what are phagocytic cells?
a cell that can engulf and digest micro-organisms and cell debris.
