Lymphoid Tissue Flashcards
Where is the spleen located?
Left hypochondrium
What is the largest lymph organ in the body?
Spleen
What are the two components of the spleen?
Red pulp
White pulp
Describe the red pulp
Small sinuses lined by endothelial macrophages and cords/spaces.
Hypoxic, low glucose, low pH environments.
Describe the white pulp
Structure similar to lymphoid follicles.
What artery takes blood to the spleen?
Splenic artery
Where does the splenic artery arise from?
Coeliac artery
What blood components pass through the red pulp?
RBC
What blood components pass through the white pulp?
WBC
Platelets
What are the functions of the spleen?
Sequestration and phagocytosis.
Extramedullary haemopoiesis
Immunological function
Blood pooling
How much blood tends to be stored in the spleen?
1/3
How much WBC mass is found in the spleen?
25% T cells and 15% B cells
What do pluripotential stemcells do?
Extramedullary haemopoiesis
How does the spleen filter, sequester and phagocytose blood?
Normal (flexible) RBC pass through red pulp into venous system.
Old/abnormal RBC damaged by red pulp sinus environment and are removed for phagocytosis. Same applies to foreign matter.
WHat happens to IgG coated RBC in the spleen?
Removed by macrophages.
What can cause splenomegaly?
Infection
Inflammation
Haematological
Portal hypertension
What haematological things can cause splenomegaly?
Haemolytic anaemia
Haemoglobinopathy
Leukemias
Lymphomas
What inflammatory things can cause splenomegaly?
Ra
Sarcoidosis
SLE
What are some symptoms of splenomegaly?
Dragging sensation in LUQ
Discomfort with eating
Pain (if infarcted)
What is hypersplenism?
Pancytopenia occurring in all patients with splenomegaly
What can cause hypersplenism?
Any but most often with: haematological disease, liver disease, RA and lymphoma
What are some symptoms of hypersplenism?
Pancytopenia
Haemolysis
Increased plasma volume
How do you treat hypersplenism?
Treat underlying cause
Splenectomy
What can cause hyposplenism/splenic atrophy?
Infarct Sickle cell- Causes microinfarcts Coeliacs UC Essential thrombocythaemia
What are some symptoms of hyposplenism/splenic atrophy?
Thrombocytosis persists
Mild lymphocytosis and monocytosis
Abnormal RBC morphology
What RBC abnormalities can be seen with hyposplenism?
Howell–jolly bodies- DNA left in RBC.
Target cells
Pitted RBC
What can a splenectomy be performed for?
Trauma
Immune thrombocytopenic purpura
Haemolytic anaemias
Hypersplenism
What are some complications of a splenectomy?
Increased platelet count (for a short time)
Thrombo-embolic phenomena
Increased risk of overwhelmic infection- Pneumococcal
Thrombocytosis persists- Too many platelets
Mild lymphocytosis and monocytosis
Abnormal RBC morphology
What are the two types of lymphoid tissue?
Primary
Secondary
What are the two primary lymphoid tissue?
Bone marrow
Thymus
What are the three main secondary lymphoid tissue?
Lymph Nodes
Spleen
Tonsils
Describe the anatomy of a LN
Small oval body up to 2.5cm in diameter with capsule and cortex
What comes out of the hilum of the LN?
Artery
Vein
Efferent lymph vessels
How does fluid move through the lymphoid system?
Passively
Where can lymph vessels drain to?
Thoracic duct
L jugular, subclavian or bronchomediastinal trunks
R jugular, subclavian or bronchomediastinal trunks
What is the function of the LN?
Defence
How do LN provide an immune defence?
Houses cells of the innate immune system
Traffic of APCs links innate and adaptive immune responses
Seat of the adaptive immune response
What immune cells are found in the LN?
B Cells T Cells NK Cells Mononuclear phagocytes (macrophages) Antigen presenting cells Dendritic cells
What are the two surfaces of the spleen?
Diaphragmatic
Visceral
What are the functions of the lymphoid system?
Return lymph to the circulation
Cell traffic
Cell trapping
Interaction with of cells and “molecules” with cells of the immune system – protective function
Why is it important to return lymph to the circulation?
Important function in fluid homeostasis
Prevent excessive accumulation of fluid in the tissues – oedema
