Practical 2: Secondary Lymphoid Organs Flashcards
What is the function of a secondary lymphoid organ?
They increase the chances that a mature lymphocyte will meet it’s antigen
List the main secondary lymphoid organs
(6)
Spleen
Appendix
Lymph nodes
Tonsils
Peyer’s patches
Lamina propria
List the different groups of lymph nodes
Cervical lymph nodes (neck)
Axillary lymph nodes
Inguinal lymph nodes
Mesenteric lymph nodes
What three things make up Waldeyer’s ring?
Lymph nodes
Tonsils
Adenoids
What is lymph?
The fluid that remains in tissue after interstitial fluid is returned to the blood
Plasma seeps into tissue -> interstitial fluid -> blood -> remainder = lymph
What does lymph consist of?
(8)
Water
Ions
Nutrients
Gases
Proteins
Hormones
Enzymes
Waste products of cells
What constituents of lymph are derived from cells?
Hormones
Enzymes
Waste products of cells
What constituents of lymph are derived from plasma?
Ions
Nutrients
Gases
Proteins
What are the four types of lymphatic vessels?
Lymphatic capillaries
Lymphatic collecting vessels
Lymphatic trunks
Lymphatic ducts
What fluid does the lymph system take up?
It only takes up the fluid that is not taken up by the venous system -> returned to blood
Write a note on lymphatic collecting vessels
Similar to veins
Have lots of valves
Both superficial and deep
Pass through lymph nodes (afferent and efferent)
Distinguish afferent from efferent.
Afferent = in
Efferent = out (exit)
Describe the gross anatomy of the lymph node
(5)
Bean shaped
Fully encapsulated with a subcapsular sinus
Has a really good blood supply - artery and vein
Afferent and efferent lymphatic supply
Hilum = indented area
Describe the structure of a lymph node
(7)
Subcapsular sinus
Cortex
Paracortex
Medulla
Medullary sinus
Lymphoid follicles (primary and secondary)
Germinal centres
What is the B cell area of a lymph node?
Lymphoid follicles
Where are lymphoid follicles found in the body?
They are found in secondary lymphoid organs
What cells are found inside the capsule?
Subcapsular macrophages
Where is considered the T cell area of the lymph node?
Para cortex
Where are plasma cells found in the lymph node?
Medullary cords
What are medullary cords?
If you look at the medulla under high magnification you can see gaps between cells (sinuses) if the cells are bundled together with a layer of endothelium - this structure is called a medullary cord
What are subcapsular macrophages?
A special population which is not great at phagocytosis but is goof at trapping antigens on their surface membranes
What type of cell is found in the medullary chords?
Plasma cells
What type of cell is found in the paracortex?
T cells
What type of cells are found in the lymphoid follicles?
B cells
What happens in primary lymphoid follicles?
(2)
B cells have not encountered an antigen yet
These follicles have no light coloured centre/germinal centre
What happens in secondary lymphoid follicles?
(3)
B cells here have encountered their antigen
There is a light centre to the follicle/germinal centre
The dark ring around the centre is called the mantel zone
How do most lymphocytes enter the lymph nodes?
Most enter through blood not through lymph
What happens at the hilum?
(2)
Blood vessels enter and leave here
The efferent lymphatic vessel leaves here
Where does the afferent lymphatic vessel attach?
It pierces the lymph node at two spots the opposite side of the hilum
What cells form the supporting tissue of the lymph node?
Fibroblast recticular cells
What does HEV stand for?
High endothelial venules
What does HEC stand for?
High endothelial cells
What do HEVs do?
Lymphocytes use these to get into the lymph node by adhering to the HECs on the edge of the HEV
What cells come together to form the Fibroblast reticular cell conduit?
This is where fibroblast reticular cells support the maintenance of naive T cells
List the four different tonsils
Lingual
Palatine
Tubal
Adenoid
Where are your lingual tonsils?
Back of throat
Where are your palatine tonsils?
Back of mouth
Where are your adenoids?
Just behind the nose
Where are tubal tonsils located?
Lateral wall of the nasopharynx
Write a note on the palatine tonsil
(3)
Hemi-capsule
Crypts are found within the tonsil and are lined with simple epithelium (M cells)
Primary and secondary follicles
Why does the palatine tonsil have a hemi-capsule?
(3)
Because the tonsil needs to have a small amount of surface area exposed to the elements
In the areas where there is no capsule there is stratified squamous epithelium
Simple epithelium is found within crypts for screening
What is the function of crypts?
They increase surface area
What is the function of the stratified squamous epithelium of the tonsils?
Protection
What is the function of the simple epithelium of the palatine tonsil?
Antigen sampling
Write a note on the anatomy of the spleen
No lymphatic vessels in or out
Really good blood supply (splenic artery, splenic vein)
Hilum
What is the function of the spleen?
Responsible for producing blood cells before birth
Responsible for protecting against blood born infection
What are the two regions of the spleen?
Red pulp
White pulp
Write about red pulp
This is where dead or old rbcs are cleared by macrophages
Write about white pulp
This is where the initiation of immune responses to blood born infections take place
Why is it usually hard to distinguish between white and red pulp?
The pulp looks the same in mammalians
What is bacteria in blood called?
Septicemia
What are the three parts of white pulp?
Lymphoid follicles
Periarterial lymphatic sheath (PALS)
Marginal zone
What are PALS?
Periarterial lymphatic sheath
These are lymphocytes which cover the central arteriole
What is the marginal zone?
(2)
Area between white pulp and red pulp
Contains APCs e.g. macrophages
What are the lymph follicles?
(2)
B cell area
between PALS and marginal zone
What is the red pulp?
Connective tissue (cords of Billroth and splenic sinusoids
Write a note on asplenia?
(4)
A rare condition whereby individuals have no spleen
Due to the RPSA gene - dominant mutation
It increases the risk of infection by encapsulated bacteria
There is a much greater affect on children than adults after a splenectomy
