Anatomy Flashcards
Importance of the lymphatic system
Balances fluid recirculation
Absorbs fats from small intestine
-lacteals in villi
Condition for spread of infection and malignancy
The lymphatic system is complementary to the cardiovascular system
Collects fluid lost from the capillaries ‘overflow’
The fluid is called lymph in lymphatic capillaries and vessels
Interspersed by lymph nodes
Drains into the veins in the neck
Contains lymphocytes
Lymph is formed from excess tissue fluid in the extracellular compartment
90% of plasma returns from tissues via cardiovascular system
10% through lymphatics
Lymph vessels are organised to drain into venous angle in the neck
Thoracic duct drains 3/4; includes all body except right upper limb/neck/thorax
Right lymphatic duct drains 1/4
Venous angle= anastomosis of internal jugular vein and subclavian vein
Drainage of the superficial and deep tissues occurs via two routes separated by investing layer of deep fascia
Tissues superficial to investing fascia= lymph drainage route 1
Tissues deep to investing fascia= lymph drainage route 2
Hematopoesis “blood making”
Constant regeneration of blood cells due to short lifespan
Stem cells in bone marrow generate cells of innate and adaptive immunity
Bone marrow contains the hematopoietic stem cells
Red marrow= blood and hematopoietic cells
Yellow marrow= adipocytes
In neonate all marrow is red and transitions to yellow
Key lymphoid tissues
Primary: thymus, bone marrow
Secondary: tonsils, MALTs, spleen, lymph nodes eg cervical, axillary, inguinal
T cells and B cells maturation
T cells mature in thymus
B cells mature in bone marrow
The thymus is present in the superior and anterior mediastinum in pre adolescents
T cells mature here
Then migrate to lymphoid organs to await activation
- lymph nodes
-MALTs
-spleen
Lymph nodes
Contains lymphocytes and macrophages
Act as a filter
Common site of metastasis of primary tumours
Pathologically changed nodes can be palpated
Structure of a lymph node
B cells matured/activated in cortex. Germinal centre matures, mantle zone activates
T cells mature/activated in the paracortex between cortex and medulla
Function of medulla: receiving lymph via medullary sinuses, multiple pathways in and single pathway out slows lymph and increases time to catch pathogens
Medullary cord are extensions of paracortex
The sentinel lymph node hypothesis
First group of lymph nodes draining a site of a primary tumour
The first detectable site of metastasis
Nodes can be surgically removed for biopsy
Eg. Virchow’s node (left supraclavicular node) as a site of primary metastasis of gastrointestinal cancers
Cisterna Chyli, lacteals —> thoracic duct—> left venous angle—> left supraclavicular node
Major lymph node groups of the body gather around important structures such as arteries and veins
Many nodes are palpable
Deep nodes are not palpable:
- eg tracheal nodes (lungs)
-eg pre aortic nodes (GI tract)
Cervical nodes: along course of internal jugular vein
Axillary nodes: in axilla
Deep nodes: related to aorta and celiac trunk and superior and inferior mesenteric arteries
Inguinal nodes: along course of inguinal ligament
Femoral nodes: along femoral vein
Tracheal nodes: nodes related to trachea and bronchi
Pericranial ring; base of head
MALTs (mucosa associated lymphoid tissues)
Secondary lymphoid tissues
Tonsils: pharyngeal, tubal, palatine, lingual
Diffuse MALTs: peyer’s patches, appendix
