Lymphoid Tissue Flashcards
Why are the respiratory and genitourinary tract prone to invasions by pathogens?
lumen is exposed to the external environment. (remember mucosa surfaces are vulnerable to infections)
3 types of lymphocytes are what?
1) Nk cells
2) T cells
3) B cells
Which lymphoid tissue is not surrounded by a capsule and why does it look like it is?
Diffuse lymphoid Tissue
Because its a lot of lymphocytes clustered together possibly forming nodules in the lamina propia.
Peyers patches are examples of what kind of lymphoid tissue?
Diffuse lymphoid tissue or MALT (mucosa associated lymphatic tissue)
The initial site of immune response is what kind of Tissue?
Diffuse lymphoid Tissue
Name the capsulated lymphoid organs:
Spleen
Thymus
Lymph node
(remember tonsils are partially encapsulated)
What makes up the framework in both lymphoid
tissue and lymphoid organs except the thymus?
Reticular fibers secreted by reticular cells
In the thymus what forms the framework?
epithelial reticular cells
What is Lymphocyte recirculation?
The continuous movement of T and B cells from one location to another they are never anchored in the lymphoid tissue or organ
Why do people present with swollen lymph nodes?
immune system has been activated to fight an invader so there is an increase of lymphocytes within the node
Where do B lymphocyte become immunocompetent?
Red Bone Marrow
Where do CFU-L cells from the bone marrow go to produce immunocompetent T cells
Thymus
Why does the cortex stain darkly as compared to the medulla?
The cortex has more lymphocytes
Why is the medulla Stain lighter?
Because there is less lymphocytes there ( REMEMBER 95% of lymphocytes die by apoptosis before they get to the medulla)
The cytoplasm of the childs thymus contain what?
Tonofilaments/Keratin filaments
What is the embryological origin of the ERCs
Endoderm
What is the embryological origin of the T lymphocytes
Mesoderm
Thymosin, Thymulin and Thymopoetin are secreted by what?
Epithelial Reticular Cells
The blood thymus barrier protects the immature thymocytes from antigens. What creates the blood thymus barrier?
type 1 ERCs
Fibroblasts in the thymus form what?
Capsule and trabeculae
All APCs contain what kind of molecules on them?
Class II MHC
In the medulla what cells are involved in the destruction of the thymocytes that recognize self?
Dendritic cells
a rounded globular mass of cells within the medulla is called what?
hassals corpuscle
Hassals corpuscles are made from what?
ERCs
The failure the thymus to develop properly is called what? What causes this to occur?
Di Georges syndrome
faulty development in the 3rd and 4th pharyngeal arches
Germinal centers are found in which lymphoid nodules?
secondary ( remember it stains lighter because the B cells are proliferating and switch their class of antibodies)
What cell would you find within the germinal center?
Follicular dendritic cell (FDC)
What is the function of the Follicular Dendritic Cell?
they can trap antigens for months or years and They form a network to attract and organize lymphoid cells
The embryological origin of FDCs are:
Mesenchymal
Why are the FDCs different when it comes to their comparison with APCs?
They dont have MHC II molecules.
The accumulation of lymphatic tissue within the ileum is called what?
peyers patch
The primary function of M cells?
they transfer antigens from the lumen by phagocytocis or pinocytosis without processing them to the lymphocytes and macrophages lying deep within.
- THEY ARE NOT APCs
How do foreign substances reach the palantine tonssils?
Crypts
Which tonsil will you not find crypts and lies beneath pseudostratified ciliated columnar epithelium?
pharyngeal tonsils
A single crypt that is lined by non-karitinized stratified squamous epithelium can be found where?
Lingual tonsil
In the lymph node where do must lymphocytes enter through?
HEVs
The endothelial cells lining the venules are what?
cuboidal
Homing is referred to as what?
the movement of T and B lymphocytes through the HEVs
Where are B cells concentrated within the spleen or lymphnode?
Outer cortex
Where are T cells concentrated?
paracortex
The subscapular sinus is composed of what?
Loose network of reticulum cells and fibers
The main cell type within the medullary cord is what?
Plasma Cells and B cells
Sinusoids and Splenic cords ( bilroth) are found where in the spleen?
Red pulp
The periarterioal lymphoid sheath is found where?
Within the white pulp
White pulp functions as what?
Location where B cell clones are found along with T-cells that come from the PALS
What is the role of the marginal zone?
To trap the antigen from circulation to present it to the lymphocytes of the spleen
In the spleen where do the antigens enter?
Through the blood ( remember antigens enter through the lymph in the lymph node)
Describe the Path of the pathogen as it enters the spleen.
Antigen enters through the blood, and goes toward white pulp through trabeculated arteries and marginal sinus»»» APCs detect them by the PALS»> T cells interact with B cells»> B cells proliferate and differentiate into plasma»> plasma secretes Igs to the blood circulation
Describe the path of open circulation.
Blood from white pulp go to»_space;>penicillar arteries»>sheathed capillaries»> percolate in the red pulp cords»> red pulp sinusoids» veins
Stave cells line what?
Splenic venous sinus
How are the damaged RBCs removed when someone does not have a spleen?
macrophages in the liver and bone marrow
What lymph organs contain efferent lymph vessels?
Thymus, Spleen, Tonsils
