Lymphatic System I & II Flashcards
How are the functions of the lymphatic system carried out by?
Cells
effector molecules
tissues
organs
what cells arise from lymphoid stem cells?
T lymphocytes
NK cells
B lymphocytes – plasma cells
what are the two types of T cells?
Helper CD 4+
Cytotoxic CD 8+
what do helper CD 4 activate?
B lymphocytes
CD 8+ with IL-2 production
what types of lymphocytes are capable of recirculation?
T cells - 60-70% of circulating lymphocytes
Where are B cells produced?
bone marrow
what do NK cells attack?
virally infected cells
cancer/tumor cells
what types of cells carryout innate responses?
neutrophils
macrophages
mast cells
NK cells
what are the characteristics of innate responses?
fast and non specific
does not produce memory cells
What cells are involved in adaptive response?
B and T cells - depends on the initial recognition of antigens
what are the characteristics of adaptive responses?
slower and specific
produces memory cells
when is antibody mediate immunity (humoral immune response) important?
bacterial infections
what cells are involved in humoral immune responses? what are the effectors?
helper T cells
B cells
plasma cells
Immunoglobin molecules
When is cell mediated immunity important?
viral and fungal infections - involved in the rejection of transplanted organs and tissue grafts
what are the cells involved in cell mediated immunity? what are the effectors?
Cytotoxic T cells
T cells (effector)
what is the characteristic of diffuse, loose lymphoid tissue?
few lymphocytes present
initial immune response
found in lamina propria
intercepts antigen
no capsule
what is the characteristic of diffuse, dense lymphoid tissue?
many lymphocytes are present
contained in meshwork of reticular fibers
No capsule
what does the GC indicate?
lymphatic tissue response to antigen
what does a primary nodule consist of?
small lymphocytes
not ever exposed to antigen
found in newborns only
what does a secondary nodule consist of?
germinal cortex (GC)
what is the germinal cortex?
where lymphocytes undergo proliferation
what is a follicular dendritic cell?
Not an antigen presenting cell
help keep the antigen-antibody complex in place
what is the major cell found in lymphoid nodules?
B lymphocytes
what cells are found around the periphery of the lymphoid nodules?
T cells
where does the thymus originate from?
3rd pharyngeal pouch
epithelium?
what is important to note about the thymus?
no afferent lymphatics - just efferent
why? - because there is no filter, just production and migration through efferent
what type of cells make up the epithelial component of the thymus?
ERC - epithelial reticular cells
what are thymocytes?
immature T lymphocytes
what are the parenchyma of the thymus?
Cortex and medulla
what is in the cortex?
immature T lymphocytes = thymocytes
ERCs
whats in the medulla?
mature T lymphocytes
ERCs
thymic corpuscle (Hassall) - consist of rings of degenerating epithelial reticular cells
what type of tissue make up the thymus capsule?
dense irregular CT - throw in septa to divide tissue into lobule = trebeculae
what are the primary support cells in the cortex?
ERCs
they form a cytoreticulum which is held together by desmosomes (keratin)
what happens to the thymus after puberty?
involution - replaced with fat (accumulation)
What condition is the thymus gland absent?
DiGeorge Syndrome 22q11
where is the defect in DiGeorge’s Syndrome?
Defect in the development of the 3rd & 4th branchial pouche s& arches.
what does the mneumonic “Catch 22” stand for?
Cardiac defects Abnormal facies Thymic hypoplasia Cleft palate Hypocalcaemia resulting from 22q11 deletions.
what types of cells are found in the paracortex (inner cortex)?
T cells
what do lymph nodes have?
afferent lymphatic vessel - drains lymph through convex margin
what does the outer cortex of lymph nodes contain?
lymphatic nodules - composed of mainly B cells
few T cells, reticular cells, macrophages, antigen presenting cells
what do HEVs allow?
transition of lymphocytes from the blood stream to lymph tissue
found in deep cortex
what are the two parts of the medulla in the lymph nodes?
medullary cords
medullary sinuses
whats in the medullary cords?
its dense lymphoid tissue
contains B cells, plasma cells, reticular cells, macrophages
what do medullary sinus contain?
separates medullary cords
contains lymph, few macrophages
granulocytes maybe present
what makes up the stroma of lymph nodes?
reticular cells (modified fibroblasts)
what is the stroma of lymph nodes a framework for?
myeloid (bone marrow) and lymphoid (lymph nodes, spleen) organs
where does lymph tissue/organs come from?
mesoderm
what is the parenchyma of the spleen?
red pulp
white pulp
what is in the red pulp?
cords of cells (cords of Billroth)
Sinusoidal capillaries
dense network of reticular fibers - numerous erythrocytes, lymphocytes, plasma cells, macrophages and other graulocytes
what is in the white pulp?
thick accumulation of lymphocytes
lymphatic nodules - GC decrease with age
what is PALS?
T lymphocytes surround the central artery
“peri arteriolar lymphatic sheath”
what surrounds PALS?
B cells - sheathed artery
what is the marginal zone?
the rim of lymphocytes (T cells and B cells) along with APCs and macrophages
where do lymphocytes first come in contact with antigens?
marginal zone
in the red pulp, the central a. gives ride to what?
penicillar arteries which ultimately become sinusoidal capillaries
what is closed circulation?
sinusoidal capillaries may continue into venues to pulp veins
what is open circulation?
sinusoidal capillaries can open into the cords, drain blood cells and eventually the pulp veins are formed
what are splenic sinusoids lined by?
elongated endothelial cells (Littoral Cells) - supported by an incomplete basal lamina of reticular fibers
what is the function of macrophages in circulation?
to remove damaged or effete erythrocytes from circulation
what secondary lymphoid organ is GALT?
“gut associated lymphoid tissue”
Tonsils
what is the function of the tonsils?
process antigens that enter the body through oral cavity and nasal passage
what are lymphatic tissue lined by epithelium?
tonsils
how many palatine tonsils do we have?
2
what are crypts and what do they do?
invagination of epithelium
contain desquamated epithelial cells, live and dead lymphocytes and bacteria
what is found in the region where crypts are found?
mainly secondary nodules (with GC)
what is the purpose of the posterior separation from the superior constrictors by a thick capsule?
prevents the spread of infection
what is pharyngeal tonsils lined with?
pseudostratified columnar epithelium = respiratory epithelium
what do you call inflammed pharyngeal tonsils?
adenoids
what is Waldeyer’s Ring?
1 pharyngeal tonsil
2 palatine tonsils
1 lingual tonsil
what do thymic corpuscles have?
keratin filaments which can be keratinized and calcify - which is why in elderly people you can see calcified spots in thymus in the superior mediastinum
if you see a central artery, what organ are we looking at?
spleen!
