Lymphoid System Flashcards
(25 cards)
Where do B cells and where do T cells mature
B - Bone Marrow
T - Thymus
Secondary Lymphoid Tissue
Lymph Nodes
Spleen
Mucosa associated lymphoid tissue (MALT) (e.g. tonsils or other diffuse cells throughout various systems)
What is lymph
Interstitial fluid from capillary beds that is not picked up by venules - 20% of interstitial fluid
How is lymph returned to the circulatory system
Via Lymphatic Vessels
Why does the body not pick up all the interstitial fluid instead of going via lymphatic vessels
On the way to the venules, they go through lymph nodes
Lymphoedema
Blocked lymph vessels causing swelling
Can be side effect of radiotherapy
What kinds of surfaces have antigen presenting cells and what are they
Exposed surfaces - Digestive system, Respiratory System, Skin
Dendritic Cells/Macrophages
Shape of lymph nodes and their structure
Bean Shaped
Composed of a cortex and medulla supported by a reticular network and surrounded by a connective tissue capsule
How does lymph enter, travel through and leave lymph nodes
Via afferent lymphatics into a network of sinuses (subcapsular, corticular and medullary) which ultimately drain into efferent lymphatics
Macrophages and dendrites enter through lymphatics as well
Where are lymphoid follicles relative to the lymph nodes
On the superficial cortex/outside of the lymph nodes
Where does lymph node blood supply enter and leave
At the hilum along with the lymphocytes
What happens to lymphocytes in a lymph node if they do not recognise any antigen
They leave within a few hours and might go to another lymph node to find antigens there
How often does an average lymph node turn over its lymphocyte population in a day
About 10-48 times per day - note that lymphocytes really are not static
Annotate
Describe Antigen Presenting Cells
Macrophages or dendritic cells that phagocytose intruders and present ingested proteins on MHC [Major Histocompatibility Complex] on their surface
Describe immunity in the lymph node
APCs travel to paracortex to present protein fragments leading to T cell activation and proliferation
B Cells pick up the antigen in the follicle, ingest it and move to B/T cell zone interface
Activated T & B cells meet at B/T cell zone interface and the specific T helper cell activates the B cell to proliferate and mature
Activated B cell moves back to cortex to proliferate and mature resulting in a germinal centre
What happens to the size of lymph nodes with higher proliferative activity
They enlarge
When do lymph nodes enlarge
When there is an infection in the body
When they are infected
Tumour of the lymphoid system (Lymphoma)
When tumour metastasises to nearby lymph nodes
Which cells are generally associated with Lymphomas
Lymph nodes and spleen cells
Lymphocytes in bone marrow and blood are sometimes involved but more commonly so in leukemia
What does the spleen do
Does to blood what lymph nodes to for lymph
Filters circulating blood through sinusoids to remove effete RBCs (approx 3 months) and platelets
Phagocytoses blood borne microorganisms and mounts an immune response to antigens in the blood
What happens following a splenectomy
Infection and an increased number of deformed RBCs/Platelets
Describe the structure of the spleen
Comprised of a collagenous capsule surrounding a reticulin network (which supports many sinusoids [red pulp] and lymphoid aggregates [white pulp])
White pulp equivalent to paracortex and superficial cortex of lymph node
Blood supply through hilum via splenic artery and vein
What happens to blood entering the spleen
Ends up in sheathed capillaries lined with macrophages
Bad cells can’t squeeze through gaps of venous sinuses and are phagocytosed; good cells pass into sinuses which pass drain into veins
Describe tissue of Mucosa Assosciates Lymphoid Tissue (MALT)
Single cells or aggregates of lymphocytes;
contains lymph follicles or nodules just underneath epithelia with no distinct connective tissue capsule
