17 Cells And Tissues Of Lymphatic System Flashcards
What are the levels of organisation in the lymphatic system?
Lymph
Lymphatic vessels
Lymphoid tissues and organs
What is chyle?
Lymph that arises in the GI tract
White cloudy substance - contains fats and dissolved lipids
What are the different lymphatic vessels in size order? (Smallest first)
Capillaries
Trunks
Ducts
Veins
How do the gaps between the endothelial cells in a lymphatic capillary open?
Oncotic/interstitial pressure causes the gaps to open
What are the anchoring filaments?
Reticulin (collagen 3)
Projections from the endothelial cells
Where are lymphatic vessels in relation to cardiovascular vessels?
Tend to lie adjacent to capillaries, arteries and veins
What happens with the lymphatic vessels in limbs?
Deep lymphatics pass through muscles where contraction aids lymph movement in trunks
Larger lymphatic vessels
Ducts and trunks
Contains smooth muscle cells in walls
In abdomen or thorax
Contraction of smooth muscle is important contributed to lymph flow
What is 3 valves together in a lymphatic vessel called?
Lymphangion
Compression by local veins and arteries propels the lymph
What are lymphatic trunks and ducts?
Equivalent to larger veins
Larger fibrocartilaginous valves
Skeletal muscle and organ movement used for flow
What is the cisterna chyli?
Large container of chyle from GI tract
Where does the lymph in the upper right quadrant of the body drain into?
Right subclavian vein or internal jugular vein
Where does the lymph from most of the body flow into?
The left subclavian vein or internal jugular vein
What are the 3 most important lymph nodes?
Neck (cervical)
Groin (inguinal)
Armpit (axillae)
Lymph nodes
Shaped like a kidney
Each node has multiple afferent lymphatic vessels entering
Single efferent lymphatic vessel leaving via concave hilum
Each lymph node has feeding artery and draining vein that also enter and leave hilum
What is the capsule of a lymph node made of?
Collagen 1 and reticulin
What do the follicles in the node contain?
Immune cells
E.g. macrophages, dendritic, B and T cells
What are follicular dendritic cells?
Located in germinal centres
Antigen antibody complexes adhere to dendritic processes
Cell can retain antigen for months
Causes proliferation of B cells
What is a difference between B and T lymphocytes?
B lymphocytes can recognise antigens
What us lymphadenopathy?
Enlarged lymph nodes
During infection, germinal centres full with lymphocytes causing swelling
Cancers can metastasise to lymph nodes
What are the lymphatic organs?
Thymus Spleen Tonsils Appendix Payer’s patches
Where is the thymus?
Superior mediastinum (middle of chest between lungs) Fully formed and functional at birth Starts to shrink after puberty by late teens, is mostly fat
What is the structure of the thymus?
Similar to lymph node but no hilum
No afferent vessel so secretes straight into bloodstream
What is the function of the thymus?
Maturation of bone marrow derived stem cells into immunocompetent T cells
‘Thymic cell education’
Where is the spleen located?
Inferior to diaphragm
Posterior to stomach
Fully formed and functional at birth
What is the structure of the spleen?
Similar to lymph node
Separated into white pulp (immune) and red pulp (haemopoesis)
What is the function of the spleen?
Filters blood
Has functions in both immune and haemopoietic systems
What are the immune functions of the spleen?
Antigen presentation by APCs
Activation and proliferation of B and T lymphocytes
Production of antibodies
Removal of macromolecular antigen from blood
What are the haemopoietic functions of the spleen?
Removal and destruction of old, damaged and abnormal erythrocytes and platelets
Retrieval of iron from erythrocyte haemoglobin for liver
Erythrocyte storage
What happens after a splenectomy in the body?
Liver and bone marrow take over removal and destruction of ageing RBCs
Splenectomy increases risk of infection by encapsulated bacteria and malaria
Where are the tonsils located?
Oropharynx and nasopharynx
Fully formed and dauntingly at birth
Affected mostly in childhood
What is the function of tonsils?
Prevents pathogen ingress through oral and nasal routes
Prevents pathogen ingress through aural route (adenoids)
Crypts increase surface area
What is the structure of tonsils?
Modules reside inferior to surface invagination (crypts)
What causes tonsils to swell?
Due to B cell and T cell proliferation
Surface epithelial have numerous micro gold (M cells)
Present antigens to underlying immune cells
Where is the appendix located?
Inferior to and attached to caecum (ascending colon)
What is the structure of the appendix?
Nodules reside inferior to surface invaginations (crypts)
Many M-fold cells in epithelial surface
What is the function of the appendix?
Prevents pathogen ingress through GI routes
Prevents pathogen ingress arriving from ileum
Crypts increase SA
Where are Payer’s patches located?
Inferior to and attached to side of ileum
What is the structure of the Payer’s patches?
Nodules reside inferior to surface dimes
Many M-fold cells in epithelial surfaces
Have germinal centres at bottom of domes
What are the main functions of the lymphatic system?
Fluid balance
Transport of fats and fat-soluble vitamins
Defence against invading pathogens and disease
Storage of and destruction of aged erythrocytes
What are sentinel lymph nodes?
First node to receive lymph from primary tumour
How can cancer cells tracks during metastatic disease?
Through newly produced vasculature
Through interstitial space
Through lymph
Sentinel lymph nodes in cancer detection
First set of lymph nodes that swell
Axilla or pectoral in Brest cancer use fluorography - inject radioactive dye, probe to see where is radioactive, remove blue stained tissues
Presence of malignant epithelial cells - mastectomy
